Autoregulation of Islet Graft Blood Flow Follows the Implantation

Background

Transplantation of pancreatic islets necessitates a revascularization, which is associated with a generalized graft vascular dysfunction, manifested, e.g., as a capillary hypertension, a decreased graft blood perfusion and graft hypoxia. Some of these changes can be due to impaired autoregulation of the newly formed vasculature in the islet grafts, and the aim of the present study was to further examine if this was the case.

Materials and Methods

We implanted 250 syngeneic islets under the renal capsule of rats and studied them 1 or 12–13 mo later. The blood perfusion of the whole kidney, renal cortex, and islet grafts were recorded in anesthetized animals with an ultrasound probe or laser-Doppler probes, respectively. The blood pressure in the kidneys was then gradually decreased by an adjustable clamp, during simultaneous measurement of blood flow values.

Results

The whole kidney, renal cortex, and islet grafts regulated their blood flow in concert with one another down to pressures of approximately 60 mmHg both 1 and 12–13 mo after implantation. However, the variability was greater at 1 mo.

Conclusion

Islets transplanted under the renal capsule show similar autoregulatory properties with the kidney. It may be that the autoregulatory capacity of the renal interlobular arteries provides the underlying mechanism. This may be of importance for the good long-term survival of transplanted islets at this implantation site in experimental studies.

Key Words: autoregulation, blood flow, engraftment, islet transplantation, islet vasculature