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Cited by 11Dermatology and Skin DiseasesAdvancements in Transdermal Drug DeliveryContact Dermatitis and Allergies

Recreating Human Skin In Vitro: Should the Microbiota Be Taken into Account?

Open access
Galvan, Andrea, Pellicciari, Carlo, Calderan, Laura·2024·International Journal of Molecular Sciences
DOI 10.3390/ijms25021165PMC PMC10816982
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Abstract

Skin plays crucial roles in the human body: besides protecting the organism from external threats, it acts as a thermal regulator, is responsible for the sense of touch, hosts microbial communities (the skin microbiota) involved in preventing the invasion of foreign pathogens, contains immunocompetent cells that maintain a healthy immunogenic/tolerogenic balance, and is a suitable route for drug administration. In the skin, four defense levels can be identified: besides the physical, chemical, and immune barriers that are inherent to the tissue, the skin microbiota (i.e., the numerous microorganisms living on the skin surface) provides an additional barrier. Studying the skin barrier function or the effects of drugs or cosmetic agents on human skin is a difficult task since snapshot evidence can only be obtained using bioptic samples where dynamic processes cannot properly be followed. To overcome these limitations, many different in vitro models of human skin have been developed that are characterized by diverse levels of complexity in terms of chemical, structural, and cellular composition. The aim of this review is to summarize and discuss the advantages and disadvantages of the different human skin models so far available and to underline how the insertion of a proper microbiota would positively impact an in vitro human skin model in an attempt to better mimic conditions in vivo.

AI snapshot

Written from the paper’s full text.

TL;DR

This review surveys in vitro human skin models from artificial membranes to organoids, organ-on-a-chip, 3D bioprinting, and ex vivo explants, comparing their complexity and limitations. It argues that incorporating the complete skin microbiota would improve fidelity to native skin, though most current models lack appendages and suitable conditions for full microbiota.

Key findings

  • The review describes four skin barriers—physical, chemical, immune, and microbiota—and states that the microbiota contributes to colonization resistance, antimicrobial peptide induction, tight-junction protein expression, lipid/pH maintenance, and immune modulation.
  • Increasing model complexity improves physiological relevance, but none fully reproduces native skin: artificial membranes lack cells; 2D models lack stratum corneum and 3D organization; HSEs lack all original cell populations, appendages, and vessels; spheroids/organoids lack an air-liquid interface, vascularization, and immune cells; organ-on-chip and bioprinting face vascularization and appendage limits; ex vivo explants preserve structure but have ethical, variability, and preservation constraints.
  • Evidence for microbiota integration includes Loomis et al., who found community effects on epidermal thickness, epidermal cell proliferation, and filaggrin production that were not entirely driven by any single microorganism, and Landemaine et al., who reported that full skin microbiota on a 3D model remained stable up to 7 days and produced a more proliferative epidermis with higher desmosome and tight-junction protein expression than S. epidermidis alone.
  • Quantitative examples include retinol permeation nearly 40-fold greater with jojoba oil in a skin PAMPA; spheroids usually between 65 and 300 µm when produced using spinner flasks; and Vahav et al. culturing an air-exposed epidermis with neopapillae spheroids under dynamic flow for 10 days, finding dose-dependent cinnamaldehyde cytotoxicity and cytokine release.

Methods

  • Narrative review; literature survey through PubMed and Scopus using “skin models”, “in vitro human skin”, and “microbiota” as search terms, considering papers published over the last ten years, with the most relevant skin-model papers since 2018.
  • No primary experimental data, sample, or statistical analysis are reported; the paper synthesizes and discusses advantages and disadvantages of different human skin models and the potential addition of microbiota.

