Abstract
Despite increasing application of the pre-grafting expansion during autologous fat transplantation in breast reconstruction, little is known about its mechanism of action. To address that, ventral skins of miniature pigs were treated over a 10-day or 21-day period, with continuous suction at −50 mm Hg via a 7-cm diameter rubber-lined suction-cup device. Soft tissue thickness increased immediately after this external volume expansion (EVE) treatment, such increase completely disappeared by the next day. In the dermis and subcutaneous fat, the EVE treated groups showed significant increases in blood vessel density evident by CD31 staining as well as in vascular networks layered with smooth muscle cells when compared with the control group. This finding was corroborated by the increased percentage of endothelial cells present in the treatment groups. There was no significant difference in the percentages of proliferating basal keratinocytes or adipocytes, nor in epidermal thickness. Moreover, the EVE had no effect on proliferation or differentiation potential of adipose stem cells. Taken together, the major effects of EVE appeared to be vascular remodeling and maturation of functional blood vessels. This understanding may help clinicians optimize the vascularity of the recipient bed to further improve fat graft survival.
Highlights
As is common with new techniques, there has been significant debate, regarding both the methods of quantifying the results and the underlying physiologic processes[4,5]
These results indicated that the external volume expansion (EVE) induced soft tissue enlargement is a transit effect even after it was applied for 21 days
The principal experiment results showed that: (1) neovascular network formation, growth, and maturation of functionalized blood vessels in adipose tissue were the major effects of external volume expansion. (2) the mechanically stretched condition in vivo modulated and stimulated vascular growth and remodeling. (3) the EVE induced soft tissue enlargement was transient even after 21 days of daily treatments
Summary
As is common with new techniques, there has been significant debate, regarding both the methods of quantifying the results and the underlying physiologic processes[4,5]. Previous studies showed effects of mechanical force on cell phenotype, growth rate, and signal transduction in a variety of cell types. These data demonstrated that mechanical loading can induce osteogenic differentiation and smooth muscle differentiation in mesenchymal stem cells[10,11,12]. The effects of in vivo mechanical loading of EVE on neovascular growth and subsequent functional maturation of blood vessels in subcutaneous fat in a swine model were examined. We performed quantitative assessments to compare the effects of different treatment interval of EVE on swine ASCs in terms of cell phenotype, proliferation capacity, differentiation potential, and stemness. A swine model was chosen because of its skin architectural and physiologic similarities to human’s, likely more relevant to actual clinical experience than rodent models, from which most of the existing knowledge has been derived
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