The Stromal Vascular Fraction of Autologous Fat Graft Induces Proliferation of Normal and Tumour-Adjacent Breast Tissue

Abstract

Autologous fat grafting is frequently used in breast cancer patients post mastectomy. Progenitor cells contained in Stromal Vascular Fraction, herein known as SVF, may have proliferative effects on breast parenchymal cells. To our knowledge, no study has looked at the direct effect of SVF on breast parenchymal cells outside the tumor free margins on mastectomy specimens. This study investigates the role of autogous fat graft SVF on the growth of normal and breast cancer adjacent parenchymal cells. Methods: Samples (n=4) of abdominal fat and histologically normal breast tissue both from a tumour-free breast and from a cancerous breast outside the tumour-free margins were obtained. The presence of multipotent mesenchymal stem cells (MSCs) within the SVF cell population was assessed using established cell surface marker and differentiation assays. Next, the presence of progenitor cells in normal breast and breast tumour-adjacent parenchymal samples were quantified using a colony-forming cell (CFC) assay. SVF cells and both populations of breast parenchymal cells were cultured together in Matrigel, with a control culture lacking SVF. After 14 days, the total cell numbers and breast progenitor cell populations from each culture group were quantified using CFC assays. Results: Differentiation assays demonstrated presence of MSCs and vascular endothelial progenitor cells in SVF samples. Cultures of normal breast parenchymal cells with SVF led to a 3.35-fold expansion of breast progenitors. Cultures of breast tumour-adjacent parenchymal cells with SVF led to a 9-fold expansion of breast progenitors, compared to a 2-fold expansion when cultured alone. Conclusion: SVF is capable of increasing the proliferation of breast progenitor cells in both non-tumour and tumour-adjacent breast tissue. This increase is larger in the tumour~adjacent tissue. As a result, this study demonstrates a s ignificant interaction between SVF w ithin autologous fat grafts and cancer-adjacent breast tissue.