Lichen planopilaris: New Mechanisms of Disease

LPP is Associated with Changes in Stem Cells

A new study has given new insight into how a particular scarring alopecia known as LPP develops. There are many parts to the hair follicle. The 'bulge' is a specific region in the hair follicle that contains stem cells. It is well known that in scarring alopecias come about when so called "epithelial stem cells" in the bulge get destroyed by the body's immune system. 

What has puzzled researchers for some time is how scarring in scarring alopecias comes about. It is well known that simply destroying stem cells does not directly lead to scarring because that has been tested in other models. New research has now shown that epithelial stem cells undergo a change in hair follicles from patients with LPP and take on an entirely different morphology. In the world of science, this is called "epithelial to mesenchymal transition" or EMT. In lay terms, it's as though epithelial stem cells in the bulge taken on a brand new appearance.

The study showed that four specific steps are needed for this so called EMT to come about in LPP. The process of EMT appears driven by chemicals inside hair follicles known as TGF-beta, epidermal growth factor (EGF) and interferon-gamma.  In addition down regulation of a specific path known as E-cadherin was also necessary for EMT to occur.  TGF-beta is a well known inducer of scarring and so this opens up new understanding of pathways that could be relevant in LPP.

 

PPAR-gamma and Pioglitazone inhibit EMT

It was interesting in the study that one of the known treatments for LPP - pioglitazone - was able to reduce EMT in hair follicles. Pioglitazone is a drug that activates a pathway known as PPAR gamma and has been used in the past for treating LPP (rarely used now because of bladder cancer risks and unfortunately it does not maintain its beneficial effects on LPP long term). It appears therefore that a reduction in PPAR gamma pathway is relevant to EMT and more studies are needed to better understand the implications of this information.  

 

Reference

Imanishi et al. Epithelial-to-Mesenchymal Stem Cell Transition in a Human Organ: Lessons from

Lichen Planopilaris. Journal of Investigative Dermatology (2017). doi:10.1016/j.jid.2017.09.047

 


Dr. Jeff Donovan is a Canadian and US board certified dermatologist specializing exclusively in hair loss. To schedule a consultation, please call the Whistler office at 604.283.1887



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