Autologous Fat Transfer: The Progenitor Cell Response to Different Recipient Environments

Autologous fat transfer is a common procedure; however, results are variable and unpredictable.Stem cell responses to hypoxic environments need to be elucidated to determine which cell types contribute to graft survival.Acellular dermal matrix (ADM) envelopes were implanted in the subcutaneous tissues of 4 swine. In each swine, 2 envelopes were inserted as controls (ADM group), and 2 were placed and injected with 5 mL of autologous fat (ADM/fat group). Two additional envelopes were inserted and filled with 5 mL of fat and an omental pedicle (A/F/O group). Animals were sacrificed and the envelopes excised at 1, 2, 4, and 16 weeks. Specimens were analyzed histologically and/or with flow cytometry.Fat was retained in ADM envelopes with and without a pedicle blood supply, although the percentage of volume retention was greater in the pedicled group. The peak number of mesenchymal progenitor cells within the ADM/fat group was significantly greater than the peak in the A/F/O group (P =.044), whereas endothelial progenitor cells in the ADM/fat group showed a prolonged increase through 4 weeks (P =.015 vs the A/F/O group at week 4). At 16 weeks, the interior surface of the matrix in the ADM/fat group had significantly more blood vessels than that of the ADM or A/F/O group (P = .0021 and .0036, respectively).Injecting fat into hypoxic environments significantly increases the mesenchymal and endothelial progenitor cell responses and enhances the formation of blood vessels.