Acta Biomaterialia

The ability to generate vascularized tissue constructs supplied by surgically accessible vessels remains a major limitation in reconstructive tissue engineering. Previous work demonstrated that positioning porous biomaterials around a vein can induce extensive vascular sprouting and generate a vascularized tissue volume without creation of an arteriovenous loop. However, this phenomenon has principally been demonstrated using rigid calcium-phosphate scaffolds, limiting its direct relevance to soft-tissue reconstruction. Here, we investigated whether a flexible decellularized dermal matrix could similarly be vascularized around a single unmodified vein and whether autologous dermal fibroblasts could further enhance this response. Decellularized rat dermis, with or without autologous dermal fibroblast seeding, was implanted either subcutaneously in the dorsal region or around the femoral vein for 8 weeks. Following Microfil perfusion, three-dimensional micro-CT demonstrated an extensive branching vascular network within perivenous constructs. Vessel volume relative to tissue volume was 0.2 +/- 0.1% in subcutaneous constructs without fibroblasts (n = 11) and 0.6 +/- 0.2% with fibroblasts (n = 9), compared with 6.+/- 1.4 % in perivenous constructs without fibroblasts (n = 10) and 7.3+/- 1.2% with fibroblasts (n = 10). Histology and immunohistochemistry similarly showed greater cellular repopulation and substantially higher CD31- and -SMA-positive vessel densities following perivenous implantation. Integrated two-way ANOVA of the same 8-week data confirmed a dominant effect of implantation site across the vascular outcomes, while fibroblast seeding significantly affected vascular volume, dermal remodeling, and nuclear density. The effect of fibroblast seeding on vascular volume was site dependent, with a significant implantation site fibroblast interaction. At 8 weeks, the vascularized dermal construct was completely dissected free from the surrounding tissues while maintaining its connection to the femoral vein. A small superficial incision into the isolated dermis produced visible bleeding, supporting an acute functional connection of the intradermal vascular network to the host circulation while the femoral venous connection was preserved. After flap elevation, perivenous constructs retained substantially greater vascular volume and showed more complete surface healing and organized skin architecture than subcutaneous constructs. Fibroblast seeding accelerated wound closure, while its effect on post-elevation vascular volume depended on implantation site: VV/TV decreased in subcutaneous constructs but increased in perivenous constructs. These findings show that single-vein vascularization can extend from rigid calcium-phosphate biomaterials to a compliant biological extracellular-matrix scaffold and may provide a simplified axial vascularization strategy without arterialization or incorporation of an arterial vessel.

A major challenge in vascular tissue engineering is the development of scalable fabrication methods capable of producing vascular grafts with suitable mechanical properties and hemocompatibility for both preclinical evaluation and future clinical translation. Using a recently developed method to generate acellular vascular grafts from densified collagen hydrogel, we present a proof-of-concept in vivo evaluation of the scalable collagen graft technology. Thick-walled, genipin-crosslinked grafts, representative of a fabrication approach applicable to clinically relevant vessel sizes, were implanted as interposition grafts in the rat abdominal aorta. These grafts supported rapid neointima formation and re-endothelialisation of the luminal surface but developed late thrombosis, highlighting the challenges of evaluating clinically scalable grafts in small-animal models. To enable assessment of the platform in millimetre-scale vessels, we developed a thin-walled (~100 {micro}m), non-crosslinked graft using a constrained densification approach and hyaluronic acid-mediated modulation of collagen fibril assembly to improve compliance matching and hemocompatibility, with the latter providing a matrix-level approach that may complement surface-bound antithrombotic coatings. These grafts remained patent for up to 17 weeks and exhibited neointima formation, re-endothelialisation, and early cellular infiltration into the graft wall. Together, these findings demonstrate in vivo functionality of densified collagen vascular grafts and establish a foundation for future evaluation in larger animal models.

