Recreating the heart's helical structure-function relationship with focused rotary jet spinning

In the paper

“they are often characterized by concomitant changes in protein expression and metabolism (11) and are limited by their ability to control cardiac alignments (12, 13). This makes it difficult to distinguish between biomolecular and biomechanical contributions to cardiac dysfunction.”

What the sources say

• ?Not checked — no full text of the sourcecites [11] source
• ?Could not verify

  The Discussion (page unavailable) says that in-vivo imaging of the right ventricle lacks sufficient resolution and that ex-vivo imaging cannot reproduce in-vivo loading conditions. Neither that passage nor the other passages found addresses an inability to control cardiac alignments or a resulting difficulty separating biomolecular from biomechanical contributions. (LLM, conf=0.72)

  cites [12] sourceExperimental — accuracy not yet measured
• ?Could not verify

  The Background discusses cardiac structural orientations and mechanical gradients, while the Discussion identifies image resolution and scan time as challenges for applying the method in vivo. Neither section says that in vivo studies cannot control cardiac alignments or that this prevents distinguishing biomolecular from biomechanical contributions to dysfunction. Searched for alignment control and molecular-versus-mechanical contributions. (LLM, conf=0.72)

  cites [13] sourceExperimental — accuracy not yet measured

In the paper

“The heart’s musculature is organized in a helical fashion, with cardiomyocytes in the left ventricle smoothly transitioning transmurally froma left- to right-handed helix (1).”

What the sources say

• Supported

  The Figure 2 caption in Final Comments (page not provided) states that left ventricular myofiber orientation changes smoothly from a left-handed helix in the subepicardium to a right-handed helix in the subendocardium. This supports the claimed transmural helical transition. (LLM, conf=0.95)

  cites [1] source

In the paper

“Over the past half-century, it has been argued that this helical arrangement represents a fundamental structural design critical to achieving large ejection fractions (EFs) (1, 3–6).”

What the sources say

• Partly supported

  The section on myofiber geometry explains how the left ventricle’s helical fibers generate twist that assists contraction and wall thickening. The section on LV dysfunction also links impaired twist mechanics with declining ejection fraction. These passages support a connection between helical architecture and ejection, but do not establish that it is critical to achieving large ejection fractions. (LLM, conf=0.78)

  cites [1] sourceExperimental — accuracy not yet measured
• Supported

  The Introduction argues that circular fibers cannot account for normal human ejection fractions with physiological shortening, while a helical-fiber model can. The Discussion likewise finds helical arrangements consistent with normal ejection fractions and circular arrangements inadequate above 0.5. This supports the citing sentence’s characterization of the paper’s argument as a modeling claim, rather than a direct demonstration that helical structure is uniquely necessary. (LLM, conf=0.90)

  cites [3] sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [4] source
• ?Not checked — no full text of the sourcecites [5] source
• Partly supported

  The Comparison with the heart section recognizes helical alignment of cardiac cell aggregates and its role in generating torsional forces. The Structure section links a complex three-dimensional myocardial mesh to the deformation underlying an approximately 60% ejection fraction, but does not identify helical alignment alone as critical to that fraction. The “Feathering” section also rejects the simpler helical-band model. (LLM, conf=0.85)

  cites [6] sourceExperimental — accuracy not yet measured

In the paper

“Because fiber-spinning techniques can reproduce these fine spatial features with higher throughputs, they offer a potential solution and have been used previously to engineer tissue scaffolds, such as heart valves (23) and ventricle models (24).”

What the sources say

• Supported

  The Discussion reports that JetValve produced heart-valve scaffolds in under fifteen minutes, with fiber resolution from hundreds of nanometers to microns. Citation (23) is attached to heart valves; the separate ventricle-model example is attributed to citation (24), not this paper. (LLM, conf=0.93)

  cites [23] source
• Supported

  The Ventricle scaffold section describes producing nanofiber ventricle chambers by pull-spinning fibers onto a rotating collector. The Methods section confirms that the ventricle scaffolds were fabricated by pull-spinning, supporting this paper as the cited example of a fiber-spun ventricle model. (LLM, conf=0.92)

  cites [24] source

In the paper

“Rotary jet spinning produces fibers by centrifugal force, pushing polymer solutions through a small orifice in the spinneret. Subsequent jet elongation results in free-floating single-micrometer fibers (29).”

