Replication of biological tissue
Biological tissues are grown in a low shear, microgravity environment by culturing connective tissue cells to form a three-dimensional structure, which is thereafter co-cultured with endothelial and epithelial cells to replicate naturally occurring tissues. Preferably, the three-dimensional connective tissue cells are first cultured with endothelial cells to form three-dimensional structures of connective tissue cells and endothelial cells, which are thereafter co-cultured with epithelial cells to replicate naturally occurring tissue. The cultured tissue is in the general shape of spheroids having a diameter between about 0.1 mm and about 5 m.
1. A method for replicating biological tissue, the method including the steps of:
a) culturing connective tissue cells in a nutrient medium in a bioreactor chamber to produce spheroids of connective tissue cells; thereafter
b) adding endothelial cells to the bioreactor chamber to contact the spheroids of the connective tissue cells in the presence of a nutrient medium and cause the endothelial cells to invade the spheroids of connective tissue cells; and thereafter
c) adding epithelial cells to the bioreactor chamber to contact the spheroids of connective tissue cells invaded with endothelial cells in the presence of a nutrient medium and cause the epithelial cells to form a tissue-like layer on the spheroids.
2. A method according to claim 1 in which the bioreactor chamber is rotated about a substantially horizontal axis to provide low shear stress during culturing of the cells.
3. A method according to claim 2 in which the bioreactor chamber includes a wall permeable to gas and impermeable to liquid, and in which the bioreactor chamber is rotated in an atmosphere which includes carbon dioxide in an amount substantially greater than that in the earth's atmosphere.
4. A method according to claim 3 , in which the bioreactor chamber is rotated in an atmosphere of air and about 5% carbon dioxide by volume.
5. A method according to claim 3 in which the chamber is isolated in an atmosphere which contains substantially less than about 20% oxygen by volume during the culturing of the endothelial cells.
6. A method according to claim 3 in which the chamber is rotated in an atmosphere of about 5% oxygen and about 95% nitrogen by volume during the culturing of the endothelial cells.
7. A method according to claim 3 in which the bioreactor chamber is rotated in an atmosphere of about 5% carbon dioxide in air by volume during the culturing of the connective tissue cells and during the culturing of the epithelial cells.
8. A method according to claim 3 , in which the bioreactor chamber is rotated in an atmosphere of about 5% carbon dioxide in air by volume during the culturing of the connective tissue cells and during the culturing of the epithelial cells, and is rotated in an atmosphere of about 5% oxygen and about 95% nitrogen by volume during the culturing of the endothelial cells.
9. A method according to claim 3 in which the replicated biological tissue is made by using malignant epithelial cells, and is processed and stained simultaneously with a tissue specimen from a patient suspected of having a tumor of the same, type as that of the epithelial cells.
10. A method according to claim 3 in which the cells are subjected to periodic change in pressure during the culturing process.
11. A method according to claim 10 in which the process changes at a rate between about 30 and about 80 times per minute, and the pressure in the chamber varies from a minimum of about 30 mm Hg to a maximum of about 180 mm Hg above atmospheric pressure.
12. A method according to claim 3 in which the number of connective tissue cells is substantially greater than that of the number of epithelial cells.
13. A method according to claim 3 in which the number of connective tissue cells is about twice that of the number of epithelial cells.
14. A method according to claim 3 in which the number of connective tissue cells and the number of endothelial cells are each substantially greater than the number of epithelial cells.
15. A method according to claim 3 in which the number of connective tissue cells and the number of endothelial cells are each about twice that of the number of epithelial cells.
16. A method according to claim 3 in which the endothelial cells are of the microvascular type.