Limitations

  • The paper states limitations of the reviewed models: artificial membranes lack cells; 2D models lack 3D organization and stratum corneum and cannot be maintained with bacteria for more than 24 h; HSEs lack original cell populations, appendages, and vessels and may have altered barrier formation; spheroids lack an air-liquid interface and vascularization and have difficult-to-control geometry/size; organoids lack immune cells and vascularization and have limited lifespan; organ-on-chip models face flow-stability and tubing issues; ex vivo explants require ethical permission, show inter- and intra-sample variability, and have limited structural/functional preservation.
  • The paper states that most current skin models lack appendages such as sebaceous glands and hair follicles, limiting co-culture of anaerobic bacteria like Cutibacterium and thus a complete human skin microbiota; pre-surgical prophylaxis may also alter the native microbiome in explants.
  • Text makes evident: as a narrative review, it does not report a systematic search strategy, inclusion/exclusion criteria, risk-of-bias assessment, or quantitative synthesis, and it presents no own experimental validation.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3390/ijms25021165

Cites

141 of 141 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

32 of 55 cited sources checked · 14 supported · 1 flagged · accuracy not yet measured

  • Premisecitation

    In the skin, four defense levels can be identified: physical, chemical, and immune barriers inherent to the tissue, plus the skin microbiota, which provides an additional barrier.

    “In the skin, four defense levels can be identified: besides the physical, chemical, and immune barriers that are inherent to the tissue, the skin microbiota (i.e., the numerous microorganisms living on the skin surface) provides an additional barrier.”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [4] Fournière, M., Latire, T., Souak, D., Feuilloley, M.G., and Bedoux, G. (2020). Staphylococcus epidermidis and Cutibacterium acnes: Two major sentinels of skin microbiota and the influence of cosmetics. Microorganisms, 8. source

      The Introduction describes the stratum corneum as a physical barrier and says skin microorganisms help maintain the skin barrier and immune system while limiting pathogen growth. Section 2.1 also describes antimicrobial substances produced by commensal bacteria. The paper does not identify four distinct defense levels or describe a separate chemical barrier inherent to the tissue; page numbers are unavailable in our copy. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
    • cites [5] Byrd, 2018, The human skin microbiome, Nat. Rev. Microbiol. source
  • Premisecitation

    A positive correlation was observed for total permeated phenoxyethanol between skin PAMPA and porcine or human skin in a Franz diffusion cell.

    “notably, the authors observed a positive correlation for the total amount of permeated phenoxyethanol between this artificial membrane and porcine or human skin placed in a Franz diffusion cell, a widely used system to test drug permeation in vitro [16,17,18].”
    Quote in the paperSubstantial claim2 of 3 sources checked
    • cites [16] Rahma, 2023, A comparative study of the in vitro permeation of 2-phenoxyethanol in the skin PAMPA model and mammalian skin, Int. J. Pharm. source
    • cites [17] Kumar, M., Sharma, A., Mahmood, S., Thakur, A., Mirza, M.A., and Bhatia, A. (2023). Franz diffusion cell and its implication in skin permeation studies. J. Dispers. Sci. Technol., 1–14. source
    • cites [18] Salamanca, 2018, Franz diffusion cell approach for pre-formulation characterisation of ketoprofen semi-solid dosage forms, Pharmaceutics source
  • Premisecitation

    Ibuprofen was more permeable through skin PAMPA and silicone membrane than through human and porcine tissue.

    “Luo et al. [20] performed a comparative study of ibuprofen permeation using human and porcine tissue, a skin PAMPA model, and a silicone membrane and found that the drug was more permeable through the PAMPA and the silicone membrane than through the animal tissues.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [20] Luo, 2016, A comparative study of the in vitro permeation of ibuprofen in mammalian skin, the PAMPA model and silicone membrane, Int. J. Pharm. source
  • Premisecitation

    Alteration of the microbial communities, due to environmental, genetic, lifestyle-associated, hygienic, and immune system-related factors, can lead to a pathological skin condition by making ordinarily beneficial bacteria disease-causing under certain conditions.

    “Indeed, as a result of environmental, genetic, lifestyle-associated, hygienic, and immune system-related factors, the alteration of the microbial communities can lead to a pathological skin condition; it means that these factors can have an impact on ordinarily beneficial bacteria, making them disease-causing under certain conditions [5,128].”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [5] Byrd, 2018, The human skin microbiome, Nat. Rev. Microbiol. source
    • cites [128] Findley, K., and Grice, E.A. (2014). The skin microbiome: A focus on pathogens and their association with skin disease. PLoS Pathog., 10. source

      Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
  • Premisecitation

    Loomis et al. found a community effect in microbiome-host signaling: effects of the microbial community on epidermal thickness, epidermal cell proliferation, and filaggrin production were not entirely driven by any single microorganism.

