Reactions Of Fibrotic Skin To Fat Grafting In A Rodent Model
William J. Bruce, MD, Kristin Delfino, PhD, Jacob A. Thayer, MD, Carrie E. Harrison, BS, Ryan W. Schmucker, MD, Michael W. Neumeister, MD, FRCSC, FACS.
Southern Illinois University School of Medicine, SPRINGFIELD, IL, USA.
PURPOSE: The chronic cutaneous fibrosis associated with scleroderma is a significant source of morbidity for patients and impairs activities of daily living. This study evaluates the hypothesis that fat grafting or injection of isolated adipose-derived stem cells (ADSC) will induce regenerative skin changes and ameliorate fibrosis in a murine model of cutaneous fibrosis.
METHODS: : Cutaneous scleroderma-like fibrosis was induced via subcutaneous bleomycin injections into 66 adult nu/nu mice. These were divided into 4 groups and treated via subcutaneous injection of murine whole fat, ADSCs suspended in matrigel, matrigel alone (control for ADSC group), or saline (sham graft, control for whole fat group). Five mice from each group (and 7 mice from sham graft group) were selected at 14, 28, and 35 day time points, and underwent laser Doppler analysis of tissue perfusion prior to euthanization. Harvested skin was subjected to dermal thickness measurement and Trichrome staining for quantification of Type I collagen content. Gene expression analysis targeting pro-sclerotic cytokines TGFβ and endothelin-I (ET-I) was performed using quantitative polymerase chain reaction (qPCR).
RESULTS: Groups treated with ADSCs showed significantly more Type I collagen and greater tissue perfusion than control at 2 weeks, but these differences progressively decreased over time and were absent at 5 weeks. Additionally ADSC-treated tissue was thicker than control at all time points and continued to thicken over time, where control skin thickness remained stable.Whole fat-treated skin showed a decrease in type I collagen as compared to control, and an increased dermal thickness. There was no difference between whole fat and control dermal thickness at any time. Gene expression analysis revealed higher endothelin expression in ADSC group over control at week 5, and no difference in TGFβ expression at any time point. Whole fat treated groups had no significant difference from control in either gene, though did trend toward an initial spike in both Endothelin and TGFβ at 2 weeks followed by a progressive decline to at or below control levels at weeks 4 and 5, while control levels remained stable.
CONCLUSION: Despite a significant body of evidence extolling benefits of fat grafting in skin rejuvenation, improvement of scarring, and inhibition of the pro-sclerotic pathways in a typical patient, the murine model suggests that this may not translate to amelioration of scleroderma symptoms. In this model injection of whole fat or its constitutive parts was detrimental and caused increased fibrosis and dermal thickness over time.
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