Anagen Phase of Hair Growth

Dr. Christiano Discovers JAK Inhibitors as Potential New Topical Treatment for Hair Loss

Dr. Angela Christiano and her team of researchers at Columbia University studying the autoimmune disease alopecia areata, have shed new light on how to move hair follicles from their resting stage (telogen) into the growth stage (anagen) in which they can produce normal hairs. The study, published in the October issue of Science Advances, introduces the possibility of a new topical medication for hair growth stemming from a class of chemicals that block enzymes in the Janus kinase (JAK) family. ((Harel S, Higgins CA, Cerise JE, Dai Z, Chen JC, Clynes R, Christiano AM. Pharmacologic inhibition of JAK-STAT signaling promotes hair growth. Sci Adv. 2015 Oct; 1(9): e1500973.)) The findings on the topical application of JAK inhibitors have implications in the treatment of common hair loss as well as alopecia areata, which causes a non-scarring form of localized hair loss.

Scientists had, until now, tried unsuccessfully to use drugs to induce follicles en masse into the anagen phase. The two FDA-approved medications currently used to treat hair loss each use a different approach. Finasteride (Propecia) blocks the conversion of testosterone to dihydrotestosterone (DHT) – the hormone that causes genetically susceptible hair follicles to progressively shrink or miniaturize. Minoxidil (Rogaine) extends the anagen phase, thereby delaying the onset of hair follicle miniaturization. JAK inhibitors could develop into a third major medical option for the treatment of hair loss.

Background: Research Investigating Alopecia Areata

Dr. Christiano, herself diagnosed with alopecia areata, has made several significant breakthroughs involving hair loss and its treatment in the past. Bernstein Medical has written extensively about her study of alopecia areata, hair loss genetics, and hair cloning.

Building on initial research in 1998 implicating a type of white blood cell known as “T lymphocytes” in the development of alopecia areata, ((Gilhar A, Ullmann Y, Berkutzki T, Assy B, Kalish RS. Autoimmune hair loss (alopecia areata) transferred by T lymphocytes to human scalp explants on SCID mice. J Clin Invest. 1998 Jan 1; 101(1):62-7.)) Dr. Christiano and her team set out to find ways to modulate them. In research published in the September 2014 issue of Nature Medicine, they looked at two different FDA-approved chemicals, ruxolitinib and tofacitinib, and how they act as inhibitors of enzymes in the family Janus kinase (JAK). Inhibiting JAK cut off communication to the T cells. Without an accumulation of T cells, alopecia areata could not progress. ((Xing L, Dai Z, Jabbari A, Cerise JE, Higgins CA, Gong W, de Jong A, Harel S, DeStefano GM, Rothman L, Singh P, Petukhova L, Mackay-Wiggan J, Christiano AM, Clynes R. Alopecia areata is driven by cytotoxic T lymphocytes and is reversed by JAK inhibition. Nat Med. 2014 Sep; 20(9):1043-9.)) The JAK inhibitors both prevented the onset of the disease, and reversed the condition where it was already established.

The most surprising finding of this study concerned the effect of topically applying the inhibitors.

“We found that topical ruxolitinib and topical tofacitinib were both highly effective in reversing disease in treated lesions (applied to back skin). A full coat of hair emerged in the ruxolitinib- or tofacitinib-treated mice by 7 weeks of treatment, and we observed complete hair regrowth within 12 weeks following topical therapy.”²

Findings: JAK Inhibitors and Hair Growth in Normal Subjects

Having successfully tested JAK inhibitors against alopecia areata, Dr. Christiano and her team sought to investigate JAK inhibition on normal mice and humans.

The researchers applied solutions of tofacitinib and ruxolitinib to one side of the backs of mice with hair in the telogen phase, while the other side was treated with a control solution. Within seven days of treatment, each mouse saw robust hair growth on the treated side, while the control side did not. This indicates a rapid transition of the hair cycle from telogen (resting) to anagen (growth). Furthermore, they found that treatment with JAK inhibitors resulted in “significant proliferation” of hair follicle stem cells, indicating that the inhibitors activated progenitor stem cells within the follicles. The topical application of JAK inhibitors in mice unmistakably resulted in rapid onset of hair growth.

Next, the team looked at the effects of JAK inhibitors on cultured dermal papilla (DP) spheres. In 2013, Dr. Christiano achieved a breakthrough in using an ingenious technique, called a “hanging drop culture.” Using this process, her team caused dermal papilla cells to clump together in a spherical (tear drop) shaped configuration. They found that DP cells in this three-dimensional mass more easily communicate with one another and are then capable of forming new hair follicles. When cultured in a solution containing the JAK inhibitor, tofacitnib, the DP spheres showed an enhanced ability to induce hair follicle development in larger sizes and in significantly greater numbers.

Conclusion/Summary

Topical application of JAK inhibitors leads to the activation and proliferation of hair follicle stem cells and a rapid transition to the anagen phase of the hair growth cycle. This research could be the catalyst for the development of a new topical treatment for hair loss that could potentially benefit individuals who are not indicated for, or who have not seen a positive response from, traditional hair loss medications or are not candidates for hair transplantation. Additionally, JAK inhibitors may be developed into a topical treatment for alopecia areata and potentially other autoimmune conditions that cause localized hair loss or other skin problems. JAK inhibitors might even aid in the development of hair cloning techniques, which could effectively cure hair loss.