During the hair follicle cycle significant epigenetic changes occur in the follicle epithelium, but much less is known about events in the mesenchyme. This study focuses on epigenetic processes potentially undergone by dermal papilla (DP) cells, in two different scenarios: in vivo, over the course of the hair follicle cycle, and in response to their transition to bidimensional in vitro primary culture. As indicators of chromatin remodelling processes, several histone methylation markers, as well as the histone-binding protein CBX5, were analysed by immunofluorescence, together with a number of other markers of cell identity, nuclear architecture, polarity and migration status. Mouse and rat vibrissa follicles, were either cryosectioned for the in vivo analyses or microdissected for DP isolation. The latter were plated onto cover glasses and cultured as explants. Mouse cornea stromal tissue was obtained by enzymatically separating this layer from the overlying epithelium, and grown in explant culture as a comparative mesenchymal cell population.
Our main results indicate a variation in the histone methylation levels in DP cells depending on the stage of the hair follicle cycle. Thus, higher methylation levels were detected in anagen (growing) than in telogen (resting) phase for all the markers analysed (H4K20me2,3; H3K9me3; H3K27me3; H3K4me3). However, during the transition from in vivo to in vitro culture, we found a drastic difference in the pattern of expression of heterochromatin vs. euchromatin related markers in DP explants. Moreover, the heterochromatin related CBX5 protein had a characteristic pattern of expression in DP compared to cornea stroma explant cultures, suggesting distinctive features of DP cells. These observations pose the question of whether these chromatin remodelling processes have functional implications, both in the course of the hair follicle cycle in vivo, and/or modifying/reprogramming the inductive ability, self-renewal capacity and differentiation potential of DP cells in vitro?

Follicle dermal papilla cells undergo chromatin remodelling processes in vivo and in vitro