What the sources say

• Partly supported

  The paper’s process description (section labeled Abstract; page unavailable) says centrifugal and hydrostatic pressure propel polymer solution through an orifice, and jet stretching reduces its diameter. It reports fiber diameters of 50–3500 nm, which include roughly one micrometer, but does not describe the resulting fibers as free-floating; it says they were collected on a surrounding collector or coverslips. (LLM, conf=0.86)

  cites [29] sourceExperimental — accuracy not yet measured

In the paper

“It has been predicted that EFs should scale as 1 – k2 for CA ventricles (eq. S5) and 1 - k2 q H(α) for HA ventricles (eq. S15) (Fig. 2D) (3), with k being the strain along the fiber axis, q being the apical shortening, and H(α) being the radial shortening based on the fiber’s helical angle (eqs. S5 to S15).”

What the sources say

• Partly supported

  The Abstract’s Fig. 2 text gives EF = 1 − k² for a cylindrical ventricle with circular fibers. The Cylinder section models helical fibers using k as the final-to-initial fiber-length ratio and q as the final-to-initial cylinder-height ratio, but gives a different EF expression involving geometry and a helix parameter; it does not give the claimed H(α) expression. Page numbers are unavailable in our copy. (LLM, conf=0.84)

  cites [3] sourceExperimental — accuracy not yet measured

In the paper

“Sallin’s model predicted an EF increase of 54 to 64% for HA ventricles, which was consistent with our experimental observations (within the standard error of the mean; Fig. 3E).”

What the sources say

• Partly supported

  The Discussion (page unavailable) calculates an ejection fraction of 0.612 for one helical-fiber model configuration and says that prediction is consistent with observations reported by Ross et al. It does not report a 54–64% increase in EF for HA ventricles. The citing authors’ comparison with their own observations, including the standard-error qualification, is not established by this source. (LLM, conf=0.85)

  cites [3] sourceExperimental — accuracy not yet measured

In the paper

“It has been hypothesized that HA ventricles would display increased apical shortening (3, 36) and reduced basal displacement (9, 36), owing to differences in myofiber lengths.”

What the sources say

• Partly supported

  The Cylinder section (page unavailable) models helical fibers and permits apex-to-base shortening during systole. It does not predict increased apical shortening or reduced basal displacement, or explain such a difference by differing myofiber lengths. (LLM, conf=0.82)

  cites [3] sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [36] source
• ?Could not verify

  Section 3.1 describes helical fiber orientation and opposite rotations of the apex and base, but does not propose increased apical shortening or reduced basal displacement. Searches for those outcomes and for apex-to-base differences in myofiber length found no passage supporting the attributed hypothesis; section 2.1 instead discusses shortening across the ventricular wall. Page numbers were not available in our copy. (LLM, conf=0.76)

  cites [9] sourceExperimental — accuracy not yet measured

In the paper

“In healthy tissues, action potentials propagate faster in the direction of cell alignment, with myocytes showing slower conduction velocities (CVs) in the transverse direction (33).”

What the sources say

• Supported

  Section 2.1 explicitly describes fast longitudinal propagation and slow transverse propagation. Section 2.2 explains that an impulse traveling along a myocyte’s long axis crosses fewer junctions per unit distance and therefore experiences less delay than an impulse traveling transversely. (LLM, conf=0.93)

  cites [33] source

In the paper

“Although the metrics presented here (e.g., EF) were greater (by a factor of ~3) than for recently reported in vitro ventricle models (24, 39), they were still substantially lower than in vivo values (tables S2 and S3).”

What the sources say

• Supported

  The Intra-ventricular pressure and volume measurements section reports ejection fractions of ~1% and ~0.2% for this paper’s in vitro ventricle models, establishing the prior-model values used in the citing authors’ comparison. The Discussion also says those values are roughly 50–250 times smaller than expected for healthy mammalian ventricles. The ~3-fold comparison concerns the citing authors’ own metrics; this source supplies the prior-model baseline, not that calculation. (LLM, conf=0.87)

  cites [24] source
• Supported

  The Results section (Figure 7g) reports an average ejection fraction of 0.7% and a maximum of 6.5% for the paper’s in vitro chambered cardiac model. This supports citing it as a recently reported model and an EF benchmark. The approximately threefold comparison concerns the citing paper’s own metrics, while its comparison with in vivo values points to its own tables; neither is a finding attributed to this source. (LLM, conf=0.86)

  cites [39] source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites (tables S2 and S3)

In the paper

“This throughput is comparable to those of melt-blowing processes (27) but is orders of magnitude greater (~106) than that of 3D extrusion printing, the speed of which declines rapidly at single-micrometer features (as a power law, with a scaling factor of ~2.8) (Fig. 4, D and E, and eq. S1).”

