Nonsurgical Induction of Alopecia Areata in C3H/HeJ Mice via Adoptive Transfer of Cultured Lymphoid Cells

Innovative strategies for the discovery of new drugs against alopecia areata: taking aim at the immune system

INTRODUCTION

The autoimmune hair loss condition alopecia areata (AA) exacts a substantial psychological and socioeconomic toll on patients. Biotechnology companies, dermatology clinics, and research institutions are dedicated to understanding AA pathogenesis and developing new therapeutic approaches. Despite recent efforts, many knowledge gaps persist, and multiple treatment development avenues remain unexplored.

AREAS COVERED

This review summarizes key AA disease mechanisms, current therapeutic methods, and emerging treatments, including Janus Kinase (JAK) inhibitors. The authors determine that innovative drug discovery strategies for AA are still needed due to continued unmet medical needs and the limited efficacy of current and emerging therapeutics. For prospective AA treatment developers, the authors identify the pre-clinical disease models available, their advantages, and limitations. Further, they outline treatment development opportunities that remain largely unmapped.

EXPERT OPINION

While recent advancements in AA therapeutics are promising, challenges remain, including the lack of consistent treatment efficacy, long-term use and safety issues, drug costs, and patient compliance. Future drug development research should focus on patient stratification utilizing robust biomarkers of AA disease activity and improved quantification of treatment response. Investigating superior modes of drug application and developing combination therapies may further improve outcomes. Spirited innovation will be needed to advance more effective treatments for AA.

CXCL12 Neutralizing Antibody Promotes Hair Growth in Androgenic Alopecia and Alopecia Areata

We had previously investigated the expression and functional role of C-X-C Motif Chemokine Ligand 12 (CXCL12) during the hair cycle progression. CXCL12 was highly expressed in stromal cells such as dermal fibroblasts (DFs) and inhibition of CXCL12 increased hair growth. Therefore, we further investigated whether a CXCL12 neutralizing antibody (αCXCL12) is effective for androgenic alopecia (AGA) and alopecia areata (AA) and studied the underlying molecular mechanism for treating these diseases. In the AGA model, CXCL12 is highly expressed in DFs. Subcutaneous (s.c.) injection of αCXCL12 significantly induced hair growth in AGA mice, and treatment with αCXCL12 attenuated the androgen-induced hair damage in hair organ culture. Androgens increased the secretion of CXCL12 from DFs through the androgen receptor (AR). Secreted CXCL12 from DFs increased the expression of the AR and C-X-C Motif Chemokine Receptor 4 (CXCR4) in dermal papilla cells (DPCs), which induced hair loss in AGA. Likewise, CXCL12 expression is increased in AA mice, while s.c. injection of αCXCL12 significantly inhibited hair loss in AA mice and reduced the number of CD8+, MHC-I+, and MHC-II+ cells in the skin. In addition, injection of αCXCL12 also prevented the onset of AA and reduced the number of CD8+ cells. Interferon-γ (IFNγ) treatment increased the secretion of CXCL12 from DFs through the signal transducer and activator of transcription 3 (STAT3) pathway, and αCXCL12 treatment protected the hair follicle from IFNγ in hair organ culture. Collectively, these results indicate that CXCL12 is involved in the progression of AGA and AA and antibody therapy for CXCL12 is promising for hair loss treatment.

Functional interrogation of lymphocyte subsets in alopecia areata using single-cell RNA sequencing

Alopecia areata (AA) is among the most prevalent autoimmune diseases, but the development of innovative therapeutic strategies has lagged due to an incomplete understanding of the immunological underpinnings of disease. Here, we performed single-cell RNA sequencing (scRNAseq) of skin-infiltrating immune cells from the graft-induced C3H/HeJ mouse model of AA, coupled with antibody-based depletion to interrogate the functional role of specific cell types in AA in vivo. Since AA is predominantly T cell-mediated, we focused on dissecting lymphocyte function in AA. Both our scRNAseq and functional studies established CD8+ T cells as the primary disease-driving cell type in AA. Only the depletion of CD8+ T cells, but not CD4+ T cells, NK, B, or γδ T cells, was sufficient to prevent and reverse AA. Selective depletion of regulatory T cells (Treg) showed that Treg are protective against AA in C3H/HeJ mice, suggesting that failure of Treg-mediated immunosuppression is not a major disease mechanism in AA. Focused analyses of CD8+ T cells revealed five subsets, whose heterogeneity is defined by an "effectorness gradient" of interrelated transcriptional states that culminate in increased effector function and tissue residency. scRNAseq of human AA skin showed that CD8+ T cells in human AA follow a similar trajectory, underscoring that shared mechanisms drive disease in both murine and human AA. Our study represents a comprehensive, systematic interrogation of lymphocyte heterogeneity in AA and uncovers a novel framework for AA-associated CD8+ T cells with implications for the design of future therapeutics.

