Assessment of the Efficacy of an LL-37-Encapsulated Keratin Hydrogel for the Treatment of Full-Thickness Wounds.

Wound healing remains a burdensome healthcare problem due to moisture loss and bacterial infection. Advanced hydrogel dressings can help to resolve these issues by assisting and accelerating regenerative processes such as cell migration and angiogenesis because of the similarities between their composition and structure with natural skin. In this study, we aimed to develop a keratin-based hydrogel dressing and investigate the impact of the delivery of LL-37 antimicrobial peptide using this hydrogel in treating full-thickness rat wounds. Therefore, oxidized (keratose) and reduced (kerateine) keratins were utilized to prepare 10% (w/v) hydrogels with different ratios of keratose and kerateine. The mechanical properties of these hydrogels with compressive modulus of 6-32 kPa and tan δ <1 render them suitable for wound healing applications. Also, sustained release of LL-37 from the keratin hydrogel was achieved, which can lead to superior wound healing. In vitro studies confirmed that LL-37 containing 25:75% of keratose/kerateine (L-KO25:KN75) would result in significant fibroblast proliferation (∼85% on day 7), adhesion (∼90 cells/HPF), and migration (73% scratch closure after 12 h and complete closure after 24 h). Also, L-KO25:KN75 is capable of eradicating both Gram-negative and Gram-positive bacteria after 18 h. According to in vivo assessment of L-KO25:KN75, wound closure at day 21 was >98% and microvessel density (>30 vessels/HPF at day 14) was significantly superior in comparison to other treatment groups. The mRNA expression of VEGF and IL-6 was also increased in the L-KO25:KN75-treated group and contributed to proper wound healing. Therefore, the LL-37-containing keratin hydrogel ameliorated wound closure, and also angiogenesis was enhanced as a result of LL-37 delivery. These results suggested that the L-KO25:KN75 hydrogel could be a sustainable substitute for skin tissue regeneration in medical applications.

Assessment of mesenchymal stem cell effect on foreign body response induced by intraperitoneally implanted alginate spheres.

Foreign body response to implanted hydrogels and consequently fibrotic overgrowth on implanted spheres will decrease in vivo performance of these biomaterials. Considering the previous reports related to the immune-privileged properties of mesenchymal stem cells (MSCs), we hypothesized that encapsulated human placenta-derived MSCs (HP-MSCs) will mitigate the foreign body response against alginate hydrogels. The HP-MSC-laden alginate hydrogel was cross-linked with a CaCl2 solution. Morphological and mechanical properties of alginate spheres were determined by scanning electron microscopy imaging, degradation, and swelling tests. The HP-MSC-laden alginate spheres or cell-free spheres were implanted into the peritoneal cavity of BALB/c mice. After intraperitoneal implantation of spheres into BALB/c mice over a period of 14 days, capsules were recovered and precapsular fibrotic tissue on their surfaces was investigated. Assessment of encapsulated HP-MSC viability using acridine orange/propidium iodide staining revealed that foreign body response against cell-laden hydrogel results in fibrous overgrowth on spheres and consequently leads to the HP-MSC necrosis. In spite of immunomodulatory effects of MSCs, the introduction of spheres into the body induces foreign body response that affects the viability of immuno-isolated HP-MSCs during 14-day posttransplant period. The presence of HP-MSCs within alginate hydrogel could not reduce the fibrotic overgrowth on spheres compared with cell-free spheres. Therefore, there is an essential need for hydrogels that mitigate the foreign body response as a key challenge in the development of tissue engineering and drug delivery technologies.

In vivo assessment of a nanofibrous silk tube as nerve guide for sciatic nerve regeneration.

A nanofibrous silk nerve conduit has been evaluated for its efficiency based on the promotion of peripheral nerve regeneration in rats. The designed tubes with or without Schwann cells were implanted into a 10 mm gap in the sciatic nerves of the rats. Four months after the surgery, the regenerated nerves were monitored and evaluated by macroscopic assessments and histology. The results demonstrated that the nanofibrous grafts, especially in the presence of Schwann cells, enabled reconstruction of the rat sciatic nerve trunk with a restoration of nerve continuity and formation of nerve fibres with myelination. Histological data demonstrated the presence of Schwann and glial cells in regenerated nerves. This study strongly supports the feasibility of using artificial nerve grafts for peripheral nerve regeneration by bridging large defects in a rat model.