Tissue Engineering Part A

Focal injuries to articular cartilage in load-bearing joints fail to heal and often progress to degeneration, underscoring the need for repair strategies that result in restored cartilage structure and function rather than fibrocartilage formation. Granular extracellular matrix (gECM) hydrogels, flowable grafts composed of densely-packed matrix particles, offer a promising approach but lack long-term functional validation in large-animal models. Here, we developed a flowable gECM hydrogel composed of decellularized cartilage microparticles incorporated within a thiol-functionalized hyaluronan matrix. Proteomic analysis confirmed enrichment of cartilage-specific gECM matrisome components. When implanted into critical-sized femoral condyle defects in a goat model and evaluated 12 months post-implantation, both gECM hydrogel and microdrilling (surgical controls) achieved >80% defect filling. However, in contrast to microdrilling, gECM repair tissue exhibited surface tribological (friction, adhesion) and compressive mechanical properties comparable to native cartilage, with a similar proteoglycan-to-collagen ratio, enrichment of type II collagen, minimal type I collagen (typical of a fibrous scar), improved quantitative MRI metrics, and evidence of lateral cartilage integration and subchondral bone remodeling. Together, these findings demonstrate that a flowable gECM hydrogel supports integrative, cartilage-like repair in a load-bearing joint, supporting advancement of this approach toward clinical translation. One Sentence SummaryA granular ECM hydrogel implanted in a goat condyle provided a robust repair, filling the defect tissue with integrated, hyaline-like cartilage at 12 months.

Patellar osteochondral allograft (OCA) transplantation is widely used to treat large full-thickness cartilage defects, yet long-term failure and reoperation rates remain high. Although surface congruity and osseous integration are emphasized clinically, cartilage thickness and mechanical compatibility between donor and recipient are not considered. Our previous work suggests that cartilage thickness mismatch can amplify local deformation at the graft boundary, potentially compromising graft longevity. This study investigates how combined mismatches in cartilage thickness and mechanical properties influence the local strain environment at the patellar OCA interface. Simplified two-dimensional axisymmetric finite element models of patellar OCA repair were developed in ABAQUS. Donor-to-recipient cartilage thickness ratios ranging from 0.33 to 3.25 were evaluated together with donor-recipient Youngs modulus mismatches (2.5-7.0 MPa). Cartilage was modeled using homogeneous linear elastic and functionally graded material formulations to account for depth-dependent stiffness. A compressive pressure of 1.0 MPa was applied to represent patellofemoral joint loading, and peak compressive and shear strains were quantified at the graft boundary. Cartilage thickness mismatch produced localized high-strain regions (HSR) of compressive and shear strain at the donor-recipient interface that were absent in thickness-matched constructs. Strain amplification increased with both thickness and mechanical property mismatch. Compressive strain exhibited directional asymmetry, with donor-side-thicker configurations producing greater amplification than recipient-side-thicker configurations. Incorporating depth-dependent cartilage stiffness reduced peak strain magnitudes but did not eliminate mismatch-driven strain amplification. These findings demonstrate that cartilage thickness and mechanical disparity can create HSR at the patellar OCA graft boundary that may predispose grafts to impaired integration and long-term failure.

Tissue engineered constructs are increasingly used for both modeling organs and disease in vitro as well as for therapeutic intervention. In addition to collagen, these constructs commonly include native extracellular matrix proteins (ECM), such as fibronectin and laminin. Given the critical role of inflammatory pathways in disease and in response to implanted materials, it is important to understand the role these proteins play in regulating the inflammatory environment. Fibronectin and laminin influence neutrophil function and endothelial activation in 2D, but their regulation of the inflammatory environment in 3D engineered constructs is not clear. For this study, we used an inflammation-on-a-chip device that includes a model blood vessel surrounded by a collagen I hydrogel with fibronectin and/or laminin. We investigated the additive effects of both proteins and a range of concentrations for each protein to determine concentration dependence. Both fibronectin and laminin have concertation dependent effects on neutrophils and the endothelium. High concentrations (50 {micro}g/mL) of fibronectin reduced neutrophil migration, while 20 {micro}g/mL laminin reduced neutrophil extravasation and migration, potentially due to lower ICAM-1 expression by the endothelium. Interestingly, 50 {micro}g/mL of laminin significantly disrupted endothelial vessel formation and reduced ICAM-1 and VE-cadherin expression, likely due to significant changes in the collagen architecture. The inclusion of fibronectin and laminin, even at physiological levels, results in significant effects on neutrophil behavior, endothelial vessel formation, and collagen architecture. These proteins impact the inflammatory environment and thus need to be considered when modeling diseases and designing therapeutics, especially when neutrophils or an endothelium are involved. Translational Impact StatementThis work uses an inflammation-on-a-chip device to study how fibronectin and laminin impact neutrophil behavior and vascular inflammation as these proteins are commonly used in engineered constructs. We found that fibronectin impairs neutrophil migration, while laminin decreases neutrophil extravasation and migration and at higher concentrations also prevents endothelial vessel formation. Therefore, researchers should be aware that these proteins will alter the inflammatory environment when including them in engineered constructs.

