Intestinal distribution of hyaluronan in small bowel allografting in the rat.

Hyaluronan (hyaluronic acid; HA) was demonstrated and quantified in small bowel tissue at different times after small bowel transplantation. Semiallogeneic or semisyngeneic rat models were used to elicit either unidirectional graft rejection or graft-versus-host disease (GVHD). In normal rat small bowel, HA was present in the villous lamina propria and around medium-sized vessels in the interstitium of the crypt area. During graft rejection a cellular infiltrate and edema appeared in the lamina propria in the crypt area where an accumulation of HA was also demonstrated. There was progressive accumulation of HA in the small bowel during rejection, and on day 6 there was a threefold increase compared to the values in syngeneic grafts. The increase in tissue HA was paralleled by an increase in the total water content of the rejecting graft. In specimens from animals suffering from GVHD, no significant changes in water or HA content and distribution were observed until day 12. The data suggest that accumulation of HA might contribute to the pathophysiology of the transplantation edema and that HA might be of potential diagnostic value in differentiating between graft rejection and GVHD.