Cell aggregate including retinal tissue and production method therefor

1. A sphere-like cell aggregate comprising:

a core part consisting of neural retina; and

a covering part continuously or discontinuously covering at least a portion of a surface of the core part, wherein

(1) in the neural retina, a neural retinal layer including at least a photoreceptor layer is formed, wherein the photoreceptor layer contains one or more types of cells selected from the group consisting of at least a photoreceptor cell, a photoreceptor progenitor cell, and a retinal progenitor cell, and the cells contained in the photoreceptor layer are continuously present in a tangential direction to the surface of the core part;

(2) the covering part contains retinal pigment epithelial cells in contact with each other;

(3) the cell aggregate is free of a crystalline lens, a vitreous, a cornea, and a blood vessel; and

(4) the retinal pigment epithelial cells in the covering part and the neural retinal layer constituting neural retina in the core part in the sphere-like cell aggregate do not have continuity as an epithelial tissue.

2. The sphere-like cell aggregate according to claim 1 , wherein an extracellular matrix is present between the photoreceptor layer in (1) and the retinal pigment epithelial cells covering at least a portion of the photoreceptor layer.

3. The sphere-like cell aggregate according to claim 2 , wherein the extracellular matrix includes one or more extracellular matrices selected from the group consisting of hyaluronic acid, laminin, type IV collagen, heparan sulfate proteoglycan, and entactin.

4. The sphere-like cell aggregate according to claim 1 , wherein a hydrogel is further present between the photoreceptor cell layer in (1) and the retinal pigment epithelium covering at least a part of the photoreceptor cell layer.

5. A method for producing the sphere-like cell aggregate according to claim 1 , comprising:

preparing a sphere-like cell aggregate containing neural retina (a cell aggregate of neural retina), wherein

(I) in the cell aggregate of neural retina, the neural retina is present on a surface of the cell aggregate; and

(II) in the neural retina, a neural retinal layer including at least a photoreceptor layer is formed, wherein in the photoreceptor layer, one or more types of cells selected from the group consisting of a photoreceptor cell, a photoreceptor progenitor cell, and a retinal progenitor cell are present;

preparing a retinal pigment epithelial cell; and

contacting the cell aggregate of neural retina with the retinal pigment epithelial cell.

6. The production method according to claim 5 , wherein in the cell aggregate of neural retina, a proportion of Chx10 positive cells present in the neural retina is 20% or more.

7. The production method according to claim 5 , wherein the contacting step is performed in the presence of an adhesion factor.

8. The production method according to claim 7 , wherein the adhesion factor is an extracellular matrix.

9. The production method according to claim 8 , wherein the extracellular matrix includes one or more extracellular matrices selected from the group consisting of hyaluronic acid, laminin, type IV collagen, heparan sulfate proteoglycan, and entactin.

10. The production method according to claim 5 , wherein at least one of the cell aggregate of neural retina and the retinal pigment epithelial cell is derived from a pluripotent stem cell.

11. The production method according to claim 5 , wherein in the step of preparing the retinal pigment epithelial cell, the retinal pigment epithelial cell is prepared as a cell sheet or a cell suspension.

12. The production method according to claim 5 , wherein after the contacting step, further culture is performed until the retinal pigment epithelial cell has a polygonal or flagstone-like cell morphology.

13. A reagent for evaluating toxicity or drug efficacy of a test substance, comprising the sphere-like cell aggregate according to claim 1 or a portion of the sphere-like cell aggregate.

14. A method for evaluating toxicity or drug efficacy of a test substance, comprising:

contacting the sphere-like cell aggregate according to claim 1 or a portion of the sphere-like cell aggregate with the test substance; and

examining an effect of the test substance on the sphere-like cell aggregate or a cell contained in the sphere-like cell aggregate.

15. A drug for treating a disease based on a disorder of a retinal pigment epithelial cell, a retinal cell or a retinal tissue or a damage of a retinal tissue, comprising the sphere-like cell aggregate according to claim 1 or a portion of the sphere-like cell aggregate.

16. A method for treating a disease based on a disorder of a retinal pigment epithelial cell, a retinal cell or a retinal tissue or a damage of a retinal tissue, comprising transplanting an effective amount of the sphere-like cell aggregate according to claim 1 or a portion of the sphere-like cell aggregate into a subject in need of transplantation.

17. A portion of the sphere-like cell aggregate according to claim 1 , wherein the portion is physically cut out from the sphere-like cell aggregate.

18. A portion of the sphere-like cell aggregate according to claim 17 , wherein the portion is in the form of a cell sheet containing a retinal pigment epithelial cell and neural retina.

19. A method for producing a portion of a sphere-like cell aggregate, comprising a step of physically cutting out the portion of the sphere-like cell aggregate according to claim 1 .

20. The method according to claim 19 , wherein the portion of the sphere-like cell aggregate is in the form of a cell sheet containing a retinal pigment epithelial cell and neural retina.