IntroductionCancer progression is driven not only by tumor cells but also by interactions between the extracellular matrix (ECM), stromal cells, and immune cells within the tumor microenvironment (TME). Cancer-associated fibroblasts (CAFs) are major drivers of ECM remodeling, assembling ECM with aberrant organization. Extra domain A fibronectin (EDA-FN), a cellular FN containing an extra type III domain, is upregulated in the TME. EDA-FN regulates cellular behavior and has been associated with poor patient prognosis. Macrophages are among the most abundant immune cells within the TME, where they contribute to TME remodeling and inflammation to promote cancer cell invasion and metastasis. However, how tumor-associated matrix-specific cues regulate macrophage behavior remains largely understudied. PurposeHere, we developed a fibroblast-derived matrix platform that captures the structural imprint of tumor-associated EDA-enriched matrices and investigated how matrix-specific cues regulate macrophage behavior in the absence of ongoing soluble factor cues. MethodHuman mammary fibroblasts (HMFs) preconditioned in incubated low-serum media (lNC, or control) and MDA-MB231 metastatic breast cancer cell-conditioned media (mTCM) were cultured on polyacrylamide gels of 2 kPa and 20 kPa, respectively, followed by decellularization. Matrix organization, including fiber alignment, width, and intrafibrillar spacing, was quantified from confocal images. Decellularized EDA-FN-enriched matrices were subsequently reseeded with macrophages to assess macrophage morphology, phenotype, and matrix interactions. ResultsThe combined effects of tumor-derived soluble factors and pathological stiffness induced a CAF-like phenotype in HMFs, accompanied by cytoskeletal reorganization and microarchitectural alterations of EDA-FN-enriched matrices. Tumor-associated matrices exhibited increased alignment, narrower fiber width, and enlarged intrafibrillar spacing compared to control matrices. These aberrant, tumor-associated matrix-derived features were associated with altered macrophage behavior, including heterogeneous morphology, enhanced localized EDA-FN matrix loss beneath the cell body, and a hybrid phenotype with a shift toward a CD206-dominant profile. ConclusionsThese findings demonstrate the feasibility of obtaining EDA-FN-enriched matrices to isolate matrix-specific cues for investigating macrophage-ECM interactions. Furthermore, this platform can be leveraged to identify matrix-targeting therapeutic approaches for modulating macrophage function within the TME.

Pathologic arterial stiffening is a hallmark of vascular disease that contributes to maladaptive vascular remodeling and neointimal hyperplasia through vascular smooth muscle cell (VSMC) phenotypic switching. Yet, because vascular disease progression is governed by both biomechanical and extracellular matrix (ECM) alterations, existing in vitro models often fail to recapitulate the full complexity of the diseased vascular microenvironment. Here, we developed a bioactive decellularized extracellular matrix (dECM) and methacrylated hyaluronic acid (MeHA) composite scaffold platform with tunable stiffness that preserves native vascular ECM components while enabling controlled investigation of stiffness-dependent cell behavior. Proteomic analyses confirmed retention of key vascular matrisome components, including collagens and glycoproteins, following decellularization. Electrospun vascular dECM scaffolds maintained an aligned fibrous architecture and spanned stiffness ranges representative of healthy and pathologically stiffened arterial microenvironments. Within this matrix-preserving platform, human VSMCs cultured on stiff dECM scaffolds exhibited increased spreading, altered morphology, enhanced nuclear localization of YAP and survivin, and broad transcriptional changes consistent with a shift toward a proliferative, matrix-remodeling VSMC phenotype. Together, this bioactive, matrix-preserving platform enables mechanobiologically relevant modeling of stiffness-driven vascular remodeling and indicates YAP and survivin as candidate regulators of maladaptive VSMC mechanotransduction.

