Human amniotic fluid stem cells have a unique potential to accelerate cutaneous wound healing with reduced fibrotic scarring like a fetus
Adult wound healing can result in fibrotic scarring (FS) characterized by excess expression of myofibroblasts and increased type I/type III collagen expression. In contrast, fetal wound healing results in complete regeneration without FS, and the mechanism remains unclear. Amniotic fluid cells could contribute to scar-free wound healing, but the effects of human amniotic fluid cells are not well characterized. Here, we determined the effect of human amniotic fluid stem cells (hAFS) on FS during wound healing. Human amniotic fluid was obtained by amniocentesis at 15–17 weeks of gestation. CD117-positive cells were isolated and defined as hAFS. hAFS (1 × 106) suspended in PBS or cell-free PBS were injected around wounds created in the dorsal region of BALB/c mice. Wound size was macroscopically measured, and re-epithelialization in the epidermis, granulation tissue area in the dermis and collagen contents in the regenerated wound were histologically analyzed. The ability of hAFS to engraft in the wound was assessed by tracking hAFS labeled with PKH-26. hAFS fulfilled the minimal criteria for mesenchymal stem cells. hAFS injection into the wound accelerated wound closure via enhancement of re-epithelialization with less FS. The process was characterized by lower numbers of myofibroblasts and higher expression of type III collagen. Finally, transplanted hAFS were clearly observed in the dermis until day 7 implying that hAFS worked in a paracrine manner. hAFS can function in a paracrine manner to accelerate cutaneous wound healing, producing less FS, a process resembling fetal wound healing.
KeywordsHuman amniotic fluid stem cell Wound healing Epithelialization Fibrosis Scar formation
This work was supported by JSPS Grant-in-Aid for Scientific Research (C) Grant number JP15K09724 (https://www.jsps.go.jp/english/e-grants/), JSPS Grant-in-Aid for Scientific Research (B) Grant number 17H04236 (https://www.jsps.go.jp/english/e-grants/), JSPS Grant-in-Aid for Challenging Exploratory Research Grant number JP16K15536 (https://www.jsps.go.jp/english/e-grants/), JAOG Ogyaa Donation Foundation (http://www.ogyaa.or.jp/), Japan Spina Bifida and Hydrocephalus Research Foundation (http://www.jikeikai-group.or.jp/jsatoshi/), Keio Gijuku Academic Development Funds research funding (individual research) (http://www.rcp.keio.ac.jp/ora/jukunai/gakushin.html#two), and Kawano Masanori Memorial Public Interest Incorporated Foundation for Promotion of Pediatrics (https://kawanozaidan.or.jp/c).
MF, DO, HM, SS, NA, MS, YK, KK, and MT conceived and designed the experiments. MF, DO, YA, and TO performed the experiments. MF, DO, HM, YA, TO, SS, NA, MS, TM, KM, YK, KK, and MT analyzed the data. SS and MS contributed reagents/materials/analytic tools. MF, DO, HM, and MT wrote the paper.
Compliance with ethical standards
Conflict of interest
The authors have no conflicts of interest to declare.
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