Chronic wounds such as diabetic foot ulcers and venous leg ulcers are common problems in people suffering from type 2 diabetes. These can cause pain, and nerve damage, eventually leading to foot or leg amputation. These types of wounds are very difficult to treat and sometimes take months or even years to heal because of many possible complications during the process. Allogeneic skin grafting has been used to improve wound healing, but the majority of grafts do not survive several days after being implanted. We have been studying the behavior of fibroblasts and keratinocytes in engineered capillary-like endothelial networks. A dermo-epidermal graft has been implanted in an athymic nude mouse model to assess the integration with the host tissue as well as the wound healing process. To build these networks into a skin graft, a modified inkjet printer was used, which allowed the deposit of human microvascular endothelial cells. Neonatal human dermal fibroblast cells and neonatal human epidermal keratinocytes were manually mixed in the collagen matrix while endothelial cells printed. A full-thickness wound was created at the top of the back of athymic nude mice and the area was covered by the bilayered graft. Mice of the different groups were followed until completion of the specified experimental time line, at which time the animals were humanely euthanized and tissue samples were collected. Wound contraction improved by up to 10% when compared with the control groups. Histological analysis showed the neoskin having similar appearance to the normal skin. Both layers, dermis and epidermis, were present with thicknesses resembling normal skin. Immunohistochemistry analysis showed favorable results proving survival of the implanted cells, and confocal images showed the human cells' location in the samples that were collocated with the bilayer printed skin graft.

Staphylococcal enterotoxins (SEs) belong to a large group of bacterial exotoxins that cause severe immunopathologies, especially when delivered as an aerosol. SEs elicit the release of lethal amounts of cytokines by binding to major histocompatibility complex (MHC) class II and cross-linking susceptible T-cell receptors. Efforts to develop effective therapeutic strategies to protect against SEs delivered as an aerosol have been hampered by the lack of small animal models that consistently emulate human responses to these toxins. Here, we report that human leukocyte antigen-DQ8 (HLA-DQ8) transgenic (Tg) mice, but not littermate controls, succumbed to lethal shock induced by SEB aerosols without potentiation. Substantial amounts of perivascular edema and inflammatory infiltrates were noted in the lungs of Tg mice, similar to the pathology observed in nonhuman primates exposed by aerosol to SEB. Furthermore, the observed pathologies and lethal shock correlated with an upsurge in proinflammatory cytokine mRNA gene expression in the lungs and spleens, as well as with marked increases in the levels of proinflammatory circulating cytokines in the Tg mice. Unlike the case for littermate controls, telemetric evaluation showed significant hypothermia in Tg mice exposed to lethal doses of SEB. Taken together, these results show that this murine model will allow for the examination of therapeutics and vaccines developed specifically against SEB aerosol exposure and possibly other bacterial superantigens in the context of human MHC class II receptors.Staphylococcus aureus and group A streptococci are responsible for a wide range of mild to life-threatening infections, including scarlet fever, pharyngitis, dermatitis, infectious arthritis, and toxic shock syndrome (2, 13, 18, 25, 31). These pathogenic bacteria use several virulence mechanisms to enhance their toxicity after infection, including the M protein, diffusible enzymes (e.g., DNase), and streptolysin. Furthermore, many strains of S. aureus produce bacterial superantigens (BSAgs), which exert a series of critical, negative immunological effects on the host. Specifically, BSAgs bind to major histocompatibility complex (MHC) class II molecules and form a ternary complex with receptive variable ␤ chains of T-cell antigen receptors. After binding, BSAg-stimulated T cells are eliminated by a Fas/Fas-ligand-mediated apoptosis or, alternatively, enter a state of specific nonresponsiveness (anergy), which may last for several months. Furthermore, BSAgs may exacerbate subclinical viral infections by removing activated T cells from their normal role in clearing invasive organisms.Mice are naturally insensitive to BSAg-induced lethal shock (23,24,32). In order to overcome the natural insensitivity of mice to staphylococcal enterotoxins (SEs), sublethal amounts of lipopolysaccharide (LPS) have been used to potentiate the lethal effects of BSAgs (7,32). Although the exact mechanism of LPS induction is not known, it has been shown that lethality is dependent on the expression of mo...

The findings in this study demonstrate that vascularized tissue flaps in the form of muscle or nonmuscle flaps provide viable options for wound coverage of osteomyelitis defects following adequate surgical debridement.