Plastic Surgery Research Council
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PSRC 60th Annual Meeting

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Adipogenesis by External Volume Expansion
Jorge R. Lujan-Hernandez, MD1, Luca Lancerotto, MD1, Christoph Nabzdyk, MD1, Kazi Z. Hassan, BS1, Roger K. Khouri, Jr., BS1, Hamed Zartab, MD, MSc1, Michael S. Chin, MD2, Franco Bassetto, MD3, Janice F. Lalikos, MD2, Dennis P. Orgill, MD, PhD1.
1Brigham and Women's Hospital- Harvard Medical School, Boston, MA, USA, 2University of Massachusetts Medical School, Worcester, MA, USA, 3Institute of Plastic Reconstructive and Aesthetic Surgery, University of Padova., Padova, Italy.

PURPOSE:
External Volume Expansion (EVE) has emerged as an adjuvant to improve the survival of fat grafting to the breast. We have previously described in an experimental animal model how EVE by mechanical stimulation, edema, hypoxia and inflammation improves vascularity and increases cellular proliferation of the potential recipient site. However, some have suggested an increase of adipose tissue in EVE-treated subjects even prior to fat grafting. Adipogenesis studies have shown that hypoxia and inflammation can stimulate differentiation of pre-adipocytes into mature adipocytes, yet no studies have evaluated this effect when preparing the recipient site.
METHODS:
28 SKH1 hairless mice were stimulated with a miniaturized model of EVE for 2 hours/day for 1 (Group 1) or 5 (Group 2) consecutive days. A rubber dome with an inner diameter of 1cm was applied to the skin on the dorsum of the mouse, 1cm lateral to the spine, and was connected to a suction pump set at 25mmHg. In each mouse, the contralateral non-stimulated site was used as control (NS). Tissue samples were harvested immediately after stimulation (n=7/group) or 48hr after stimulation (n=7/group). Paraffin-embedded samples stained with H&E were examined for gross morphology and edema. IHC staining and quantification was performed for CD45 (inflammatory cells) and Perilipin-1 (marker of metabolically active adipocytes). Western Blot was performed for PPAR-gamma expression (transcription factor inducing adipogenesis).
RESULTS:
Immediately after stimulation, tissues were edematous and enriched in CD45+ cells in both groups. 48hr after the last stimulation, edema had regressed and inflammation was decreased in both 1-day and 5-day stimulated tissues. The number of adipocytes/mm of tissue increased 2.1-fold in group 1 and 3-fold in group 2 compared to NS (p<0.05). WB showed significant up-regulation of PPAR-gamma immediately after five days of stimulation compared to NS.
CONCLUSION:
EVE induces a significant increase in number of adipocytes/mm of tissue, CD45+ cells and PPAR-gamma expression compared to NS skin. These changes are immediate, even after short periods of stimulation. Inflammation and hypoxia are known adipogenic cues that might be responsible for this finding. Further studies are needed to better understand the mechanisms of action of these elements separately.



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