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Objective: To investigate whether intravitreally applied haemangioblasts (HB) derived from human embryonic stem cells (hESCs) are helpful for the repair of vascular damage caused in animals by an oxygen-induced retinopathy (OIR), by an induced diabetic retinopathy (DR) or by an induced retinal ischaemia with subsequent reperfusion., Methods: Human embryonic stem cell-derived HBs were transplanted intravitreally into C57BL/6J mice (OIR model), into male Wistar rats with an induced DR and into male Wistar rats undergoing induced retinal ischaemia with subsequent reperfusion. Control groups of animals received an intravitreal injection of endothelial cells (ECs) or phosphate-buffered saline (PBS). We examined the vasculature integrity in the mice with OIR, the blood-retina barrier in the rats with induced DR, and retinal thickness and retinal ganglion cell density in retina flat mounts of the rats with the retinal ischaemic-reperfusion retinopathy., Results: In the OIR model, the study group versus control groups showed a significantly (p < 0.001) smaller retinal avascular area [5.1 ± 2.7%;n = 18 animals versus 12.2 ± 2.8% (PBS group; n = 10 animals) and versus 11.8 ± 3.7% (EC group; n = 8 animals)] and less retinal neovascularization [6.3 ± 2.5%;n = 18 versus 15.2 ± 6.3% (n = 10; PBS group) and versus 15.8 ± 3.3% (n = 8; EC group)]. On retinal flat mounts, hESC-HBs were integrated into damaged retinal vessels and stained positive for PECAM (CD31) as EC marker. In the DR model, the study group versus the EC control group showed a significantly (p = 0.001) better blood-retina barrier function as measured at 2 days after the intravitreal injections [study group: 20.2 ± 12.8 μl/(g × hr); n = 6; versus EC control group: 52.9 ± 9.9 μl/(g × hr; n = 6)]. In the retinal ischaemia-reperfusion model, the groups did not differ significantly in retinal thickness and retinal ganglion cell density at 2, 5 and 7 days after baseline., Conclusion: By integrating into damaged retinal vessels and differentiating into ECs, intravitreally administered hESC-HBs may have partially repaired a retinal vascular injury caused by OIR model and DR., (© 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.)

Efforts to recapitulate haematopoiesis, a process guided by spatial and temporal inductive signals, to generate haematopoietic progenitors from human pluripotent stem cells (hPSCs) have focused primarily on exogenous signalling pathway activation or inhibition. Here we show haemogenic niches can be engineered using microfabrication strategies by micropatterning hPSC-derived haemogenic endothelial (HE) cells into spatially-organized, size-controlled colonies. CD34+VECAD+ HE cells were generated with multi-lineage potential in serum-free conditions and cultured as size-specific haemogenic niches that displayed enhanced blood cell induction over non-micropatterned cultures. Intra-colony analysis revealed radial organization of CD34 and VECAD expression levels, with CD45+ blood cells emerging primarily from the colony centroid area. We identify the induced interferon gamma protein (IP-10)/p-38 MAPK signalling pathway as the mechanism for haematopoietic inhibition in our culture system. Our results highlight the role of spatial organization in hPSC-derived blood generation, and provide a quantitative platform for interrogating molecular pathways that regulate human haematopoiesis.

Donor-recipient cell interactions are essential for functional engraftment after nonautologous cell transplantation. During this process, transplant engraftment is characterized and defined by interactions between transplanted cells with local and recruited inflammatory cells. The outcome of these interactions determines donor cell fate. Here, we provide evidence that lineage-committed embryonic stem cell (ESC)-derived vascular progenitor cells are the target of major histocompatibility complex (MHC) class I-dependent, natural killer (NK) cell-mediated elimination in vitro and in vivo. Treatment with interferon γ was found to significantly upregulate MHC class I expression on ESC-derived vascular progenitor cells, rendering them less susceptible to syngeneic NK cell-mediated killing in vitro and enhancing their survival and differentiation potential in vivo. Furthermore, in vivo ablation of NK cells led to enhanced progenitor cell survival after transplantation into a syngeneic murine ischemic hindlimb model, providing additional evidence that NK cells mediate ESC-derived progenitor cell transplant rejection. These data highlight the importance of recipient immune-donor cell interactions, and indicate a functional role for MHC-I antigen expression during successful ESC-derived syngeneic transplant engraftment.