    “From the obtained results, the authors suggested a community effect in microbiome-host signaling since the effects obtained by the presence of the microbial community (i.e., changes in epidermal thickness, epidermal cell proliferation, and filaggrin production) were not entirely driven by any single microorganism.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [136] Loomis, K.H., Wu, S.K., Ernlund, A., Zudock, K., Reno, A., Blount, K., and Karig, D.K. (2021). A mixed community of skin microbiome representatives influences cutaneous processes more than individual members. Microbiome, 9. source
  • May combine two claims. 27
  • Classified as probably not a substantial claim. 5

  • May combine two claims.

    Premisecitation

    AD is associated with increased abundance of S. aureus in lesions, which interferes with host immunity and damages the skin barrier; psoriasis is associated with abnormal colonization of S. aureus and decreased S. epidermidis abundance in psoriatic lesions; seborrheic dermatitis involves Malassezia in its pathogenesis.

    “Further examples of disease-microbiota association in human skin are AD (where the increased abundance of S. aureus in the lesions interferes with the host immunity, directly damaging the skin barrier), psoriasis (with abnormal colonization of S. aureus and decrease of S. epidermidis abundance in psoriatic lesions), and seborrheic dermatitis (where the most abundant fungal skin commensal, Malassez”
    Quote in the paperSubstantial claim4 of 4 sources checked
    • cites [122] Grice, 2011, The skin microbiome, Nat. Rev. Microbiol. source

      Split into 3 atoms — 0 confirmed, 2 partially supported, 1 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
    • cites [126] Lee, H.J., and Kim, M. (2022). Skin barrier function and the microbiome. Int. J. Mol. Sci., 23. source

      Split into 2 atoms — 1 confirmed, 0 partially supported, 0 disputed, 0 misattributed, 1 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [128] Findley, K., and Grice, E.A. (2014). The skin microbiome: A focus on pathogens and their association with skin disease. PLoS Pathog., 10. source

      Split into 3 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 1 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [129] Carmona-Cruz, S., Orozco-Covarrubias, L., and Sáez-de-Ocariz, M. (2022). The human skin microbiome in selected cutaneous diseases. Front. Cell Infect. Microbiol., 12. source

  • May combine two claims.

    Interpretationcitation

    Artificial membranes are distant from the in vivo condition because they lack cells and intercellular matrix, but they are useful for screening chemical-physical characteristics of compounds.

    “The first cited models consist of artificially generated membranes: they are quite distant from the in vivo condition due to the lack of cells and intercellular matrix, but they can be useful for screening with respect to the chemical-physical characteristics of the compounds to be tested.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [11] Moniz, 2020, Human skin models: From healthy to disease-mimetic systems; characteristics and applications, Br. J. Pharamcol. source

      Section 4.2 describes artificial membranes as distinct from cell cultures and says simple membrane models lack similarity with human skin but are useful for testing diffusion and drug permeation. It also describes a lipid-based membrane model that can screen drug candidates. The section does not specifically say that these membranes screen compounds’ physicochemical characteristics or identify the absence of intercellular matrix as the reason they differ from living skin. (LLM, conf=0.82)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    During organism growth, bacterial populations gradually adapt to the skin environment, and microbiota colonization continues until equilibrium is reached in adulthood.

    “During the organism’s growth, the bacterial populations gradually adapt to the skin environment, and the microbiota colonization continues until equilibrium is reached in adulthood [8,9,10].”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites [8] Somerville, 1969, The normal flora of the skin in different age groups, Br. J. Dermatol. source
    • cites [9] Leyden, 1975, Age-related changes in the resident bacterial flora of the human face, J. Investig. Dermatol. source
    • cites [10] Hu, 2023, Changes in the skin microbiome during male maturation from 0 to 25 years of age, Skin Res. Technol. source

  • May combine two claims.

    Premisecitation

    In humans, skin microbiota is acquired at birth because the skin is sterile in utero; colonization occurs minutes after birth by the mother's commensal microorganisms, and this neonatal process is crucial to establish immune tolerance towards them.

