Circ004463 promotes fibroblast proliferation and collagen I synthesis by sponging miR-23b and regulating CADM3/MAP4K4 via activation of AKT/ERK pathways

Skin thickness is closely related to the appearance of human skin, such as sagging and wrinkling, which primarily depends on the level of collagen I synthesized by fibroblasts in the dermal layer. To explore the underlying genetics of the development of skin thickness, we used the indigenous Chinese Chenghua pigs, considered to have superior skin thickness, as model animals. We first performed whole transcriptome sequencing analysis to identify significant skin morphological differences between Chenghua pigs and Large White pigs and obtained some differentially expressed coding RNAs (454 mRNAs) and noncoding RNAs (612 circRNAs, 188 miRNAs, and 19 lncRNAs); moreover, some competing endogenous RNA (ceRNA) networks were constructed. Interestingly, we then identified a circRNA, namely circ0044633, which plays an important role in promoting fibroblast proliferation along with myofibroblast transition and collagen I synthesis by sponging miR-23b and regulating CADM3 and MAP4K4 expression via activation of the downstream AKT and ERK pathways in vitro. Furthermore, overexpression of circ004463 increased the mouse skin thickness and collagen I content in vivo. These results revealed a whole transcript profile of skin tissue and identified an important circ0044633-miR-23b-CADM3/MAP4K4 axis related to fibroblast proliferation and collagen I synthesis during the development of skin thickness.