Urine excretion strategy for stem cell-generated embryonic kidneys

Abstract

There have been several recent attempts to generate, de novo, a functional whole kidney from stem cells using the organogenic niche or blastocyst complementation methods. However, none of these attempts succeeded in constructing a urinary excretion pathway for the stem cell-generated embryonic kidney. First, we transplanted metanephroi from cloned pig fetuses into gilts; the metanephroi grew to about 3 cm and produced urine, although hydronephrosis eventually was observed because of the lack of an excretion pathway. Second, we demonstrated the construction of urine excretion pathways in rats. Rat metanephroi or metanephroi with bladders (developed from cloacas) were transplanted into host rats. Histopathologic analysis showed that tubular lumina dilation and interstitial fibrosis were reduced in kidneys developed from cloacal transplants compared with metanephroi transplantation. Then we connected the host animal's ureter to the cloacaldeveloped bladder, a technique we called the "stepwise peristaltic ureter" (SWPU) system. The application of the SWPU system avoided hydronephrosis and permitted the cloacas to differentiate well, with cloacal urine being excreted persistently through the recipient ureter. Finally, we demonstrated a viable preclinical application of the SWPU system in cloned pigs. The SWPU system also inhibited hydronephrosis in the pig study. To our knowledge, this is the first report showing that the SWPU system may resolve two important problems in the generation of kidneys from stem cells: construction of a urine excretion pathway and continued growth of the newly generated kidney.cloned pig | kidney generation | metanephros | somatic cell nuclear transfer | transplantation

Successful development of vitrified embryonic kidney after laparoscopy transplantation into non-immunosuppressed hosts

“…In this paper we demonstrated than metanephroi vitrification using M22 medium as vitrification solution support the developmental capability of both 15 days-old and 16 days-old metanephroi. However, although we have focused the study solely from the point of the cryobiological effect, it is important to say that some authors have already shown that transplants of fresh kidney precursors are able to filter blood producing urine [33,35] and synthetizing renal hormones [31,32] such as renin and erythropoietin. In the future, it would be interesting demonstrate the same capacities in developed kidneys from vitrified metanephroi.…”

“…However, it's known that new renal tissue developed from metanephroi not only provide an excretion function but also an endocrine function, synthesising renal hormones such as renin and erythropoietin [31,32]. Furthermore, if metanephroi are transplanted beside bladders developed from cloacas, and if cloacaldeveloped bladder was connected to the host ureters, new metanephrodeveloped kidney produces and excretes urine through the recipient ureter, avoiding hydronephrosis and allowing the nascent kidney to continue their growth [33]. These findings, together with the scientific capability to produce specific pathogen-free animals [34] suggest than metanephroi transplantation could be a possible solution for kidney need [26,35].…”

A transgenic-cloned pig model expressing non-fluorescent modified Plum

“…This concept is applicable to cell and tissue transplants between cloned pigs created from identical cells [30,31,32]. Our ultimate goal was to produce two types of animals, individuals that expressed Plum and individuals that expressed mPlum, in a group of cloned pigs sharing a syngenic background.…”

Current Concepts of Using Pigs as a Source for Beta-Cell Replacement Therapy of Type 1 Diabetes

“…While such pancreatic progenitor tissue buds could also be formed from differentiated human iPSC derivatives, the size of a mouse as host for further differentiation into pancreatic progenitor tissue is not sufficient to generate tissue grafts for human patients. Pigs could be more suitable interim hosts for this approach, as demonstrated by the development of de novo kidneys of reasonable size from metanephroi transplanted into the omentum of pigs ( [29]; comment in [30]). Potential immune rejection of human tissue buds in pig hosts could be overcome by using genetically immuno-compromised or immune-deficient pigs [31].…”