Catechol-Functionalized Hyaluronic Acid Hydrogels Enhance Angiogenesis and Osteogenesis of Human Adipose-Derived Stem Cells in Critical Tissue Defects

Over the last few decades, stem cell therapies have been highlighted for their potential to heal damaged tissue and aid in tissue reconstruction. However, materials used to deliver and support implanted cells often display limited efficacy, which has resulted in delaying translation of stem cell therapies into the clinic. In our previous work, we developed a mussel-inspired, catechol-functionalized hyaluronic acid (HA-CA) hydrogel that enabled effective cell transplantation due to its improved biocompatibility and strong tissue adhesiveness. The present study was performed to further expand the utility of HA-CA hydrogels for use in stem cell therapies to treat more clinically relevant tissue defect models. Specifically, we utilized HA-CA hydrogels to potentiate stem cell-mediated angiogenesis and osteogenesis in two tissue defect models: critical limb ischemia and critical-sized calvarial bone defect. HA-CA hydrogels were found to be less cytotoxic to human adipose-derived stem cells (hADSCs) in vitro compared to conventional photopolymerized HA hydrogels. HA-CA hydrogels also retained the angiogenic functionality of hADSCs and supported osteogenic differentiation of hADSCs. Because of their superior tissue adhesiveness, HA-CA hydrogels were able to mediate efficient engraftment of hADSCs into the defect regions. When compared to photopolymerized HA hydrogels, HA-CA hydrogels significantly enhanced hADSC-mediated therapeutic angiogenesis (promoted capillary/arteriole formation, improved vascular perfusion, attenuated ischemic muscle degeneration/fibrosis, and reduced limb amputation) and bone reconstruction (mineralized bone formation, enhanced osteogenic marker expression, and collagen deposition). This study proves the feasibility of using bioinspired HA-CA hydrogels as functional biomaterials for improved tissue regeneration in critical tissue defects

Plant Flavonoid-Mediated Multifunctional Surface Modification Chemistry: Catechin Coating for Enhanced Osteogenesis of Human Stem Cells

Application of surface chemistry using bioactive compounds enables simple functionalization of tissue-engineering scaffolds for improved biocompatibility and regenerative efficacy. Recently, surface modifications using natural polyphenols have been reported to serve as efficient multifunctional coating; however, there has yet to be any comprehensive application in tissue engineering. Here, we report a simple, multifunctional surface modification using catechin, a phenolic compound with many biological functions, found primarily in plants, to potentiate the functionality of polymeric scaffolds for bone regeneration by stem cells. We found that catechin hydrate can be efficiently deposited on the surface of various substrates and can greatly increase hydrophilicity of the substrates. While identifying the chemical mechanisms regulating catechin surface coating, we found that catechin molecules can self-assemble into dimers via cation−π interactions. Interestingly, the intrinsic biochemical functions of catechin coating provided the polymer scaffolds with antioxidative and calcium-binding abilities, resulting in enhanced adhesion, proliferation, mineralization, and osteogenic differentiation of human adipose-derived stem cells (hADSCs). Ultimately, catechin-functionalized polymer nanofiber scaffolds significantly promoted <i>in vivo</i> bone formation by hADSC transplantation in a critical-sized calvarial bone defect. Our study demonstrates that catechin can provide a biocompatible, multifunctional, and cost-effective surface modification chemistry to produce functional scaffolds with improved tissue regenerative efficacy

Thermoresponsive Nanofabricated Substratum for the Engineering of Three-Dimensional Tissues with Layer-by-Layer Architectural Control

Current tissue engineering methods lack the ability to properly recreate scaffold-free, cell-dense tissues with physiological structures. Recent studies have shown that the use of nanoscale cues allows for precise control over large-area 2D tissue structures without restricting cell growth or cell density. In this study, we developed a simple and versatile platform combining a thermo­responsive nanofabricated substratum (TNFS) incorporating nano­topo­graphical cues and the gel casting method for the fabrication of scaffold-free 3D tissues. Our TNFS allows for the structural control of aligned cell monolayers which can be spontaneously detached <i>via</i> a change in culture temperature. Utilizing our gel casting method, viable, aligned cell sheets can be transferred without loss of anisotropy or stacked with control over individual layer orientations. Transferred cell sheets and individual cell layers within multilayered tissues robustly retain structural anisotropy, allowing for the fabrication of scaffold-free, 3D tissues with hierarchical control of overall tissue structure

Harnessing Sphingosine-1-Phosphate Signaling and Nanotopographical Cues To Regulate Skeletal Muscle Maturation and Vascularization

Despite possessing substantial regenerative capacity, skeletal muscle can suffer from loss of function due to catastrophic traumatic injury or degenerative disease. In such cases, engineered tissue grafts hold the potential to restore function and improve patient quality of life. Requirements for successful integration of engineered tissue grafts with the host musculature include cell alignment that mimics host tissue architecture and directional functionality, as well as vascularization to ensure tissue survival. Here, we have developed biomimetic nanopatterned poly­(lactic-<i>co</i>-glycolic acid) substrates conjugated with sphingosine-1-phosphate (S1P), a potent angiogenic and myogenic factor, to enhance myoblast and endothelial maturation. Primary muscle cells cultured on these functionalized S1P nanopatterned substrates developed a highly aligned and elongated morphology and exhibited higher expression levels of myosin heavy chain, in addition to genes characteristic of mature skeletal muscle. We also found that S1P enhanced angiogenic potential in these cultures, as evidenced by elevated expression of endothelial-related genes. Computational analyses of live-cell videos showed a significantly improved functionality of tissues cultured on S1P-functionalized nanopatterns as indicated by greater myotube contraction displacements and velocities. In summary, our study demonstrates that biomimetic nanotopography and S1P can be combined to synergistically regulate the maturation and vascularization of engineered skeletal muscles