Next, they acquired follicles from a hair transplant clinic and transplanted them onto mice. Normally, these follicles go dormant for a couple of months after transplantation. However, Plikus suspected that osteopontin could accelerate the reactivation of the transplanted follicles. After grafting, some mice were injected with osteopontin thirty days later. Twenty days after the injections, only those mice had sprouted human hair.
The lab’s new paper has been well received, particularly regarding the findings on hair growth. Valerie Horsley, a cell biologist at Yale University, praised the study for identifying the follicle protein (CD44) that responds to osteopontin’s signal. Horsley believes that manipulating either the protein or osteopontin could aid in regrowing human hair and possibly inhibiting hair growth in unwanted areas.
Etienne Wang, a clinician-scientist specializing in hair at National Skin Centre Singapore, expressed excitement about the study and its implications for understanding hair growth. However, Wang cautioned against jumping to conclusions about its effectiveness on human scalps and the ability to regrow dense hair. He noted that most nevi only produce a few sparse hairs.
The study’s implications for cell senescence elicited mixed responses. Claire Higgins, an expert in human hair biology at Imperial College London, found Plikus’ case convincing and believed it challenged existing understandings of dormant cells. However, others, including Horsley, urged caution, highlighting the need for more evidence on how melanocytes affect their environment and the connection between osteopontin secretion and cell senescence.
Plikus acknowledged the bold nature of his hypothesis but referenced animal research that supports it. For instance, studies on zebrafish, mouse embryos, and regrowth in mouse livers and salamander limbs have shown that senescent cells release proteins that aid in healing. Plikus believes it’s possible that molecules from aged cells could promote hair growth.
Plikus’ startup, Amplifica, initiated human clinical trials of a proprietary version of osteopontin in June. The treatment involves microneedle injections into the scalp. Amplifica is also continuing preclinical studies of SCUBE3.
It remains uncertain whether the lab has uncovered a phenomenon common to aging tissues or if nevi are simply unique. Nevertheless, Higgins finds the research on hair growth fascinating and commends Plikus for his foresight in pursuing these observations.