What the sources say

• Supported

  The citation is attached to the melt-blowing throughput comparison, not the later claims about 3D printing. Section 2, “Melt Blowing Process and Related Polymeric Materials,” reports melt-blowing production and throughput rates, providing the cited basis for that comparison. (LLM, conf=0.86)

  cites [27] source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites (Fig. 4, D and E, and eq. S1)

In the paper

“We developed focused rotary jet spinning (FRJS), an additive manufacturing method that uses centrifugal jet spinning to rapidly form polymeric micro/nanofibers, which are then focused and spatially patterned by means of a controlled airstream.”

In the paper

“Next, in a phenomenon known as entrainment (31), fibers are pulled into a jet stream blown from the center of the spinneret. Because air speeds are orders of magnitude slower outside of the jet (fig. S2), this entrainment process minimally perturbs fiber formation (fig. S3).”

What the sources say

• ?Not checked — no full text of the sourcecites [31] source

In the paper

“This yielded average EFs of 1.6 ± 1.1% and 3.3 ± 1.7% in the CA and HA case, respectively (n = 8 samples each), with a maximum EF of 5.9% observed in the helical case (Fig. 3E).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites (Fig. 3E)

In the paper

“we manufactured both a dual-chambered ventricle (DCV) with multiple helical angles and a full-scale human heart model (Fig. 4).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites (Fig. 4)

In the paper

“Isochrones of the calcium propagation revealed that CA scaffolds displayed only modest CVs (8.3 cm/s) along the ventricle’s long axis, whereas HA ventricles showed increased CVs (19.1 cm/s) with respect to CA ventricles (Fig. 2C and movie S7).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites (Fig. 2C and movie S7)

In the paper

“As predicted, CA ventricles displayed greater deformations near the base of the ventricle, whereas HA scaffolds showed more-uniform deformations (Fig. 2E).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites (Fig. 2E)

In the paper

“hiPSC-CMs were differentiated in vitro for 15 days total before seeding, forming visible spontaneous contractions after 7 days and staining positive for sarcomeric α-actinin (fig. S9).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites (fig. S9)

In the paper

“In each case, targets were coated in ~5 min, forming standalone structures that could be removed and manipulated.”

In the paper

“fibers were collected on an inclined rotating cylinder to generate helical alignments (Fig. 1F and movie S3) and on an incrementally rotating disk to generate multilayered fiber sheets (fig. S6C and movie S4).”

In the paper

“We observed higher CVs in the direction of fiber alignment [longitudinal CVs (LCVs)] with respect to transverse CVs (TCVs), with LCVs and TCVs of 14.9 ± 5.8 cm/s and 9.0 ± 3.7 cm/s, respectively (n = 9 samples) at ratios of ~1.5 to 2.0.”

In the paper

“Together, these findings demonstrated that our tissues maintained their alignment and confluence over the length of the ventricle (~1 cm)”

In the paper

“The resulting fibers displayed angle-dependent anisotropy, with tangential, intermediate, and perpendicular collection leading to highly anisotropic (θ = 0°, OOP = 0.60 ± 0.15), intermediate (θ = 60°, OOP = 0.50 ± 0.08), and randomly aligned (θ = 90°, OOP = 0.18 ± 0.03) fiber distributions, respectively.”

In the paper

“Summation of the fluid displacement over systole yields the total CO, with values of 11.7 ± 8.9 μl/s and 24.3 ± 13.5 μl/s (n = 8 samples each) for CA and HA ventricle scaffolds, respectively (fig. S15G).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites (fig. S15G)

In the paper

“Conversely, HA scaffolds displayed approximately four times as much twist (5.4 ± 3.6°, n = 7 ventricles) (movie S9), modeling physiological ventricular twist in an in vitro system.”

In the paper

“This observation represented a significant (P < 0.05) CO increase based purely on ventricular tissue alignment.”

In the paper

“CA samples showed greater basal and minimal longitudinal constriction, whereas HA ventricles displayed significant apical shortening with reduced basal deformation (n≥ 5 ventricles for each condition) (fig. S12).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites (fig. S12)

In the paper

“In each case, targets were coated in <35 min with micro/nanofibers, generating conformal coatings on the exterior.”

