Abstract
Using a novel Microplate Biomaterial Microarray (MBM™) technology, we have created an artificial hematopoietic stem cell niche that can sustain growth and differentiation of human embryonic stem cells-derived (hES) early hematopoietic progenitors. This hydrogel based ex-vivo niche allows uploading of human embryonal stem cells, human mesenchymal stem cells (MSC), genes (bcl-2 preventing apoptosis and HoxB4 enhancing hematopoiesis) and extracellular matrices to support growth and differentiation of human ES cells. These experiments were done using NIH-approved hES cell lines H1 and H9. Serum-free, feeder-free culture conditions were established and early hematopoietic progenitors grown using SCF, TPO, VEGF and IL-3 with high efficiency. At day 3–5 dual CD34+/CD31+ progenitors were identified, while on day 7–8 CD34+ hematopoietic progenitors were isolated, which formed typical hematopoietic colonies. These progenitors expressed genes related to early hematopoiesis, such as TAL1/SCL, FLT1, GATA2, GATA1, EPOR and TPOR. The early dual endothelio-hematopoietic progenitor (hemangioblast) expressed PECAM-1 and CD34 and showed typical blast-like morphology. Based on mathematical simulations, various micro-niches were designed to establish optimal differentiation conditions for this progenitor using IL-3, IL-6, TPO, EPO, VEGF, SFC, Flt-3 ligand and various extracellular matrices. Specific micro-niches were created for generation of CFU-E, BFU-E, CFU-GM, CFU-GEMM, CFU-M, CFU-G, and CFU-MK progenitors from human ES-derived hemangioblast. Kinetic uploading of TPO, EPO, SCF and VEGF created a niche-sustaining growth of ES-derived hemangioblast with high efficiency and low apoptosis rate. These niches used pulse -delivery of anti-apoptotic bcl-2 gene and hematopoiesis-enhancing Hoxb4 gene. The model of artifical niche sustaing growth and differentiation of human ES-derived hemangioblast was established. In the future, this system will allow optimized and upscaled generation of early hematopoietic progenitors from human ES cells, as a first step towards clinical applications of human embryonic stem cells.
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