Elucidating brain transport pathways and cell type-dependent gene silencing of a durable lipid–siRNA conjugate administered into cerebrospinal fluid

May combine two claims.

Unconjugated siRNA administered carrier-free into CSF penetrates throughout the CNS but is not sufficiently internalized by cells to achieve potent gene silencing.

“For example, unconjugated siRNA structures administered carrier-free into CSF penetrate throughout the CNS but are not sufficiently internalized by cells to achieve potent gene silencing [8].”

• cites [8] Brown, 2022, Expanding RNAi therapeutics to extrahepatic tissues with lipophilic conjugates, Nat Biotechnol sourceDisputed

  The Discussion says siRNAs lacking C16 are functionally taken up near the injection site but do not disperse broadly into CNS parenchyma. That is contrary to the claim that unconjugated siRNA penetrates throughout the CNS but fails because cells do not sufficiently internalize it. The optimization results also report minimal activity for an unconjugated siRNA, but do not establish the claimed distribution or uptake mechanism. (LLM, conf=0.88)

  Checked by a reasoning model — may be wrong.

  Experimental — accuracy not yet measured

Classified as probably not a substantial claim.

L2-siRNA was optimized in the context of navigating systemic delivery to tumors.

“We recently developed a lipid–siRNA conjugate termed “L2-siRNA” that was optimized in the context of navigating systemic delivery to tumors [12].”

• cites [12] Hoogenboezem, 2024, Structural optimization of siRNA conjugates for albumin binding achieves effective MCL1-directed cancer therapy, Nat Commun sourceSupported

May combine two claims.

L2-siRNA exhibited balanced cell uptake and transport properties in serum, modulated by reversible shielding of the lipids due to albumin binding.

“The L2-siRNA conjugate exhibited balanced cell uptake and transport properties in serum, which was modulated by reversible shielding of the lipids due to albumin binding [12].”

• cites [12] Hoogenboezem, 2024, Structural optimization of siRNA conjugates for albumin binding achieves effective MCL1-directed cancer therapy, Nat Commun sourceSupported

Classified as probably not a substantial claim.

Conjugation of siRNA to lipophilic moieties is intended to improve cellular uptake through membrane interactions.

“Conjugation of siRNA to lipophilic moieties is intended to improve cellular uptake through membrane interactions [9, 10].”

• cites [9] Osborn, 2018, Improving siRNA delivery in vivo through lipid conjugation, Nucleic Acid Ther sourceSupported
• cites [10] Wolfrum, 2007, Mechanisms and optimization of in vivo delivery of lipophilic siRNAs, Nat Biotechnol sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

A hydrophilic linker helped offset the lipid hydrophobicity that promoted potent cellular entry.

“This prior work studied the effects of linker and lipid structure and revealed that a hydrophilic linker helped offset the lipid hydrophobicity that promoted potent cellular entry.”

• cites [12] Hoogenboezem, 2024, Structural optimization of siRNA conjugates for albumin binding achieves effective MCL1-directed cancer therapy, Nat Commun sourceSupported

May combine two claims.

Prior studies have shown that albumin-binding dyes have reduced clearance to the periphery after ICV infusion in mice and accumulate in perivascular compartments after ICV injection in rats.

“because prior studies have shown that albumin-binding dyes have reduced clearance to the periphery after ICV infusion in mice [23] and accumulate in perivascular compartments after ICV injection in rats [24, 25].”

• cites [23] Ma, 2017, Outflow of cerebrospinal fluid is predominantly through lymphatic vessels and is reduced in aged mice, Nat Commun sourceSupported
• cites [24] Rey, 2023, Perivascular network segmentations derived from high-field MRI and their implications for perivascular and parenchymal mass transport in the rat brain, Sci Rep sourcePartly supported

  The Results report extensive perivascular uptake after intraventricular infusion in rats, supporting the rat portion of the cited claim. The Methods identify the tracer as gadolinium-labeled albumin (Gd-DTPA-albumin), not an albumin-binding dye. The mouse clearance claim is attached to a different citation [23] and is not assessed here. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [25] Magdoom, 2019, MRI of whole rat brain perivascular network reveals role for ventricles in brain waste clearance, Sci Rep sourceSupported

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

Disease-associated genes are usually expressed by many CNS cell types, but select populations play an outsized role in driving disease progression.

“Disease-associated genes are usually expressed by many CNS cell types, but select populations play an outsized role in driving disease progression [48].”

