Studies on Intraocular Transplantation of Pancreatic Cells in a Large-eyed Preclinical Animal Model.

Abstract

Purpose : Pancreatic islet transplantation to the anterior chamber of the eye (ACE) has been shown to correct hyperglycemia and restore/improve glycemic control in rodents and non-human primates. These studies also suggested that the eye may be in several ways a superior host site compared to the conventional hepatic portal system. In order to bring this technology to the clinic, it is essential to establish a large-eyed non-primate transplantation model. This proposal aims at establishing a rabbit ACE model of allogeneic islet cell transplantation. We expect to gain insight into isolated islets function as well as ACE grafting efficiency and histological morphology in the large-eyed rabbit model.

Methods : Pancreatic islets were isolated from Dutch Belted rabbits by injection of collagenase A into the pancreatic interstitium, digestion and hand picking under a stereo microscope. Islets were cultured in RPMI medium overnight in a standard tissue culture incubator prior to assessment of purity. In vitro functional capacity of rabbit islets was assessed by glucose-stimulated insulin release and intracellular Ca2+ imaging assays. Islets were injected into the ACE an allogeneic Dutch Belted rabbit using surgical procedures routinely applied in ophthalmology. Islets engraftment and cellular content was analyzed by anterior segment optical coherence tomography (ASOCT) and immunohistofluorescence (IHF).

Results : Isolated islets were of high purity with an approximate yield of 600-800 islets per pancreas. Preliminary results of functional capacity demonstrate that islets are responsive to high glucose stimulus, despite some variability. Allogeneic transplantation of isolated islets into the ACE of a Dutch Belted rabbit was followed by ASOCT. Engraftment was confirmed by IHF for vimentin. IHF suggests ACE engrafted islets are viable and maintain alpha, beta and delta cells with positive staining for glucagon, insulin and somatostatin, respectively.

Conclusions : The presented isolation method renders high purity and functional rabbit pancreatic islets. Allogeneic transplantation of pancreatic islets into the ACE was successful using clinically relevant procedures, and resulted in islets engraftment and long-term survival. These results may have implications for the clinical treatment of diabetes mellitus, particularly regarding patients with indications for pancreatic islet transplantation.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.