Increased hair growth and density following controlled expansion of guinea pig skin and soft tissue.

The goal of this study was to investigate the effect of controlled tissue expansion on hair growth and density using the guinea pig model. Thirty white guinea pigs were randomly divided into three groups: a group to undergo expansion (EXP), an operated control group (OC), and a nonoperated control group (NOC). All groups were shaved to create a 1 cm X 2 cm tuft of dorsal hair, which was subsequently dyed. Only the EXP and OC group members underwent construction of a pocket beneath the tuft. Only the EXP group was implanted and expanded over four weeks. The EXP group revealed a significant increase (p less than 0.005) over the controls in both the number of new white hairs produced (W) and density proportion (W/A). The OC group exhibited a significant increase (p less than 0.005) over the NOC group in both W and W/A. Mechanisms to explain the results are postulated. These include the possible roles of increased follicular mitotic activity (hair follicle transformation and cycle dynamics) and improved perifollicular vascularity (capsule formation and the delay phenomenon of skin pocket construction). Clinical implications are discussed.