Current treatment of orthopedic ligament injury relies principally on non-regenerative materials and surgical repair rather than strategies that promote intrinsic tissue regeneration. This study evaluated whether biologic augmentation with XWRAP, a human amniotic membrane allograft, combined with a cryopreserved amniotic-fluid-derived biologic containing micronized human amnion membrane, promotes regeneration of ligament architecture in a rabbit medial collateral ligament (MCL) gap-defect model. Standardized 4-mm mid-substance MCL gap defects were created in New Zealand White rabbits (n=3) and either treated with the amniotic membrane/amniotic-fluid biologic combination or left untreated, with intact contralateral or adjacent MCL serving as native controls; ligaments were evaluated by transmission electron microscopy at 2 and 6 weeks post-procedure, with collagen fibril diameter quantified from calibrated high-magnification micrographs. Treated defects developed significantly larger mean collagen fibril diameters than untreated defects at both time points (75 vs. 50 nm at 2 weeks and 88 vs. 62 nm at 6 weeks; p<0.0001 for each comparison), reaching approximately 90% of native, uninjured ligament fibril diameter (98 nm) by 6 weeks. Treated defects also developed a broader, bimodal fibril-diameter distribution resembling native ligament architecture, whereas untreated defects remained characterized by a narrow, unimodal population of small-diameter fibrils typical of scar-associated repair. These findings indicate that biologic augmentation with XWRAP combined with an amniotic-fluid-derived biologic promotes a regenerative, rather than purely reparative, healing response following ligament injury, progressively restoring collagen fibril architecture toward that of native tissue in this preclinical model.

Despite lacking a dedicated structural function, brain tissue is exposed to severe mechanical loading during accidents and trauma, with potentially permanent or lethal consequences. Therefore, characterizing its mechanical behavior assumes particular importance for designing protective equipment, planning surgeries, and training neurosurgeons, tasks that often rely on physical brain replicas made from phantom materials. Although the mechanics of brain tissue has been extensively studied, the selection of suitable phantom materials still relies on simplified metrics that fail to capture the highly nonlinear and rate-dependent behavior of the brain. In this work, we characterize the mechanical response at low-to-medium strain rates of common synthetic brain phantom materials, including Sylgard 527, Ecoflex Gel, and a composite hydrogel, and establish rigorous comparisons with porcine brain tissue as a benchmark. To this end, we employ a multi-step stress relaxation protocol under both uniaxial extension and compression across two different strain rates, introduce thermodynamic metrics, and perform comparisons based on rigorous statistical analysis. In particular, we isolate the thermodynamic equilibrium stress-strain curves, representing the baseline material's response, from rate-dependent dissipative inelastic effects, relatable to viscoelastic and poroelastic mechanisms. Our results provide a thorough comparison, revealing critical limitations in existing simulant materials and highlighting significant space for developing improved brain surrogates. The comprehensive dataset collected can also support the calibration of constitutive models, enhancing the predictive accuracy of numerical simulations involving brain tissue and its surrogates. More broadly, this study highlights the need to move beyond simplistic, scalar-metric-based comparisons of mechanical responses across materials.

Introduction: The femoropopliteal artery undergoes substantial axial compression, bending, torsion, and pinching during limb flexion. When an implanted stent does not accommodate these deformations, repetitive biomechanical mismatch may alter the vascular response to implantation and contribute to restenosis. We tested whether designing a peripheral stent to better accommodate physiologic limb-flexion deformation reduces the subsequent inflammatory and neointimal response. Methods: A nitinol stent was developed using multi-objective computational optimization to maintain arterial apposition while reducing wall stress and luminal pinching during physiologic deformation. Sixteen Yucatan minipigs were studied in independent 3- and 6-month cohorts (n=8 each). Each animal received the optimized stent in one limb and a commercial stent with representative biomechanical behavior contralaterally. CTA quantified in vivo limb-flexion deformation, while CT and histology assessed stenosis, neointimal accumulation, inflammatory-cell burden, SMA-positive tissue, and extracellular-matrix composition. Results: The optimized stent accommodated greater axial shortening than the commercial comparator at both 3 months (11.2{+/-}2.7% vs. 6.6{+/-}2.1%, p=0.003) and 6 months (13.7{+/-}4.4% vs. 6.8{+/-}2.3%, p=0.004). Intimal hyperplasia volume was lower with the optimized stent at 3 months (227.5{+/-}85.2 vs. 350.0{+/-}130.5 mm3, p=0.002) and 6 months (183.6{+/-}46.2 vs. 261.2{+/-}60.6 mm3, p=0.001), with significantly lower maximum, mean, and median stenosis at both timepoints. At 3 months, macrophage and total inflammatory-cell counts were 51% and 45% lower, respectively, with the optimized stent. Histologic tissue area was 28% lower at 3 months and 12% lower at 6 months. SMA-positive tissue fraction was higher with the optimized stent at both timepoints, whereas elastin, glycosaminoglycan, and collagen fractions were similar between devices. Discussion: Improved accommodation of limb-flexion deformation was associated with a smaller inflammatory and neointimal response to stent implantation through 6 months, while overall neointimal matrix composition remained largely unchanged. These findings provide in vivo evidence that biomechanical compatibility with the dynamic lower-limb environment can influence vascular healing and should be considered a mechanistic design criterion for peripheral artery stents.

