Generation of keratinocytes from pluripotent stem cells and maintenance of keratinocyte cultures
Provided herein are methods for the generation of functional keratinocyte stem cells that are differentiated directly from human ESCs/iPSCs in a chemically defined serum-free cell culture system, as well as cells derived therefrom and methods of use thereof. Also provided are methods for culturing primary keratinocytes.
1. A method for providing engraftable human keratinocyte stem cells by differentiation of human pluripotent stem cells comprising:
(a) forming aggregates of the pluripotent stem cells in a suspension culture in the presence of a defined basal medium;
(b) culturing the aggregates in a suspension culture in the presence of an initiation culture medium comprising retinoic acid and bone morphogenetic protein 4 (BMP4) to effect the formation of initiated aggregates;
(c) culturing the initiated aggregates in a keratinocyte progenitor culture medium comprising cholera toxin and a transforming growth factor beta receptor 1 (TGFBR1) kinase inhibitor to effect the formation of a cell population comprising keratinocyte progenitors; and
(d) culturing the keratinocyte progenitors in a keratinocyte stem cell maturation medium comprising cholera toxin and vascular endothelial growth factor (VEGF) to effect the formation of a cell population comprising engraftable keratinocyte stem cells,
wherein the keratinocyte stem cells express cytokeratin 15 and CD49f.
2. The method of claim 1 , further comprising maintaining the keratinocyte stem cells in culture in a keratinocyte stem cell maintenance medium comprising cholera toxin and a TGFBR1 kinase inhibitor.
3. The method of claim 2 , wherein the keratinocyte stem cells are maintained for at least five population doublings.
4. The method of claim 3 , wherein the keratinocyte stem cells are maintained for at least ten population doublings.
5. The method of claim 1 , wherein the keratinocyte stem cells are at least 90% pure.
6. The method of claim 1 , wherein the keratinocyte stem cells are at least 95% pure.
7. The method of claim 1 , wherein the pluripotent stem cells are induced pluripotent stem (iPS) cells.
8. The method of claim 1 , wherein the pluripotent stem cells are cultured in a serum-free medium prior to step (a).
9. The method of claim 1 , wherein the pluripotent stem cells are cultured on a non-cellular matrix component prior to step (a).
10. The method of claim 1 , wherein the culture medium in step (a) is a chemically-defined culture medium.
11. The method of claim 1 , wherein the culturing in step (a) is performed for a time period of about one day.
12. The method of claim 1 , wherein the culturing in step (a) is further performed in the presence of a myosin light chain kinase inhibitor.
13. The method of claim 1 , wherein the culturing in step (b) is performed for a time period from about one day to about five days.
14. The method of claim 13 , wherein the culturing in step (b) is performed for a time period of about three days.
15. The method of claim 1 , wherein the suspension culture in step (a) and/or (b) is maintained as a static suspension culture.
16. The method of claim 1 , wherein the suspension culture in step (a) and/or (b) is maintained as a dynamic suspension culture.
17. The method of claim 1 , wherein the culturing in step (c) is performed for a time period from about eight to about 14 days.
18. The method of claim 17 , wherein the culturing in step (c) is performed for a time period of about ten days.
19. The method of claim 1 , wherein the keratinocyte progenitor culture medium further comprises epidermal growth factor (EGF), fibroblast growth factor 1 (FGF1), a cyclic AMP analog, niacinamide, ascorbic acid, or a combination thereof.
20. The method of claim 19 , wherein the keratinocyte progenitor culture medium further comprises EGF and niacinamide.
21. The method of claim 1 , wherein the culturing in step (c) is performed as an adherent culture.
22. The method of claim 1 , wherein the culturing in step (c) is performed on an extracellular matrix component.
23. The method of claim 1 , wherein the culturing in step (c) is performed on a non-cellular matrix component.
24. The method of claim 1 , wherein the keratinocyte progenitors formed in step (c) express cytokeratin 14 and/or p63.
25. The method of claim 1 , wherein a calcium level in the keratinocyte progenitor culture medium is not greater than about 0.2 mM.
26. The method of claim 1 , wherein the culturing in step (d) is performed for a time period from about four days to about eight days.
27. The method of claim 1 , wherein the culturing in step (d) is performed for a time period of about six days.
28. The method of claim 1 , wherein the keratinocyte stem cell maturation medium further comprises EGF, FGF1, a cyclic AMP analog, niacinamide, or a combination thereof.
29. The method of claim 1 , wherein the culturing in step (d) is performed as an adherent culture.
30. The method of claim 1 , wherein the culturing in step (d) is performed on an extracellular matrix component.
31. The method of claim 1 , wherein the culturing in step (d) is performed on a non-cellular matrix component.