Functionalized Silk Vascular Grafts with Decellularized Human Wharton's Jelly Improves Remodeling via Immunomodulation in Rabbit Jugular Vein

Microfluidic human physiomimetic liver model as a screening platform for drug induced liver injury

The pre-clinical animal models often fail to predict intrinsic and idiosyncratic drug induced liver injury (DILI), thus contributing to drug failures in clinical trials, black box warnings and withdrawal of marketed drugs. This suggests a critical need for human-relevant in vitro models to predict diverse DILI phenotypes. In this study, a porcine liver extracellular matrix (ECM) based biomaterial ink with high printing fidelity, biocompatibility and tunable rheological and mechanical properties is formulated for supporting both parenchymal and non-parenchymal cells. Further, we applied 3D printing and microfluidic technology to bioengineer a human physiomimetic liver acinus model (HPLAM), recapitulating the radial hepatic cord-like structure with functional sinusoidal microvasculature network, biochemical and biophysical properties of native liver acinus. Intriguingly, the human derived hepatic cells incorporated HPLAM cultured under physiologically relevant microenvironment, acts as metabolic biofactories manifesting enhanced hepatic functionality, secretome levels and biomarkers expression over several weeks. We also report that the matured HPLAM reproduces dose- and time-dependent hepatotoxic response of human clinical relevance to drugs typically recognized for inducing diverse DILI phenotypes as compared to conventional static culture. Overall, the developed HPLAM emulates in vivo like functions and may provide a useful platform for DILI risk assessment to better determine safety and human risk.

Bioactive Patch for Rotator Cuff Repairing via Enhancing Tendon-to-Bone Healing: A Large Animal Study and Short-Term Outcome of a Clinical Trial

Tissue engineering has demonstrated its efficacy in promoting tissue regeneration, and extensive research has explored its application in rotator cuff (RC) tears. However, there remains a paucity of research translating from bench to clinic. A key challenge in RC repair is the healing of tendon-bone interface (TBI), for which bioactive materials suitable for interface repair are still lacking. The umbilical cord (UC), which serves as a vital repository of bioactive components in nature, is emerging as an important source of tissue engineering materials. A minimally manipulated approach is used to fabricate UC scaffolds that retain a wealth of bioactive components and cytokines. The scaffold demonstrates the ability to modulate the TBI healing microenvironment by facilitating cell proliferation, migration, suppressing inflammation, and inducing chondrogenic differentiation. This foundation sets the stage for in vivo validation and clinical translation. Following implantation of UC scaffolds in the canine model, comprehensive assessments, including MRI and histological analysis confirm their efficacy in inducing TBI reconstruction. Encouraging short-term clinical results further suggest the ability of UC scaffolds to effectively enhance RC repair. This investigation explores the mechanisms underlying the promotion of TBI repair by UC scaffolds, providing key insights for clinical application and translational research.

Decellularized Umbilical Cord as a Scaffold to Support Healing of Full-Thickness Wounds

The umbilical cord is a material that enhances regeneration and is devoid of age-related changes in the extracellular matrix (ECM). The aim of this work was to develop a biodegradable scaffold from a decellularized human umbilical cord (UC-scaffold) to heal full-thickness wounds. Decellularization was performed with 0.05% sodium dodecyl sulfate solution. The UC-scaffold was studied using morphological analysis methods. The composition of the UC-scaffold was studied using immunoblotting and Fourier transform infrared spectroscopy. The adhesion and proliferation of mesenchymal stromal cells were investigated using the LIVE/DEAD assay. The local reaction was determined by subcutaneous implantation in mice (n = 60). A model of a full-thickness skin wound in mice (n = 64) was used to assess the biological activity of the UC-scaffold. The proposed decellularization method showed its effectiveness in the umbilical cord, as it removed cells and retained a porous structure, type I and type IV collagen, TGF-β3, VEGF, and fibronectin in the ECM. The biodegradation of the UC-scaffold in the presence of collagenase, its stability during incubation in hyaluronidase solution, and its ability to swell by 1617 ± 120% were demonstrated. Subcutaneous scaffold implantation in mice showed gradual resorption of the product in vivo without the formation of a dense connective tissue capsule. Epithelialization of the wound occurred completely in contrast to the controls. All of these data suggest a potential for the use of the UC-scaffold.