    “In humans, skin microbiota is acquired at birth since, in utero, the skin is sterile; skin colonization occurs a few minutes after birth by the mother’s commensal microorganisms, and this process in the neonatal stage is crucial to establish immune tolerance towards them [6,7].”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [6] Mueller, 2015, The infant microbiome development: Mom matters, Trends Mol. Med. source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [7] Capone, 2011, Diversity of the human skin microbiome early in life, J. Investig. Dermatol. source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    The skin microbiota, or dermobiota, comprises bacteria, fungi, viruses, archaea, and mites on the skin surface and forms a complex ecosystem that keeps pathogenic bacteria under control and releases activating/modulating substances for epidermal and immune cells, favoring maintenance of whole barrier functions.

    “the skin microbiota, or dermobiota (i.e., the bacteria, fungi, viruses, archaea, and mites present on the skin surface) forms a complex ecosystem that keeps pathogenic bacteria under control and releases activating/modulating substances for the epidermal and immune cells, thus favoring the maintenance of the whole barrier functions [4,5].”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [4] Fournière, M., Latire, T., Souak, D., Feuilloley, M.G., and Bedoux, G. (2020). Staphylococcus epidermidis and Cutibacterium acnes: Two major sentinels of skin microbiota and the influence of cosmetics. Microorganisms, 8. source
    • cites [5] Byrd, 2018, The human skin microbiome, Nat. Rev. Microbiol. source

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Skin PAMPAs are 96-well plate-based systems with an artificial membrane between donor and acceptor compartments, used as high-throughput assays for preliminary screening and permeation- and stability-related insights into topical and transdermal formulations.

    “the skin PAMPAs are 96-well plate-based systems where an artificial membrane is interposed between a donor and an acceptor compartment, in a sandwich-like structure. These systems attracted the attention of researchers as high-throughput assays for the preliminary screening and for obtaining permeation- and stability-related insights into topical and transdermal formulations [14,15].”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [14] Mossahebi, 2019, Investigation of the compatibility of the skin PAMPA model with topical formulation and acceptor media additives using different assay setups, AAPS PharmSciTech source
    • cites [15] Neupane, R., Boddu, S.H., Renukuntla, J., Babu, R.J., and Tiwari, A.K. (2020). Alternatives to biological skin in permeation studies: Current trends and possibilities. Pharmaceutics, 12. source

      Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    Skin PAMPAs lack stratified epidermal tissue, skin macromolecules, cell populations, and appendages, and their stratum corneum-mimicking lipid mixture does not contain all lipid subclasses normally present in human skin.

    “In particular, they lack the stratified epidermal tissue and all the wide set of skin macromolecules, cell populations, and appendages, while the lipid mixture mimicking the stratum corneum does not contain all the lipid subclasses normally present in the human skin [9,10].”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [9] Leyden, 1975, Age-related changes in the resident bacterial flora of the human face, J. Investig. Dermatol. source
    • cites [10] Hu, 2023, Changes in the skin microbiome during male maturation from 0 to 25 years of age, Skin Res. Technol. source

      The Discussion describes changes in the facial skin microbiome during male maturation, not the composition or limitations of skin PAMPAs. Searches for stratified epidermal tissue and for missing stratum corneum lipid subclasses found no passage addressing the claim. Page numbers were not available in our copy. (LLM, conf=0.77)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    The array of microorganisms colonizing the epidermal surface is fairly stable and depends on the skin site (biogeography), with changes in the relative abundance of bacterial taxa associated with moist-, dry-, and sebum-rich microenvironments.

    “The array of microorganisms colonizing the epidermal surface is fairly stable and depends on the skin site (the so-called “biogeography” factor), with changes in the relative abundance of the bacterial taxa associated with moist-, dry- and sebum-rich microenvironments.”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [5] Byrd, 2018, The human skin microbiome, Nat. Rev. Microbiol. source
    • cites [123] Boxberger, M., Cenizo, V., Cassir, N., and La Scola, B. (2021). Challenges in exploring and manipulating the human skin microbiome. Microbiome, 9. source

  • May combine two claims.

    Premisecitation

    The skin consists of four morphologically and functionally related barriers-physical, chemical, immune, and microbiotic-that form an interactive network whose disruption may lead to infection, inflammation, allergy, or cancer.