Matrix-bound nanovesicles (MBVs) are a type of small extracellular vesicle (EV) embedded in the extracellular matrix (ECM) throughout the body. MBVs have been previously isolated from various tissues and in vitro-cultured cell sheets, demonstrating remarkable attributes in regenerative medicine. However, differences between MBVs and conditioned culture medium-derived EVs (liquid-EVs) have yet to be characterized, and the field currently lacks specific protein markers that can identify MBVs from other EV subtypes. Here, we isolate MBVs and liquid-EVs from bone marrow mesenchymal stem cell (MSC) sheets and define differences in size, protein, and zeta potential between these EVs. We show that there is a correlation between cell-driven ECM deposition and MBV and liquid-EV production. We also find that MBVs are smaller, contain less protein per particle, and possess lower zeta potential than liquid-EVs. Interestingly, MBVs also comprise a distinct tetraspanin profile compared to liquid-EVs, with MBVs containing more CD63 and little to no CD81. Finally, we define that CD63, LAMP1, Alix, ITG{beta}1, and GRP94 and their abundance, may be markers specifically used to identify MBVs from liquid-EVs. Our study paves the way for the characteristic differentiation between MBVs from liquid-EVs, elucidates their differences in biogenesis, and reveals a potential connection between EV and ECM production.

Spinal cord injury (SCI) is a devastating neurological condition with limited regenerative capacity. Stem cell-based approaches have emerged as promising strategies due to their neuroprotective and immunomodulatory properties, largely mediated by small extracellular vesicles (sEVs) and their molecular cargo, including miRNAs. In this study, we aimed to evaluate the neuroprotective and anti-apoptotic potential of sEVs derived from SPC-01 and iMR-90 neural stem cell sources using an in vitro rat model of SCI. sEVs were isolated from conditioned media and characterized by multi-angle dynamic light scattering and Western blot analysis. Organotypic spinal cord slices (SCS) were used as an in vitro SCI model, with injury induced at 18-20 days, followed by immediate sEV application. After 72 h, tissue samples were collected and tissue was analyzed for markers of apoptosis, cytoskeletal integrity, and survival-related signaling pathways. Results show that SCI induced cytoskeletal disruption and increased apoptotic markers. Treatment with sEVs mitigated these changes, reducing injury-associated protein levels toward baseline. Both SPC-01- and iMR-90-derived sEVs exerted comparable neuroprotective effects, accompanied by decreased PTEN expression, enhanced STAT3 phosphorylation, and increased levels of the anti-apoptotic protein Bcl-xL. In parallel, reduced Nogo-A expression and normalization of RhoA suggested improved cytoskeletal stability and attenuation of inhibitory signaling. Together, these findings demonstrate that neural stem cell-derived sEVs promote early neuroprotective responses in vitro by modulating key signaling pathways, reducing apoptosis, and stabilizing cytoskeletal dynamics, supporting their potential as a cell-free therapeutic strategy for SCI.

BackgroundCurrent microphysiological models do not support long-term investigations into the chronic effects of vascular risk factors and the development of vascular diseases. Prolonged culture frequently leads to cellular senescence and loss of functional integrity, resulting in variability and inconsistency in modeling chronic vascular responses. Here we aimed to develop and sustain a long-term multicellular human vascular avatar, addressing the critical need for long-term disease modeling and drug testing. MethodsTo identify the optimal media for longevity, cell identity and function were assessed by morphology, qPCR, beta-gal staining, ELISA, bulk RNA-seq and single cell RNA-seq analysis. After optimizing the culture media, iPSCs-derived ECs and VSMCs from unaffected and Hutchinson-Gilford Progeria Syndrome (HGPS) donors were grown in Gravitational Lumen Patterning (GLP) Vessel- Chips for 1-6 months to generate a long-lived vascular avatar for the study of vascular aging. ResultsGuided by quantitative morphological analyses and bulk RNAseq profiling, we generated a novel optimized culture media VSL (VEGF, SB431542 as a TGF-{beta} inhibitor, low fetal bovine serum) that enhances the long-term health of vascular endothelial cells (ECs). Furthermore, we modified the VSL formulation (mVSL) by modulating 8Br-cAMP, FGF, PDGF, and a cell viability enhancer HMH1015 levels to enhance EC-VSMC (vascular smooth muscle cell) crosstalk and support long-term cellular viability. Subsequently, we maintained and characterized a human vascular avatar with a three-dimensional extracellular matrix environment and 3D vascular architecture for over 180 days. Finally, we demonstrated that this long-lived human vascular avatar enabled modeling vascular aging using iPSC-derived vascular cells from patients with Hutchinson-Gilford Progeria Syndrome (HGPS). ConclusionsWe have successfully engineered and maintained a human vascular avatar for over 180 days. The vascular avatar provides a robust platform for modeling disease-associated vascular aging and for evaluating therapeutic strategies targeting chronic vascular disorders.

