MicroRNAs as biomarkers of graft outcome

Dramatic improvements in short-term graft outcomes after solid organ transplantation over the past decade have not translated into major improvements in long-term allograft acceptance and patient survival. Innovative approaches to develop individualized therapy for the graft recipient are critically needed and have stimulated active research in the field of biomarker discovery. MicroRNAs (miRNAs) are small non-coding RNAs that function as important regulators of gene and protein expression by RNA interference. They are implicated in many biological processes and diseases. Their characteristics prompted their evaluation as candidate molecular markers to evaluate the transplant patient: their expression profile is specifically altered in pathological conditions, they can be easily detected and quantified in tissues, and they are highly stable in almost all body fluids, allowing the development of non-invasive approaches. We aimed to review the existing knowledge about miRNA biogenesis and function and summarize the recent findings demonstrating their potential use as biomarkers in solid organ transplantation. Although they still need to be validated in larger patient cohorts, miRNAs are not far from being used in transplant clinical practice as usefulness biomarkers. Ongoing multi-center trials should help to further define the clinical utility of miRNA profiles as biomarkers of allograft status and outcome.