Methods and cellular structures

1. A method of producing a multi-layered cellular structure or blastocyst-like structure, the method comprising the following steps in order:

a) increasing the protein expression or amount of one or more factors in a population of somatic cells, wherein the factors are for reprogramming the somatic cells towards a dedifferentiated or pluripotent state;

b) culturing the cells for a sufficient time and under conditions to allow the reprogramming of the cells towards a dedifferentiated or pluripotent state to obtain a population of reprogramming intermediate cells;

c) contacting the reprogramming intermediate cells with a culture medium comprising an activator of WNT pathway signalling selected from the group consisting of glycogen synthase kinase 3 (GSK-31 inhibitor), at least one transforming growth factor beta (TGF-β) inhibitor, a histone deacetylase (HDAC) inhibitor, epidermal growth factor (EGF), and bone morphogenic protein 4 (BMP4) under conditions that allow aggregation;

d) culturing the cells in the culture medium for a sufficient time and under conditions that allow aggregation and/or allow the cells to exhibit at least one characteristic of a blastocyst-like structure,

thereby producing a multi-layered cellular or blastocyst-like structure.

2. The method of claim 1 , wherein the culture medium in step c) further comprises a Rho-kinase (ROCK) inhibitor.

3. The method of claim 1 , wherein the protein expression, or amount, of the factors for reprogramming the somatic cells towards a pluripotent state, is increased by introducing at least one nucleic acid comprising a nucleotide sequence encoding at least one factor for reprogramming the somatic cells towards a pluripotent state, or encoding a functional fragment thereof, in the cell.

4. The method of claim 1 , wherein the cell is cultured under the conditions of step b) for at least 1 day, or at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, days or at least 22, at least 24, at least 28 or more days.

5. The method of claim 1 , wherein the markers characteristic of the somatic cell are reduced prior to the step of culturing the reprogrammed somatic cells under conditions that allow aggregation to obtain a multi-layered cellular structure or blastocyst-like structure; or prior to the step of contacting the cells with a culture medium in step c).

6. A method of producing a multi-layered cellular structure or blastocyst-like structure, the method comprising the following steps in order:

a) increasing the protein expression or amount of one or more factors in a population of somatic cells, wherein the factors are for reprogramming the somatic cells towards a dedifferentiated or pluripotent state;

b) culturing the cells for a sufficient time and under conditions to allow the reprogramming of the cells towards a dedifferentiated or pluripotent state;

c) contacting the cells with a culture medium comprising an activator of WNT pathway signalling (selected from the group consisting of glycogen synthase kinase 3 (GSK-3) inhibitor), at least one transforming growth factor beta (TGF-β) inhibitor, a histone deacetylase (HDAC) inhibitor, epidermal growth factor (EGF), and bone morphogenic protein 4 (BMP4) under conditions that allow aggregation;

d) culturing the cells in the culture medium for a sufficient time and under conditions that allow aggregation and/or allow the cells to exhibit at least one characteristic of a blastocyst-like structure, wherein step b) comprises culturing the cells towards a dedifferentiated or pluripotent state in a medium that induces upregulation of the epiblast(EPI, trophectoderm (TE) and primitive endoderm (PE) lineage transcriptional signatures.

7. The method of claim 1 , wherein the conditions that allow aggregation may comprise culturing on any culture plate, culture vessel or culture system that allows three-dimensional aggregation of cells.

8. The method of claim 1 , wherein the multi-layered cellular structure or blastocyst-like structure comprises an inner cell layer and an outer cell layer, the inner cell layer comprises cells that exhibit one or more characteristics of cell of the epiblast (EPI) and/or the primitive endoderm (PE) lineage, and the outer cell layer comprises cells that exhibit one or more characteristics of a cell of the trophectoderm (TE).

9. The method of claim 1 , wherein the multi-layered cellular structure or blastocyst-like structure comprises an inner cell layer wherein the inner cell layer further comprises a cluster of cells that exhibit one or more characteristics of the PE.

