MedicalResearch.com Interview with: Jamil R. Azzi MD Associate Professor of Medicine, Harvard Medical School Medical Director, Vascularized Composite Allotransplantation Associate Director, Kidney and Pancreas Transplantation Director, Kidney Transplant Fellowship Engineering in Medicine, Brigham and Women’s Hospital Renal Division, Brigham and Women's Hospital MedicalResearch.com: What is the background for this study? Would you explain what is meant by an exosome?  Response: Kidney transplant recipients are always at risk of developing rejection where the immune system recognizes the transplanted kidney as “foreign body” and attacks it. The risk is up to 20% the first year after transplant and many more develop chronic rejection which ultimately leads to kidney failure. Currently, most clinicians monitor for kidney rejection by measuring serum creatinine and urine protein. However, creatinine is neither sensitive nor specific for rejection. On the other hand, performing kidney biopsies to make accurate diagnosis of rejection is invasive and has many complications. In our study, when clinicians decided on performing biopsies based on the clinical informations they have including changes in serum creatinine, the biopsies did not show rejection in almost 70% of the cases. Furthermore, serum creatinine can remain stable while the patient may be undergoing a rejection (subclinical rejection). In fact, some centers currently perform routine biopsies at different time points for all their patients regardless of creatinine despite the high risks, costs and inconveniences of doing biopsies. Out of this frustration with the current tools, we have been working on novel technologies to diagnose rejection through the urine. The idea started from the bench as we were studying exosomes, those are tiny vesicles (less than 100 nm in size) released by all cells. We were interested on how immune cells communicate via those vesicles so we developed assays to identify them. We then showed that if immune cells are invading the kidney during rejection, vesicles derived from those immune cells are found in the urine. This gave us the idea of developing a urine test based on these findings. (more…)