Assessment of replication rates of human keratinocytes in engineered skin substitutes grafted to athymic mice

Stable closure of skin wounds with engineered skin substitutes (ESS) requires indefinite mitotic capacity to generate the epidermis. To evaluate whether keratinocytes in ESS exhibit the stem cell phenotype of label retention, ESS (n = 6–9/group) were pulsed with 5‐bromo‐2'‐deoxyuridine (BrdU) in vitro, and after grafting to athymic mice (n = 3–6/group). Pulse and immediate chase in vitro labeled virtually all basal keratinocytes at day 8, with label uptake decreasing until day 22. Label retention in serial chase decreased more rapidly from day 8 to day 22, with a reorganization of BrdU‐positive cells into clusters. Similarly, serial chase of labeled basal keratinocytes in vivo decreased sharply from day 20 to day 48 after grafting. Label uptake was assessed by immediate chases of basal keratinocytes, and decreased gradually to day 126, while total labeled cells remained relatively unchanged. These results demonstrate differential rates of label uptake and retention in basal keratinocytes of ESS in vitro and in vivo, and a proliferative phenotype with potential for long‐term replication in the absence of hair follicles. Regulation of a proliferative phenotype in keratinocytes of ESS may improve the biological homology of tissue‐engineered skin to natural skin, and contribute to more rapid and stable wound healing.     

A manganese-porphyrin complex decomposes H(2)O(2), inhibits apoptosis, and acts as a radiation mitigator in vivo

Ionizing radiation triggers mitochondrial overproduction of H(2)O(2) with concomitant induction of intrinsic apoptosis, whereby clearance of H(2)O(2) upon overexpression of mitochondrial catalase increases radioresistance in vitro and in vivo. As an alternative to gene therapy, we tested the potential of Mn((III))-porphyrin complexes to clear mitochondrial H(2)O(2). We report that triphenyl-[(2E)-2-[4-[(1Z,4Z,9Z,15Z)-10,15,20-tris(4-aminophenyl)-21,23-dihydroporphyrin-5-yl]phenyl]iminoethyl]phosphonium-Mn((III)) compartmentalizes preferentially into mitochondria of mouse embryonic cells, reacts with H(2)O(2), impedes γ-ray-induced mitochondrial apoptosis, and increases the survival of mice exposed to whole body irradiation with γ-rays.     

What Steps to Take? How to Approach Concerning Anxiety in Youth

Anxiety in youth is a concern, and stepped care provides appropriate services for differential levels of distress and increases the number of youth able to receive services. Youth, and families, with mild anxiety benefit from print and Internet resources. Youth whose anxiety persists can receive direct guidance (e.g., computer‐assisted programs). A third step increases the intensity of services (e.g., therapy). Finally, for severely problematic anxiety, intensive programs may be needed. Throughout, it is important to monitor anxiety and related impairment as well as to take into account client and family characteristics. Research on interventions within each step has identified many to be efficacious, but studies are needed to examine the decision‐making features as well as the effectiveness of a stepped care approach.