Pulling Force Deforms Hair Follicle Root Sheath Nuclei and Surrounding Dermal Collagen Matrix Differently at Infundibulum, Isthmus, and Suprabulbar Regions

The study investigated how different regions of hair follicles respond to mechanical pulling forces, focusing on the deformation of nuclei in the root sheath and changes in the surrounding dermal collagen matrix. Using nuclear dimensions as indicators, it was found that the isthmus region's nuclei were most affected, showing significant compression in keratin-14 and involucrin-positive cell layers. In contrast, the infundibulum and suprabulbar regions exhibited more variable responses. The deformation did not correlate with lamin A/C expression. Additionally, collagen fibrils in the dermal matrix showed distinct changes, being compressed near the upper suprabulbar follicle and pulled apart near the infundibulum. These findings highlighted that responses to mechanical force are region-specific within the follicle, with permanent and cycling parts behaving differently.