Oncofetal fibronectin (oFN) is a known biomarker of cancer progression and is involved in events such as epithelial mesenchymal transition and multidrug resistance. It is also understood that fibronectin (FN) and its splice variants are differentially arranged by cancer associated fibroblasts (CAFs) to support cancer cell proliferation and migration. Contrastingly, little is understood about the mechanobiology of oFN, a post-translationally modified FN isoform defined by O-glycosylation of a specific threonine residue. To investigate the architectural features of the oFN matrix, CAFs were simulated by culturing human mammary fibroblasts (HMFs) on stiff polyacrylamide gels (20 kPa) in media collected from HCC-1937 (primary site breast adenocarcinoma) and MDA-MB-231 (metastatic breast adenocarcinoma) cells. As a control, HMFs were also cultured on softer gels representing healthy adipose tissue (2 kPa) in media not exposed to cancer cells. After immunocytochemical analysis, tumor conditioned HMFs displayed an expected CAF-like phenotype that was most prominent with MDA-MB-231 conditioned media. Matrices produced by tumor-conditioned HMFs contained more oFN with structural features mostly following that of the overall dense, aligned FN matrix. Cancer cells reseeded on their corresponding decellularized tumor-associated matrices had greater F-actin/oFN colocalization than control matrix. The lack of distinct oFN topographical cues may indicate that oFN O-glycosylation is more directly involved in biochemical signaling than mechanosignaling through matrix architecture. Together, this study established a platform for investigating stromal oFN which revealed that tumor-conditioned media sourced from cancer cells with different metastatic potential influences HMF activation, leading to distinct total FN and thus oFN matrix microarchitecture features.

Bone formation and remodeling depend on dynamic biochemical and biomechanical signaling from the collagen-rich osteoid that precedes mineralization, yet the role of osteoid nonlinear mechanics in regulating osteocyte-like network formation remains poorly understood. Here, we engineered a synthetic bottlebrush polymer hydrogel (BB) that mimics key mechanical features of osteoid and compared it to collagen type-I (Col1) matrices with matched shear modulus (~70 Pa) and strain-stiffening behavior. Human bone marrow-derived mesenchymal stem/stromal cells (hMSCs) were cultured for 28 days in growth (GM) or osteogenic media (OM) to examine network formation, and functional connectivity using live cell fluorescence recovery after photobleaching. hMSCs cultured in BB networks and OM showed upregulation of early osteocyte markers compared to Col1. We find that strain-stiffening materials with minimal stress relaxation promote osteocyte-like cell differentiation with functional connectivity, establishing osteoid-mimetic BB hydrogels as a promising matrix to study human osteocytogenesis and osteocyte mechanotransduction in vitro.

Large shear deformation in cartilage can lead to tissue failure and injury, which are often precursors to diseases such as post-traumatic osteoarthritis. Under shear, cartilage strain-stiffens prior to failure, which makes stiffening an important indicator of changes to the loading of the extracellular matrix that gives rise to this tissue's properties. While a variety of stiffening mechanisms ranging from uncrimping to fiber-alignment have been explored, whether such mechanisms apply to the depth dependent shear strain stiffening in articular cartilage remains poorly understood. Here, we present experiments and theory that support the idea that the strain-stiffening behavior is caused by a mechanical phase transition from a random isotropic network whose mechanics arise primarily from bending-dominated modes to one where the mechanics arise from stretching-dominated modes. Indeed, consistent with network model predictions, we find that stress-strain data for all depths can be collapsed onto a single universal curve that diverges at a depth-dependent critical strain. These results show that increasing the local concentration of collagen, which constitutes the primary load-bearing network in cartilage, decreases the critical strain at which the strain-stiffening transition occurs, while increasing the low-strain elastic modulus. Furthermore, we demonstrate that bulk compression leads to a higher critical strain and decreased low-strain elastic modulus. Network simulations capture this rich behavior, and indicate that under compression the network collapses, which allows for larger strains before the transition from bending-dominated to stretching-dominated mechanics occurs. Collectively, these findings shed light on the roles that tissue composition and axial strain play in the mechanisms that organize how articular cartilage stiffens during the lead-up to injury.

