Plastic Surgery Research Council

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The optimal timing of Adipose Derived Stem Cells injection to improve skin Flap Survival in a Rat model
Ahmed Atef, MD.
Mataria Teaching Hospital, Cairo, Egypt.

PURPOSE: Skin flap surgery is a cornerstone in plastic surgery. Flaps may encounter postoperative partial or complete necrosis. Different modalities have been used to enhance skin flap survival. Adipose Derived Stem Cells (ASCs) can promote angiogenesis and improve skin flap survival. We aimed to investigate the appropriate timing of use of ASCs to get the maximal angiogenic effect and better skin flap survival in rat model.
METHODS: 32 male albino wistar rats where used to study the role of ASCs on caudally based (2x8cm) random pattern skin flap survival , the 32 male albino rats were equally divided into 4 groups according to timing of ASCs injection. We applied the ASCs at three different timing, Group A: (local injection of ASCs along the flap axis simultaneously with flap elevation), Group B: (two days preoperatively) and Group C: (seven days preoperatively), In the control group (Group D): the flap was injected with saline at the time of flap elevation. Skin flap survival was evaluated on the seventh postoperative day through: percentage of flap survival, capillary density and VEGF expression.
RESULTS: ASCs led to a statistically significant increase in skin flap viability when administered simultaneously with flap elevation or two days prior to flap elevation. This went along with the significant increase of capillary density and VEGF expression. However, the ASCs had no effect on flap survival when injected one week prior to flap elevation.

Survival percentage %
68.6-72.870.5+1.5Group A
54.4-65.760.7+3.8Group B
29.7-37.433.7+3Group C
25.5-35.431.5+3Group D
331F Statistic
< 0.001HSP value

number of capillaries/ field
17-3123+4Group A
14-1815.7+1.5Group B
6-107.9+1.5Group C
6-117.8+1.8Group D
61F Statistic
< 0.001HSP value

140-280211+49Group A
140-280186+50Group B
20-3227+3Group C
20-3025+4Group D
66F Statistic
< 0.001HSP value

We could explain our findings by the angiogenic potentials of ASCs,which were evident by the significant increase in VEGF expression in bothgroup A and group B. ASCs are affected by their environment, the hypoxicconditions help ASCs to secrete more angiogenic factors. That is why thetransplantation of ASCs is usually performed at the time of surgery. The flap elevation leads to hypoxia, and this stimulates ASCs in the most efficient way Thus, the injection of the ASCs two days before flap elevation might decrease their effectiveness and concentration due to the absence of the trigger at the time of application, most of ASCs die within 1 week of injection if injected one week prior to flap elevation.
CONCLUSION: We demonstrate that the skin flap viability can be enhanced by local ASCs administration simultaneously with flap elevation or two days prior to flap elevation. Their beneficial effect is attributed to paracrine secretion VEGF which enhanced the skin flap vascularity. The angiogenic effect of ASCs can be maximized when the ASCs are injected at the time of flap elevation.

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