• cites [48] Fu, 2018, Selective vulnerability in neurodegenerative diseases, Nat Neurosci sourcePartly supported

  The Abstract says disease-related proteins often have widespread expression while particular cell populations are selectively affected. The ‘Primary and secondary selective neuronal vulnerability’ section describes pathology arising in initially vulnerable cells and spreading to other regions. However, ‘Insight from genomics’ says many disease-associated loci are expressed in particular cell types; the paper does not establish that disease-associated genes are usually expressed across many CNS cell types. (LLM, conf=0.84)

  Experimental — accuracy not yet measured

May combine two claims.

Htt is a disease-relevant target that is ubiquitously expressed by CNS cells, and a well-validated siRNA sequence exists for it.

“we chose Htt as a disease-relevant target that is ubiquitously expressed by CNS cells and for which a well-validated siRNA sequence exists (“Htt10150”) [11].”

• cites [11] Alterman, 2015, Hydrophobically modified siRNAs silence huntingtin mRNA in primary neurons and mouse brain, Mol Ther Nucleic Acids sourcePartly supported

  The Introduction identifies Htt as the causative gene in Huntington’s disease. The Results (‘Potent and specific silencing with unformulated hsiRNAs in primary neurons’; page unavailable) show that HTT10150 silences Htt in primary neurons, and the in vivo Results report dose-dependent silencing in mouse brain. These passages support the disease relevance and validated siRNA sequence, but do not establish that Htt is ubiquitously expressed by CNS cells. (LLM, conf=0.87)

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

There is a growing appreciation for the role brain borders play in disease.

“There is a growing appreciation for the role brain borders play in disease [32], but no prior studies have rigorously evaluated siRNA delivery to the cells residing in these borders.”

• cites [32] Rustenhoven, 2022, Brain borders at the central stage of neuroimmunology, Nature sourceSupported

May combine two claims.

Single-nucleus atlases are not suitable for siRNAs, which only degrade cytoplasmic mRNA.

“While single-nucleus atlases have generated informative datasets for ASOs, this method is not suitable for siRNAs, which only degrade cytoplasmic mRNA [49].”

• cites [49] Mortberg, 2023, A single-cell map of antisense oligonucleotide activity in the brain, Nucleic Acids Res sourcePartly supported

  The Introduction and Discussion report that single-nucleus transcriptomics produced informative ASO target-engagement data. The Discussion’s limitations section says the method measured target engagement only in nuclei, but the paper does not establish that it is unsuitable for siRNAs or that siRNAs only degrade cytoplasmic mRNA. Page numbers were not provided in our copy. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

May combine two claims.

Leveraging convective CSF flow along perivascular spaces could overcome diffusional limitations and provide a direct mechanism for transport to deep brain structures.

“Leveraging convective CSF flow along perivascular spaces could overcome diffusional limitations and provide a direct mechanism for transport to deep brain structures [13–15].”

• cites [13] Abbott, 2018, The role of brain barriers in fluid movement in the CNS: is there a ‘glymphatic’ system?, Acta Neuropathol sourceSupported
• cites [14] Murlidharan, 2016, Glymphatic fluid transport controls paravascular clearance of AAV vectors from the brain, JCI Insight sourcePartly supported

  The Introduction describes convective CSF currents along paravascular compartments, and the Results report widespread AAV distribution after intra-CSF administration in wild-type mice but more localized distribution when AQP4-mediated flow is impaired. The paper does not establish that this flow overcomes diffusional limitations or provides a direct transport route specifically to deep brain structures; its observations of AAV in the thalamus and hypothalamus do not establish that mechanism. (LLM, conf=0.84)

  Experimental — accuracy not yet measured
• cites [15] Naseri, 2021, Harnessing cerebrospinal fluid circulation for drug delivery to brain tissues, Adv Drug Deliv Rev sourceSupported

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

Sequencing coverage results in some dropout (apparent zeroes) for each gene, and scRNA-seq is conventionally used to characterize cell types and pathways governed by changes in multiple transcripts.

“Because sequencing coverage results in some dropout (apparent zeroes) for each gene, scRNA-seq is conventionally used to characterize cell types and pathways, processes governed by changes in multiple transcripts [50].”

