Bioprocess for producing uniform embryoid bodies from embryonic stem cells in a high density bioreactor
The present inventors identified aggregation of embryonic stem cells and embryoid bodies (EBs) as the cause of the difficulty in generating large numbers of the embryonic stem cells (ES) cell-derived tissues. To counter this, the invention provides a novel bioprocess where aggregation of spheroid forming cells, such as embryonic stem cells and spheroids, such as EBs is controlled, such as by encapsulation of within a matrix. As a result, EBs can be generated with high efficiency and cultured in high cell density, well-mixed systems. Well-mixed conditions facilitate measurement and control of the bulk media conditions and allow for the use of scalable bioreactor systems for clinical production of tissue. Therefore, the invention enables generation of ES cell-derived tissue on a clinical scale. The invention is also applicable to any spheroid-forming cells and other types of pluripotent cells.
1. A bioprocess for controlling aggregation of embryoid bodies during differentiation, comprising:
a) monitoring E-cadherin expression over time in a differentiating embryoid body;
b) determining a time when E-cadherin is down-regulated sufficiently in said embryoid body to prevent aggregation of embryoid bodies;
c) encapsulating one or more embryonic stem cells expressing E-cadherin in a biodegradable matrix so as to form a cell capsule, wherein the capsule is of a size to enable an embryoid body formed within the capsule to emerge from the capsule after down regulation of E-cadherin;
d) introducing the encapsulated cells into a cell culture environment comprising cell culture media, growth factors, and other factors to promote cell growth;
e) culturing the encapsulated cells from d) so as to form an embryoid body, said culturing being for a time as determined in b), such that the embryoid body formed within the capsule will emerge from the capsule and will not aggregate with other embryoid bodies upon emergence from the capsule;
f) optionally harvesting differentiated cells derived from the embryoid body that emerged from the capsule from the culture in step e).
2. The bioprocess of claim 1 , wherein the matrix is agarose or alginate.
3. The bioprocess of claim 1 , wherein the capsules are between 35 and 85 μm in diameter.
4. The bioprocess of claim 1 , wherein the cell culture environment is a stirred bioreactor.
5. The bioprocess of claim 1 , wherein the cells are cultured at a density of at least 10 5 cells per mL.
6. The bioprocess of claim 1 , wherein the cell culture media contains bovine serum or retinoic acid.
7. The bioprocess of claim 1 , which is part of a bioprocess for producing hematopoietic cells, neural cells, endothelial cells, or cardiomyocytes.
8. The bioprocess of claim 1 , further comprising determining expression of cell surface markers by the harvested differentiated cells of step (f).
9. The bioprocess of claim 1 , further comprising selecting a desired differentiated cell type according to its phenotype.
10. The bioprocess of claim 9 , wherein the differentiated cells are selected using a promoter-reporter construct introduced into the differentiated cells.
11. The bioprocess of claim 1 , further comprising determining functional activity of the differentiated cells in a methylcellulose colony assay.
12. The bioprocess of claim 1 , further comprising harvesting hematopoietic or endothelial cells from the culture.
13. The bioprocess of claim 1 , further comprising harvesting cardiac myocytes from the culture.
14. The bioprocess of claim 13 , wherein the harvested cells are over 70% positive for MF-20.
15. The bioprocess of claim 1 wherein cell differentiation continues after the embryoid body emerges from the capsule.
16. The bioprocess of claim 1 wherein the capsule holds up to 35,000 cells.
17. The bioprocess of claim 2 wherein the capsule holds up to 4200 cells at time of emergence of the embryoid body.
18. The bioprocess of claim 1 , wherein in step (c), 1-1000 embryonic stem cells are initially encapsulated in one capsule.
19. The process of claim 1 , wherein steps (a) to (e) are done in a static culture, and wherein the embryoid body is transferred to a stirred bioreactor after step (e) and before step (f).
20. The bioprocess of claim 1 wherein the time E-cadherin is down-regulated to prevent aggregation of embryoid bodies is 4 days.
21. The bioprocess of claim 20 , wherein the embryoid bodies are produced from mouse ES cells.
22. The bioprocess of claim 21 wherein the capsule is 70-100 μm in diameter.