SP6.7 - Exploring the Mechanistic Basis of the Adipose Derived Stem Cell Secretome on Extracellular Matrix Remodelling in Radiation Induced Fibrosis

Abstract Background Radiation-induced fibrosis (RIF) is a debilitating complication following radiotherapy, characterised by fibroblast proliferation and excessive extracellular matrix (ECM) deposition, leading to functional and aesthetic impairments. Although autologous fat grafting (AFG) has shown promise in reversing RIF, the mechanisms, largely attributed to adipose-derived stem cells (ADSCs), remain elusive. This study aimed to investigate ADSCs’ and their secretome on ECM remodelling in RIF management. Methods The anti-fibrotic potential of the ADSC secretome on HDFs subjected to ionising radiation was assessed via a series of in vitro experiments. Control HDFs were compared with irradiated HDFs to assess any phenotypical changes. Irradiated HDFs were treated with ADSC pre-conditioned media (CM) or ADSC co-culture (CC). Gene expression (COL1A1, TGF-β1, CCN-2, MMP-1, MMP-3, TIMP-1, ACTA2, TNC) was assessed via real-time quantitative PCR (RT-qPCR). ProCollagen1a1 and CCN2 protein concentrations were assessed by ELISA. Results Irradiated HDFs demonstrated changes in fibrotic gene expression. ADSC-CM treatment significantly reduced COL1A1 expression, although protein levels remained unchanged. TGF-β1, CCN2, MMP-3, TIMP-1 and ACTA-2 exhibited reduced expression post-ADSC-CM treatment whereas TNC expression was found to be significantly increased. Co-culture with ADSCs led to a general, but not statistically significant, decrease in pro-fibrotic gene expression. Notably, CCN-2 protein expression significantly increased. Conclusion This study demonstrates that ionising radiation results in a pathological pro-fibrotic phenotype in HDFs. The ADSC secretome potentially mitigates this, reducing pro-fibrotic gene expression. Unexpectedly, co-culture experiments highlighted a complex interaction with upregulation of fibrosis-associated genes. Further research is needed to clarify these interactions to improve therapeutic interventions for RIF.