• cites [50] Sarkar, 2021, Separating measurement and expression models clarifies confusion in single-cell RNA sequencing analysis, Nat Genet sourcePartly supported

  The Introduction describes scRNA-seq as a way to investigate cell types, cellular processes, and pathways. The Modeling scRNA-seq measurement section says lower sequencing depth contributes to the high proportion of zeros, but also identifies low or truly zero expression as a cause; it does not say that coverage causes dropout for each gene. The paper also cautions in A call to simplify terminology that “dropout” is ambiguous and recommends calling these observations zeros. (LLM, conf=0.87)

  Experimental — accuracy not yet measured

Classified as probably not a substantial claim.

The most common therapeutic route for CSF drug delivery is intrathecal administration into the lumbar cistern.

“The CSF has several access points for drug delivery, the most common therapeutic route being intrathecal administration into the lumbar cistern.”

• cites [43] Miller, 2022, Trial of antisense oligonucleotide Tofersen for SOD1 ALS, N Engl J Med sourcePartly supported

  The Trial Design section says tofersen was delivered by intrathecal injection through a lumbar puncture, supporting this route as an example of therapeutic CSF drug delivery. It does not say that this is the most common route, identify the lumbar cistern specifically, or compare CSF access points. (LLM, conf=0.86)

  Experimental — accuracy not yet measured

May combine two claims.

Chemically stabilized siRNA can remain intact and slowly escape from endolysosomal vesicles, gradually achieving intracellular bioavailability over time.

“which suggests that once delivered, chemically stabilized siRNA remains intact and slowly escapes from sequestration within intracellular endolysosomal vesicles, gaining access to the cytoplasmic gene silencing machinery; this phenomenon allows the internalized siRNA to gradually achieve intracellular bioavailability over time”

• cites [44] Brown, 2020, Investigating the pharmacodynamic durability of GalNAc–siRNA conjugates, Nucleic Acids Res sourceSupported

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

Border-associated macrophages reside in CSF outside the brain parenchyma, primarily in the choroid plexus, meninges, and perivascular spaces, and are central players in maintaining homeostasis and mediating CNS inflammatory responses.

“Border-associated macrophages also reside in CSF outside of the brain parenchyma, primarily in the choroid plexus, meninges, and perivascular spaces, and are central players both in maintaining homeostasis and mediating CNS inflammatory responses [34, 35].”

• cites [34] Park, 2017, Brain perivascular macrophages initiate the neurovascular dysfunction of Alzheimer Aβ peptides, Circ Res sourcePartly supported

  The Introduction places perivascular macrophages in the perivascular space, and the Discussion describes their role in innate immunity and Aβ-induced neurovascular dysfunction (page numbers unavailable). The paper does not establish that border-associated macrophages reside in CSF or primarily occupy the choroid plexus and meninges, nor does it describe a general role for them in maintaining homeostasis. (LLM, conf=0.86)

  Experimental — accuracy not yet measured
• cites [35] Gerganova, 2022, CNS border-associated macrophages in the homeostatic and ischaemic brain, Pharmacol Ther sourceSupported

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

MHCII+ macrophages express genes involved in antigen presentation, and Lyve1+ scavenger macrophages perform essential functions including regulation of CSF flow dynamics.

“we stained for macrophages based on recent work that subdivided border-associated macrophages into MHCII+ macrophages, which express genes involved in antigen presentation, and Lyve1+ scavenger macrophages, which perform a variety of essential functions, including the regulation of CSF flow dynamics [36].”

• cites [36] Drieu, 2022, Parenchymal border macrophages regulate CSF flow dynamics, Nature sourceSupported

May combine two claims.

∼2000 cytoplasmic siRNAs are estimated to achieve maximal silencing, whereas ∼50 000 are required for an ASO.

“∼2000 cytoplasmic siRNAs are estimated to achieve maximal silencing, whereas ∼50 000 are required for an ASO [54, 55].”

• cites [54] Wittrup, 2015, Visualizing lipid-formulated siRNA release from endosomes and target gene knockdown, Nat Biotechnol sourceSupported
• cites [55] Buntz, 2019, Quantitative fluorescence imaging determines the absolute number of locked nucleic acid oligonucleotides needed for suppression of target gene expression, Nucleic Acids Res sourcePartly supported

  The Discussion (page unavailable) reports efficient downregulation with fewer than 2,000 siRNA molecules per cell, but does not describe that as maximal silencing or specify a cytoplasmic count. The Results (page unavailable) report that approximately 100,000 LNA-ASO molecules produced more than 50% knockdown, not that 50,000 ASOs were required for maximal silencing. (LLM, conf=0.90)

  Experimental — accuracy not yet measured

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

Several ASO therapies targeting genes in the spinal cord provide clinical benefit after intrathecal administration; Spinraza and Tofersen have extended survival for patients with spinal muscular atrophy and amyotrophic lateral sclerosis, respectively.

