Lymphatic disruption drives lung transplant fibrosis through interleukin-1–mediated hyaluronan accumulation

The consequence of lymphatic disruption during transplantation of solid organs remains unknown. Long-term survival after organ transplantation is limited by chronic rejection, a poorly understood process involving fibrotic remodeling and functional decline of the graft. Here, we found that transplanted human lungs and hearts with chronic rejection exhibited fibrosis distributed along dysmorphic lymphatics in areas densely concentrated with hyaluronan, an interstitial glycosaminoglycan that depends on lymphatic drainage for clearance. We illustrated similar findings in transplanted mouse lungs and hearts, which were accompanied by lymphographic findings of graft lymphedema. Using unsupervised clustering, we found a subset of stromal cells present in fibrotic syngeneic mouse lung grafts and human lung and heart grafts with chronic rejection that coexpressed hyaluronan synthase 1 and interleukin-1 receptor 1. Shortly after reperfusion of syngeneic mouse lung grafts, we identified neutrophilic expression of <i>interleukin-1</i>β (<i>Il1b</i>) as a driver of hyaluronan synthase 1 up-regulation. We found interleukin-1-mediated hyaluronan accumulation as a mechanism driving fibrosis that occurred independent of alloimmunity in the setting of lymphatic disruption after transplantation. Development of fibrotic remodeling in transplanted mouse lungs was inhibited by preventing hyaluronan synthesis through the administration of 4-methylumbilliferone, accelerating lymphangiogenesis with pharmacologic activation of VEGF (vascular endothelial growth factor) receptor-3, or inhibiting interleukin-1 receptor 1 signaling in the graft. These therapeutic interventions lay the foundation for future clinical strategies to prevent chronic rejection.