Serum hyaluronan - A potential marker of cardiac allograft rejection?

Background: The connective tissue component hyaluronan accumulates within the transplanted organ at rejection. Increased tissue content of hyaluronan is seen also in synovial tissue in rheumatoid arthritis and in skin in scleroderma. In these diseases, the elevated hyaluronan levels are reflected by increased concentrations of hyaluronan in serum. The aim of the present study was to study the changes in serum hyaluronan after organ transplantation. Methods: The experiments were performed in a rat model of heterotopic heart transplantation. Serum hyaluronan was assessed at various times after allogeneic (rejection) and syngeneic (non-rejection) transplantation and correlated with tissue hyaluronan. In addition, serum hyaluronan in animals who had long-term-surviving allogeneic grafts was studied. Results: The hyaluronan concentration in serum was significantly higher in the rejecting than in the non-rejecting group 4 and 6 days after transplantation (p < 0.01). On Day 6, serum hyaluronan had increased by 400% in animals with an allogeneic transplant and by 100% in those with a syngeneic transplant. There was a positive correlation between serum hyaluronan and tissue hyaluronan (p < 0.05). Animals with long-term-surviving grafts displayed normal serum hyaluronan levels. Conclusions: Rejection of rat heart transplants is associated with strongly increased serum hyaluronan that parallels the hyaluronan accumulation within the transplant.