Investigation of hub genes and immune infiltration in androgenetic alopecia using bioinformatics analysis.

Original Article Page 1 of 13 Investigation of hub genes and immune infiltration in androgenetic alopecia using bioinformatics analysis Yuan Zhou1#, Zhongbo Huang2#, Chen Wang1, Jinping Su1, Ping Jiang1, Lili Li1, Jinglin Qin1, Zhi Xie1 1 Department of Dermatology, The People’s Hospital of Guangxi Zhuang Autonomous Region, Nanning, China; 2Department of Laboratory Medicine, The People’s Hospital of Guangxi Zhuang Autonomous Region, Nanning, China Contributions: (I) Conception and design: Y Zhou, Z Huang; (II) Administrative support: X Zhi; (III) Provision of study materials or patients: C Wang, J Su; (IV) Collection and assembly of data: Y Zhou; (V) Data analysis and interpretation: Y Zhou, Z Huang; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors. # These authors contributed equally to this work. Correspondence to: Zhi Xie. The People’s Hospital of Guangxi Zhuang Autonomous Region, 6 Taoyuan Road, Nanning 530021, China. Email: . Background: Androgenetic alopecia (AGA) is a type of non-scarring hair loss. Current drugs for AGA are accompanied by adverse reactions and a high recurrence rate. Thus, the discovery of diagnostic biomarkers and therapeutic targets for AGA remains imperatively warranted. Methods: The GSE90594 dataset, which contained scalp skin biopsies from 14 male AGA cases and healthy volunteers, was used to identify the differentially expressed genes (DEGs). Functional enrichment analysis was subsequently performed. Next, the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database combined with the cytoHubba plugin of Cytoscape were used to obtain the key genes of AGA. Thereafter, the Cell-type Identification by Estimating Relative Subsets of RNA Transcripts (CIBERSORT) algorithm was performed to evaluate the relative abundance of immune cells between male AGA patients and healthy controls. The correlation between key genes and infiltrating immune cells was analyzed to obtain the significant immune-cell related genes (IRGs), then intersected with the DEGs between immortalized balding and non-balding human dermal papilla cells (DPCs) of the GSE93766 dataset as well as the DEGs obtained by the GSE90594 dataset, thus obtaining the hub genes of AGA. Finally, the hub genes were validated using GSE36169, which contained expression profiling of tissues biopsied from haired and bald scalps of five individuals with AGA. Results: A total of 234 DEGs were obtained from the GSE90594 dataset, which were mainly enriched in the extracellular matrix (ECM)-related pathways and immune-related activities. The STRING database and ten algorithms in the cytoHubba plugin of Cytoscape disclosed 21 key DEGs. The results of the CIBERSORT algorithm revealed the relative abundances of 20 kinds of immune cells between diseased and healthy individuals, and yielded 15 IRGs involved in the pathogenesis of AGA. Next, the intersection analysis identified four hub genes of AGA, comprising COL1A2, PCOLCE, ITGAX, and LOX. The GSE36169 dataset validated the expression pattern of hub genes in the haired scalp of AGA patients. Conclusions: We discovered that the hub genes identified are closely linked with the causative factors of AGA, which could be used as the viable diagnostic and therapeutic target in the clinical applications. Keywords: Androgenetic alopecia (AGA); immune cells infiltration; diagnostic biomarker; human dermal papilla cells; hair follicle (HF) Submitted Aug 30, 2022. Accepted for publication Nov 07, 2022. doi: 10.21037/atm-22-4634 View this article at: https://dx.doi.org/10.21037/atm-22-4634 © Annals of Translational Medicine. All rights reserved. Ann Transl Med 2022;10(22):1226 | https://dx.doi.org/10.21037/atm-22-4634 Page 2 of 13 Introduction Androgenetic alopecia (AGA), also known as androgenic alopecia (1), is a type of non-scarring hair loss mainly characterized by a receding hairline on the forehead and sideburns, while the temporal and occipital areas remain unaffected, forming a characteristic “horseshoe” pattern (2), which is a intricated disorder with the interplay of genetic, mental, and environmental factors precipitating its onset (3). Intriguingly, the clinical manifestation of AGA is not identical in males and females, and the latter presents as top hair thinning and diffuse hair loss or a Christmas tree pattern (4). The prevalence of AGA varies by ethnicity and age (5), with a higher incidence in males than females (6). Despite taking a benign clinical course, the negative influence on the life quality of AGA patients is profoundly substantial (7), especially in psychological terms; it can be associated with depression, anxiety, and psychological illnesses (1,8), taking a considerable toll on individuals and societies. Currently, finasteride and minoxidil are the only two types of drugs approved by the US Food and Drug Administration (FDA) (9) for the management of AGA; however, certain drug reactions and a high recurrence rate limit the value of these drugs (10). Besides, despite the straightforward diagnostic approach of AGA in clinical settings, its characteristics of hair loss are sometimes similar to other types of disorders (e.g., telogen effluvium, alopecia areata) (11,12). Thus, diagnostic biomarkers and therapeutic targets for AGA remain in demand. Pathologically, the hair follicle (HF) takes the center stage in the initiation and progression of AGA, which manifests as shortening of the anagen phase and prolongation of the telogen phase, eventually contributing to miniaturization and progressive hair loss (13,14). Notably, HF has its own unique immune system (15), which ensures normal hair growth and plays a pivotal role in immune protection (16,17), with compelling evidence of in vivo data elucidating that immune cells function as an activator for hair follicle stem cells (HFSCs) and the telogen-to-anagen transition of HF (16,18,19). Besides the immune component, HFSCs are also essential parts of the local environment that participate in the cycle of hair regeneration which remain quiescent and fail to differentiate into HF precursors in the alopecia region of AGA (20). Previous research elucidated the intricate and dynamic interplay among various components of the local environment of HF, thus affording an opportunity to overcome the lack of major breakthroughs against AGA. © Annals of Translational Medicine. All rights reserved. Zhou et al. Hub gene identification of androgenetic alopecia In the work presented here, the GSE90594 dataset, which contains scalp skin vertex biopsies from 14 cases of male AGA and healthy volunteers, was used to investigate the expression patterns of AGA, thereby identifying the differentially expressed genes (DEGs). Functional enrichment analysis was subsequently performed to reveal the biological functions and related pathways of the DEGs. Next, a protein-protein interaction (PPI) network was constructed using the Search Tool for the Retrieva (...truncated)