Wound healing is the physiologic response to a disruption in normal skin architecture and requires both spatial and temporal coordination of multiple cell types and cytokines. This complex process is prone to dysregulation secondary to local and systemic factors such as ischemia and diabetes that frequently lead to chronic wounds. Chronic wounds such as diabetic foot ulcers are epidemic with great cost to the healthcare system as they heal poorly and recur frequently, creating an urgent need for new and advanced therapies. Stem cell therapy is emerging as a potential treatment for chronic wounds, and adult-derived stem cells are currently employed in several commercially available products; however, stem cell therapy is limited by the need for invasive harvesting techniques, immunogenicity, and limited cell survival in vivo. Induced pluripotent stem cells (iPSC) are an exciting cell type with enhanced therapeutic and translational potential. iPSC are derived from adult cells by in vitro induction of pluripotency, obviating the ethical dilemmas surrounding the use of embryonic stem cells; they are harvested non-invasively and can be transplanted autologously, reducing immune rejection; and iPSC are the only cell type capable of being differentiated into all of the cell types in healthy skin. This review focuses on the use of iPSC in animal models of wound healing including limb ischemia, as well as their limitations and methods aimed at improving iPSC safety profile in an effort to hasten translation to human studies.

Mannitol overuse-induced acute renal failure (ARF) has rarely been described. We report four cases, all male, between the ages of 20 and 42 years, who developed acute renal failure (3 anuric, 1 nonoliguric) after receiving mannitol 1,172 ± 439 g (mean ± SD) during a time period of 58 ± 28 h. The infusion rate was 0.25 ± 0.02 g/kg/h. The onset of acute renal failure was detected 48 ± 22 h after infusion. In 2 of the 3 cases in which urinary cytology was evaluated, the presence of vacuole-containing renal tubular cells was observed. All patients had hyponatremia (120 ± 11 mEq/l), and hyperosmolality (osmolar gap 70 ± 11 mosm/kg water). No other factors could be pointed to as causing acute renal failure. In the 3 anuric cases in which hemodialysis was performed, immediate recovery of diuresis was observed. Two patients recovered renal function on the fifth and sixth days, and 2 died due to endocranial hypertension – one of them while recovering – on the fourth and sixth days. In the present report, mannitol-induced ARF occurred at clustered doses of 0.25 mg/kg/h.

Objective: Arteriovenous fistulae (AVF) are the preferred vascular access for hemodialysis, but the primary success rate of AVF remains poor. Successful AVF maturation requires vascular wall thickening and outward remodeling. A key factor determining successful AVF maturation is inflammation that is characterized by accumulation of both T-cells and macrophages. We have previously shown that anti-inflammatory (M2) macrophages are critically important for vascular wall thickening during venous remodeling; therefore, regulation of macrophage accumulation may be an important mechanism promoting AVF maturation. Since CD4+ T-cells such as T-helper type 1 cells, T-helper type 2 cells, and regulatory T-cells can induce macrophage migration, proliferation, and polarization, we hypothesized that CD4+ T-cells regulate macrophage accumulation to promote AVF maturation. Approach and Results: In a mouse aortocaval fistula model, T-cells temporally precede macrophages in the remodeling AVF wall. CsA (cyclosporine A; 5 mg/kg, sq, daily) or vehicle (5% dimethyl sulfoxide) was administered to inhibit T-cell function during venous remodeling. CsA reduced the numbers of T-helper type 1 cells, T-helper type 2, and regulatory T-cells cells, as well as M1- and M2-macrophage accumulation in the wall of the remodeling fistula; these effects were associated with reduced vascular wall thickening and increased outward remodeling in wild-type mice. However, these effects were eliminated in nude mice, showing that the effects of CsA on macrophage accumulation and adaptive venous remodeling are T-cell-dependent. Conclusions: T-cells regulate macrophage accumulation in the maturing venous wall to control adaptive remodeling. Regulation of T-cells during AVF maturation may be a strategy that can improve AVF maturation.

Fibronectin (Fn) affects the interaction of polymorphonuclear leukocytes (PMNLs) with certain bacteria. Fn alone enhanced the response, in a chemiluminescence (CL) assay, of PMNLs to Staphylococcus aureus (P less than .05) and Staphylococcus epidermidis (P less than .01) but had no effect on type III, group B streptococci (GBS) or Escherichia coli. When GBS or E. coli were first preopsonized in antibody, Fn significantly enhanced the CL response of PMNLs (P less than .05). The intracellular metabolic inhibitor NaN3 but not the extracellular scavengers superoxide dismutase or human serum albumin inhibited Fn-enhanced CL; this fact suggests that enhancement of the respiratory burst by Fn is an intracellular event. We used an acridine orange-crystal violet monolayer assay to examine the effects of Fn on ingestion and intracellular killing of bacteria by PMNLs. Fn alone promoted uptake and killing of S. aureus (P less than .01) and S. epidermidis (P less than .05) by PMNLs but did not enhance monolayer phagocytosis of GBS or E. coli, unless these bacteria were preopsonized in antibody (P less than .01).

The mechanisms by which phlebotomy promotes the mobilization of hepatic iron stores are not well understood. NCOA4 (nuclear receptor coactivator 4) is a widely-expressed intracellular protein previously shown to mediate the autophagic degradation of ferritin. Here, we investigate a local requirement for NCOA4 in the regulation of hepatic iron stores and examine mechanisms of NCOA4 regulation. Hepatocyte-targeted Ncoa4 knockdown in non-phlebotomized mice had only modest effects on hepatic ferritin subunit levels and non-heme iron concentration. After phlebotomy, mice with hepatocyte-targeted Ncoa4 knockdown exhibited anemia and hypoferremia similar to control mice with intact Ncoa4 regulation, but showed a markedly impaired ability to lower hepatic ferritin subunit levels and hepatic non-heme iron concentration. This impaired hepatic response was observed even when dietary iron was limited. In both human and murine hepatoma cell lines, treatment with chemicals that stabilize hypoxia inducible factor (HIF), including desferrioxamine, cobalt chloride, and dimethyloxalylglycine, raised NCOA4 mRNA. This NCOA4 mRNA induction occurred within 3 hours, preceded a rise in NCOA4 protein, and was attenuated in the setting of dual HIF-1a and HIF-2a knockdown. In summary, we show for the first time that NCOA4 plays a local role in facilitating iron mobilization from the liver after blood loss and that HIF regulates NCOA4 expression in cells of hepatic origin. Because the prolyl hydroxylases that regulate HIF stability are oxygen and iron-dependent enzymes, our findings suggest a novel mechanism by which hypoxia and iron deficiency may modulate NCOA4 expression to impact iron homeostasis.