Preventing alloimmune rejection using circular RNA FSCN1-silenced dendritic cells in heart transplantation.

Background: While heart transplantation is used as a standard treatment for heart failure, transplant rejection continues to pose a challenge. Recent evidence has shown that circular RNA (circRNA) is a new type of gene regulator in cell development. Our aim was to demonstrate that treatment with tolerogenic dendritic cells (Tol-DCs) generated by circular RNA FSCN1 (circFSCN1) silencing could prevent alloimmune rejection and prolong heart graft survival in heart transplantation.

Methods: Bone marrow-derived DCs were transfected with circFSCN1 siRNA in vitro. The circFSCN1 level was measured by qRT-PCR. DC maturation was determined by flow cytometry. Mixed lymphocyte reactions (MLRs) were conducted to assess the function of DCs to activate T cells and to generate regulatory T cells (Tregs). In situ RNA hybridization and fluorescent microscopy were performed to detect the distribution of circFSCN1 in DCs. A heterotopic allogeneic murine heart transplantation was conducted where recipients were pre-treated with donor derived circFSCN1-silenced Tol-DCs. Heartbeat was monitored to assess immune rejection.

Results: Exonic circFSCN1 was highly expressed in the cytoplasm of mature DCs. Knockdown of circFSCN1 using siRNA arrested DCs at an immature state, impaired DC's ability to activate T cells and enhanced Treg generation. Treatment with circFSCN1-silenced Tol-DCs prevented alloimmune rejection, prolonged allograft survival, reduced fibrosis, and induced Tregs in vivo.

Conclusions: Knockdown of circFSCN1 induces Tol-DCs and treatment with these Tol-DCs prevents alloimmune rejection and prolongs allograft survival. This is a promising therapeutic target to combat transplant rejection in heart transplantation and increases our understanding of circRNA in the immune system.