In the paper

“Throughout this process, fibers were produced with a total throughput rate of 0.1 g/min, or 0.03 ghm (grams per hole per minute).”

In the paper

“Examining excised segments of the left ventricle, cultured with hiPSC-CMs, we observed that cells adhered to the fibers, forming aligned tissues (fig. S18B).”

What the sources say

• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites (fig. S18B)

In the paper

“To study the role of helical muscular alignment on cardiac function, it is necessary to recreate the multiscale architectures of the heart, with both controlled alignments and three-dimensional (3D) geometries.”

In the paper

“Printing the ECM components at current resolutions (~250 μm feature sizes) takes hours to days (22), but at native feature sizes (1 μm) could take hundreds of years if current scaling trends are followed (eq. S1).”

What the sources say

• ?Not checked — no full text of the sourcecites [22] source
• ?Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  cites (eq. S1)

In the paper

“However, unlike 3D printing, fiber-spinning approaches often fail to recreate complex 3D geometries while maintaining controlled alignments.”

In the paper

“This EF is comparable to values experienced during borderline heart failure and underscores the importance of multiple helical alignments in maintaining healthy cardiac function.”

In the paper

“Because cardiomyocytes contract along their long axis during systole, while connecting transversely as a bulk material (37), they generate forces primarily along the length of the fibers.”

What the sources say

• ?Not checked — no full text of the sourcecites [37] source

In the paper

“This suggested that FRJS could be effectively employed in hierarchical biofabrication, in which the focused air stream provides gross structural morphology (centimeter scale), whereas fibers provide fine structural (single-micrometer scale) cues to promote tissue morphogenesis.”

In the paper

“This indicated that our model system was capable of preserving these fundamental scaling laws, signifying that helical alignments of the ventricular myocardium result in increased EFs.”

In the paper

“HA fiber orientations were selected on the basis of energy minimization constraints, with angles between 20° and 45° predicted to be the most energy efficient for pumping fluids (4).”

What the sources say

• ?Not checked — no full text of the sourcecites [4] source

In the paper

“Additionally, this suggested the possibility for variable EFs on the basis of fiber alignment, as these differences in deformation could result in distinct volumetric displacements.”

In the paper

“For HA ventricles, however, fiber length should vary minimally, as fibers extend uniformly from the apex to the base of the ventricle. Overall, this should result in more homogenous deformations for HA ventricles, with increased apical shortening.”

In the paper

“For CA ventricles, which are made up of concentric rings, fiber length is greatest at the base, where the radius is largest, and smallest at the apex (Fig. 2D). This should result in nonuniform deformations, with greater displacements in the basal region and negligible displacements at the apex.”

In the paper

“However, the work presented here provides an initial pathway toward achieving hierarchical patterning while maintaining 3D cell alignment.”

In the paper

“In addition to biofabrication, FRJS may serve an important role in other additive manufacturing applications, as it provides production rates comparable to those of current industrial processes while enabling micro/nanoscale feature sizes and controlled 3D alignments.”

In the paper

“With our fiber-based approach, these local structures can be preserved across entire tissue volumes, allowing for the hierarchical assembly of tissues.”

In the paper

“The high surface area–to–volume ratio of micro- and nanofibers makes them ideal candidates for the controlled absorbance and release of chemical species.”

In the paper

“Collectively, these observations demonstrated that FRJS is amenable to rapidly manufacturing fiber scaffolds spanning multiple length scales and can be adapted to different geometries.”

In the paper

“This suggests that FRJS may be an important technique for industrial manufacturing process that use hierarchical design principles, for which control over several orders of spatial magnitude is needed.”

In the paper

“Biofabrication using FRJS allowed for the rapid assembly of functional 3D ventricle models capable of recapitulating emergent phenomena in vitro, including ventricular twist, strain displacement, and myocardial angle-dependent EFs.”

In the paper

“These proof-of-concept 3D organ models demonstrate that FRJS scaffolds support human-derived tissues and allow for rapid assembly of full-size models of the musculature.”

In the paper

“Although full-size anatomical models have previously been produced with thermoplastics and hydrogels (22), these systems typically lack the micrometer-scale features needed to direct myocyte alignment.”

What the sources say

• ?Not checked — no full text of the sourcecites [22] source