Efficient generation of NKX6-1+ pancreatic progenitors from multiple human pluripotent stem cell lines

Abstract

Human pluripotent stem cells (hPSCs) represent a renewable source of pancreatic beta cells for both basic research and therapeutic applications. Given this outstanding potential, significant efforts have been made to identify the signaling pathways that regulate pancreatic development in hPSC differentiation cultures. In this study, we demonstrate that the combination of epidermal growth factor (EGF) and nicotinamide signaling induces the generation of NKX6-1(+) progenitors from all hPSC lines tested. Furthermore, we show that the size of the NKX6-1(+) population is regulated by the duration of treatment with retinoic acid, fibroblast growth factor 10 (FGF10), and inhibitors of bone morphogenetic protein (BMP) and hedgehog signaling pathways. When transplanted into NOD scid gamma (NSG) recipients, these progenitors differentiate to give rise to exocrine and endocrine cells, including monohormonal insulin(+) cells. Together, these findings provide an efficient and reproducible strategy for generating highly enriched populations of hPSC-derived beta cell progenitors for studies aimed at further characterizing their developmental potential in vivo and deciphering the pathways that regulate their maturation in vitro.

Graphical abstract

Figure 1

NOGGIN, EGF, and Nicotinamide Induce NKX6-1 Expression (A) Schematic of the protocol used to differentiate hESCs toward pancreatic endoderm. At the final stage of differentiation, cells were treated with NOGGIN, EGF, and nicotinamide, singly or in combinations. (B) Flow-cytometric analysis for GFP was carried out at d13 of differentiation. (C) Average percentage of NKX6-1:GFP⁺ cells as measured by flow-cytometry analysis at d13 of differentiation in the different treatment groups (−, untreated; N, NOGGIN; E, EGF; NA, nicotinamide; NE, NOGGIN+EGF; NNA, NOGGIN+nicotinamide; NENA, NOGGIN+EGF+nicotinamide). Error bars represent SD of the mean (n = 3 independent experiments). (D) Kinetic analysis of NKX6-1:GFP expression as measured by flow cytometry between d7 and d17 of differentiation. Error bars represent SD from the mean of three experiments. ^∗∗p < 0.05, ^∗∗∗p < 0.001 using Student’s t test for statistical analysis. (E) qPCR analysis for NKX6-1, PDX1, PTF1A, and SOX9 expression during pancreatic differentiation of the NKX6-1^GFP/w hESC line (d7–d17). NKX6-1^GFP/w cells were differentiated as described in (A). Expression levels are normalized to the housekeeping gene TBP and compared with adult pancreas (AP, dashed bar). Error bars represent SD of the mean (n = 3 independent experiments). See also Figures S1 and S2.

Figure 2

NOGGIN, EGF and Nicotinamide Induce NKX6-1 Expression in Non-Targeted hESC Lines (A) Flow-cytometric analysis of intracellular NKX6-1. H1 cells and H9 hESCs were differentiated according to a published protocol (Nostro et al., 2011) up to stage 3 and then treated with NOGGIN, EGF and nicotinamide, alone or in combination, for 6 days. Flow-cytometric analysis was performed at d13 of differentiation. Triple treatment was sufficient to induce the highest percentage of NKX6-1⁺ cells. Error bars represent SD of the mean (n = 3 independent experiments). ^∗∗∗p < 0.001 using Student’s t test. (B) qPCR analysis for NKX6-1, PDX1, PTF1A, SOX9, NEUROD1, and NGN3 expression between d7 and d17 of pancreatic differentiation. Expression levels are normalized to the housekeeping gene TBP and compared with adult pancreas (AP, dashed bar). Error bars represent SD of the mean (n = 5 independent experiments). (C) Immunofluorescence image of d13 culture, showing NKX6-1 in green and PDX1 and SOX9 in red. The solid bar is 200 μm. See also Figures S1 and S2.

Figure 3

Short RA/Cyclopamine/FGF10 Exposure and Activin Treatment Favor NKX6-1 Development (A) Schematic of the protocol used to differentiate hPSCs toward first- and/or second-transition progenitors. Stage 3 of differentiation consisted of NOGGIN, cyclopamine, RA, and FGF10 (NCRF). Sant-1 was used as a substitute for cyclopamine and purmorphamine (2.5, 7.5, and 22.5 μM) was used to activate hedgehog signaling in the absence of Sant-1 and cyclopamine. (B–E) NCRF treatment lasted for 1–4 days. Stage 4 of differentiation was supplemented with SB431542 (SB) or activin A at 0.3, 1, 3, and 9 ng/ml (A 0.3, A 1, A 3, and A 9). Average percentage of NKX6-1:GFP⁺ cells in red (B and D) and C-peptide⁺ in black (C and E) as measured by flow-cytometry analysis at d11, d12, d13, and d14 of differentiation. Error bars represent SD of the mean of the percentage of C-peptide⁺ and NKX6-1⁺ cells (n = 5 independent experiments, except for C-peptide 38-2: n = 3 independent experiments). ^∗∗p < 0.01 using Student’s t test. (F and G) The NRF treatment lasted 2 or 4 days and hedgehog signaling was activated during this stage by purmorphamine (2.5, 7.5, and 22.5 μM) or inhibited by treatment with Sant-1 (2.5 mM). Average percentage of NKX6-1:GFP⁺ cells in red (F) and C-peptide⁺ in black (G) as measured by flow-cytometry analysis at d12 and d14 of differentiation. Error bars represent SD of the mean of the percentage of C-peptide⁺ and NKX6-1⁺ cells (n = 4 independent experiments); ^∗p < 0.05 using one-way ANOVA and Student’s t test for comparisons between d12-d14 NSRF treatments. See also Figure S3.

Figure 4

NKX6-1 Cells Generated Using NOGGIN, EGF, and Nicotinamide Have the Potential to Generate Islet-like Structures Immunohistochemical analysis of NKX6-1, INS, GCG, SST, PP, CK19, and TRYP expression in the graft recovered from the mammary fat pad at 6 months post-transplantation of H1 d13 differentiated cells. Scale bar, 200 μm. See also Figures S4 and S5.

Figure 5

Model of Pancreatic Specification from hPSCs hPSCs can be efficiently differentiated into definitive endoderm, which can be patterned to a posterior-foregut-like population that has the potential to upregulate PDX1 expression upon treatment with RA and FGF10, and inhibition of SHH (using Sant-1 or cyclopamine) and BMP (using NOGGIN). PDX1-expressing cells have the potential to generate two distinct pancreatic lineages: (1) a multi-potent pancreatic progenitor expressing NKX6-1 with the potential to give rise to adult-like monohormonal cells, and (2) a polyhormonal population that lacks expression of NKX6-1 and the ability to generate functional beta cells, but generates glucagon⁺ cells (Basford et al., 2012). Our findings in this study uncover important differences in the regulation of the two programs and show that the monohormonal cell progenitor is specified within 24 hr by treatment with a combination of stage 3 agonists and the antagonists RA, FGF10, and NOGGIN, independently of hedgehog signaling, and that the generation of the NKX6-1⁺ progenitor population from this specified pancreatic endoderm is dependent on EGF and nicotinamide signaling. In contrast, specification of the polyhormonal program requires 72–96 hr of treatment with RA, FGF10, and NOGGIN. Crucially, hedgehog inhibition and expansion of the derivative lineages are not dependent on the addition of exogenous EGF and nicotinamide.