“Notably, several ASO therapies targeting genes in the spinal cord provide clinical benefit after intrathecal administration; Spinraza and Tofersen have extended survival for patients with spinal muscular atrophy and amyotrophic lateral sclerosis, respectively [43,51].”

• cites [43] Miller, 2022, Trial of antisense oligonucleotide Tofersen for SOD1 ALS, N Engl J Med sourcePartly supported

  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 [51] Finkel, 2017, Nusinersen versus sham control in infantile-onset spinal muscular atrophy, N Engl J Med sourceSupported

Probably not a substantial claim: may not pass S3 (load-bearing).

ASOs possess modularity-they can be designed to modulate splicing, degrade mRNA, or inhibit miRNAs.

“One advantage ASOs do possess over siRNA is their modularity—they can be designed to modulate splicing, degrade mRNA, or even inhibit miRNAs”

• cites [56] Schoch, 2017, Antisense oligonucleotides: translation from mouse models to human neurodegenerative diseases, Neuron sourceSupported

May combine two claims.

L2-siRNAPpib potentiates gene silencing in homeostatic microglia (~40%), activated microglia (~50%), and resident CNS macrophages (~70%) compared to nontargeting control.

“Compared to the nontargeting control, L2-siRNAPpib potentiated gene silencing in homeostatic (∼40%) and activated microglia (∼50%), as well as resident CNS macrophages (∼70%) (Fig. 4E and Supplementary Fig. S9D).”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

L2-siRNA levels in spinal cord are lower than in parenchyma, but L2-siRNAHtt gene silencing activity remains high in all spinal cord segments at both mRNA and protein levels, whereas unconjugated siRNA does not mediate knockdown of HTT protein.

“These levels are lower than the parenchyma; however, L2-siRNAHtt gene silencing activity remained high in all segments of the spinal cord at both the mRNA and protein levels, whereas unconjugated siRNA did not mediate knockdown of HTT protein (Fig. 3A and B).”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

At 3 months, mice receiving L2-siRNAHtt exhibit sustained gene and protein knockdown, with significant reduction in HTT protein in striatum, hippocampus, cortex, and cerebellum.

“In contrast, mice receiving L2-siRNAHtt exhibited sustained gene and protein knockdown; we note significant reduction in HTT protein at 3 months in the striatum, hippocampus, cortex, and cerebellum.”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

Knockdown is observed in all fibroblast-like populations in the leptomeninges, with dural border cells experiencing the least gene silencing.

“Impressively, knockdown was observed in all fibroblast-like populations, with dural border cells experiencing the least gene silencing, possibly because of their location on the opposing side of the arachnoid membrane.”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

At 3 months post-injection, HTT protein returns to baseline in mice receiving siRNAHtt, and only the hippocampus exhibits a reduction in Htt mRNA.

“At 3 months post-injection, HTT protein returned to baseline in mice receiving siRNAHtt, and only the hippocampus exhibited a reduction in Htt mRNA, likely because this region is near the injection site.”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

RT-qPCR confirms Ppib gene silencing in both Cd11bpos and Cd11bneg populations, with an average of 45% and 65% Ppib knockdown, respectively.

“To verify gene silencing with orthogonal methodology, cells not utilized for scRNA-seq were analyzed using RT-qPCR, which confirmed gene silencing in both Cd11bpos and Cd11bneg populations with an average of 45% and 65% Ppib knockdown, respectively (Fig. 4B).”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

At 1 month, at the protein level, siRNAHtt generates silencing in cortex and hippocampus, but less than L2-siRNAHtt, which also induces robust knockdown in striatum.

“Similarly, at the protein level, siRNAHtt generated silencing in the cortex and hippocampus, but less than L2-siRNAHtt, which also induced robust knockdown in the striatum (Fig. 2C and Supplementary Fig. S6).”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

Endothelial cells show low but significant Ppib knockdown in arterial endothelial cells and slightly higher silencing in venous/capillary cells.

