Exclusive expression of KANK4 promotes myofibroblast mobility in keloid tissues
Keloids are characterized by abnormal wound healing with excessive accumulation of extracellular matrix. Myofibroblasts are the primary contributor to extracellular matrix secretion, playing an essential role in the wound healing process. However, the differences between myofibroblasts involved in keloid formation and normal wound healing remain unclear. To identify the specific characteristics of keloid myofibroblasts, we initially assessed the expression levels of well-established myofibroblast markers, a-smooth muscle actin (a-SMA) and transgelin (TAGLN), in scar and keloid tissues (n = 63 and 51, respectively). The objective was to evaluate the enrichment of myofibroblasts in these tissues. Although myofibroblasts were present in significant quantities in keloids and immature scars, they were absent in mature scars. Next, we conducted RNA sequencing using myofibroblast-rich areas from keloids and immature scars to investigate the difference in RNA expression profiles among myofibroblasts. Comparison of the results with publicly available RNA-sequencing datasets revealed that 112 genes were significantly upregulated and 108 genes were downregulated in keloid samples compared with immature scar samples. Among them, KN motif and ankyrin repeat domains 4 (KANK4) was identified as a specifically upregulated gene in keloids. Immunohistochemical analysis showed that KANK4 protein was expressed in myofibroblasts in keloid tissues; however, it was not expressed in any myofibroblasts in immature scar tissues. There are two main isoforms of KANK4 transcripts, with short isoforms being dominantly expressed in keloid tissue. Overexpression of the short isoform of KANK4 enhanced cell mobility in keloid myofibroblasts. Our results suggest that the KANK4-mediated increase in myofibroblast mobility contributes to keloid pathogenesis. Overall design: To identify the transcriptome of myofibroblasts in keloids and immature scars, we performed RNA sequencing from TAGLN-positive tissue in keloid samples (n=3) and immature scar samples (n=2).