The potential role of circRNA_004229 in hair/epidermal regulation after MED1 ablation in keratinocytes

Screening of hair follicle telogen-associated circRNAs in sheep and construction of their ceRNA network

Sheep breeds with hair-shedding traits have many advantages over non-shedding sheep breeds, not only because of reduced shearing labor and feeding management costs but also because it reduces in vitro parasites and improves adaptability to summer heat stress. The wool of Dorper sheep naturally sheds in spring due to the periodic growth of hair follicles. CircRNAs primarily regulate the morphogenesis of hair follicles through the ceRNA mechanism. In this study, five 2-year-old Dorper ewes with extreme hair-shedding phenotype (S) and three Dorper ewes with non-shedding (N) phenotype were selected for subsequent analyses. For RNA extraction, skin tissues were collected on 27th September 2019 (S1, N1), 3rd January 2020 (S2, N2), and 17th March 2020 (S3, N3), which were then subjected to RNA-seq. RNA-seq technology revealed 20,185 novel circRNAs in the hair follicles of Dorper sheep. Among them, 1450 circRNAs were differentially expressed (DE). Clustering heatmap and expression pattern analyses were performed on DE circRNAs, which indicated 78 circRNAs with T pattern (Telogen, highly expressed in telogen), and the source genes for candidate circRNAs were further screened by functional enrichment analysis, which identified 13 crucial genes enriched in pathways associated with hair follicle development. Additionally, a ceRNA regulatory network comprising 4 circRNAs, 11 miRNAs, and 13 target genes was constructed. Overall, this study screened circRNAs that may be associated with the telogen phase of hair follicles in sheep, providing a relevant theoretical basis for wool shedding in sheep and for breeding Dorper sheep with automatic wool shedding.

CircAGK regulates high dihydrotestosterone-induced apoptosis in DPCs through the miR-3180-5p/BAX axis

The incidence of androgen alopecia (AGA), also known as seborrheic alopecia, has surged in recent years, and onset is occurring at younger ages. Dermal papilla cells (DPCs) are key to maintaining hair cycling, and apoptosis-driven processes in DPCs are closely related to hair follicle regeneration. Circular RNAs (circRNAs) are widely present in the human body and are closely related to the occurrence and development of many diseases. Currently, the biological functions of circRNAs in AGA are largely unknown. Whole-transcriptome sequencing was used to screen differential circRNA expression profiles between AGA patients and non-AGA patients. We found that hsa_circ_0002980 (circAGK) was significantly highly expressed in the AGA group. CircAGK promoted DPC apoptosis in the presence of high dihydrotestosterone (DHT) (15 nmol/L). By regulating the miR-3180-5p/BAX axis, circAGK promotes DPC apoptosis in a high DHT environment in vitro and inhibits hair growth in AGA mice in vivo, indicating that circAGK is a potential target for the clinical treatment of AGA.

Circ_PRKDC knockdown promotes skin wound healing by enhancing keratinocyte migration via miR-31/FBN1 axis

Circular RNA protein kinase, DNA-activated, catalytic subunit (circ_PRKDC) has been found to impede wound healing in diabetic foot ulcers via regulating keratinocyte proliferation and migration. However, the mechanisms underlying circ_PRKDC in skin wound healing remain unclear. The expression of circ_PRKDC, microRNA (miR)-31 and fibrillin 1 (FBN1) was detected using quantitative reverse transcription-polymerase chain reaction and Western blot assays. The migration ability and the changes of matrix metallopeptidase 9 (MMP-9) and MMP2 levels were determined using wound healing, transwell and Western blot assays. The interaction between miR-31 and circ_PRKDC or FBN1 was verified by dual-luciferase reporter assay. The expression of circ_PRKDC was gradually down-regulated in wound edge at 1 and 7 days after injury relative to the unwounded skin. In human epidermal keratinocytes (HEKa), knockdown of circ_PRKDC promoted cell migration partly through up-regulating MMP-2 and MMP9, while circ_PRKDC overexpression showed opposite effects. In a mechanical study, we confirmed that miR-31 was a target of circ_PRKDC, and inhibition of miR-31 reversed the promotive effect of circ_PRKDC knockdown on HEKa migration. Besides that, miR-31 was verified to target FBN1, and ectopic overexpression of miR-31 accelerated HEKa migration via FBN1. Importantly, we also demonstrated that FBN1 overexpression attenuated the effects of circ_PRKDC knockdown on HEKa migration. In all, circ_PRKDC knockdown promoted HEKa migration during wound healing through miR-31/FBN1 axis, suggesting the therapeutic potential for circ_PRKDC on skin wound healing.

Circular RNA: A novel potential biomarker for skin diseases

Circular RNA (circRNA) has been classified as noncoding RNA with a covalent closed continuous loop, the 3'and 5' ends of which are normally joined together to increase its own stability. More recently, circRNA has been shown to encode proteins and may be involved in the regulation of gene transcription. This provides more evidence for the involvement of circRNA in disease progression. Accumulating investigations have found that the expression of many circRNAs is abnormal in plenty of skin diseases such as malignant melanoma, psoriasis, and abnormal wound healing. Herein, in addition to the summary of recent studies on the nuclear export, N⁶-methyladenosine (m⁶A) modification, degradation, and other biogenesis and properties of circRNA, we highlight the importance of circRNAin skin diseases. Although their exact roles and mechanisms in most skin disease remain preliminary, circRNAs have potential applications as diagnostic biomarkers and novel therapeutic targets for skin diseases due to its structural and functional properties (stability, specificity and sensitivity), which is worthy of deeper exploration and greater research efforts.