Evaluation of Copper and Hydrogen Peroxide Treatments on the Biology, Biomechanics, and Cytotoxicity of Decellularized Dermal Allografts.

Decellularized tissue allografts are paving the way as an alternative to cellular tissue transplantation. Effective sterilization or decontamination of tissue allografts is paramount for the safety of the allograft; however, some of the current sterilization procedures have a detrimental effect on the tissue scaffold. The bactericidal and virucidal activity of copper (II) ions and hydrogen peroxide (H2O2) have been widely reported, however, their effect on the biology, biochemistry, and biocompatibility of decellularized tissue have yet to be elucidated. In this study, decellularized human dermis (dCELL human dermis) was treated with copper (II) chloride (CuCl2) and H2O2; both singly and in combination, and parameters, including concentration, pH, and synergy between CuCl2 and H2O2, were evaluated to identify conditions where any detrimental effects on the tissue scaffold were observed. Skin from 13 human donors was retrieved with appropriate consent and processed into dCELL human dermis. The dCELL human dermis was then treated for 3 h with 0.1 mg/L-1 g/L (w/v) CuCl2 and 0.01-7.5% (v/v) H2O2 and combinations of both of these in the same concentration range. dCELL human dermis treated with solutions of 0.1 mg/L-1 g/L CuCl2 or 0.01-7.5% H2O2 caused no detrimental effects on gross histology, collagen denaturation, collagen orientation, and biomechanical properties of the tissue or cytotoxicity. The highest combined concentration of CuCl2 and H2O2 demonstrated an increase in ultimate tensile strength, loss of collagen type IV immunostaining at the dermal-epidermal junction, and in vitro cytotoxicity. Combinations within the range of up to 10 mg/L CuCl2 with up to 0.5% H2O2 had no effect. The data identify the concentrations of CuCl2 and H2O2 solutions that have no effect on the biological, biomechanical, and biochemical properties of dCELL human dermis, while retaining biocompatibility. These treatments may be suitable for use as sterilization/decontamination agents on human decellularized tissues.

Experimental stroke-induced changes in the bone marrow reveal complex regulation of leukocyte responses.

Stroke induces a systemic response that involves rapid activation of inflammatory cascades, followed later by immunodepression. Experimental stroke-induced responses in the bone marrow, which is the primary source of circulating monocytes and granulocytes, have not been investigated previously. We show that cerebral ischaemia induced early (4 hours) release of CXCR2-positive granulocytes from the bone marrow, which was associated with rapid systemic upregulation of CXCL1 (a ligand for CXCR2) and granulocyte-colony-stimulating factor, a key cytokine involved in the mobilisation of bone marrow leukocytes. This process involves rapid activation of nuclear factor-κB and p38 mitogen-activated protein kinase in bone marrow myeloid cells. T-cell numbers in the bone marrow increased after stroke, and bone marrow cells did not show suppressed cytokine response to bacterial endotoxin stimulation in vitro. Stroke-induced laterality observed in the brain stem and in the bone marrow indicates direct involvement of the autonomic nervous system in stroke-induced cell mobilisation. We also show that systemic inflammatory changes and leukocyte responses in the bone marrow are profoundly affected by both anaesthetic and surgical stress. We conclude that stroke influences leukocyte responses in the bone marrow through multiple mechanisms and suggest that preclinical studies should take into consideration the effect of surgical manipulation in experimental models of stroke.