“Endothelial cells were subclustered into venous/capillary and arterial populations (Fig. 4F); there was low but significant knockdown in arterial endothelial cells, and slightly higher silencing in the venous/capillary cells (Fig. 4G).”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

Chol-siRNA has high brain retention at both 2 and 48 h after ICV injection, but its distribution is characterized by steep concentration gradients away from the CSF-brain interface.

“In contrast, Chol-siRNA possessed high brain retention at both time points, but the distribution was characterized by steep concentration gradients away from the CSF–brain interface (Fig. 1C).”

May combine two claims.

Intrathecal delivery of L2-siRNA in rats produces effective transport and knockdown.

“Intrathecal delivery of L2-siRNA in rats further illustrates effective transport and knockdown using a clinically relevant route of administration.”

May combine two claims.

L2-siRNA accumulation decreases after 1 month but remains detectable at 3 and 5 months.

“While siRNA accumulation decreased after 1 month (as expected), siRNA-L2 was still detectable at 3 and 5 months (Fig. 2D).”

May combine two claims.

Neurons experience modest gene silencing, but neuron subtypes could not be subclustered due to low capture after dissociation.

“Neurons experienced modest gene silencing, but as expected, we could not subcluster into neuron subtypes due to the low capture of this population after dissociation.”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

Astrocytes and oligodendrocytes exhibit considerable Ppib knockdown, as do ependymal cells.

“For example, glial cells such as astrocytes and oligodendrocytes exhibited considerable Ppib knockdown, as well as ependymal cells, which line the ventricles and directly interface with CSF (Fig. 4G).”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

At 5 months, L2-siRNAHtt reduces protein levels in some regions (striatum, hippocampus), while other regions return to basal levels.

“The protein levels were also reduced by L2-siRNAHtt treatment in some regions (striatum, hippocampus), while others returned to basal levels.”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

At 1 month after injection, L2-siRNAHtt demonstrates potent Htt mRNA knockdown (>50%) in all brain regions tested, whereas unconjugated siRNAHtt only exhibits silencing in cortex and brainstem.

“At 1 month after injection, Htt-targeting L2-siRNA (referred to as L2-siRNAHtt) demonstrated potent mRNA knockdown (>50%) in all brain regions tested, whereas siRNAHtt only exhibited silencing in the cortex and brainstem, highlighting the benefit of L2 conjugation (Fig. 2B).”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

L2-siRNA shows greater cell internalization than unconjugated parent siRNA in neuroblastoma cells, while Chol-siRNA shows the highest uptake in serum-free media.

“There was more cell internalization of L2-siRNA than the parent siRNA, while Chol-siRNA, a benchmark chosen for its known cell penetration capacity [10], had the highest level of uptake in serum-free media (Supplementary Fig. S1A).”

• cites [10] Wolfrum, 2007, Mechanisms and optimization of in vivo delivery of lipophilic siRNAs, Nat Biotechnol sourceNot checked — no full text of the source

May combine two claims.

L2-siRNA uptake into neurons is the lowest among the examined cell types, but this may be due to challenges in recovering neurons after dissociation (<2% of total population).

“L2-siRNA uptake into neurons was the lowest out of the cells examined, but this may have been due to known challenges in recovering neurons after dissociation (<2% of total population).”

• AssumptionRests on an assumption: Neurons are difficult to recover after dissociation.

May combine two claims.

L2-siRNA is delivered at a high level to choroid plexus epithelial cells, corresponding to robust gene silencing.

“Lastly, we examined delivery to other cells in the choroid plexus and noted a high level of delivery to choroid plexus epithelial cells corresponding to robust gene silencing (Fig. 5H and I).”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

May combine two claims.

L2 conjugation increases total and cell-specific uptake of siRNA in CNS cells.

“We found that total and cell-specific uptake were increased by L2 conjugation (Supplementary Fig. S8), in agreement with our prior in vitro data (Supplementary Fig. S1A).”

May combine two claims.

Delivery and gene inhibition were effective throughout the spinal cord after intrathecal L2-siRNAHtt in rats.

“delivery and gene inhibition were effective throughout the spinal cord as well (Supplementary Fig. S18 and S19).”

May combine two claims.

L2-siRNA formulations did not cause seizures or acute neuronal activation response in mice or rats.

“Yet, we never observed this phenomenon in mice or rats with our formulations.”

May combine two claims.

Intrathecal delivery of L2-siRNA in rats achieves broad CNS distribution and Htt knockdown.

“Intrathecal delivery of L2-siRNA in rats achieves broad CNS distribution and Htt knockdown.”

