1464 The effects of decreased sensory innervation and substance P on wound healing and stem cell division fate

Neuropeptides improve wound healing, but little is known about how they affect stem cells (SC), committed progenitors (CP), and relevant signaling pathways to increase proliferation. Mice with Capsaicin-induced decreased sensory innervation (DSI) were treated with Substance P (SP). 6mm wounds were analyzed at 4 days post- wounding (in the most proliferative phase of healing). Keratinocyte division analysis was studied using Numb and keratin 1 expression. In Capsaicin vs. vehicle treated mice, wound healing was delayed, (24.8±0.3 days vs. 14.5±0.3 days (n= 8,P<.0001), as previously shown. SP vs. vehicle improved wound healing in mice with DSI (18.8±0.3d vs. 24.0±0.3d, n=8, P<.0001). In vitro, division fate of normal keratinocytes obtained post-wounding showed increases in both asymmetric SC self-renewal (ASR) 3.3±0.11 vs 2.1±0.13 (P=0.01) and symmetric self-renewal (SSR) 0.7±0.07 vs 0.3 ±0.07 (P=0.02), with no change in the proportions of ASR/SSR and with no evidence of a CP response. The wound healing response for epidermis with DSI vs. normal epidermis was associated with a decrease in all division fates: ASR 1.4±0.9 vs. 2.3±0.12 (P=0.0002), SSR 0.45±0.06 vs. 0.68±0.14 (P=0.15), symmetric differentiation (SD): 4.7±0.16 vs. 6.3±0.6 (P=0.03). SP treatment of wounds with DSI was associated with an increase in ASR and SD, with no detected change in SSR (ASR: 2.11±0.02 vs. 1.35±0.12, P= 0.0007, SD: 6.68±0.22 vs. 4.96±0.26, P=0.0023, n=4). Thus, DSI results in decreased proliferation of SCs and CPs. Decreased CP proliferation may be a direct effect of DSI on CPs, or may be secondary to a reduction in their numbers due to the decreased ASR. Notably, SP effectively reversed both the delay in wound healing and decrease in ASR caused by DSI, indicating that SP is a key neuropeptide in neuropeptide-induced proliferation.