Successful in vitro reconstruction of skin requires the inclusion of several cell types that give rise in coculture to the specific elements present in native skin, and the appropriate scaffolding structure to house and support these cells. In addition to the two main structural components, epidermis and dermis, one critical apparatus of the skin is a capillary network that guarantees adequate perfusion of nutrients and oxygen. The aim of the present study was to develop an in vitro coculture system that assumed the human dermal-epidermal architecture and included a microcapillary network in a three-dimensional biomaterial that guaranteed ease of handling in a clinical setting. Endothelialized skin (ES) was prepared by coculturing three human cell types: keratinocytes, fibroblasts, and endothelial cells, obtained from human full-thickness skin samples, in scaffolds produced from modified hyaluronic acid. Results were evaluated by histological and immunohistochemical analyses at different time points. In vitro, engineered skin obtained with this composite culture developed into a well-differentiated upper layer of stratified keratinocytes lining a dermal-like structure, in which fibroblasts, extracellular matrix and a microvascular network were present. Furthermore, the biodegradable fabric produced from hyaluronic acid and used as the scaffolding support for this in vitro constructed skin graft greatly facilitated handling in the perioperative period.

The difficulty of obtaining significant long-term patency and good wall mechanical strength in vivo has been a significant obstacle in achieving small-diameter vascular prostheses. The aim of the present study was to develop a prosthetic graft that could perform as a small-diameter vascular conduit. Tubular structures of hyaluronan (HYAFF-11 tubules, 2 mm diameter, 1 cm length) were grafted in the abdominal aorta of 30 rats as temporary absorbable guides to promote regeneration of vascular structures. Performance was assessed by histology, immunohistochemistry, and ultra-structural analysis. These experiments resulted in three novel findings: 1) complete endothelialization of the tube's luminal surface occurred; 2) sequential regeneration of vascular components led to complete vascular wall regeneration 15 days after surgery; and 3) the biomaterial used created the ideal environment for the delicate regeneration process during the critical initial phases, yet its biodegradability allowed for complete degradation of the construct four months after implantation, at which time, a new artery remained to connect the artery stumps. This study assesses the feasibility to create a completely biodegradable vascular regeneration guide in vivo, able to sequentially orchestrate vascular regeneration events needed for very small artery reconstruction.

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The hyaluronan-based graft allowed complete regeneration of a newly formed vascular tube in which all the cellular and extracellular components are present and organized in a well defined architecture similar to native artery.

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