Ximo García-Domínguez

Vitrification of kidney precursors as a new source for organ transplantation.

Kidney transplantation from deceased or living human donors has been limited by donor availability as opposed to the increasing demand, and by the risk of allograft loss rejection and immunosuppressive therapy toxicity. In recent years, xenotransplantation of developed kidney precursor cells has offered a novel solution for the unlimited supply of human donor organs. Specifically, transplantation of kidney precursors in adult hosts showed that intact embryonic kidneys underwent maturation, exhibiting functional properties, and averted humoural rejection post-transplantation from non-immunosuppressed hosts. Even if supply and demand could be balanced using xenotransplants or lab-grown organs from regenerative medicine, the future of these treatments would still be compromised by the ability to physically distribute the organs to patients in need and to produce these products in a way that allows adequate inventory control and quality assurance. Kidney precursors originating from fifteen-day old rabbit embryos were vitrified using Cryotop® as a device and VM3 as vitrification solution. After 3 months of storage in liquid nitrogen, 18 kidney precursors were transplanted into non-immunosuppressed adult hosts by laparoscopy surgery. Twenty-one days after allotransplantation, 9 new kidneys were recovered. All the new kidneys recovered exhibited significant growth and mature glomeruli. Having achieved these encouraging results, we report, for the first time, that it is possible to create a long-term biobank of kidney precursors as an unlimited source of organs for transplantation, facilitating the inventory control and distribution of organs.

Trasplante laparoscópico de metanefros: un paso inicial al xenotrasplante renal

BACKGROUND Embryonic kidney xenotransplantation could represent a new solution to the scarcity of kidneys for transplantation. OBJECTIVE To determine the feasibility of allogeneic laparoscopic transplantation of metanephroi (M) in rabbits. MATERIAL AND METHOD Microscopic dissection was conducted to obtain metanephroi from 14-day-old (24M), 15-day-old (20M) and 16-day-old (26M) embryos. Using single-port abdominal laparoscopy, a spinal needle was inserted percutaneously, through which the metanephroi were deposited (using an epidural catheter) close to a patent blood vessel in the retroperitoneal fat. Seventy metanephroi were transplanted to 18 rabbits. Three weeks later, the animals were examined through open surgery. We compared the embryonic maturity, the morphometric variables of the metanephroi and the development rate of the transplanted metanephroi. RESULTS The lower time limit for the extraction of metanephroi from the rabbits was day 14. Three weeks after transplantation, only 3/24 14-day-old metanephroi grew at minimal expression (12.5%). In contrast, 10/20 (50%) 15-day-old and 12/26 (46.1%) 16-day-old metanephroi grew. These metanephroi had differentiated sufficiently for the glomeruli, proximal and distal tubules and collecting ducts to develop normally. We detected no relevant immunological changes in the peripheral blood. CONCLUSIONS We have described for the first time in the literature the allogeneic laparoscopic transplantation of metanephroi from embryos as a feasible and noninvasive technique. The recipients did not require immunosuppression.

Embryonic Organ Transplantation: The New Era of Xenotransplantation

Here, we review the recent advances towards the use of organs from embryonic donors, antecedent investigations, and the latest work from our own laboratory exploring the utility for transplantation of embryonic kidney as an organ replacement therapy. In addition, we have recently reported, for the first time, that it is possible to create a longterm biobank of kidney precursors as an unlimited source of organs for xenotransplan‐ tation, facilitating inventory control and the distribution of organs. Kidney transplantation from deceased or living human donors has been limited by donor availability as opposed to the increasing demand. Simultaneously, the risk of loss of graft by rejection or toxicity of immunosuppressive therapy exacerbates this organ shortage. In recent years, xenotransplantation of developing pancreas and kidney precursor cells has offered a novel solution for the unlimited supply of human donor organs. Specifical‐ ly, transplantation of kidney precursors in adult hosts showed that intact embryonic kidneys underwent maturation, exhibiting functional properties, and averted humoral rejection post-transplantation from non-immunosuppressed hosts. Organ primordia engraft, attract a host vasculature, and differentiate following transplantation to ectopic sites. Attempts have been made to exploit these characteristics to achieve clinically relevant endpoints for end-stage renal disease using animal models. We focused on two main points: (a) performing transplantation by a minimally invasive laparoscopic procedure and (b) creating a long-term biobank of kidney precursors, as an unlimited source of organs for transplantation, facilitating the inventory control and the distribution of organs. Because even if supply and demand could be balanced using xenotransplants or laboratory-grown organs from regenerative medicine, the future of these treatments would still be compromised by the ability to physically distribute the organs to patients in need and to produce these products in a way that allows adequate inventory control and quality assurance.

Long-term phenotypic effects following vitrified-thawed embryo transfer in a rabbit model

Since the first human was conceived through in vitro fertilisation in 1978, over 6.5 million babies have been born by assisted reproductive technologies (ARTs). Although most ART babies and children seem healthy, in recent years several studies have evidenced a potential impact of ARTs on long-term development and health. Herein, we have developed an animal model to determine whether vitrified embryo transfer procedure induces phenotypic changes over the growth performance and in the complementary transcriptomic and proteomic analyses at hepatic level. To this end, 2 populations were developed; vitrified embryos transferred to the surrogate mothers (VT) and naturally conceived animals (NC). After delivery, animals were weighed weekly from 1 to 20 weeks of age. In adulthood, animals were euthanized and organs were harvested and weighed. After that, liver tissue was used to identify changes in the transcriptomic and proteomic profile. At adulthood, VT group showed significant lower body, liver and heart weight. After functional analysis of RNA-Seq data, a subset of 96 differentially expressed transcripts in VT animal were related to alteration in zinc homeostasis, lipid metabolism, and hepatic immune pathways. After proteomic analysis, a subset of 76 differentially expressed proteins also revealed some disturbed metabolic pathways related with the lipid and glycan metabolism, and an impaired oxidative metabolism related to ATP synthesis in the mitochondria. Current findings suggest that progeny derived after transfer of vitrified embryos have long-term consequences on growth rate and vital organs weights in adulthood, correlated with molecular signatures at transcriptomic and proteomic level of hepatic tissue.