Effects of poly-N-acetyl glucosamine (pGlcNAc) patch on wound healing in db/db mouse.

BACKGROUND: Poly-N-acetyl glucosamine (pGlcNAc) nanofiber-based materials, produced by a marine microalga, have been characterized as effective hemostatic agents. In this study, we hypothesized that a pGlcNAc fiber patch may enhance wound healing in the db/db mouse. METHODS: pGlcNAc patches were applied on 1-cm, full-thickness, skin wounds in the db/db mouse model. Wounds (n = 15 per group) were dressed with a pGlcNAc nanofiber patch for 1 hour, 24 hours, or left untreated. After the application time, patches were removed and wounds were allowed to heal spontaneously. The rate of wound closure was evaluated by digital analysis of unclosed wound area as a function of time. At day 10, wounds (n = 7 per group) were harvested and quantified with immunohistochemical markers of proliferation (Ki-67) and vascularization (platelet endothelial cell adhesion molecule). RESULTS: Wounds dressed with pGlcNAc patches for 1 hour closed faster than control wounds, reaching 90% closure in 16.6 days, 9 days faster than untreated wounds. Granulation tissue showed higher levels of proliferation and vascularization after 1-hour treatment than the 24-hour and left-untreated groups. Foreign body reaction to the material was not noted in applications up to 24 hours. DISCUSSION: In addition to its hemostatic properties, the pGlcNAc material also appears to accelerate wound closure in healing-impaired genetically diabetic mice. This material, with its combination of hemostatic and wound healing properties, has the potential to be effective agent for the treatment of complicated wounds.

Tensile forces stimulate vascular remodeling and epidermal cell proliferation in living skin.

OBJECTIVES: To quantify tissue remodeling induced by static and cyclical application of tensional forces in a living perfused tissue. BACKGROUND: Cells are able to respond to mechanical cues from the environment and can switch between proliferation and quiescence. However, the effects of different regimens of tension on living, perfused skin have not been characterized. METHODS: The ears of living rats were mechanically loaded by applying tensile forces (0.5 Newtons) either statically or cyclically and then analyzing tissue responses using in vivo microscopy, immunohistochemistry, and corrosion casting. RESULTS: Quantitative immunohistochemistry showed that in the static group (4-day continuous tension) there was up to 4-fold increase in cellular proliferation in the epidermis after 4 days and a 2.8-fold increase in the vascularity in the dermis that peaked after 2 days. Comparable effects could be achieved in just 8 hours using a cyclic loading protocol. We also modeled the resultant stress produced in the ear using a linear finite element model and demonstrated a correlation between the level of applied stress and both epidermal cell proliferation and blood vessel density. CONCLUSIONS: Mechanical forces stimulate cell proliferation and vascular remodeling in living skin. As cell growth and vascular supply are critical to wound healing and tissue expansion, devices applying controlled mechanical loads to tissues may be a powerful therapy to treat tissue defects.