Background: Autologous fat grafting (AFG) is a favourable surgical option for oncologic breast reconstruction post breast cancer surgery; however, retention rates are variable, limiting AFGs clinical utility. Low graft retention is largely due to a failure of the graft to integrate into the recipient site. Extracellular vesicles (EVs) released by adipose-derived stem cells (ADSCs) could be used as an acellular therapeutic for enhancing AFG retention by promoting angiogenesis and stimulating a favourable inflammatory and fibrotic state.
Methods: Lipoaspirates were collected from patients undergoing AFG and ADSCs were isolated enzymatically and cultured. ADSC-EVs were isolated from culture media by SEC and characterised by TRPS, Western blot, and TEM. ADSC-EVs were added to single-cell cultures of human monocyte-derived-macrophages (MDMs), HUVECs, and fibroblasts. 3D multicellular models were created to mimic the breast microenvironment and further assess the functional role of ADSC-EVs. Models were imaged using fluorescent confocal microscopy.
Results: ADSC-EV replicates from three donors significantly reduced the expression of markers associated with antigen presentation, adhesion, and scavenging on MDMs and high dimensional analysis of a 10-marker panel demonstrated a reduction in expression of inflammatory clusters across all MDM phenotypes. ADSC-EVs also increased fibroblast proliferation under unstimulated (1.14-fold, p=0.0009) and pro-inflammatory (1.15-fold, p=0.0006) conditions, but decreased proliferation under pro-fibrotic conditions (0.84-fold, p=0.0002). In multicellular models, ADSC-EVs consistently increased tube formation in HUVECs (2.60-fold, p<0.0001) and increased co-localization of MDMs and HUVECs (1.21-fold, p=0.0246).
Conclusions: ADSC-EVs have pro-angiogenic and anti-inflammatory effects, indicating that ADSC-EVs may be an appropriate therapeutic in the context of AFG.