May combine two claims.

L2-siRNA accumulation and huntingtin lowering were detectable 5 months after a single ICV injection in mice.

“Notably, L2-siRNA accumulation and huntingtin lowering were detectable 5 months after a single injection.”

May combine two claims.

After rat intrathecal injection, L2-siRNA transport and knockdown were widespread in all regions examined, but gene silencing activity was attenuated in distal structures (thalamus, striatum) compared to regions proximal to the injection site (spinal cord, brainstem, posterior cortex).

“while we observed widespread L2-siRNA transport and knockdown in all regions examined after rat intrathecal injection, we noted an attenuation in gene silencing activity in distal structures (thalamus, striatum) compared to regions proximal to the injection site (spinal cord, brainstem, posterior cortex).”

May combine two claims.

In mice, L2-siRNAHtt was more potent than ASOHtt at 1 month after ICV injection, with statistically significant enhancement of mRNA knockdown in all parenchymal and spinal cord regions except the hippocampus, where both compounds caused robust knockdown.

“We found that L2-siRNAHtt was more potent than ASOHtt in these experimental conditions, demonstrating statistically significant enhancement of mRNA knockdown in all parenchymal and spinal cord regions except the hippocampus, where both compounds caused robust knockdown (Fig. 7A).”

May combine two claims.

After intrathecal administration of Cy5-labeled L2-siRNA (30 nmol, ∼400 μg) in rats, L2-siRNA was transported along the caudal-rostral neuroaxis and penetrated the parenchyma from subarachnoid and perivascular CSF pathways after 48 h.

“After 48 h, we performed histology of the entire rat brain, which showed that L2-siRNA was transported along the caudal–rostral neuroaxis, where it penetrated the parenchyma from subarachnoid and perivascular CSF pathways (Fig. 6A).”

May combine two claims.

Ppib knockdown measured by scRNA-seq and RT-qPCR closely match for both CD11bpos and CD11bneg populations, supporting the accuracy of measuring cell-specific gene silencing with scRNA-seq.

“We compared Ppib knockdown measured by scRNA-seq and RT-qPCR and these outputs closely matched for both CD11bpos and Cd11bneg populations (Fig. 4C), providing confidence in the accuracy of measuring cell-specific gene silencing with scRNA-seq.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Single color compensation controls were run for each fluorophore.

“Single color compensation controls were run for each fluorophore.”

Probably not a substantial claim: may not pass S3 (load-bearing).

A new standard curve was prepared for each conjugate type and siRNA sequence.

“A new standard curve was prepared for each conjugate type and siRNA sequence.”

May combine two claims.

ACSA2 gating of astrocytes was validated by cell sorting and RT-qPCR showing enrichment of astrocytes and depletion of endothelial cells.

“To validate ACSA2 gating of astrocytes, cells were sorted on a four-laser BD FACSAria III and RT-qPCR was performed as described using TaqMan probes to show enrichment of astrocytes (Mm01253033_m1) and depletion of endothelial cells (Mm00727012_s1).”

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

Conventional RT-qPCR controls (no-template control and no reverse transcriptase control) were run on every plate and did not amplify.

“Conventional RT-qPCR controls (no-template control and no reverse transcriptase control) were run on every plate and did not amplify.”

May combine two claims.

L2-siRNA is a good candidate to potentially leverage albumin for perivascular transport while also having sufficient capacity for intracellular delivery within the CNS.

“These outcomes suggested that L2-siRNA is a good candidate to potentially leverage albumin for perivascular transport, while also having sufficient capacity for intracellular delivery within the CNS.”

May combine two claims.

Unconjugated siRNA is not efficiently internalized by brain cells, causing it to pass through and be eliminated quickly from the CNS.

“these results suggest that unconjugated siRNA is not efficiently internalized by brain cells, causing it to pass through and be eliminated quickly from the CNS.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The flow cytometry gating scheme to identify Cy5-positive cells leveraged fluorescence-minus-one (FMO) controls.

“The gating scheme to identify Cy5-positive cells leveraged fluorescence-minus-one (FMO) controls, which are samples stained with identical antibodies to the experimental groups but lack Cy5 signal (originating from an uninjected mouse).”

May combine two claims.

L2-siRNAPpib exhibits broad gene silencing activity that varies in magnitude across diverse CNS cell types.