Biodegradable electrospun nanofiber (NF) scaffolds have emerged as promising materials for tissue engineering applications, including vascular grafts, because their mechanical properties and degradability can be tuned. However, their in vivo degradation behavior remains poorly understood. In this study, we characterized the in vivo degradation profiles of representative biodegradable NF materials widely used in small-caliber vascular graft research, namely polycaprolactone (PCL), poly(D,L-lactide) (PLA), polyglycolic acid (PGA), and a PCL/PLA blend, by monitoring molecular weight changes in subcutaneous and vascular environments. Electrospun NF sheets were implanted subcutaneously in mice, and tubular NF grafts were implanted into the abdominal aorta of rats. Samples were harvested for up to 48 weeks after implantation and analyzed primarily by size-exclusion chromatography (SEC) to assess time-dependent changes in molecular weight. Scanning electron microscopy (SEM) and solid-state 13C nuclear magnetic resonance (NMR) were additionally performed to evaluate ultrastructural and chemical changes associated with degradation. SEC analysis revealed distinct material-specific degradation patterns. PCL showed the slowest degradation and retained a relatively high weight-average molecular weight (Mw) in both environments. PLA exhibited marked environment dependence, with near-complete degradation in the subcutaneous environment by 48 weeks, whereas scaffold structure was maintained in the vascular environment. The PCL/PLA blend showed earlier reduction in the high-molecular-weight fraction than PCL, indicating faster scaffold breakdown. PGA degraded most rapidly and could not be evaluated beyond 2 weeks in the subcutaneous model or in the vascular model because of early graft rupture. SEM analysis further demonstrated that progressive loss of fibrous ultrastructure over time was a common feature across all materials. In addition, NF scaffolds became resistant to organic solvent after implantation in vivo, and solid-state 13C NMR analysis of the solvent-insoluble fractions detected polymer-derived signals together with additional signals consistent with biological constituents. These findings indicate that in vivo degradation of biodegradable NF scaffolds is material dependent, environment dependent, and more complex than simple hydrolytic chain cleavage alone. This study provides a quantitative framework for evaluating NF degradability and offers new insight into the design of biodegradable vascular grafts. HighlightsO_LISEC quantified long-term in vivo degradation of PCL, PLA, PGA, and PCL/PLA. C_LIO_LIDegradation was both material dependent and implantation environment dependent. C_LIO_LIIn vivo nanofiber degradation involved structural and chemical changes beyond hydrolysis. C_LI

Oligodendrocyte-enriched cortical organoids (OCOs) are a powerful platform for modeling oligodendrogenesis in a human cellular context. However, neuronal activity is impaired in conventional culture media, limiting assessment of neuronal function in conjunction with oligodendrocyte biology. To address this, we used a modified BrainPhys medium termed neuronal activity medium (NAM) and defined the optimal developmental window for NAM exposure to generate OCOs with robust neuronal activity (NAM-OCOs). Stage-specific exposure to NAM, prior to oligodendrocyte expansion, leads to enhanced structural maturation, as evidenced by increased organoid size, heightened synaptogenesis, and upregulation of transcripts associated with neuronal complexity. Further, NAM-OCOs display increased cellular heterogeneity, including greater representation of GABAergic interneurons while preserving oligodendrocyte development and maturation. Altogether, our studies demonstrate that stage-specific exposure to an activity-permissive environment enhances neuronal activity, establishing an OCO model which integrates neuronal activity with oligodendrocyte development and maturation. HighlightsO_LIIncreased neuronal activity in oligodendrocyte-enriched cortical organoids (OCOs) C_LIO_LIStage-specific Neuronal Activity Medium (NAM) optimizes activity C_LIO_LINAM-OCOs display increased cellular heterogeneity and neuronal maturation C_LIO_LIOligodendrogenesis is preserved in NAM-OCOs C_LI eTOC blurbIn this article, Chung et al enhance neuronal activity in oligodendrocyte-enriched cortical organoids (OCOs) through stage-specific exposure to Neuronal Activity Medium (NAM). OCOs exposed to NAM display elevated cellular heterogeneity, structural maturation, and synaptogenesis, while preserving oligodendrocyte development and maturation. These results establish an increasingly comprehensive OCO model for studying neuronal function and oligodendrogenesis.

