Method for producing polyploidized megakaryocyte and platelets

1. A method of producing polyploidized megakaryocytes, comprising:

inducing expression of an apoptosis suppressor gene, a MYC family gene, and a BMI1 gene in megakaryocytes before polyploidization, and

culturing the resulting cells from the inducing step, wherein the oncogene is different from the apoptosis suppressor gene.

2. The method according to claim 1 , wherein the apoptosis suppressor gene is a BCL-XL gene.

3. The method according to claim 1 , wherein the culturing step comprises inhibiting expression or function of a p53 gene product.

4. The method according to claim 1 , wherein the megakaryocytes before polyploidization are subjected to at least one of the following (a) to (c):

(a) treatment with an actomyosin complex function inhibitor;

(b) treatment with an Rho-associated coiled-coil forming kinase/Rho associated kinase (ROCK) inhibitor; and

(c) treatment with an Histone deacetylase (HDAC) inhibitor.

5. The method according to claim 4 , wherein the ROCK inhibitor is [(R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexane carboxamide. 2HCl. H 2 O] (Y27632); the HDAC inhibitor is valproic acid; and the actomyosin complex function inhibitor is blebbistatin.

6. The method according to claim 1 , wherein the culturing step is conducted at a temperature higher than 37° C.

7. The method according to claim 1 , wherein the MYC family gene is a c-MYC gene.

8. The method according to claim 1 , wherein the megakaryocytes before polyploidization are derived from cells selected from the group consisting of induced pluripotent stem (iPS) cells, embryonic stem (ES) cells, hematopoietic stem cells derived from cord blood, bone marrow blood, peripheral blood, and hematopoietic stem cells.

9. A method of producing platelets, comprising:

obtaining polyploidized megakaryocytes by the method according to claim 1 ,

culturing the polyploidized megakaryocytes to produce culture of the polyploidized megakaryocytes; and

collecting the platelets from the culture of the polyploidized megakaryocytes.

10. The method according to claim 9 , wherein the step of culturing the polyploidized megakaryocytes is conducted while suppressing the expression of the apoptosis suppressor gene that has been induced, or after the apoptosis suppressor gene is removed from the cells.

11. The method according to claim 9 , wherein the step of culturing the polyploidized megakaryocytes is conducted in the absence of serum and/or in the absence of a feeder cell.

12. The method according to claim 9 , wherein the step of culturing the polyploidized megakaryocytes is conducted from 1 day to 15 days.

13. The method according to claim 9 , wherein the step of culturing the polyploidized megakaryocytes is conducted at 37° C.

14. The method according to claim 9 , wherein in the step of culturing the polyploidized megakaryocytes, an ROCK inhibitor and/or an actomyosin complex function inhibitor is added to a medium.

15. The method according to claim 14 , wherein the ROCK inhibitor is Y27632, and the actomyosin complex function inhibitor is blebbistatin.

16. The method according to claim 1 , further comprising treating the megakaryocytes before polyploidization with one or more inhibitors selected from the group consisting of an actomyosin complex function inhibitor; an Rho-associated coiled-coil forming kinase/Rho associated kinase (ROCK) inhibitor; and an Histone deacetylase (HDAC) inhibitor.

17. The method according to claim 9 , wherein the method comprises treating the megakaryocytes before polyploidization with the Rho-associated coiled-coil forming kinase/Rho associated kinase (ROCK) inhibitor.