# CD133-positive dermal papilla cells are a major driver in promoting hair follicle formation

## TL;DR

CD133-positive dermal papilla cells are more effective at promoting hair follicle formation than their CD133-negative counterparts.

## Contribution

Identifies CD133+ dermal papilla cells as a key driver in hair follicle formation using a new transgenic mouse model.

## Key findings

- CD133+ dermal papilla spheroids showed stronger alkaline phosphatase staining and higher expression of signature genes.
- Mice grafted with CD133+ spheroids grew more hairs in healed wounds compared to CD133− spheroids.
- Three-dimensional spheroid culture restored versican expression in both CD133+ and CD133− cells.

## Abstract

A major contributing factor to the failure of cell-based human hair follicle (HF) engineering is our inability to cultivate highly specialized, inductive mesenchymal fibroblasts, which reside in a unique niche at the HF base, called the dermal papilla (DP). We and other groups have discovered a unique DP fibroblast subpopulation that can be identified by the cell surface marker CD133. However, the biological difference between CD133-positive (CD133+) and CD133-negative (CD133−) DP cells remains unknown. Using a newly developed double fluorescent transgenic mouse strain, we isolated CD133 + and CD133− DP cells from mouse anagen HFs. In monolayer culture, both DP populations gradually lost expression of the anagen DP signature gene, versican. When maintained in three-dimensional spheroid culture, versican expression was restored in both CD133 + and CD133− DP cells. Importantly, CD133 + DP spheroids appeared more compact, showed stronger alkaline phosphatase staining (AP), and expressed higher levels of DP signature genes. In in vivo skin reconstitution assays, mice grafted with CD133 + DP spheroids grew more hairs in healed wounds than those grafted with CD133− DP spheroids. The data underscore the importance of CD133 + DP cells as a driver of HF formation, which may present a unique opportunity to improve the use of human DP cells in tissue-engineered skin substitutes (TESS).