Autologous Fat Transfer: The Progenitor Cell Response to Hypoxia

Goals/Purpose:

Autologous fat transfer is now a common procedure; however, results are variable and often unpredictable.  The latest techniques improve results by maximizing nutrient supply; however, the donor and recipient stem cell response to hypoxic environments needs to be elucidated to determine what cell type contributes to long-term results.

Methods/Technique:

Acellular dermal matrix (ADM) envelopes were created by folding a 6cm by 8cm and sealing all sides.  Six envelopes were each implanted into the subcutaneous tissue of four farm swine.  In each swine, two Alloderm envelopes served as positive controls, two envelopes were injected with 5cc of autologous fat harvested via standard suction techniques, and two envelopes were injected with fat and wrapped around an omental pedicle.  In addition, 5cc of harvested fat was re-injected as a negative control.  Envelopes were excised en bloc at one, two, four and 16 weeks.  Specimens were analyzed for weight and volume and fine cuts via H&E and Masson's trichrome staining.  Intra-envelope cells and fluid were analyzed with FACS for CD markers 14, 31, 34, 45, and 90.

Results/Complications:

Autologous fat was found in the ADM envelopes with and without an omental blood supply at all time-points.  The volume retention was greatest with the ADM only envelopes and is attributed to the overt immune response (Figure 1).  Placing autologous fat regardless of blood supply significantly reduced the initial inflammatory response and delayed and prolonged the progenitor cell population (Figure 2).  There were significantly more hematopoietic stem cells in the hypoxic environment, and the presence of ADM significantly increased the endothelial stem cell population (Figure 3).

Conclusion:

Injecting fat within an Alloderm envelope alters the initial inflammatory response and increases the progenitor cell population.  Hematopoietic stem cells are more abundant in fat transferred in hypoxic environments, and the addition of a robust blood supply improves results.

Figure1

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