191 ROBUST GENERATION OF NEURAL STEM CELLS FROM PIG INDUCED PLURIPOTENT STEM CELLS FOR TRANSLATIONAL NEURAL REGENERATIVE MEDICINE

Abstract

The generation of pig induced pluripotent stem cells (iPSC) opened the possibility to evaluate autologous neural cell therapy as a viable option for human patients. However, it is necessary to demonstrate whether pig iPSC are capable of in vitro neural differentiation similar to human iPSC in order to perform in vitro and in vivo comparative studies. Multiple laboratories have generated pig iPSC that have been characterised using pluripotent markers such as SSEA4 and POU5F1. However, correlations of pluripotent marker expression profiles among iPSC lines and their neural differentiation potential has not been fully explored. Because neural rosettes (NR) are composed of neural stem cells, our goal was to demonstrate that NR from pig iPSC can be generated, isolated, and expanded in vitro from multiple porcine iPSC lines similar to human iPSC and that the level of pluripotency in the starting porcine iPSC population (POUF51 and SSEA4 expression) could influence NRs development. Three lines of pig iPSC L1, L2, and L3 were cultured on matrigel-coated plates in mTeSR1 medium (Stemcell Technologies Inc., Vancouver, BC, Canada) and passaged every 3 to 4 days. For neural induction (NI), pig iPSC were disaggregated using dispase and plated. After 24 h, cells were maintained in N2 media [77% DMEM/F12, 10 ng mL^–1 bovine fibroblast growth factor (bFGF), and 1X N2] for 15 days. To evaluate the differentiation potential to neuron and glial cells, NR were isolated, expanded in vitro and cultured for three weeks in AB2 medium (AB2, 1X ANS, and 2 mM L-Glutamine). Immunostaining assays were performed to determine pluripotent (POU5F1 and SSEA4), tight junction (ZO1), neural epithelial (Pax6 and Sox1), neuron (Tuj1), astrocyte (GFAP), and oligodendrocyte (O4) marker expression. Line L2 (POU5F1^high and SSEA4^low) showed a high potential to form NR (6.3.5%, P < 0.05) in comparison to the other 2 lines L1 (POU5F1^low and SSEA4^low) and L3 (POU5F1^low and SSEA4^high) upon NI. The NR immunocytochemistry results from Line L2 showed the presence of Pax6+ and Sox1– NRs cells at day 9 post-neural induction and that ZO1 started to localise at the apical border of NRs. At day 13, NRs cells were Pax6+ and Sox1+, and ZO1 was localised to the lumen of NR. After isolation and culture in vitro, NR cells expressed transcription factors PLAGL1, DACH1, and OTX2 through 2 passages, but were not detected in later passages. However, rosette cytoarchitecture was present up until passage 7 and were still Pax6+/Sox1+. NRs at passage 2 were cryopreserved and upon thaw showed normal NR morphology and were Pax6+/Sox1+. To characterise the plasticity of NRs, cells were differentiated. Tuj1 expression was predominant after differentiation indicating a bias towards a neuron phenotype. These results demonstrate that L2 pig iPSC (POUF51^high and SSEA4^low) have a high potential to form NR and neural differentiation parallels human iPSC neurulation events. Porcine iPSC should be considered as a large animal model for determining the safety and efficacy of human iPSC neural cell therapies.