BackgroundBone graft biomaterials play a critical role in bone regeneration by influencing osteoblast differentiation and mineralization. However, comparative data regarding the osteogenic potential of commonly used graft materials under standardized conditions remain limited. Method and materialIn this in vitro experimental study, osteoblast-like cells (MG-63) were cultured with four bone graft materials, including Bio-Oss, Cerasorb, Bio-Tiss Cerabone, and Pro Osteon. The relative mRNA expression of osteogenic markers (COL1 and OPN) was evaluated at 1, 7, 14, and 21 days using real-time PCR. Alkaline phosphatase (ALP) activity and mineralization capacity were also assessed using colorimetric assay and Alizarin Red staining. Data were analyzed using one-way ANOVA and Tukey post hoc test (P < 0.05). ResultsSignificant differences were observed among the tested materials across all evaluated parameters. Bio-Oss and Cerasorb demonstrated higher gene expression levels and ALP activity compared to Bio-Tiss Cerabone and Pro Osteon (P < 0.05). Mineralization analysis showed significantly greater calcium deposition in the Bio-Oss and Cerasorb groups, whereas Pro Osteon consistently exhibited the lowest osteogenic performance. ConclusionBone graft biomaterials significantly influence osteogenic activity in osteoblast-like cells. Bio-Oss and Cerasorb showed superior osteogenic potential, while Pro Osteon demonstrated weaker performance. These findings highlight the importance of material properties in optimizing bone regeneration.

Fv-HSP72 is a rapid cell-penetrating human heat shock protein for the treatment of traumatic organ injuries. We have shown this re-engineered protein (HSP72) is capable of crossing the blood brain barrier (BBB) of rats suffering a controlled cortical impact (CCI) and remains in brain tissue for up to 12 hours; long after clearance from the cortex of uninjured rats. Peptide sequences unique to Fv-HSP72 allow for its differential detection from endogenous HSP72. Male Sprague-Dawley rats were divided into 10 groups of n=10 with those animals receiving a CCI subjected to a unilateral cortical contusion simulating a moderate to severe brain injury using an electronically controlled pneumatic impact device. Control groups were either uninjured (Sham), injured (TBI Only), or injured and given buffer (TBI+Vehicle). Rats treated with one of three Fv-HSP72 variants were dosed at 10 or 30mg/kg 15m post-impact, then sacrificed 48 hours later. Cortical tissues were extracted from the ipsilateral and contralateral hemispheres for biomarker analysis. Here we report results of our drug inhibiting neurodegeneration based on five biomarkers (NF-L, pNF-H, pTau [T181, T231, S396]). These results were statistically significant, especially for one of the Fv-HSP72 variants, when comparing differences both between treatment groups and within groups (i.e. when comparing ipsi-vs. contralateral hemispheres). Significant inhibition of oxidative stress (3-NT) and inflammatory (IL-6) biomarkers were also observed (both p<0.0001). With similar results obtained for a blast injury model being published elsewhere, the analyses suggest Fv-HSP72 is neuroprotective following a direct impact brain injury. One sentence summaryThis study describes the effectiveness of a biologic agent, Fv-HSP72, in significantly inhibiting neuronal tissue damage in the brain when administered after a direct cortical impact.

BackgroundDirect conversion of human somatic cells into functional neurons could offer a faster way to generate patient-specific neurons for use in regenerative medicine, disease modelling, and drug development. Although it has been reported that neuronal direct reprogramming bypasses the intermediate pluripotent state, no reports have included time-lapse experiments, potentially overlooking transient intermediate states. Recent studies have shown that the conversion of human mesenchymal stromal cells (hMSCs) into neuron-like cells involves a transition through a transient intermediate state. Therefore, further research is needed to fully understand the process by which human somatic cells can become neurons without cell division. In this study we investigates whether direct neuronal reprogramming of human bone marrow-derived MSC (hBM-MSCs), dental pulp-derived MSC (hDP-MSCs), and adult human dermal fibroblasts (HDFa), involves a transient intermediate state, and sought to further validate the neuronal identity of hMSC-derived induced neurons. MethodsIn this study, we conducted time-lapse experiments to observe the transformation of hBM-MSCs, hDP-MSCs and HDFa, into neurons using a small-molecule-based direct reprogramming protocol. Cellular and ultrastructural changes were further characterized by confocal and electron microscopy. ResultsDirect conversion of hBM-MSCs, hDP-MSCs and HDFa into neuron-like cells occurred rapidly and in absence of cell division. Time-lapse analyses revealed that reprogramming proceeds through a transient intermediate state characterized by distinct morphological changes and dynamic nuclear remodelling. Furthermore, we found that neuron-like cells derived from hBM-MSCs and hDP-MSCs exhibit neuronal polarization, expressed specific neuronal and synaptic markers, formed interconnected cellular networks, and exhibited functional plasticity, providing further evidence that hMSCs can become functional neurons. ConclusionsThis study provides clear evidence that the direct neuronal reprogramming process involves a transition through an intermediate, transient state. Our findings also provide further evidence that hMSCs can become functional neurons. In summary, our work provides new insights into the direct neuronal reprogramming process, which is essential for advancing both developmental biology and regenerative medicine.