Biochemical and immunomodulatory insights of extracellular matrix from decellularized human whole cervix: recellularization andin vivoECM remodeling interplay

Extracellular matrix (ECM) rich whole organ bio-scaffolds, preserving structural integrity and essential growth factors, has potential towards regeneration and reconstruction. Women with cervical anomalies or trauma can benefit from clinical cervicovaginal repair using constructs rich in site specific ECM. In this study, complete human cervix decellularization was achieved using a modified perfusion-based stir bench top decellularization method. This was followed by physico-chemical processes including perfusion of ionic agents, enzymatic treatment and washing using detergent solutions for a duration of 10-12 d. Histopathological analysis, as well as DNA quantification confirmed the efficacy of the decellularization process. Tissue ultrastructure integrity was preserved and the same was validated via scanning electron microscopy and transmission electron microscopy studies. Biochemical analysis and structural characterizations like Fourier transform infrared, Raman spectroscopy of decellularized tissues demonstrated preservation of important proteins, crucial growth factors, collagen, and glycosaminoglycans.In vitrostudies, using THP-1 and human umbilical vein endothelial cell (HUVEC) cells, demonstrated macrophage polarization from M1 to M2 and vascular functional genes enhancement, respectively, when treated with decellularized human cervical matrix (DHCp). Crosslinked DHC scaffolds were recellularized with site specific human cervical epithelial cells and HUVEC, showing non-cytotoxic cell viability and enhanced proliferation. Furthermore, DHC scaffolds showed immunomodulatory effectsin vivoon small rodent model via upregulation of M2 macrophage genes as compared to decellularized rat cervix matrix scaffolds (DRC). DHC scaffolds underwent neo-vascularization followed by ECM remodeling with enhanced tissue integration.

Decellularized extracellular matrix and silk fibroin-based hybrid biomaterials: A comprehensive review on fabrication techniques and tissue-specific applications

Biomaterials play a fundamental role in tissue engineering by providing biochemical and physical cues that influence cellular fate and matrix development. Decellularized extracellular matrix (dECM) as a biomaterial is distinguished by its abundant composition of matrix proteins, such as collagen, elastin, fibronectin, and laminin, as well as glycosaminoglycans and proteoglycans. However, the mechanical properties of only dECM-based constructs may not always meet tissue-specific requirements. Recent advancements address this challenge by utilizing hybrid biomaterials that harness the strengths of silk fibroin (SF), which contributes the necessary mechanical properties, while dECM provides essential cellular cues for in vitro studies and tissue regeneration. This review discusses emerging trends in developing such biopolymer blends, aiming to synergistically combine the advantages of SF and dECM through optimal concentrations and desired cross-linking density. We focus on different fabrication techniques and cross-linking methods that have been utilized to fabricate various tissue-engineered hybrid constructs. Furthermore, we survey recent applications of such biomaterials for the regeneration of various tissues, including bone, cartilage, trachea, bladder, vascular graft, heart, skin, liver, and other soft tissues. Finally, the trajectory and prospects of the constructs derived from this blend in the tissue engineering field have been summarized, highlighting their potential for clinical translation.

Silk fibroin bioscaffold from Bombyx mori and Antheraea assamensis elicits a distinct host response and macrophage activation paradigm in vivo and in vitro

Biomaterials composed of silk fibroin from both mulberry and non-mulberry silkworm varieties have been investigated for their utility in tissue engineering and drug delivery, but these studies have largely excluded any evaluation of host immune response. The present study compares the macrophage activation response towards mulberry (Bombyx mori, BM) and non-mulberry (Antheraea assamensis, AA) silk types, individually and as a blend (BA) in a partial thickness rat abdominal wall defect model and in vitro primary murine bone marrow-derived macrophage (BMDM) assay. Biologic materials composed of liver extracellular matrix (LECM) and small intestinal submucosa (SIS) ECM that are recognized for constructive tissue remodeling, and polypropylene mesh that is associated with pro-inflammatory macrophage phenotype activation are used as controls in the animal model. The AA silk graft shows a host response similar to SIS with few foreign body multinucleate giant cells, vascularization, high CD206 expression, and high M2-like: M1-like macrophage phenotype ratio. Exposure to AA silk degradation products in vitro induces a higher arginase: iNOS ratio in both naive BMDM and pro-inflammatory activated BMDM; and higher Fizz1: iNOS ratio in pro-inflammatory activated BMDM. These data suggest that the AA silk supports a pro-remodeling macrophage response with potential therapeutic applications.

