OR2803 Corticotroph Fate Weighted Cell Differentiation Paradigm For Human Induced Pluripotent Stem Cells

Disclosure: M.E. Moore: None. K.G. Chen: None. K. Park: None. D. Asuzu: None. N. Ramavenkat: None. S. Walbridge: None. D. Mullaney: None. M. Arhin: None. D. Maric: None. D. Mandal: None. P. Chittiboina: None. Introduction: The vertebrate anterior pituitary gland is a highly conserved ‘master’ organ that controls hormonal milieu in real-time. Pituitary adenomas and their treatments (surgery, chemotherapy or radiation) can result in pituitary organ failure, specifically hypocortisolism, a challenging condition to manage. Here, we created an optimized paradigm (anterior pituitary corticotroph or APcor) to preferentially drive human induced pluripotent stem cells (hiPSCs) towards a pituitary corticotroph fate. Methods: We directed U112I hiPSCs towards terminally differentiated cell types using a combination of rho-associated kinase inhibitor (Y-27632), bone morphogenic protein 4 (BMP4), transforming growth factor β inhibitor (SB431542), sonic hedgehog (SHH), fibroblast growth factor 8b (FGF8b), fibroblast growth factor 10 (FGF10) and leukemia inhibitory factor (LIF). Markers for pluripotent stem cells, cranial placode (CP), Rathke’s Pouch (RP), anterior pituitary progenitors and mature cell types were assessed at 10-day intervals using quantitative qRT-PCR and multiplex immunocytochemistry (mICC) or immunohistochemistry (IHC). ACTH activity was measured using ELISA (MD Bio). Results: We tested initial differentiation conditions and found optimal CP initiation in presence of SB431542. We observed decrease in embryonic stem cell markers OCT4 and NANOG by day 10, with concomitant increase in CP/RP markers SIX1, PAX6 and SIX6 using mICC/IHC and qRT-PCR. Continuation of differentiation paradigm with LIF showed strong expression of anterior pituitary progenitor markers PITX1, TBX19 and POU1F1 at day 20. pRT-PCR analysis at this time point confirms differentiation towards pituitary cell types without needing enrichment for SIX1. At day 30, POMC expression was observed by IHC in 10-15% of cells as measured by quantitative analysis (Qupath 0.2.0), indicating mature corticotrophs. Corticotroph cell fate was confirmed with corticotropin releasing hormone (CRH) stimulation which led to up to 40x-fold increase in ACTH expression detected by ELISA (D30 w/CRH vs Pluripotent w/CRH). Conclusions: We found with the APcor paradigm, we can reliably drive towards corticotroph cell fate. We successfully differentiated hiPSCs into mature functioning corticotrophs with ability to recapitulate pituitary organ function. Our method is amenable to 3D organoid formation and pre-clinical implantation in animal models of hypophysectomy as a novel hormone replacement therapy. Presentation: Sunday, June 18, 2023