In the murine osteochondral unit, morphology of chondrocyte lacunae (CCL) within calcified articular cartilage and osteocyte lacunae (OCL) within the underlying subchondral bone reflects local biomechanical conditions that are altered in disease, making reliable discrimination of both lacunar populations important for studying osteochondral physiology and pathology. Histology is generally considered the gold standard for identifying CCL and OCL. However, it is inherently limited to two-dimensional assessment and a relatively small tissue section, restricting comprehensive characterisation of three-dimensional lacunar structure. Synchrotron-radiation micro-computed tomography (SR-microCT) enables volumetric quantification of lacunae; where classification is typically based on the position of each lacuna relative to the cement line separating calcified cartilage from bone, requiring manual delineation of this convoluted interface. Such approaches are labour-intensive, operator-dependent, and rely on access to specialised synchrotron infrastructure that is not widely available. To address these limitations, we present a fully automated, annotation-free pipeline for classifying OCL and CCL in the mouse osteochondral unit based on desktop micro-computed tomography (microCT), independent of cement line identification. The proposed unsupervised workflow requires neither tissue separation nor labelled training data, enabling objective and scalable discrimination of lacunar populations directly from volumetric image data. Seven morphometric and positional features per lacuna were extracted from SR-microCT and desktop microCT datasets and analysed using Uniform Manifold Approximation and Projection (UMAP). Validation of the pipeline outcome on SR-microCT against manual classification across specimens yielded very-high agreement, with Gwet's AC1, the Matthews correlation coefficient, and balanced accuracy each approaching 0.99, in both healthy and post-traumatic osteoarthritis specimens. Such a workflow can be readily adapted for the investigation of osteochondral interface in various other species.

The growing demand for three-dimensional (3D) in vitro models that accurately replicate human tissue to investigate disease mechanisms, enable tissue replacement, and support drug testing is driving the need for more advanced manufacturing platforms. Mesenchymal stem/stromal cells (MSCs) are promising candidates for tissue engineering and stem cell therapies due to their regenerative potential and ethical advantages. However, the reproducible and scalable production of 3D models that truly mimic the human complexity and function poses a major challenge. To address these challenges, we have developed a scalable and semi-automated 3D differentiation process for generating osteogenic microtissue derived from MSCs encapsulated in core-shell capsules (CSCs). To validate material-dependent, osteo-inductive effects of hyaluronic acid (HA), we systematically characterised our encapsulation process with regard to CSC integrity, spheroid formation and viability, as well as diffusion and shear thinning properties. Osteogenic differentiation was performed in static and dynamic culture, using either conventional 6-well plate format or a rotating wall vessel bioreactor. HA-CSCs were compared with inert carboxymethyl cellulose (CMC)-CSCs. In addition, hypoxic culture condition and the implementation of human platelet lysate (hPL) further supported physiological relevance. HA led to the formation of larger spheroids with high cell viability and increased metabolic activity compared to CMC. Calcium phosphate deposition within the extracellular matrix (ECM) and elevated ALP activity confirmed successful osteogenesis in all conditions. Furthermore, both HA and dynamic culture promote osteogenesis, and when combined, synergistically enhance the osteogenic differentiation. In conclusion, we present a semi-automated, high-throughput and xeno-free platform process for the 3D differentiation of MSCs towards osteogenic lineage. By integrating HA, hypoxia and dynamic culture conditions, this capsule-based system enhances the physiological relevance, enabling advanced in vitro disease modelling, drug testing, and scalable microtissue generation while reducing reliance on animal models.