Strategies to counteract adverse remodeling of vascular graft: A 3D view of current graft innovations

Vascular grafts are widely used for vascular surgeries, to bypass a diseased artery or function as a vascular access for hemodialysis. Bioengineered or tissue-engineered vascular grafts have long been envisioned to take the place of bioinert synthetic grafts and even vein grafts under certain clinical circumstances. However, host responses to a graft device induce adverse remodeling, to varied degrees depending on the graft property and host's developmental and health conditions. This in turn leads to invention or failure. Herein, we have mapped out the relationship between the design constraints and outcomes for vascular grafts, by analyzing impairment factors involved in the adverse graft remodeling. Strategies to tackle these impairment factors and counteract adverse healing are then summarized by outlining the research landscape of graft innovations in three dimensions-cell technology, scaffold technology and graft translation. Such a comprehensive view of cell and scaffold technological innovations in the translational context may benefit the future advancements in vascular grafts. From this perspective, we conclude the review with recommendations for future design endeavors.

Monocyte Recruitment for Vascular Tissue Regeneration

A strategy to recruit monocytes (MCs) from blood to regenerate vascular tissue from unseeded (cell-free) tissue engineered vascular grafts is presented. When immobilized on the surface of vascular grafts, the fusion protein, H2R5 can capture blood-derived MC under static or flow conditions in a shear stress dependent manner. The bound MC turns into macrophages (Mϕ) expressing both M1 and M2 phenotype specific genes. When H2R5 functionalized acellular-tissue engineered vessels (A-TEVs) are implanted into the mouse aorta, they remain patent and form a continuous endothelium expressing both endothelial cell (EC) and MC specific proteins. Underneath the EC layer, multiple cells layers are formed coexpressing both smooth muscle cell (SMC) and MC specific markers. Lineage tracing analysis using a novel CX3CR1-confetti mouse model demonstrates that fluorescently labeled MC populates the graft lumen by two and four weeks postimplantation, providing direct evidence in support of MC/Mϕ recruitment to the graft lumen. Given their abundance in the blood, circulating MCs may be a great source of cells that contribute directly to the endothelialization and vascular wall formation of acellular vascular grafts under the right chemical and biomechanical cues.

Silk-Based Bioengineered Diaphyseal Cortical Bone Unit Enclosing an Implantable Bone Marrow toward Atrophic Nonunion Grafting

Postnatal fracture healing of atrophic long bone diaphyseal nonunions remains a challenge for orthopedic surgeons. Paucity of autologous spongiosa has potentiated the use of tissue engineered bone grafts to improve success rates of bone marrow engraftment used in plate reosteosynthesis. Herein, the development and in vitro validation of a "sandwich-type" biofabricated diaphyseal cross-sectional unit, with an outer mechanically robust bioprinted cortical bone shell, encompassing an engineered bone marrow, are reported. Channelized silk fibroin blend sponges derived from Bombyx mori and Antheraea assama help in developing compartmentalized endosteum, exhibiting specialized osteoblasts (endosteal niche) and discontinuous endothelium (vascular niche). The cellular cross-talk between these two niches triggered via integrin-mediated cell adhesion, enables in preserving quiescence state of CD34⁺ /CD38^- hematopoietic stem cells and their recycling in the engineered marrow. The outer cortical bone strut is developed through multimaterial microextrusion bioprinting strategy. Osteogenically primed mesenchymal stem cells-laden silk fibroin-nano-hydroxyapatite bioink is bioprinted alongside paramagnetic Fe-doped bioactive glass-polycaprolactone blend thermoplastic ink, reinforcing it for mechanical stability. Pulsed magnetic field actuation positively influences the osteogenic commitment and maturation of the bioprinted constructs via mechanotransductory route. Therefore, the assembled engineered marrow and bioprinted cortical shell hold promise as potential orthobiologic substitutes toward atrophic nonunion repairs.