Abstract
For research in regenerative medicine, not only the study of cellular pluripotency but also knowledge of the reorganization of tissue structure is crucial. However, the latter will probably be more difficult to acquire. When small fragments of kidney (approx. 1 × 1 mm) were implanted in the liver of syngeneic LEW rats, the tissue survived at least 2 weeks with retention of normal structure including glomeruli and tubules. In contrast, no kidney structure survived when transplanted to subcutaneous sites, omentum, or spleen. Molecules involved in renal tubular function, such as megalin and glut2 transporter protein, were detectable in the implanted tissue by immunohistochemistry, suggesting that the cells were biologically active. Survival of cortex, medulla, and calyx tissues was then compared. All three components were still detectable 8 weeks after transplantation but cortex and medulla were replaced by granuloma at 6 months. Only calyx tissue survived for up to 12 months after transplantation. There was no marked difference in tissue survival, either when the recipient liver was partially resected or when infantile donor kidney was implanted instead of adult kidney. The present method opens new avenues in the development of regenerative medicine (i.e., tissue transplantation) as an intermediate modus between organ transplantation and cell transplantation.