Receptor activity-modifying protein 1 regulates the differentiation of mouse skin fibroblasts by downregulating α-SMA expression via suppression of high mobility group AT-hook 1 to promote skin wound repair.

Background: Skin innervation is very important for normal wound healing, and receptor activity-modifying protein 1 (RAMP1) has been reported to modulate calcitonin gene-related peptide (CGRP) receptor function and thus be a potential treatment target. This study aimed to elucidate the intricate regulatory effect of RAMP1 on skin fibroblast function, thereby addressing the existing knowledge gap in this area.

Methods: Immunohistochemical staining and immunofluorescence (IF) staining were used to measure the dynamic changes in the expression of RAMP1 and α-smooth muscle actin (α-SMA) in skin wound tissue in mice. Mouse skin fibroblasts (MSFs) stably transfected with Tet-on-Flag-RAMP1 overexpression (OE) and Tet-on-Flag control (Ctrl) lentiviruses were constructed for experiments. High mobility group AT-hook 1 (HMGA1) plasmids and α-SMA plasmids were used to overexpress HMGA1 and α-SMA, respectively. An α-SMA siRNA was used to silence α-SMA. Quantitative real-time polymerase chain reaction (qPCR), western blot and IF staining analyses were used to determine the mRNA and protein levels in the cells in different groups. A scratch wound healing assay was used to evaluate the cell migration ability of different groups. Cleavage under targets and release using nuclease (CUT & RUN) assays and dual-luciferase reporter assays were used to predict and verify the interaction between HMGA1 and the α-SMA promoter.

Results: RAMP1 and α-SMA protein expression levels in the dermis changed dynamically and were negatively correlated during dorsal skin wound healing in mice. RAMP1 OE inhibited the differentiation and promoted the migration of MSFs by decreasing α-SMA expression via the suppression of HMGA1, which was shown for the first time to bind to the α-SMA promoter and increase α-SMA transcription. RAMP1 OE also modulated extracellular matrix (ECM) synthesis and remodeling by promoting collagen III and MMP9 expression and decreasing collagen I, MMP2, and tissue inhibitor of metalloproteinases 1 expression.

Conclusions: Our findings suggest that RAMP1 OE decreases differentiation and promotes migration in MSFs by downregulating α-SMA expression via the suppression of HMGA1 and modulates ECM synthesis and remodeling, revealing a novel mechanism regulating α-SMA transcription, providing new insights into the RAMP1-mediated regulation of fibroblast function, and identifying effective nerve-related targets for skin wound repair.