Cellulose has long been viewed as the major load-bearing component in plant primary cell walls. Recent studies, however, suggest that pectin plays a significant role in cell wall mechanics despite a kPa-scaled modulus. Here we quantify the mechanical properties of centimeter-sized internodal cell walls of Chara corallina following treatments to remove calcium crosslinks or digest pectin. We also characterize the flow of water and gas through the cell wall as a function of pressure. We found that removal of calcium crosslinks did not affect wall strength and stress-relaxation behavior, yet it decreased the elastic modulus and increased permeability to water. In contrast, pectin removal had a dramatic impact on all measurements. Samples from which pectin had been removed exhibited lower strength and stiffness and had greater stress relaxation under constant strain. Pectin removal increased the permeability of the cell wall to water above that observed when calcium was removed and reduced the pressure at which gas "tunnels" through the cell wall ~ 2-fold. Our findings support the idea that pectin locally restricts the movement of cellulose microfibrils, with implications for understanding functional properties of primary cell walls in vascular plants and developing high-performance double-network materials.

Cardiomyocyte contraction is essential for the pumping action of the heart and deteriorates after myocardial damage, either as a consequence of irreversible cardiomyocyte injury or stiffening of the extracellular matrix, a process described as fibrosis. Cell geometry and substrate stiffness not only influence sarcomere architecture and contractility, they also determine how much work the cardiomyocytes can transfer to their environment. Human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes provide a model system to examine these effects in a controlled manner, enabling us to mimic key features of the cardiac environment in vitro. Here we show that geometric confinement and substrate stiffness influence different aspects of cardiomyocyte force generation. By combining traction force microscopy and live-cell imaging of hiPSC-derived cardiomyocytes on soft and patterned substrates, we find that geometric confinement leads to longer resting sarcomeres and more pronounced sarcomere shortening on substrates with both physiological (10 kPa) and fibrotic (30 kPa) stiffness. Interestingly, the substrate stiffness itself has little effect on resting sarcomere length, but influences the peak contractile stress. On 10 kPa substrates, confined cells generate higher peak contractile stresses than unconfined cells, whereas this difference is not observed at 30 kPa. Confinement also results in faster mechanical relaxation at 10 kPa, with no detectable difference at 30 kPa. The combination of defined cell geometry and physiological stiffness leads to longer resting sarcomere lengths, more pronounced sarcomere shortening, higher peak contractile stress, and faster relaxation, features associated with a more mature cardiomyocyte phenotype. These findings show that the mechanical consequences of cell geometry depend on substrate stiffness and, therefore, both aspects have to be considered when employing hiPSC-derived cardiomyocytes as a model system in mechanobiology research, disease modeling and drug testing.

Tissue expansion is an established technique for the reconstruction of skin defects, but the cost of conventional silicone expanders may limit its application in contexts with lower resource availability. This study evaluated, in an experimental model, whether a container for storing saline solution could act as a low-cost alternative device for tissue expansion. An experimental, prospective, controlled and randomized study was carried out with 10 Wistar rats, distributed in two groups: conventional silicone expander and saline storage container. Both underwent the same surgical and expansion protocol. Abdominal circumference gain, final expanded skin length, histological and histomorphometric aspects of the skin, including collagen types I and III, as well as exploratory cost analysis, were analyzed. The conventional expander produced a greater gain in abdominal circumference, but the final length of the expanded skin was similar between the groups. Microscopic evaluation showed preservation of the cutaneous architecture, intact epidermis, cellularized dermis, and collagen deposition in both groups. There was no significant difference in the proportion of type I or type III collagen. The saline solution container had a substantially lower cost per centimeter of expanded skin than the conventional expander. These findings suggest that the saline container can produce experimental skin expansion with final length and collagen composition similar to the conventional method, at a lower cost, although additional studies are needed before clinical application.

Dynamic covalent hydrogels formed through reversible acylhydrazone crosslinking have emerged as promising injectable biomaterials. However, a fundamental gap remains in understanding how the macromolecular structure of oxidized polysaccharides (OxPs) governs gelation kinetics and how these kinetics pathways translate into material properties and cellular responses. We address this question by developing an acylhydrazone hydrogel library composed of alginate adipohydrazide crosslinked with oxidized alginate (OxA) or oxidized dextran (OxD), two reactive aldehyde-bearing polymers with comparable chemical functionality but fundamentally distinct backbone structure. By varying polysaccharide type, oxidation degree, and reaction pH, we decoupled the effects of chemical functionality from macromolecular structure and established quantitative structure-kinetics-property-function relationships. OxD-based hydrogels undergo rapid, largely pH-independent gelation, whereas OxA-based systems display pronounced pH-dependent kinetics with significantly delayed network formation under physiological pH. These differences in gelation kinetics and OxPs macromolecular structures lead to marked variations in hydrogel mechanics, including stiffness, stress relaxation, stability, injectability, and post-injection recovery. Importantly, differences in gelation kinetics modulate cell-matrix interactions in three-dimensional culture. Slowly forming OxA hydrogels maintained rounded chondrocyte shape, while rapidly gelling OxD networks induced transient cell elongation. Mesenchymal stem cells displayed similar shapes regardless of gelation kinetics, indicating cell-type-specific responses to matrix formation dynamics.

