P4.42 VARIABLE EXPRESSION OF WOUND-HEALING MARKERS IN MATCHED SETS OF INTERFOLLICULAR AND FOLLICULAR FIBROBLAST SUBTYPES IN VITRO

Ros Karoo ^{1, 2}, S Kauser¹, WL Lam^{1, 2}, JM Rawlings^{1, 2}, DT Sharpe², DJ Tobin¹

Dept. of Biomedical Sciences, University of Bradford, West Yorkshire, England; Plastic Surgery and Burns Unit, University of Bradford, West Yorkshire, England

Animal studies indicate that wounds heal faster, with greater contraction and with less scar formation in furred animals than in hair-sparse human skin. However, human scalp is a valuable donor site for repeated split-skin grafts. Phenotypically-distinct fibroblast subtypes exist in skin and include interfollicular dermal fibroblasts (DF), follicular dermal papilla (DP) and dermal sheath fibroblasts (DS). Given their relatively high numbers in densely-haired skin, both DS and DP fibroblasts may participate in wound healing. “Wound fibroblasts” express smooth muscle cytoskeletal markers, including the contractile protein a-smooth muscle actin (a-SMA), and both secrete and respond to wound-healing associated cytokines [e.g. platelet derived growth factor (PDGF) and transforming growth factor b (TGFb)]. Whether DF, DP and DS fibroblasts differ in their expression of receptors for wound-healing cytokines is not known.

We isolated and cultured, as matched sets, DF, DP and DS fibroblasts from 3 normal healthy individuals and examined their expression of a-SMA, PDGFR-B, and TGFbRI and RII. Marker expression was assessed as both the mean % of positive-staining cells per field of 50 cells, and mean relative staining intensity per positive cells by densitometry.

The incidence of a-SMA expression was greatest in DS cells (77% of cells), followed by DF (48%) and DP cells (29%), while comparison of relative expression levels in a-SMA-positive cells revealed that DF and DS cells expressed similar levels of a-SMA/cell, significantly higher than in DP cells. By contrast, incidence of PDGFR-B was greatest in DP cells (76% of cells), followed by DF (55%) and DP cells (43%), though the expression level of this marker was similar for all fibroblast subtypes. No significant differences were detected in either incidence or expression level of TGFbRI between fibroblast subtypes, although DP cells were more commonly TGFbRI-positive (89%) than DF (78%). Lastly, both incidence and expression level of TGFb-RII were lower than for TGFb-RI, though the former was more commonly detected in DF and DS cells than in DP cells. This preliminary study reveals significant phenotypic heterogeneity among follicular skin fibroblasts that may reflect a greater contribution by DS cells to wound healing than by DP or DF cells.