Abstract 21075: Heat Shock Factor 1 Modulates Exosomes Biogenesis and Cargo

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Introduction: Cardiac Progenitor cells (CPCs, identified by ckit+/CD45-/lin-) are being used in 21 clinical trials (recruiting and completed) to restore heart function and promote tissue regeneration in response to injury and their exosomes (EXO) has been identified to be critical for their functional activity.

Hypothesis: We hypothesized that heat shock factor 1 (HSF1) modulates EXO biogenesis from CPCs and their enrichment with therapeutic miRs.

Methods and Results: EXOs were isolated from cultured CPCs, generated from the biopsies of right atrial appendage (RAA) at the time of cardiac surgery from neonatal (nCPCs, < 1 month) and adult (aCPCs, > 40 years) patients with normal functioning myocardium using size exclusion chromatography (CL-2B). EXOs were analyzed by transmission electron microscopy, Nanosight (LM10) and the flow cytometry for EXO markers as CD63 and ALIX. Our results showed that physiological changes as ageing affects EXOs biogenesis and their functional potential as nCPCs generate significantly more EXOs than aCPCs. HSF1 overexpression in aCPCs significantly enhanced their EXO biogenesis. nCPCs derived EXOs (nEXOs) are significantly more effective (nEXOs 62.14±2.9% vs aEXO 56 ± 3.6%, p<0.05) to improve cardiac function and tissue repair in a myocardial infarction (MI) model in rats as compared to aCPCs derived EXOs. In a rat MI model, using florescent labelled HLA-A antibodies, nEXOs were identified to be retained for longer duration in rat serum as compared to aEXOs, which correlated with myocardial functional recovery. miRNA sequencing of EXOs identified significantly higher expression of cardio protective miRs like miR199a, 146a, 454, 590, 130a in nEXOs as compared to aEXOs. We also identified that HSF1 overexpression in aCPCs significantly enriched them with miR199a, miR130a and miR590 suggesting that HSF1 can affect EXO biogenesis and its miR Cargo. The results of large scale production of EXOs using hollow fibre systems will also be presented.

Conclusion: We showed that nEXOs are functionally more active and modulation of HSF1 can affect EXOs biogenesis and its cargo from CPCs. These results also suggest that nEXOs has the potential to be utilized as an off the shelf cell-free therapy.

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