“We found that L2-siRNAPpib exhibits broad gene silencing activity that varied in magnitude across diverse CNS cell types.”

• AssumptionRests on an assumption: Luciferase is not expressed in mice.

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

Each sample is normalized to Ppib as a housekeeping gene unless Ppib is the target of the siRNA, in which case Actb is the housekeeping gene.

“Each sample is normalized to Ppib as a housekeeping gene unless Ppib is the target of the siRNA, in which case Actb is the housekeeping gene.”

Classified as probably not a substantial claim.

Successful placement of the rat intrathecal catheter was confirmed by visualization of CSF backflow.

“Successful placement of the catheter was confirmed by visualization of CSF backflow.”

May combine two claims.

L2-siRNA delivered into the CSF is trafficked through perivascular spaces, providing a conduit for transport into deeper parenchymal structures.

“These results collectively indicate that L2-siRNA delivered into the CSF is trafficked through perivascular spaces, providing a conduit for transport into deeper parenchymal structures.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Bicinchoninic acid (BCA) assay was used to quantify protein and normalize loading of each sample.

“Bicinchoninic acid (BCA) assay (Thermo, 23225) was used to quantify protein and normalize loading of each sample.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Recent characterization of fibroblast-like cells in the meninges identified five transcriptionally and spatially unique cell populations.

“Recent characterization of fibroblast-like cells in the meninges identified five transcriptionally and spatially unique cell populations [33].”

• cites [33] Pietilä, 2023, Molecular anatomy of adult mouse leptomeninges, Neuron sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Chol-siRNA is a benchmark chosen for its known cell penetration capacity.

“while Chol-siRNA, a benchmark chosen for its known cell penetration capacity [10], had the highest level of uptake in serum-free media”

• cites [10] Wolfrum, 2007, Mechanisms and optimization of in vivo delivery of lipophilic siRNAs, Nat Biotechnol sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Oligodendrocytes were removed from analysis based on O1+ staining because myelin can promote nonspecific antibody binding.

“Oligodendrocytes were removed from analysis based on O1+ staining, as myelin can promote nonspecific antibody binding [26].”

• cites [26] Ullman, 2020, Brain delivery and activity of a lysosomal enzyme using a blood–brain barrier transport vehicle in mice, Sci Transl Med sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing).

Potent siRNA sequences had been designed and validated against Ppib elsewhere.

“Potent siRNA sequences had also been designed and validated against Ppib elsewhere [28].”

• cites [28] Reynolds, 2004, Rational siRNA design for RNA interference, Nat Biotechnol sourceNot checked — no full text of the source

May combine two claims.

L2-siRNA is effective in most CNS cell types, particularly those near CSF flow.

“Overall, this cell-specific investigation showed us that L2-siRNA is effective in most CNS cell types, particularly those near CSF flow.”

• AssumptionRests on an assumption: Ependymal cells line the ventricles and experience the highest concentration of siRNA after an ICV injection.

May combine two claims.

The greater striatal effectiveness of L2-siRNAHtt compared to ASOHtt is highly relevant for Huntington's disease because the striatum is the region predominantly affected by HD.

“which is highly relevant considering the striatum is the region predominantly affected by HD.”

• AssumptionRests on an assumption: The striatum is the region predominantly affected by Huntington's disease.

May combine two claims.

Single-stranded ASOs form a less rigid and more globular structure and may exhibit nonspecific protein association, thereby limiting deep brain penetration.

“In contrast, single-stranded ASOs form a less rigid and more globular structure and may exhibit nonspecific protein association, thereby limiting deep brain penetration.”

May combine two claims.

L2-siRNA possesses unique properties that enhance its transport and brain-wide distribution relative to other conjugates, yielding a promising platform technology for silencing genes implicated in CNS disorders.

“Collectively, these data suggest that L2-siRNA possesses unique properties that enhance its transport and brain-wide distribution relative to other conjugates, thus yielding a promising platform technology for silencing genes implicated in CNS disorders.”

• AssumptionRests on an assumption: The central translational challenge for nucleic acid therapies is achieving gene silencing throughout the brain.

May combine two claims.

siRNAs form a linear duplex and diffuse effectively through the narrow extracellular spaces of the brain.

“as siRNAs form a linear duplex and diffuse effectively through the narrow extracellular spaces of the brain [53].”

• cites [53] Pizzo, 2017, Chapter 6: The extracellular and perivascular spaces of the brain sourceNot checked — no full text of the source