    “As already recalled, the skin has been described as consisting of four morphologically and functionally related barriers: the physical, chemical, immune, and microbiotic barriers that form an interactive network whose disruption may lead to infection, inflammation, allergy, or even cancer [4,5].”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [4] Fournière, M., Latire, T., Souak, D., Feuilloley, M.G., and Bedoux, G. (2020). Staphylococcus epidermidis and Cutibacterium acnes: Two major sentinels of skin microbiota and the influence of cosmetics. Microorganisms, 8. source

      The Introduction describes a physical barrier and says skin microorganisms help maintain the skin barrier and immune system. Section 2.2 links barrier disturbance and microbiota imbalance with inflammatory skin disease, but says the causal relationship remains unclear. The paper does not describe the claimed four-barrier framework or link its disruption to allergy or cancer; page numbers are not available in our copy. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [5] Byrd, 2018, The human skin microbiome, Nat. Rev. Microbiol. source

  • May combine two claims.

    Premisecitation

    The human skin microbiota contains a variety of bacterial species and, unlike the gut microbiota, is mostly made of Gram-positive Actinobacteria (e.g., Cutibacterium spp. and Corynebacterium spp.), including Gram-positive Staphylococcus.

    “Genomics-based investigation showed that a variety of different bacterial species coexist in the human skin microbiota, which, in contrast to the gut microbiota, is mostly made of Gram-positive Actinobacteria (e.g., Cutibacterium spp. and Corynebacterium spp.), including the Gram-positive Staphylococcus [122].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [122] Grice, 2011, The skin microbiome, Nat. Rev. Microbiol. source

      The Molecular analysis of skin microbiota section reports diverse skin bacteria and says Actinobacteria are more abundant on skin than in the gut. The Variation by skin site subsection identifies Corynebacterium and Staphylococcus on skin, but the paper places Actinobacteria and Firmicutes in separate phyla; it does not support describing Staphylococcus as included among Actinobacteria. Our copy uses Propionibacterium rather than Cutibacterium. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    Staphylococcus epidermidis inhibits colonization by pathogenic S. aureus and induces AMP expression, resulting in innate immune alertness; it may also enhance epidermal barrier function by increasing expression of tight-junction proteins occludin and ZO-1.

    “For example, the natural cutaneous commensal, Staphylococcus epidermidis inhibits the colonization by the pathogenic S. aureus and induces the expression of AMPs, resulting in S. epidermidis-orchestrated innate immune alertness; additionally, it may enhance the epidermal barrier function stimulating the increased expression of the tight-junction proteins, occludin and ZO-1 [124,125].”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [124] Brandwein, 2017, Endogenous antimicrobial peptide expression in response to bacterial epidermal colonization, Front. Immunol. source

      Split into 2 atoms — 0 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 1 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [125] Ohnemus, 2008, Regulation of epidermal tight-junctions (TJ) during infection with exfoliative toxin-negative Staphylococcus strains, J. Investig. Dermatol. source

  • May combine two claims.

    Premisecitation

    The efficacy of the epidermal barrier is the outcome of crosstalk between the different skin barrier levels, with the microbiota contributing physically, chemically, microbially, and immunologically; these functions are guaranteed by a strictly-regulated and finely balanced microbiota.

    “Thus, the efficacy of the epidermal barrier is the outcome of the crosstalk between the different skin barrier levels, with the microbiota contributing to the skin barrier from a physical, chemical, microbial, and innate/adaptive immunological point of view; these functions are guaranteed by a strictly-regulated and finely balanced microbiota [126].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [126] Lee, H.J., and Kim, M. (2022). Skin barrier function and the microbiome. Int. J. Mol. Sci., 23. source

  • May combine two claims.

    Premisecitation

    Some components of the skin microbiota secrete lipase enzymes that hydrolyze free fatty acids from sebum triglycerides, maintaining low skin pH, preserving the acid mantle, and stimulating production of β-defensin 2.

    “From the chemical barrier point of view, some components of the skin microbiota have an important role in secreting lipase enzymes that hydrolyze free fatty acids from the triglycerides present in sebum, maintaining in this way a low skin pH, preserving the acid mantle, but also stimulating the skin immunity in producing β-defensin 2 [123,126].”
    Quote in the paperNot a substantial claim2 of 2 sources checked
    • cites [123] Boxberger, M., Cenizo, V., Cassir, N., and La Scola, B. (2021). Challenges in exploring and manipulating the human skin microbiome. Microbiome, 9. source

      The ‘maintenance of skin homeostasis’ section says microbial lipases help break down the skin’s surface lipid film and that sebum and free fatty acids help regulate skin pH. The Introduction also links fatty acids to skin acidification. Neither passage specifies hydrolysis of sebum triglycerides, preservation of the acid mantle, or stimulation of β-defensin 2 production; the immune-system section discusses antimicrobial peptides only generally. Page numbers are unavailable in our copy. (LLM, conf=0.87)

      Experimental — accuracy not yet measured
    • cites [126] Lee, H.J., and Kim, M. (2022). Skin barrier function and the microbiome. Int. J. Mol. Sci., 23. source

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    Adding the complete microbiota to colonize the apical side of human skin models would make them closer to the in vivo condition.

