Implantation of E42 pig pancreatic precursors in the subcutaneous space of Non-human primates (NHP)

C. Rosen, G. Hecht, S. Eventov-Friedman, E. Shezen, D. Tchorsh, A. Aronovich, E. Freud, H. Golan, R. El-Hasid, H. Katchman, B.J. Hering, A. Zung, Z. Kra-Oz, P. Shaked-Mishan, A. Yusim, A. Shtabsky, P. Idelevitch, A. Tobar, A. Harmelin, E. Bachar-Lustig, Y. Reisner

Weizmann Institute of Science, Immunology, Rehovot, Israel

Objective: Our studies in the NHP model during the past few years, have demonstrated the proof of concept for correction of diabetes by transplantation in the omentum of E42 pig embryonic pancreatic tissue . Consequently, we are trying to ‘fine tune’ our immune suppression protocol and to define an optimal protocol prior to clinical translation. An attractive option for further improvement is to use a subcutaneous site for implantation instead of the omental site.

Methods: Our study was conducted in two non-diabetic immunosuppressed NHP. Pig embryonic pieces were injected in the first experiment by fine needle under the subcutaneous space. In the second experiment inplantation was carried out under direct vision, through a one cm long incision thus creating a subcutaneous pocket . Biopsy was performed at 3 months posttransplant comparing implant size to our previous implants in the omentum.

Results: The results of the first experiment revealed that the implanted embryonic tissue could grow and develop subcutaneously, as judged by the presence of pig islets. The second experiment demonstrated robust graft growth (Fig A), presence of islets by H&E (Fig B) as well as by staining for insulin (Fig. C). These islets were clearly dividing based on Ki67 staining. Similarly to previous implants in the omentum, islets in the subcutaneous sites were predominantly vascularized by host blood vessels and morphometric analysis of this implant demonstrated an islet mass comparable to that found in the omental graft.

Conclusions:Based on these results, further experiments testing the efficacy of subcutaneous transplantation in diabetic animals are warranted.