10. The method of claim 1 , wherein the multi-layered cellular structure or blastocyst-like structure comprises an inner cell layer that comprises cells that exhibit one or more characteristics of cell of the epiblast (EPI) and/or the primitive endoderm (PE) lineage, wherein the characteristic of an EPI cell is presence of any one or more of the markers NANOG, OCT4 (also known as POU5F1) or SOX2.

11. The method of claim 1 , wherein the multi-layered cellular structure or blastocyst-like structure comprises an outer cell layer that comprises cells that exhibit one or more characteristics of a cell of the trophectoderm (TE), wherein the characteristic of a TE cell is presence of one or more the markers CDX2 and GATA2 and/or a flattened or elongated epithelial morphology.

12. The method of claim 1 , wherein the multi-layered cellular structure or blastocyst-like structure comprises an inner cell layer that comprises cells that exhibit one or more characteristics of cell of the epiblast (EPI) and/or the primitive endoderm (PE) lineage, wherein the characteristic of a PE cell is presence of the marker SOX17 or GATA6.

13. The method of claim 1 , wherein the multi-layered cellular structure or blastocyst-like structure exhibits the main morphological features of human blastocysts at E5-7, preferably E6-7.

14. The method of claim 1 , wherein the multi-layered cellular structure or blastocyst-like structure comprises a cell free cavity, or blastocoel-like cavity.

15. A method of producing a multi-layered cellular structure or blastocyst-like structure, the method comprising:

culturing an iPSC and iTSC cell under conditions that allow assembly and aggregation of the cells to obtain a multi-layered cellular structure, wherein the cells are cultured in culture medium for promoting cells to exhibit at least one characteristic of a blastocyst-like structure and wherein the culture medium comprises: an activator of WNT pathway signalling selected from the group consisting of glycogen synthase kinase 3 (GSK-31 inhibitor), at least one transforming growth factor beta (TGF-β) inhibitor, a histone deacetylase (HDAC) inhibitor, epidermal growth factor (EGF), and bone morphogenic protein 4 (BMP4);

thereby producing a multi-layered cellular or blastocyst-like structure.

16. The method of claim 15 , wherein the iPSC and iTSCs are derived from human cells.

17. The method of claim 15 , wherein the conditions allowing assembly and aggregation of the cells comprise co-culturing of the iPSCs and iTSCs in any culture vessel which promotes self-organisation and assembly of the cells.

18. The method of claim 6 , wherein the culture medium in step c) further comprises a Rho-kinase (ROCK) inhibitor.

19. The method of claim 6 , wherein the protein expression, or amount, of the factors for reprogramming the somatic cells towards a pluripotent state, is increased by introducing at least one nucleic acid comprising a nucleotide sequence encoding at least one factor for reprogramming the somatic cells towards a pluripotent state, or encoding a functional fragment thereof, in the cell.

20. The method of claim 6 , wherein the cell is cultured under the conditions of step b) for at least 1 day, or at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, days or at least 22, at least 24, at least 28 or more days.

21. The method of claim 6 , wherein the conditions that allow aggregation comprise culturing on any culture plate, culture vessel or culture system that allows three-dimensional aggregation of cells.

22. The method of claim 15 , wherein the culture medium comprises: a GSK-3 inhibitor in the form of CHIR99021, at least one TGF-β inhibitor selected from SB431542 and A83-01, a HDAC inhibitor in the form of valproic acid, EGF and BMP4.

23. The method of claim 15 , wherein the medium further comprises a ROCK inhibitor.

24. The method of claim 22 , wherein the medium further comprises a ROCK inhibitor in the form of Y-27632.

25. The method of claim 1 , wherein the multi-layered cellular structure or blastocyst-like structure comprises an inner cell layer wherein the inner cell layer further comprises a cluster of cells that exhibit one or more characteristics of the PE and wherein the cells that exhibit one or more characteristics of the PE are, or are predominantly, peripheral to the cells that exhibit one or more characteristics of a cell of the epiblast.

26. The method of claim 15 wherein the iPSC and iTSCs are obtained by reprogramming of human somatic cells.