Fgf7, also known as keratinocyte growth factor, is a member of the fibroblast growth factor (FGF) family. It is secreted exclusively by the mesenchyme and specifically activates the "b" isoforms of FGFR1 (FGFR1b) and FGFR2 (FGFR2b) in the overlying epithelium, contributing to the development of essentially all organs, glands, and limbs [2].

Single-cell RNA-seq analysis revealed that Fgf7 mediates a novel interaction between muscle fibro-adipogenic progenitors (FAPs) and satellite cells. Exogenous FGF7 enhances satellite cell proliferation, benefits muscle regeneration, and counteracts age-related myopathy [1]. FGF7 can also enhance the expression of ACE2 in human islet organoids, facilitating SARS-CoV-2 infection and impairing insulin secretion [3]. In osteoblasts, FGF7 increases the expression of E11, promotes dendrites elongation and functional gap junctions formation [4]. In fusion-positive rhabdomyosarcomas, FGF7-FGFR2 autocrine signaling increases growth and chemoresistance [5]. FGF7 peptide (FGF7p) can mitigate bladder urothelial injury from cyclophosphamide [6]. Cancer-associated fibroblast-secreted FGF7 promotes ovarian cancer progression [7]. Pea sprout extract can enhance the expression of FGF7, potentially promoting hair growth [8]. In non-small lung cancer, CAFs with high FGF7 expression can robustly or moderately protect cancers [9]. FGF7 shows opposite effects in osteoporosis and osteoarthritis, protecting against osteoporosis but exacerbating osteoarthritis [10].

In conclusion, Fgf7 plays crucial roles in multiple biological processes and disease conditions. Its functions range from muscle regeneration, islet cell-virus interaction, bone-related cell regulation, to cancer progression and hair growth. The study of Fgf7 in different research models helps to understand its diverse biological functions and provides potential therapeutic targets for related diseases.