Apocrine glands are bystanders in hidradenitis suppurativa and their involvement is gender specific.

Background: Apocrine glands have been long considered as the initial targeted skin compartment in hidradenitis suppurativa/acne inversa (HS).

Objective: Detection of apocrine gland involvement in HS.

Methods: Apocrine glands were isolated from skin biopsies of involved and uninvolved skin of HS patients (n = 16, females : males 1 : 1) by laser capture microscopy and studied by whole transcriptome profiling. Dysregulated genes were detected by comparing lesional and non-lesional skin obtained from female and male HS patients using the Agilent array platform.

Results: SULF1 was the only gene, whose expression levels were found upregulated in apocrine glands of HS lesions of the entire group. Further dysregulated genes associated with vascular functions (FGF1, IL17D and S100A9) were detected. Genes, which are characteristic for glandular epithelia, confirmed the glandular origin of the studied tissue. The gene upregulation profile of female apocrine glands included several genes (MRO, DYRK3, SDK2, GLB1L, CATSPERB and PRPS2), which are specifically transcribed during testis differentiation and/or regulated by androgens. Genes related to lipid metabolism (AGPAT3, GAL, ELOVL3, THRSP, DGAT2L3, OLAH, THRSP, FADS1, NR2F2, FADS2, PTGDS and HAO2) were mostly downregulated in the apocrine glands of male patients. The levels of RECK and PCSK5, which are upstream genes of metalloproteinase-9 and -1, and of S100A9, which encodes calgranulin B, were commonly increased in the apocrine glands of female and male patients, respectively, and in our previous whole skin study.

Conclusion: Our findings indicate that apocrine glands are bystanders in HS. Inflammatory signalling is not prominent but a gender-specific response was detected, which is mostly associated with androgen-responsive genes in females and alterations of lipid metabolism in males.