The ability to revascularize target tissues and organs through cell-based therapy would provide a novel approach for the treatment of a range of ischemic disorders including cardiovascular diseases, stroke and peripheral artery disease. Towards this goal, we have identified a human pluripotent stem cell (hPSC)-derived vascular progenitor (VP) population generated via an epicardial intermediate with functional engraftment properties. VP cells efficiently engraft the mammary fat pad and hind limb skeletal muscle of NSG recipient mice and form vessel-like structures that integrate with the host vasculature. In an ischemic hind limb mouse model, VPs generate extensive vascular grafts that improve perfusion, restore some function and preserve muscle integrity over a three-month period post-transplant. Single-cell transcriptomic and flow cytometric analyses show that the VP population, initially identified by the co-expression of CD140b, CD13 and KDR, displays an epicardial lineage signature and expresses a spectrum of genes and proteins indicative of vascular progenitor stage cells. Together, these findings demonstrate that it is possible to revascularize both normal and ischemic tissue through the transplantation of an appropriate hPSC-derived progenitor and in doing so, lay the foundation for developing cell-based therapy approaches to treat ischemic diseases. Graphical Abstract LegendHuman pluripotent stem cells are differentiated through an epicardial intermediate to generate vascular progenitor (VP) cells characterized by expression of CD140b, CD13 and KDR. These VP cells demonstrate the capacity to engraft both mammary fat pad and skeletal muscle tissue where they form stable perfused vascular networks. In a hindlimb ischemia model, VP cell transplantation restores blood flow and improves functional outcomes. eTOC BlurbFernandes et al. develop a protocol to generate engraftable vascular progenitors from human pluripotent stem cells through an epicardial intermediate. These cells form functional vessels in vivo, restore perfusion in ischemic tissue, and demonstrate tissue-specific adaptation while maintaining endothelial identity, providing a foundation for therapeutic revascularization. HighlightsO_LIA staged differentiation protocol generates vascular progenitors (VPs) from hPSCs via an epicardial intermediate. C_LIO_LIVP cells form stable, perfused vascular networks following transplantation into multiple tissue sites. C_LIO_LIVP cell therapy with or without VEGF nanoparticles restores perfusion and improves functional outcomes in hindlimb ischemia. C_LIO_LISingle-cell analysis reveals tissue-specific adaptation while maintaining endothelial identity. C_LI

Critical-sized bone defects represent a challenge in bone tissue engineering, due to insufficient vascularization that results in implant failure. Scaffold pre-vascularization is a promising strategy to create a functional microvascular network that integrates with host vasculature. In this study, we present a hybrid 3D construct comprising a hyaluronic acid-based hydrogel and a 3D printed polycaprolactone/{beta}-tricalcium phosphate scaffold, to support vascular network formation and osteogenic differentiation. Peptide-functionalized (i.e. RGD, YIGSR, IKVAV, QK) hydrogels were obtained via thiol-ene chemistry, using two crosslinkers (PEG-diSH or MMP-diSH). Preliminary biological experiments assessed human mesenchymal stromal cells (hMSCs), endothelial cells (hUVECs), and their co-culture, on different gel formulations. All cell conditions displayed enhanced spreading and metabolic activity on gel formulations comprising RGD; thus these (i.e. RGD only and a combination of RGD/YIGSR) were selected for further studies. Cells were then mixed with the hydrogel precursor solutions, which were injected to embed the scaffolds and crosslinked using a UV lamp. After 7 days, tubule formation was observed only in co-culture conditions, highlighting the importance of cellular crosstalk for the formation of a vascular network. Significant differences were found across the tested formulations. In the RGD-PEG constructs, hUVECs formed tubule-like structures, surrounded by hMSCs, exhibiting pericyte-like behavior, supported by the upregulation of SMA gene. Conversely, in the RGD/YIGSR-MMP conditions, hMSCs were mostly located on the scaffold fibers, and showed the highest expression of early osteogenic markers (RUNX2 and ALP). Overall, we demonstrated that the hybrid system with tailored hydrogel chemistry can support simultaneous microvascular organization and osteogenic commitment, offering a promising platform for bone tissue engineering applications. However, further studies involving longer culture periods will aim at clarifying the complex interplay between material composition, cell crosstalk and spatial organization and their influence on the maturation and stability of the vascular network.