    “For this reason, it is to be foreseen to improve human skin models by adding the complete microbiota to colonize the apical side of the model in order to get closer and closer to the in vivo condition [130,131,132].”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites [130] Niehues, 2018, 3D skin models for 3R research: The potential of 3D reconstructed skin models to study skin barrier function, Exp. Dermatol. source
    • cites [131] Rademacher, 2018, Skin microbiota and human 3D skin models, Exp. Dermatol. source
    • cites [132] Bojar, 2015, Studying the human skin microbiome using 3D in vitro skin models, Appl. Vitr. Toxicol. source

  • May combine two claims.

    Premisecitation

    2D models are not suitable for emulating the relationship between skin and microbiota because they lack the stratum corneum, causing microorganisms to contact proliferating keratinocytes and fibroblasts (which does not happen in vivo), and because bacteria grow faster than human cells, preventing maintenance for more than 24 h.

    “Even the 2D models are not suitable for the development of systems capable of emulating the relationship between skin and microbiota. In fact, they lack the stratum corneum, and so the microorganisms would come in direct contact with proliferating keratinocytes and fibroblasts, which does not happen in vivo; moreover, these systems are disadvantaged by the faster growth rate of bacteria compared”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [28] Pérez-Salas, J.L., Moreno-Jiménez, M.R., Rocha-Guzmán, N.E., González-Laredo, R.F., Medina-Torres, L., and Gallegos-Infante, J.A. (2023). In Vitro and Ex Vivo Models for Screening Topical Anti-Inflammatory Drugs. Sci. Pharm., 91. source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured
    • cites [123] Boxberger, M., Cenizo, V., Cassir, N., and La Scola, B. (2021). Challenges in exploring and manipulating the human skin microbiome. Microbiome, 9. source

      Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    van Der Krieken et al. developed a simplified human skin model consisting of the stratum corneum only (human callus on top of agar in phosphate-buffered saline) and planted the complete microbiota from the back of healthy volunteers onto it; the model supported growth of the most relevant strains and the complete set of skin microbes normally found in vivo, which remained relatively stable for 7天.

    “An interesting study was performed by van Der Krieken et al. [140], who planted the complete microbiota taken from the back of healthy volunteers onto an originally developed simplified human skin model, which consisted in the reproduction of the stratum corneum only by using human callus on top of agar in phosphate-buffered saline. Since in vivo skin bacteria live attached to the dead corneocytes”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [140] Ederveen, 2016, An in vitro model for bacterial growth on human stratum corneum, Acta Derm. Venereol. source

  • May combine two claims.

    Interpretationcitation

    The use of human skin explants is more suitable for hosting the complete microbiota, but systemic pre-surgical prophylaxis may affect the integrity of the native microbiome, a problem that can only be overcome by using skin explants from non-prophylaxed donors.

    “Therefore, the use of human skin explants is certainly more suitable, but the systemic pre-surgical prophylaxis normally performed before surgical operations may affect the integrity of the native microbiome, a problem that can only be overcome by using skin explants deriving from non-prophylaxed donors [133].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [133] Larson, 2021, Challenges in developing a human model system for skin microbiome research, J. Investig. Dermatol. source

      Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    Rodent skin has its own microbiota that differs from human skin microbial communities, and attempts to model human microbiota on animal skin are prevented by competition from the native flora, in addition to intrinsic morphological differences with human skin.

