VIP receptors are present in healthy hair follicles but downregulated in alopecia areata, and VIP treatment can prevent — but not fully reverse — the immune privilege collapse that triggers hair loss.
VIP receptors downregulated in AAHair follicles in alopecia areata lesions showed significantly reduced VIP receptor expression despite intact VIP nerve fibers — a potential therapeutic target
What the researchers found
This study provided the first evidence that VIP receptors (VPAC1 and VPAC2) are expressed in the epithelium of healthy human hair follicles at both gene and protein levels. In lesional hair bulbs of alopecia areata patients, VIP receptor protein expression was significantly downregulated, while VIP-positive nerve fibers remained present — suggesting a defect in receptor-mediated signaling rather than peptide supply.
In hair follicle organ culture, VIP treatment protected follicles from interferon-γ-induced immune privilege collapse but did not fully restore immune privilege once it had already collapsed. This indicates VIP acts as a preventive 'guardian' of hair follicle immune privilege rather than a restorative agent.
Why it matters
Alopecia areata affects millions of people worldwide and current treatments are limited. This study identifies a specific molecular defect — reduced VIP receptor signaling — in the disease process and demonstrates that the peptide VIP can guard against the immune attack that causes hair loss. This opens a new therapeutic avenue: delivering VIP or VIP receptor agonists to the scalp could potentially prevent disease progression.
How the study worked
VIP and VIP receptor expression were assessed in human scalp hair follicles from healthy volunteers and lesional skin from alopecia areata patients using gene expression analysis and immunohistochemistry. Hair follicle organ cultures were treated with VIP and/or interferon-γ to model immune privilege collapse and test VIP's protective effects. Key immune privilege markers were quantified by immunohistomorphometry.
What this study cannot tell us
This was a pilot study using in vitro organ culture models, not a clinical trial. The sample sizes for both healthy and alopecia areata tissue were limited. VIP could protect but not fully restore immune privilege, which may limit its therapeutic window. The route and formulation for delivering VIP therapeutically to hair follicles were not addressed.
How to read the evidence
This is a pilot in vitro study using human tissue organ culture. It provides strong mechanistic evidence for VIP's role in hair follicle immune privilege, but the findings have not been tested in a clinical setting with alopecia areata patients.
When this study was published
Published in 2016, this study predates the JAK inhibitor era in alopecia areata treatment. The VIP-based therapeutic approach it proposes has not yet advanced to clinical trials, but the underlying biology remains relevant to current research.
The bigger picture
This study sits at the intersection of neuroimmunology and dermatology. Hair follicle immune privilege is maintained partly by neuropeptides released from local nerve endings, and its collapse is the triggering event in alopecia areata. Identifying VIP as a key guardian of this privilege connects the nervous system directly to autoimmune hair loss, a concept that could extend to other immune-privileged tissues like the eye and placenta.
Questions still open
- Can topical or intradermal VIP delivery prevent alopecia areata progression in clinical patients?
- Why are VIP receptors downregulated in alopecia areata lesions while VIP-producing nerve fibers remain intact?
- Would combining VIP with existing alopecia areata treatments (JAK inhibitors) provide synergistic benefit by addressing immune privilege from two different angles?
Common questions
What is hair follicle immune privilege and why does it matter in alopecia areata?
Could VIP be used as a treatment for hair loss?
Read the original research
Vasoactive intestinal peptide, whose receptor-mediated signalling may be defective in alopecia areata, provides protection from hair follicle immune privilege collapse.
The British journal of dermatology, 175(3), 531-41
Citation
Bertolini, M; Pretzlaff, M; Sulk, M; Bähr, M; Gherardini, J; Uchida, Y; Reibelt, M; Kinori, M; Rossi, A; Bíró, T; Paus, R. (2016). Vasoactive intestinal peptide, whose receptor-mediated signalling may be defective in alopecia areata, provides protection from hair follicle immune privilege collapse.. The British journal of dermatology, 175(3), 531-41. https://doi.org/10.1111/bjd.14645