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Physically crosslinked gelatin microgels were functionalized with a bioadhesive molecule, catechol, to study the effect of in situ generated H2O2 on full-thickness wound repair in diabetic mice. Due to the physically crosslinked nature of the microgels, they transition into a hydrogel film upon hydration. The formation of a hydrogel film was confirmed by the changes in their morphology and viscoelastic properties. Additionally, these microgels released up to 86 μM of H2O2 as a result of catechol autoxidation. The generated H2O2 completely eradicated Staphylococcus epidermidis with an initial concentration of 103 CFU mL−1. These microgels were not cytotoxic and promoted VEGF upregulation in immortalized human keratinocytes (HaCaT) in vitro. When the microgels were applied to a full-thickness dermal wound in diabetic mice, dermal wound closure was accelerated over 14 days, achieving a wound closure of 90% based on the wound area. Microgel-treated wounds also resulted in complete re-epithelialization and regeneration of new dermal tissues with morphology and structure resembling those of native tissues. These results indicate that the release of micromolar concentrations of H2O2 can accelerate wound healing in a healing-impaired animal. 

Abstract Preparation of human mesenchymal stem cell (hMSC) suspension for lymphedema treatment relies on conventional enzymatic digestion methods, which severely disrupts cell–cell and cell–extracellular matrix (ECM) connections, and drastically impairs cell retention and engraftment after transplantation. The objective of the present study is to evaluate the ability of hMSC‐secreted ECM to augment lymphangiogenesis by using an in vitro coculturing model of hMSC sheets with lymphatic endothelial cells (LECs) and an in vivo mouse tail lymphedema model. Results demonstrate that the hMSC‐secreted ECM augments the formation of lymphatic capillary‐like structure by a factor of 1.2–3.6 relative to the hMSC control group, by serving as a prolymphangiogenic growth factor reservoir and facilitating cell regenerative activities. hMSC‐derived ECM enhances MMP‐2 mediated matrix remodeling, increases the synthesis of collagen IV and laminin, and promotes lymphatic microvessel‐like structure formation. The injection of rat MSC sheet fragments into a mouse tail lymphedema model confirms the benefits of the hMSC‐derived ECM by stimulating lymphangiogenesis and wound closure. 

Abstract Secondary lymphedema is a life‐long disorder characterized by chronic tissue swelling and inflammation that obstruct interstitial fluid circulation and immune cell trafficking. Regenerating lymphatic vasculatures using various strategies represents a promising treatment for lymphedema. Growth factor injection and gene delivery have been developed to stimulate lymphangiogenesis and augment interstitial fluid resorption. Using bioengineered materials as growth factor delivery vehicles allows for a more precisely targeted lymphangiogenic activation within the injured site. The implantation of prevascularized lymphatic tissue also promotesin situlymphatic capillary network formation. The engineering of larger scale lymphatic tissues, including lymphatic collecting vessels and lymph nodes constructed by bioengineered scaffolds or decellularized animal tissues, offers alternatives to reconnecting damaged lymphatic vessels and restoring lymph circulation. These approaches provide lymphatic vascular grafting materials to reimpose lymphatic continuity across the site of injury, without creating secondary injuries at donor sites. The present work reviews molecular mechanisms mediating lymphatic system development, approaches to promoting lymphatic network regeneration, and strategies for engineering lymphatic tissues, including lymphatic capillaries, collecting vessels, and nodes. Challenges of advanced translational applications are also discussed.