Predictive biomechanical models of the tricuspid valve require accurate representation of the chordae tendineae, yet subject-specific chordal geometry is difficult to reconstruct from non-invasive imaging. Here, we adopt a framework for generating functionally equivalent synthetic chordae without prior knowledge of in vivo chordal attachments. To this end, we first adapt an anatomy-informed hyperelastic shape-matching method that establishes correspondence between end-diastolic and end-systolic leaflet configurations using chordal-mimicking forces, a rigid contact template, and a Gaussian-smoothed locally corrective pressure field. We then generate synthetic chordal insertion sites using zone-based rejection sampling and calibrate the unloaded length of each chord by combining reaction forces with the chordal stress-stretch relationship. The framework was evaluated using Texas TriValve 1.1, a high-fidelity finite element model of a human tricuspid valve validated against beating-heart echocardiography. We found that shape matching reproduced the target end-systolic geometry with a mean inter-surface distance of 0.29 {+/-} 0.35 mm. Moreover, synthetic chordal insertions faithfully reproduce end-systolic leaflet deformations. We subsequently examined synthetic chordal configurations containing 202, 225, and 450 insertions, informed by measurements from eight explanted human tricuspid valves. Here, increasing insertion number reduced mean inter-surface distance from 0.63 {+/-} 0.52 mm to 0.49 {+/-} 0.44 mm and reduced contact area errors from 3.52% to 0.59%. Across all configurations, mean maximum principal stretch errors in leaflet belly regions remained below 2.4%, while areal strain errors ranged from 0.34% to 10.01%. These results demonstrate that anatomically informed shape matching coupled with stress-based chordal calibration can reproduce tricuspid valve closure without explicit subject-specific chordal geometry. This framework provides a foundation for generating synthetic subvalvular anatomy for future imaging-derived, predictive tricuspid valve models.

Background: Ascending thoracic aortic aneurysm (ATAA) is characterized by progressive biomechanical remodeling that is incompletely captured by maximum aortic diameter. The relationships between age, sex, aortic valve phenotype (BAV vs TAV), and aneurysmal mechanics remains incompletely understood. Methods: Ascending aortic specimens from 54 patients undergoing elective ATAA repair were evaluated. Biaxial testing quantified Green strain and local stiffness at membrane tensions of 60 and 120 N/m. Opening angle was used to assess circumferential residual stress and stretch. Associations with age were evaluated using Pearson correlations, and differences between sex and valve phenotype were also explored. Multivariable linear regression models including age, sex, and valve phenotype were used to evaluate their adjusted associations with each mechanical outcome. Results: Increasing age was associated with increased local stiffness and reduced Green strain and remained the strongest determinant of biaxial mechanical properties after adjustment. Compared with tricuspid aortic valve specimens, BAV specimens exhibited lower Green strain together with lower local stiffness. Females demonstrated greater Green strain in unadjusted analyses; however, after adjustment, sex remained associated only with longitudinal Green strain at 60 N/m. None of the evaluated clinical characteristics consistently explained opening angle or residual stretch. Conclusions: Age was the predominant clinical determinant of biaxial mechanical remodeling in ATAA, whereas valve phenotype demonstrated selective associations and sex contributed comparatively little after adjustment. Circumferential residual stress appeared largely independent of these clinical characteristics, suggesting that residual stress and biaxial mechanics capture complementary aspects of aneurysmal remodeling.