Altered T cell subpopulations and serum anti-TYRP2 and tyrosinase antibodies in the acute and chronic phase of alopecia areata in the C3H/HeJ mouse model

BACKGROUND

C3H/HeJ mouse models progress gradually in hair loss from acute to chronic phase and reflect the symptoms of patients with alopecia areata (AA). However, the underlying pathological characteristics alteration associated with disease progression and autoantigens remain unclear.

OBJECTIVE

We aimed at elucidating the pathological differences between acute and chronic-AA in the C3H/HeJ mouse model.

METHODS

We analyzed populations of PBMCs, skin-draining lymph node (SDLN) cells, and cutaneous cells of AA mice using flow cytometry. The cytokine and chemokine expressions in the serum and skin were determined using multiplex assay and qPCR. The antibody serum levels were determined using ELISA and the antigen-specific T cells were detected using the MHC class I tetramer.

RESULTS

The CD8⁺NKG2D⁺ T and CD8⁺ T_EM cell percentage in the chronic-AA SDLNs or among the unaffected and acute-AA mice PBMCs increased. The Th1 and CD4⁺ T_EM cell percentage in the SDLNs and among PBMCs increased in the unaffected and AA mice. The percentage of CD8⁺ T_EM/T_RM cells and MHC class I expression increased in the lesions of acute-AA or the non-lesions and lesions of chronic-AA. The Th1 cells, dendritic cell-related cytokines, CD11c⁺ cells and MHC class II expression increased in the skin of AA mice. The antibody levels and TYRP2 and tyrosinase-specific CD8⁺ T cell percentages were upregulated in AA mice.

CONCLUSION

These results suggest that the CD8⁺ and CD4⁺ T cell subpopulations, cytokine and chemokine expressions differ between the disease phases. Moreover, TYRP2 and tyrosinase are potential autoreactive targets in the AA mouse model.

NLRP3 inflammasome activation contributes to development of alopecia areata in C3H/HeJ mice

Alopecia areata (AA) is an autoimmune non‐scarring hair loss disease. Recently, several reports have suggested that innate immune systems such as interferon‐α (IFN‐α)‐producing plasmacytoid dendritic cells and NOD‐like receptor family pyrin domain‐containing protein 3 (NLRP3) inflammasomes play a role in the pathogenesis of AA. However, critical studies about their involvement in the initiation of AA have not yet been reported. Therefore, we investigated the expression of innate immune cytokines in serum and skin, and examined the effect of a selective NLRP3 inhibitor, MCC950, on AA in C3H/HeJ mice, induced by transferring cultured skin‐draining lymph node cells. IFN‐α production was upregulated in lesions of AA‐affected mice, and interleukin‐1β in serum and skin was highly expressed before onset as well as postonset. Furthermore, MCC950 treatment prevented AA development and promoted hair growth in AA mouse models by reducing NLRP3 signalling and Th1/Tc1 chemokines and cytokines in the skin. These results suggest that NLRP3 inflammasome contributes to AA onset and chronicity, and NLRP3 inhibitor may be a potential therapeutic agent for AA.

Induction of alopecia areata in C3H/HeJ mice using cryopreserved lymphocytes

BACKGROUND

Alopecia areata (AA) is an autoimmune disease resulting in non-scarring hair loss. Animal models are useful means to identify candidates for therapeutic agents. The C3H/HeJ mouse AA model induced via transferring cultured lymphoid cells isolated from AA-affected mice is widely used for AA research. However, this conventional method requires the continuous breeding of AA mice.

OBJECTIVE

We aimed to establish a new method to generate AA model using the transfer of cryopreserved cells, which allows the rapid induction of a large number of AA mice when needed.

METHODS

We cryopreserved lymph node cells soon after isolation from AA-affected mice and injected thawed-cultured cells into recipient mice. H&E staining, immunohistochemical staining, quantitative real-time PCR and ELISA were conducted to identify pathological characteristics. Flow cytometry was performed to reveal the profile of transferred cells.

RESULTS

More than 90 % of recipient mice developed AA-like hair loss and showed inflammatory cell infiltration around anagen hair follicles, markedly increased mRNA expressions of interferon-γ, CXCL11, and granzyme B, and elevated interferon-α protein levels in the skin compared with naïve mice. Higher percentages of effector memory T cells and dendritic cells in transferred cells resulted in a higher incidence of AA.

CONCLUSION

This is the first report to establish a method for generating AA mice using cryopreserved lymphocytes. These AA mice have similar pathological characteristics to AA mice generated with the conventional method and AA patients. This convenient and reproducible method is expected to be valuable for AA study.