Fibrosis process activation in patients with acute cardiac rejection: a novel noninvasive diagnostic approach

Abstract Background Finding a standardised, non-invasive method to diagnose cardiac allograft rejection remains challenging, making serum biomarkers a promising alternative for improving diagnostic accuracy. Cardiac allograft fibrosis is an important limiting factor for long-term graft survival. However, the fibrotic mechanisms involved in acute cellular rejection (ACR) are still not fully understood, highlighting the need to explore fibrosis-related molecules as potential diagnostic biomarkers. Purpose This study aimed to identify altered fibrosis-related coding mRNAs in the serum of patients with ACR and evaluate their diagnostic accuracy as potential non-invasive biomarkers for detecting mild (grade 1R) and moderate/severe (grade ≥2R) cellular rejection. Methods A total of 40 serum samples from recipients of transplants undergoing routine endomyocardial biopsies were included in an RNA sequencing analysis that included 28 diagnosed with ACR (grade 1R, n=16; and grade ≥2R, n=12) and 12 without cardiac rejection. Results We detected several altered mRNAs associated with fibrosis in patients with ACR. Specifically, the activators of fibroblasts and myofibroblasts (TNS1, FAP and ACTA2; p0.05), TGF-β signalling (TGFBR1 and JAK1; p0.05) and WNT signalling (WNT7A and WLS; p0.01) pathways showed significant differences in their relative abundance when we compared grade ≥2R ACR and/or grade 1R ACR groups with the non-rejection group. Further, TNS1 and WLS presented an area under the curve value 0.90 for identifying patients with moderate and severe grades of cardiac rejection. Conclusion We found alterations in the relative abundance of circulating activators of fibroblasts and myofibroblasts, such as FAP or ACTA2, as well as in major profibrotic pathways, including TGF-β and WNT signaling, particularly in clinically relevant cardiac rejection. These findings may contribute to improving the surveillance of patients with cardiac transplant and provide new therapeutic strategies for targeting fibrosis.