    “Indeed, besides having intrinsic morphological differences with human skin, disadvantaging germ-free animal models, rodent skin is characterized by its own microbiota, which obviously differs from the microbial communities of human skin; thus, the attempts to model human microbiota on animal skin are prevented due to the competition exerted by the native flora [133,134].”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [133] Larson, 2021, Challenges in developing a human model system for skin microbiome research, J. Investig. Dermatol. source
    • cites [134] Emmert, 2020, Skin microbiota analysis in human 3D skin models—“Free your mice”, Exp. Dermatol. source

      Split into 2 atoms — 1 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

      Experimental — accuracy not yet measured

  • May combine two claims.

    Premisecitation

    Most skin models used nowadays for the study of barrier functions lack skin appendages such as sebaceous glands and hair follicles; as a consequence, it is difficult or even impossible to co-culture bacteria strains that grow within anaerobic environments like Cutibacterium, limiting the culturing of a complete human skin microbiota.

    “However, most of the skin models used nowadays for the study of barrier functions lack skin appendages such as sebaceous glands and hair follicles; as a consequence, it is difficult or even impossible to co-culture bacteria strains that grow within anaerobic environments like Cutibacterium, limiting in this way the culturing of a complete human skin microbiota [136].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [136] Loomis, K.H., Wu, S.K., Ernlund, A., Zudock, K., Reno, A., Blount, K., and Karig, D.K. (2021). A mixed community of skin microbiome representatives influences cutaneous processes more than individual members. Microbiome, 9. source

  • Classified as probably not a substantial claim. May combine two claims.

    Premisenone given

    In vitro skin models have been designed to obtain reliable data on biocompatibility, penetrability, safety, and efficacy of tested compounds, and their complexity has progressively improved to approach native skin.

    “The skin models in vitro have been designed to obtain reliable data on the biocompatibility, penetrability, safety, and efficacy of tested compounds, and their complexity has progressively improved to approach a reliable similarity to the native skin.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    The skin microbiota prevents pathogen invasion, but when the balance between commensals and pathogens is altered, the barrier may break and skin diseases or systemic disorders can occur.

    “Serving as a physical barrier, the skin microbiota prevents the invasion of pathogens, but when the balance between commensals and pathogens is altered, the barrier may be broken, and skin diseases (and sometimes even systemic disorders) can occur [5].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [5] Byrd, 2018, The human skin microbiome, Nat. Rev. Microbiol. source

  • May combine two claims.

    Premisecitation

    Cellulose acetate membranes lack the fluid lipid component normally present in the stratum corneum of in vivo skin, which is one of the main barriers to drug penetration.

    “In addition, CA membranes also lack the fluid lipid component, which is normally present in the stratum corneum of the in vivo skin and is one of the main barriers to drug penetration [12,13].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [12] Haq, 2018, Membrane properties for permeability testing: Skin versus synthetic membranes, Int. J. Pharm. source
    • cites [13] Simon, 2013, Nanoemulsion containing dapsone for topical administration: A study of in vitro release and epidermal permeation, Int. J. Nanomed.

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Cellulose acetate membranes have a pore size larger than human skin, causing a higher permeation rate than the native biological barrier; dapsone permeated more through CA membranes than through pig ear epidermis.

    “However, these systems have several disadvantages, e.g., the pore size of CA is larger than in human skin, thus causing a higher permeation rate than that found in the native biological barrier (in fact, de Almedida Borges and colleagues [13] observed a higher permeation of dapsone through CA membranes compared to the permeation observed in pig ear epidermis).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13] Simon, 2013, Nanoemulsion containing dapsone for topical administration: A study of in vitro release and epidermal permeation, Int. J. Nanomed.

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning

    The development of skin appendages-containing human skin models would be important.

    “Thus, the development of skin appendages-containing human skin models would be important.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Landemaine et al. showed that adding a full skin microbiota collected from the inner forearm of a volunteer to a 3D skin model results in a stable number of bacteria up to 7 days, with a more proliferative epidermis showing higher expression of desmosome and tight junction proteins compared to the same model with only S. epidermidis added.

    “This aspect was also underlined by Landemaine et al. [137], who showed that the addition of a full skin microbiota collected from the inner forearm of a volunteer to a 3D skin model results in a stable number of bacteria up to 7 days, with a more proliferative epidermis showing a higher expression of proteins of desmosomes and tight junctions when compared to the same model but with the addition”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [137] Landemaine, 2018, 961 Colonization of a 3D skin model with a complete microbiota is more beneficial to the skin barrier than with Staphylococcus epidermidis alone, J. Investig. Dermatol. source

  • May combine two claims.

