Manipulation of Outer Root Sheath Cell Survival Perturbs the Hair-Growth Cycle

The study demonstrated that overexpression of the anti-apoptotic gene bcl-xL in transgenic mice led to shorter hair due to alterations in the hair-growth cycle, specifically a shortened anagen phase and prolonged telogen phase. This was linked to increased survival of outer root sheath (ORS) cells, which produce fibroblast growth factor-5 (FGF-5), a factor that inhibits precursor cell division during anagen. The short hair phenotype was largely reversed in FGF-5-deficient mice, indicating that ORS cell survival and growth inhibitory factors like FGF-5 play a crucial role in regulating the hair-growth cycle.