Ancestry-associated immune differences influence fibrosis risk, however, how fibrosis-associated pathways vary across individuals remains poorly understood. Fibroblasts are a main cell type involved in fibrosis. The fibroblast response is shaped by cytokine signaling and macrophage activation. The extent to which these pathways vary across individuals, and how ancestry-associated immune differences influence fibrosis risk, remains poorly understood. Here, a poly(ethylene glycol) (PEG)-based hydrogel microphysiological system was leveraged to model fibroblast-macrophage interactions following oxidative stress and to integrate donor-specific immune signals using matched macrophages and serum. Individuals of self-reported African ancestry exhibited higher monocyte expression of CCL4, lower monocyte expression of OXER1, and increased serum IL-10, compared to individuals of European ancestry. Within the hydrogel, oxidative stress reduced fibroblast prevalence while inducing Ki67 and p16. Exogenous TGF-{beta}1 increased fibroblast prevalence and collagen 3 production but did not independently increase -SMA. Incorporating donor-specific macrophages and serum revealed that cultures from individuals of European ancestry demonstrated higher fibroblast -SMA and p16 expression. Pharmacologic inhibition of IL-10 further increased -SMA, particularly in African ancestry-derived cultures, identifying IL-10 as a key protective signal limiting fibroblast activation. This hydrogel system provides a platform for dissecting inter-individual immune variation and identifying mechanisms underlying ancestry-associated fibrosis risk.

Human cardiac microtissues are a promising model to study cardiac biology and disease, but their application is constrained by therapeutic remodelling strategies and limited knowledge of their functional protein expression profiles. Here, we define the use of human cardiac microtissue (hCMT) model generated by assembling iPSC-derived endothelial cells, cardiac fibroblasts, and cardiomyocytes to model ischemia-reperfusion injury (IRI) through a model of hypoxia and reoxygenation and nanovesicle-mediated functional remodelling. Engineered nanovesicles (NVs), generated directly from human stem cells, have been shown to influence cardiac tissue and cell repair, and provide a platform for scalable and reproducible cell free-mediated therapy. We show the functional regulation of the hCMT model and define that administration of NVs (from human induced pluripotent stem cell origin) during reoxygenation significantly increase cardiomyocyte survival and preserve contractility function (contractile duration, relaxation time, relaxation:contraction velocity). Quantitative proteomics was applied to decipher the cell proteome dynamics and molecular mechanisms of IRI in our in vitro model following NV treatment, linked with networks associated with cell survival, energy production, and stress response regulation. Conserved proteome dynamics in NVs from different iPSC source reveal conserved upregulation of cellular protein networks involved in tissue repair (HSP70, CYFIP1), cardiac function (XIRP1, SLMAP, MYH6, CTNNA1, NDUFS2, GPD2), response to stress (CANX, PDCD6,), pro-survival (MDH2, LRPPRC, NIPSNAP1) and pro-angiogenic (FARSA, ECE1, RRAS) relative to vehicle treatments in context of IRI. Finally, we show that NVs also mediate differential remodelling in hCMT in response to IRI based on their cell origin, including altered wound healing and tissue repair response. Our findings provide an advanced human stem cell-based platform to understand underlying mechanisms of IRI and assess cell-free therapeutic cardioprotective strategies. SummaryAdvanced human stem cell-based platform provides a cardiac microtissue model to understand nanovesicle-based function and proteome remodelling, with potential applications for disease modelling and therapeutic intervention.

Cultivated meat is an emerging biotechnology that aims to produce edible tissues in an ethical and sustainable manner. However, the recreation of skeletal muscle tissue that replicates the protein composition and sensory characteristics of traditional meat is a major challenge. Skeletal muscle tissue engineering requires non-animal-based scaffolds which are inexpensive and food-safe, while meeting specific mechanical requirements with respect to viscosity, stress-relaxation and stiffness. While many of these characteristics can be fulfilled by alginate-based biomaterials, a key limitation of alginate is its lack of intrinsic attachment sites for animal cells, preventing efficient adhesion, differentiation and tissue formation. Here, we established a screening platform to evaluate extracellular matrix (ECM)-mimicking peptides as functionalisations of alginate scaffolds in 2D. Our platform enables high-throughput assessment of cell/peptide interactions, serving as a predictive tool for 3D tissue constructs. Our screen identified two RGD-containing sequences (vitronectin- and fibronectin-mimicking peptides) as most effective in promoting attachment and myogenic fusion of bovine satellite cells. Notably, these peptides outperformed more complex mixtures containing up to seven different ECM-mimicking peptides. Our findings provide a streamlined approach for optimising biomaterial functionalisations for cultivated meat applications, and lay the groundwork for future advancements in scalable, sustainable skeletal muscle tissue engineering.