Healing of the gastrointestinal (GI) tract following surgical interventions is governed by coupled mechanobiological processes and may lead to severe complications such as perforation or stricture formation. A first comprehensive mechanobiological modeling framework of GI healing is herein proposed. The framework addresses two clinically relevant applications of bioprinting: endoscopic treatment of GI tissue defects and bioprinting-assisted surgical anastomosis. Tissue remodeling is based upon a hyperelastic material model with fiber dispersion coupling the spatiotemporal reaction diffusion dynamics of fibroblasts and cytokines with collagen deposition, reorientation, and plastic deformation. An active stress formulation drives fibroblasts and myofibroblast contraction while a multiplicative decomposition approach is adopted for collagen remodeling as a permanent change. The governing equations are discretised in time with an implicit Euler scheme, finite element in space and solved by a staggered algorithm implemented in the open-source platform FEniCS. Numerical simulations show that the initial collagen fibers content and orientation strongly influence fibroblast infiltration and scar contracture formation. The study quantifies the advantage of having a collagen bioprinted architecture aligned with tissue fibers, to reduce structural remodeling distortion. The model also predicts a strong correlation between collagen deposition and luminal burst pressure during the recovery of mechanical integrity in GI anastomosis.

In breast cancer, collagen fiber alignment and the second harmonic generation forward-to-backward ratio (F/B), an optical measurement sensitive to fibril-scale organization within collagen fibers, have each been associated with metastatic outcome. Although both are measured at the tumor-stromal interface, in vitro studies have largely examined them separately, because experimental systems have not allowed the two to be varied independently. To address this technical gap, we used a microfluidic biofabrication approach to generate paired aligned and unaligned regions within 3D collagen hydrogels via extensional strain and varied measured F/B across gels by changing the pre-gel pH. The resulting library covered alignment values reported in breast tumors and F/B values associated with poorer metastatic outcome in invasive ductal carcinoma at matched matrix stiffness, pore diameter, and fiber fraction. In MDA-MB-231 cells, alignment biased migration along the fiber axis without changing migration speed, as expected, but the magnitude of the contact guidance response varied with measured F/B. In contrast, MCF-7 cells showed little overall contact guidance, yet migrated ~30% faster in high F/B than low F/B gels in both aligned and unaligned regions. Together, these results show that cells migrated differently in matrices with similar fiber alignment. Thus, including measured F/B may provide additional information to help anticipate how cells migrate in collagen environments that appear similar based on alignment alone.

A persistent challenge in cartilage tissue engineering is identifying cell sources capable of regenerating cartilage with native-like properties. Variability in chondrogenic potential among human- and animal-derived cells complicates graft development and disease modeling. Here we benchmarked ten chondrogenic cell sources under standardized culture conditions using hyaluronan-alginate biomaterials and implementing a functionality index combining histological and mechanical metrics referenced to native tissue. Mesenchymal stem cells and fetal chondroprogenitors demonstrated superior regenerative capacity, achieving 103% and 95% of native cartilage functionality, respectively. In contrast, adult articular chondrocytes from healthy and osteoarthritic donors produced fibrocartilaginous tissue with functionality scores below 50%. These findings provide a quantitative framework to guide cell source selection and optimize cartilage graft standardization for clinical applications and physiologically relevant disease models, addressing regulatory demands for product characterization.

Fibrotic strictures are among the most disabling complications of Crohn's disease, permanently narrowing the bowel and impairing motility, yet no approved therapy reverses them. Chronic inflammation alters pacemaker-network coupling, smooth-muscle excitability, and calcium-dependent contractility, while fibrosis thickens the bowel wall, narrows the lumen, and changes tissue mechanics. The relative contributions of these coupled electrical, contractile, and structural alterations to motility loss remain unclear. To address this gap, we develop an integrated electromechanical finite-element framework for fibrostenosing Crohn's disease that couples a fibrosis-driven growth model with a FitzHugh-Nagumo electromechanical model. A full-factorial 25 design of experiments is used to quantify the relative effects of electrical diffusivity, excitation threshold, peak active stress, wall stiffness, and hypertrophic remodeling on cyclic lumen-volume deformation. Motility is quantified by the standard deviation of lumen volume over one contraction cycle. Within the parameter ranges examined, increased wall stiffness emerged as the dominant contributor to motility loss, followed by impaired smooth-muscle contractility. Changes in excitation threshold, hypertrophic remodeling, and electrical diffusivity produced substantially smaller effects. Pairwise interactions were small relative to the dominant main effects, indicating that the mechanisms contributed largely through their individual effects. Our findings suggest that limiting wall stiffening while preserving smooth-muscle contractile function may provide a therapeutic strategy for maintaining intestinal motility in fibrostenosing Crohn's disease.