Bacterial CRISPR‐Cas9 system has emerged as an effective tool for sequence‐specific gene knock‐out through non‐homologous end joining (NHEJ), but it remains inefficient for precise editing of genome sequences (gene knock‐in) via homology‐directed repair (HDR). Because of this a long and tedious screening process via cell sorting or selection, expansion, and sequencing is often required to identify correctly edited cells. Improving the efficiency of precise CRISPR gene editing remains a major challenge for many applications, such as generating sufficient numbers of genome‐edited animals or genome edited patient reprogrammed cell lines for disease modeling. Using our patented technology to develop Artificial 3D Microenvironment Niche (US Patent # 904737), we have developed a reporter based screening approach for high‐throughput identification of chemical compounds that can modulate precise genome editing through HDR. In preliminary experiments, we have identified small molecule classes that enhance CRISPR mediated HDR efficiency more than 9 fold. Additionally, we have found that small molecules that inhibit HDR, enhance insertion and deletion mutations via NHEJ and “vice versa”. We plan to further test this refined genome editing methodology for growth hormone gene modifications in dog (Canis familiaris) induced pluripotent stem cells (diPSC), attempting to correct genetically inherited disorders in dogs and for the development of “designer pets” of the future. Our preliminary findings with this experimental system will be presented.Support or Funding InformationThis project was supported by Internal R&D funds from DNAmicroarray, Inc.

Bottlenose dolphins (Tursiops sp.) typically survive deep soft tissue injuries from shark bites via an impressive, less understood, wound healing process which in comparison to humans is rapid (days vs. weeks), efficient (no need for external intervention), and has a much higher success rate (little if any scarring while completely regenerates damaged tissues).In this study, directed reprogramming of fibroblasts into pluripotent stem cells (iPSC) in humans and dolphins was compared. Molecular and Cellular analyses were designed to determine whether mammalian stem cell pluripotency‐inducing factors are also involved in inducing pluripotency in skin fibroblasts obtained from bottlenose dolphins possibly contributing to the observed efficient and rapid wound healing and tissue regeneration in these animals.Our results indicate that dolphin skin fibroblasts are much more efficiently reprogrammed to induced pluripotency in‐vitro. The presence of an inherent in‐vivo reprogramming process unique to dolphin fibroblasts (absent in human fibroblasts) that may be involved in the observed efficient wound healing process in dolphins was also detected. Further understanding of Pluripotency inducing intracellular pathways and their triggering mechanisms should enable better understating of the similarities and differences between stem cell mediated wound healing in dolphins and human.

Abstract Abstract 4334 It is estimated that for every unit of donated blood, two units are required in North America. The current rate of blood donation is stagnant while the need increases by 6–8% annually. In order to overcome this difficulty, we have developed an improved method to generate red blood cells from human embryonic stem cells (H9) with increased efficacy. In addition to xeno-free conditions and standard cytokine cocktail used for hematopoietic differentiation of human embryonic stem cells (Carrier et al. J Transl Med. 2009; Vol 7: 27), we have introduced a new method of improved growth and differentiation of human ES cells with hypoxia-induced mesenchymal stem cells, obtained from allogeneic adult bone marrow donors. This technique increased efficacy of red blood cell production by 5–25 fold. We have developed a bioscaffold–> microsphere-based culture system with highly porous surface allowing culturing of a very large number of embryonic stem cells per one culture condition. This culture system avoids shear forces and damage to the cells, and facilitates removal and recycling of the microspheres. The in vitro obtained human ES-derived red blood cells are enucleated and do not produce tumors (efficacy of enucleation is 65–95%). The laser-based system is utilized to eliminate nucleated cells from the culture. The problem with hES-derived red blood cells is that they are produced in small numbers and process is very costly. We are developing a 3-phase bioreactor with computerized programming, which will increase every step of the differentiation process and allow recycling of feeder cells and cytokines. In this system we will utilize iron-loaded microspheres coated with hypoxia-processed mesenchymal stem cells as a main culture unit. The in vitro generated human ES-derived red blood cells upscaled in a bioreactor will be used for the off-shelf production of red blood cells for clinical use. Disclosures: Srivastava: Giostar: Employment, Equity Ownership. Azad:Dnamicroarray, Inc.: Employment, Equity Ownership. Carrier:Giostar: Consultancy; Samaritan Pharmaceuticals: Consultancy; Entest Biomedical: Consultancy, Equity Ownership; America Stem Cells: Consultancy, Equity Ownership; Millenium: Speakers Bureau; NovaRx: Employment, Equity Ownership.

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. Figure Figure

The role of thrombopoietin (TPO) in adult hematopoiesis is well-established. A recent report suggests that TPO and vascular endothelial growth factor (VEGF) play a role in promoting formation of early erythropoietic progenitors in a nonhuman primate embryonic stem cell (ES) model. No such report exists for human ES cells as yet. Because TPO may become an important factor promoting human ES cell-derived hematopoiesis, we sought to investigate whether TPO in combination with VEGF can enhance human ES-derived hematopoiesis in an EB-derived culture system. The emphasis of this work was to demonstrate the molecular mechanisms involved in this process, specifically the role of c-mpl and its ligand TPO. Human ES cells were cultured to the EB state, and EB-derived secondary cultures supporting hematopoietic differentiation were established: condition 1, control (stem cell factor [SCF] and Flt3 ligand [Flt3L]); condition 2, SCF, Flt3L, and TPO; and condition 3, SCF, Flt3L, TPO, and VEGF. Cells were harvested daily, starting at day 2 and continuing until day 8, for reverse transcription-polymerase chain reaction and Western blot. There was no evidence of expression of c-mpl and VEGF receptor on the gene or protein level until day 8, when the formation of well-established hematopoietic colonies began. This correlated with the formation of CD34+/CD31- negative progenitors, mostly found in blast-forming units-erythroid-like colonies. We concluded that TPO and VEGF play an important synergistic role in the formation of early ES-derived hematopoietic progenitors that occurs through the c-mpl and VEGF receptors. Disclosure of potential conflicts of interest is found at the end of this article.