Interleukins decrease epithelial protein and gene expression by K14 + CD105+ equine hoof progenitor cells

Progenitor cell epithelial to mesenchymal transition (EMT) could impact healing in the epidermal-dermal junction of the equine hoof stratum internum (SI). The hypothesis of this study was that K14 + CD105+ equine hoof SI progenitor cells assume a mesenchymal phenotype in the presence of inflammatory interleukins in vitro.

K14 + CD105+ progenitor cell percentages isolated from proliferative scarred (fibrous) and healthy SI were quantified. Decellularized matrix was prepared from and K14 + CD105+ cells localized in healthy SI. Gene expression (CD44, CD105, E-cadherin, N-cadherin, β-catenin, K1, K10, p63, TGF-β1, -β2, -β3) and E- and N-cadherin+ cell percentages were determined in continuously cultured cells. Revitalized K14 + CD105+ cells were cultured in stromal medium with or without interleukins 2 and 6 (IL medium) or on decellularized SI matrix in stromal medium. After 21 days, cell gene expression (K1, K10, p63, β-catenin, TGF-β1, -β2, -β3), E-cadherin + and K14 + cell percentages, and medium TGF-β1 levels were measured.

Most cells from healthy and fibrous SI were K14 + CD105+, and K14 and CD105 antigens were present on cells in situ and in vitro. K14 + CD105+ equine hoof SI progenitor cells maintained the immunophenotype over multiple cell passages in vitro. E-cadherin+ cell percentages were higher and K1 expression lower in K14 + CD105+ versus unsorted cells and more K14 + CD105+ cells were E- versus N-cadherin+. K14 + CD105+ cells cultured on matrix had the highest E-cadherin+ cell percentage and p63 and K10 gene expression. Cell TGF-β2 and β-catenin expression was highest with stromal medium, and cell TGFβ-1 and TGF β-3 expression was lowest with IL medium and on matrix, respectively. Cell TGF-β2, TGF-β3 and β-catenin expression was lower on matrix versus in stromal medium. Cells in IL medium had higher TGF-β3 expression than those on matrix. TGF- β1 levels were lower in IL versus stromal medium.

The cell genetic and antigen profiles suggest that inflammatory interleukins drive mesenchymal differentiation while healthy matrix supports epidermal differentiation. K14 + CD105+ progenitor cells from the SI epidermal-dermal niche provide a platform to elucidate progenitor cell EMT capabilities and restore normal tissue healing. These findings have important implications for improving treatment strategies for injuries and disease of the epidermal-dermal junction.