Wound Healing Society

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Angiogenesis Through Stimulation With External Volume Expansion Improves Adipose Tissue Graft Retention In A Radiation Fibrosis Model
Jorge Lujan-Hernandez, M.D., Robert Slamin, B.S., Michael S. Chin, M.D., Janice F. Lalikos, M.D..
University of Massachusetts Medical School, Worcester, MA, USA.

Introduction: Post-mastectomy radiation therapy (RT) has improved breast cancer survival but has complicated the breast reconstruction process. Autologous fat grafting (FG) is a novel reconstruction tool used by plastic surgeons. However the hypovascular environment after radiation exposure hampers the retention of adipose grafts. Pre-treatment with External Volume Expansion (EVE) is known to induce angiogenesis through mechanical stimulation and hypoxia. We hypothesized that could improve vasculature in irradiated tissue and improve fat graft retention.

Methods: Forty mice were divided into 4 groups of 10 mice each. 50gy of topical radiation was applied to mice on their flanks and were monitored for 8 weeks until development of chronic fibrosis. Group 1 received unilateral RT. Group 2 received bilateral RT and EVE application for 5 days unilaterally with 25mmHg of negative pressure. Group 3 (n=10) was not irradiated and received human fat graft as control. Group 4 received bilateral RT application, then EVE as group 2, followed by bilateral fat grafting. Skin perfusion was measured using Hyperspectral Imaging. Fat graft volumes were quantified 8 weeks post-grafting using CT scans. Histology of tissues was analyzed for vascularity (CD31) and cell proliferation (ki67).

Results: Group 1. Irradiated skin was less perfused compared to control side.
Group 2. EVE application induced a 37% increase in vascularity in the overlying skin and a 45% increase in proliferating cells in skin in the RT treated areas compared to RT without EVE.
Group 3 and 4. Fat graft retention after 8 weeks was 74% in the control group, 66% on irradiated and 79% on irradiated and EVE preconditioned group.

Conclusions:
Radiation injures microvasculature and reduces skin perfusion affecting fat graft survival. EVE increased volume retention of fat grafts likely via angiogenesis and mechanotransductive preconditioning phenomena.


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