Downregulation of let-7b promotes COL1A1 and COL1A2 expression in dermis and skin fibroblasts during heat wound repair.

MicroRNAs (miRs), a class of non‑coding RNAs 18‑25 nucleotides in length, generally serve suppressive role in the regulation of gene expression via directly binding to the 3'‑untranslated region (UTR) of their target mRNA. Previous studies have identified several miRs to be involved in thermal injury repair. However, the role of miR let‑7b during the recovery of thermal injury, in addition to the underlying mechanisms, has not previously been studied. In the present study, the expression of let‑7b was observed to be significantly increased in skin tissue shortly following thermal injury, however, gradually reduced during the recovery of thermal injury. Notably, similar findings were observed in heat‑denatured skin fibroblasts. Furthermore, collagen, type I, alpha 1 (COL1A1) and collagen, type I, alpha 2 (COL1A2), which are associated with the synthesis of type I collagen, were identified as two targets of let‑7b in skin fibroblasts. The overexpression of let‑7b was observed to upregulate the protein expression levels of COL1A1 and COL1A2, while knockdown of let‑7b reduced the levels of COL1A1 and COL1A2 in skin fibroblasts. Furthermore, COL1A1 and COL1A2 were significantly downregulated shortly following thermal injury, while gradually upregulated during healing, in heat‑damaged skin tissue and skin fibroblasts, with the expression profiles opposite to that of let‑7b. Taken together, this suggests that the downregulation of let‑7b in heat‑damaged dermis promotes the synthesis of type I collagen and thus aids in burn wound repair.