Multipotent mesenchymal stem cells (MSCs) including bone marrow stromal cells (BMSCs) have shown analgesic efficacy in recent years. Studies suggested that the therapeutic effect of MSCs was mediated by their secreted small extracellular vesicles (sEVs) mainly exosomes. The present study evaluated the antihyperalgesic effect of BMSC-related sEVs in a mouse model of neuropathic pain involving chronic constriction injury of the infraorbital nerve (CCI-ION). Our separation protocol generated EV particles mostly sized in the range of exosomes (30-170 nm) and express exosome marker proteins CD9, CD81, and Tsg101, suggesting their endosome origin. We show that intravenous injection of BMSC-related sEVs attenuated pain hypersensitivity induced by CCI-ION as indicated by decreased mechanical hypersensitivity (von Frey test) and reduced aversion to noxious stimulation (conditioned place avoidance test). The antihyperalgesic effect of sEVs was observed in both female and male animals, and the effect was dose-dependent. sEVs from NAIVE serum-treated BMSC cultures produced short-lasting antihyperalgesia in male but not female mice, suggesting a subtle sex difference. The antihyperalgesia of sEVs from BMSC culture was blocked by the pretreatment of the culture with GM4869, the antagonist of exosome secretion, suggesting that the effect was not related to other co-isolated soluble mediators but mediated by MSC-derived exosomes. Interestingly, the prior injury condition in which sEVs were isolated favors the pain-relieving effect of sEVs. sEVs isolated from the serum of BMSC-treated animals receiving tendon ligation (TL) injury attenuated hyperalgesia for 24 h, while sEVs from the serum of BMSC-treated NAIVE animals only attenuated hyperalgesia at 3 h after injection. sEVs from the BMSC culture treated with the serum of TL rats were antihyperalgesic, but sEVs from the BMSC culture treated with the serum of naive animals were ineffective. Our results indicate that BMSC-related sEVs produced antihyperalgesia similar to that produced by BMSCs. The results suggest that the interactions between BMSCs and injury conditions are crucially important for producing efficacious sEVs/exosomes and support that the effect of sEVs could be optimized by priming BMSCs with injury-related conditions.

Osteoporotic bone degeneration involves progressive deterioration of trabecular microarchitecture, yet most scaffold-based bone tissue engineering studies evaluate osteogenesis in structurally favorable architectures that poorly represent compromised bone environments. Here, we establish a degeneration-inspired Voronoi scaffold platform in which point spacing serves as a single tunable architectural parameter to model transitions from dense mechanically integrated to severely deteriorated trabecular-like microenvironments. Increasing point spacing from 1.25 to 2.5 mm progressively reduced scaffold connectivity and stiffness while shifting deformation behavior from distributed load transfer to localized stress concentration, as confirmed by finite element analysis and mechanical testing. Benchmarking against clinically reported HR-pQCT datasets from postmenopausal women demonstrated that the intermediate 1.75 mm point spacing scaffold represents a clinically relevant compromised trabecular-like state, whereas the 2.5 mm scaffold represents a more severely deteriorated architectural condition. These architecture-dependent mechanical and structural transitions directly regulated hMSC behavior, where high point spacing scaffolds reduced cytoskeletal organization, stress fiber density, and osteogenic mineralization, establishing an architecture-associated osteogenic dysfunction regime. Polydopamine (PDA) coating progressively enhanced cytoskeletal organization and mineralization within architecturally compromised scaffolds without altering scaffold geometry. To quantitatively assess biointerface-mediated functional recovery, a Mineralization Rescue Percentage (MRP) framework was introduced, demonstrating up to 43% restoration of architecture-associated mineralization loss following PDA coating. Collectively, this work establishes a clinically contextualized degeneration-to-rescue biomaterials framework that shifts current scaffold design paradigms beyond structurally favorable architectures toward systematic investigation and functional rescue of architecture-associated osteogenic dysfunction within compromised bone-like microenvironments. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=79 SRC="FIGDIR/small/725650v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@26833forg.highwire.dtl.DTLVardef@72b2b7org.highwire.dtl.DTLVardef@333083org.highwire.dtl.DTLVardef@b5f2d1_HPS_FORMAT_FIGEXP M_FIG C_FIG Statement of SignificanceMost scaffold-based bone tissue engineering studies evaluate osteogenesis in structurally favorable architectures that poorly represent compromised bone microenvironments associated with osteoporosis. Here, a clinically contextualized Voronoi scaffold platform is established in which point spacing serves as a single tunable architectural parameter to model transitions from mechanically integrated to structurally deteriorated trabecular-like states. By decoupling architectural and surface biointerface effects, the study demonstrates that architectural deterioration alone can drive cytoskeletal disruption and osteogenic failure. Importantly, polydopamine-mediated surface engineering partially restored cytoskeletal organization and mineralization within architecturally compromised scaffolds without altering bulk geometry. A Mineralization Rescue Percentage (MRP) framework was further introduced to quantitatively assess biointerface-mediated functional recovery within degeneration-inspired scaffold microenvironments.