As a general rule, people care too much about their hair and too little about their blood vessels. One can live without hair. It is interesting to see both (a) just how much work goes into the regeneration of lost hair, and (b) just how little is known of the fine details by which the capacity to grow hair fades with age. It is this lack of knowledge that leads to the present state of uncertain and largely ineffective interventions for hair growth. No-one is entirely sure as to where the root of the problem lies, or where the most effective points of intervention might be. A great deal of exploration takes place, but success is all too much a matter of luck rather than design. With that in mind, the research materials here bridge a number of approaches to regeneration that are broadly used in the field: cell therapies, exosome therapies as a way of mimicking the effects of a cell therapy that primarily acts via cell signaling, and identification of specific signaling molecules that can change native cell behavior.

Hair growth depends on the health of dermal papillae (DP) cells, which regulate the hair follicle growth cycle. Current treatments for hair loss can be costly and ineffective, ranging from invasive surgery to chemical treatments that don’t produce the desired result. Recent hair loss research indicates that hair follicles don’t disappear where balding occurs, they just shrink. If DP cells could be replenished at those sites, the thinking goes, then the follicles might recover.

Researchers cultured DP cells both alone (2D) and in a 3D spheroid environment. A spheroid is a three-dimensional cellular structure that effectively recreates a cell’s natural microenvironment. In a mouse model of hair regeneration, the team looked at how quickly hair regrew on mice treated with 2D cultured DP cells, 3D spheroid-cultured DP cells in a keratin scaffolding, and the commercial hair loss treatment Minoxidil. In a 20-day trial, mice treated with the 3D DP cells had regained 90% of hair coverage at 15 days.

“The 3D cells in a keratin scaffold performed best, as the spheroid mimics the hair microenvironment and the keratin scaffold acts as an anchor to keep them at the site where they are needed. But we were also interested in how DP cells regulate the follicle growth process, so we looked at the exosomes, specifically, exosomal miRNAs from that microenvironment.” Exosomes are tiny sacs secreted by cells that play an important role in cell to cell communication. Those sacs contain miRNAs, small molecules that regulate gene expression. The team measured miRNAs in exosomes derived from both 3D and 2D DP cells. In the 3D DP cell-derived exosomes, they pinpointed miR-218-5p, a miRNA that enhances the molecular pathway responsible for promoting hair follicle growth. They found that increasing miR-218-5p promoted hair follicle growth, while inhibiting it caused the follicles to lose function.