    Premisecitation

    Both a transepidermal and a transappendageal pathway exist in skin for formulation permeation.

    “since both a transepidermal and a transappendageal pathway exist [142]”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [142] Vitorino, 2015, Overcoming the skin permeation barrier: Challenges and opportunities, Curr. Pharm. Des. source

  • May combine two claims.

    Interpretationcitation

    The symbiotic relationship between the tissue and the microorganisms living on its surface underlines the importance of integrating them in in vitro systems, obtaining positive effects on the growth and cohesion of skin cells, which are reflected on an improved barrier function.

    “The symbiotic relationship existing between the tissue and the microorganisms living on its surface underlines the importance of integrating them in these in vitro systems, obtaining in this way positive effects on the growth and cohesion of skin cells, which are then reflected on an improved barrier function.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning

    For a correct evaluation of formulation permeability, the chosen in vitro model should have the same complexity as the skin organ.

    “It is easy to understand that the same complexity found in this organ should be present in the chosen model for a correct evaluation of the formulation permeability”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    To better mimic human skin, in vitro models should be able to host complete microbiota communities; to do so, the presence of skin appendages like sebaceous glands is important for skin-related microbes living in anaerobic environments.

    “Thus, to better mimic the human skin, these models should also be able to host the complete microbiota communities: to do so, the presence of skin appendages like sebaceous glands is important for all those skin-related microbes living in these anaerobic environments.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The use of human skin explants could solve the issues of hosting complete microbiota, but preservation after explant, difficulty in finding them, inter-subject variability, and possible alteration of microbiota due to pre-surgical prophylaxis could limit their use.

    “The use of human skin explants could solve all these issues, but the preservation after the explant, the difficulty in finding them, the inter-subject variability, and the possible alteration of the microbiota due to pre-surgical prophylaxis could limit their use.”
    Quote in the paperSubstantial claim
30 of 30

  • The paper relies on this without support.

    Synthetic membranes lack cells, so microorganisms cannot establish symbiotic relationships.

    “Synthetic membranes have an intrinsic limitation: the cells are not present in these models, and the different microorganisms could not establish any symbiotic relationship.”

  • The paper relies on this without support.

    In the literature, very few human skin models have used the complete skin microbiota.

    “In the literature, it is possible to find human skin models where single commensal species were added, but very few used the complete skin microbiota.”

  • The paper relies on this without support.

    Skin microbiota is a constituent normally found in vivo.

    “including the skin microbiota”
3 of 3

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. Haigh, J.M., Beyssac, E., and Aiache, J.-M. (1998, January 25–28). Can shed snake skin be considered to be a ‘model’ membrane for human stratum corneum?. Proceedings of the 2nd World Meeting APGI/APV, Paris, France.

Cited by

Sorted by citations

Related

Authors
Galvan, A., Pellicciari, C., & Calderan, L.
Affiliations
  • University of Verona (IT)
  • University of Pavia (IT)
Corresponding author
Pellicciari, Carlo
ORCID
Venue
International Journal of Molecular Sciences
Publisher
MDPI AG
Published
2024-01-18
Volume
25
Issue
2
Pages
1165
ISSN
1422-0067 (ISSN-L)
DOI
10.3390/ijms25021165
PMC
PMC10816982
OpenAlex
W4390985411
Semantic Scholar
7c313a5fe37b550025f4b96e023fb63c0656a774
Cited by
11
References
140
Citations by year
2026: 5 · 2025: 4 · 2024: 2
FWCI
3.70
Type
journal article
Language
en
Open access
Licence
Locations
  • International Journal of Molecular Sciences (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • PubMed Central (submittedVersion, cc-by)
Topics
  • Health Sciences › Medicine › Dermatology › Dermatology and Skin Diseases
  • Life Sciences › Pharmacology, Toxicology and Pharmaceutics › Pharmaceutical Science › Advancements in Transdermal Drug Delivery
  • Health Sciences › Medicine › Dermatology › Contact Dermatitis and Allergies
Keywords
in vitro skin model, skin microbiome, skin barrier function, human skin, skin barrier, cosmetic agents, drug administration routes
MeSH terms
Health Status, Humans, Skin, Touch, Internationality, Microbiota

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-22.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-22.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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