AUTHOR=Zhang Mingzhao , Liu Hengchen , Shi Manyu , Zhang Tingting , Lu Wenjun , Yang Shulong , Cui Qingbo , Li Zhaozhu 

TITLE=Potential Mechanisms of the Impact of Hepatocyte Growth Factor Gene-Modified Tendon Stem Cells on Tendon Healing

JOURNAL=Frontiers in Cell and Developmental Biology

VOLUME=Volume 9 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2021.659389

DOI=10.3389/fcell.2021.659389

ISSN=2296-634X

ABSTRACT=The therapeutic impact of stem cells is potentially largely attributable to secretion of exosomes and soluble factors. The present study evaluated the impact of hepatocyte growth factor (HGF)-expressing tendon stem cells (TSCs) on tendon healing in a rat model. Patellar tendon TSCs were isolated and underwent transfection with lentiviral vectors containing HGF or green fluorescent protein (GFP) genes. In vivo, immunohistochemistry of tendons sampled one week post-surgery demonstrated that all stem cell-treated groups exhibited higher numbers of CD163+ M2 monocytes and IL-10+ cells (anti-inflammatory), and lower numbers of CCR7+ M1 monocytes and IL-6+ as well as COX-2+ cells (pro-inflammatory). Effects were most pronounced in the HGF-expressing TSCs (TSCs+HGF) treated group. Histology ± immunohistochemistry of tendons sampled four and eight weeks post-surgery demonstrated that all stem cell-treated groups exhibited more ordered collagen fiber arrangement and lower levels of COLIII, α-SMA, TGF-β1, and fibronectin (proteins relevant to fibroscarring). Effects were most pronounced in the TSCs+HGF-treated group. For the in vitro study, isolated tendon fibroblasts pretreated with TGF-β1 to mimic the in vivo microenvironment of tendon injury were indirectly co-cultured with TSCs, TSCs+GFP, or TSCs+HGF using a transwell system. Western blotting demonstrated that all stem cell types decreased TGF-β1-induced increases in fibroblast levels of COX-2, COLIII, and α-SMA, concomitant with decreased activation of major TGF-β1 signaling pathways (p38 MAPK, ERK1/2, but not Smad2/3). This effect was most pronounced for TSCs+HGF, which also decreased the TGF-β1-induced increase in activation of the Smad2/3 signaling pathway. The presence of specific inhibitors of these pathways during fibroblast TGF-β1 stimulation also attenuated increases in levels of COX-2, COLIII, and α-SMA. In conclusion, TSCs+HGF, which exhibit sustained HGF secretion, may promoting tendon healing via decreasing inflammation and fibrosis, perhaps partly via inhibiting TGF-β1-induced signaling. These findings identify a novel potential therapeutic strategy for tendon injuries, warranting additional research.