Embryo production by intracytoplasmic injection of sperm retrieved from Meishan neonatal testicular tissue cryopreserved and grafted into nude mice

Xenotransplantation of Cryopreserved Calf Testicular Tissues

The cryopreservation of testicular tissues meets the demands for the germplasm preservation of humans and animals. Previously, we reported on the cryopreservation of bovine testicular tissues. To further evaluate the viability of these tissues, subcutaneous xenotransplantation of the frozen-thawed calf testicular tissues was performed with castrated nude mice as the recipients. After 28 days (D28), the survival and development of the grafts were examined. The grafts from 1-day-old (D1) calf testes were recovered and angiogenesis around the grafts was observed. Histologically, the seminiferous cords in the grafts were well maintained and capillaries in the interstitium were observed. Quantitative real-time PCR (qRT-PCR) analysis showed that the grafts expressed germline genes Gfrα-1, C-kit, and Sycp3 and somatic genes Sox9, Acta2, and Star. The expressions of C-kit, Sox9, Acta2, and Star were higher in 28D grafts than those in 1D and 30-day-old (30D) calf testicular controls. Together, we initially demonstrate that cryopreserved calf testicular tissues retain their viability and developmental capacity after xenotransplantation.

Sperm immotility is associated with epididymis metabolism disorder in mice under obstructive azoospermia

Obstructive azoospermia (OA) accounts for approximately 40% of males who suffer from azoospermia of male infertility. Currently, available treatment for OA consists of reproductive tract surgical reconstruction and sperm retrieval from the testis. However, both treatments result in low fertility compared to normal pregnancy, and the main reason remains largely unknown. Previous studies have shown that the quality of sperm retrieved from OA patients is poor compared with normal adult males but without an in-depth study. Herein, we generated a mouse OA model with vasectomy to evaluate sperm quality systematically. Our results showed that the testis had normal spermatogenesis but increased apoptotic activity in both OA patients and mice. More importantly, epididymal morphology was abnormal, with swollen epididymal tubules and vacuole-like principal cells. Especially, sperm retrieved from the epididymis of OA mice showed poor motility and low fertilization ability in vitro. Using mass spectrometry in epididymal fluid, we found differences in the expression of key proteins for sperm maturation, such as Angiotensinogen (AGT), rhophilin-associated tail protein 1 (ROPN1), NPC intracellular cholesterol transporter 2 (NPC2), and prominin 1 (PROM1). Furthermore, our results demonstrated that AGT, secreted by epididymal principal cells, could regulate sperm motility by managing PKCα expression to modify sperm phosphorylation. In conclusion, our data evaluate sperm quality systematically in OA mice and contribute to the understanding between the sperm and epididymis, which may provide novel insight into treating male infertility.

An Efficacious Transgenic Strategy for Triple Knockout of Xeno-Reactive Antigen Genes GGTA1, CMAH, and B4GALNT2 from Jeju Native Pigs

Pigs are promising donors of biological materials for xenotransplantation; however, cell surface carbohydrate antigens, including galactose-alpha-1,3-galactose (α-Gal), N-glycolylneuraminic acid (Neu5Gc), and Sd blood group antigens, play a significant role in porcine xenograft rejection. Inactivating swine endogenous genes, including GGTA1, CMAH, and B4GALNT2, decreases the binding ratio of human IgG/IgM in peripheral blood mononuclear cells and erythrocytes and impedes the effectiveness of α-Gal, Neu5Gc, and Sd, thereby successfully preventing hyperacute rejection. Therefore, in this study, an effective transgenic system was developed to target GGTA1, CMAH, and B4GALNT2 using CRISPR-CAS9 and develop triple-knockout pigs. The findings revealed that all three antigens (α-Gal, Neu5Gc, and Sd) were not expressed in the heart, lungs, or liver of the triple-knockout Jeju Native Pigs (JNPs), and poor expression of α-Gal and Neu5G was confirmed in the kidneys. Compared with the kidney, heart, and lung tissues from wild-type JNPs, those from GGTA1/CMAH/ B4GALNT2 knockout-recipient JNPs exhibited reduced human IgM and IgG binding and expression of each immunological rejection component. Hence, reducing the expression of swine xenogeneic antigens identifiable by human immunoglobulins can lessen the immunological rejection against xenotransplantation. The findings support the possibility of employing knockout JNP organs for xenogeneic transplantation to minimize or completely eradicate rejection using multiple gene-editing methods.

Strategies for cryopreservation of testicular cells and tissues in cancer and genetic diseases

Cryopreservation of testicular cells and tissues is useful for the preservation and restoration of fertility in pre-pubertal males expecting gonadotoxic treatment for cancer and genetic diseases causing impaired spermatogenesis. A number of freezing and vitrification protocols have thus been tried and variable results have been reported in terms of cell viability spermatogenesis progression and the production of fertile spermatozoa. A few studies have also reported the production of live offspring from cryopreserved testicular stem cells and tissues in rodents but their replication in large animals and human have been lacking. Advancement in in vitro spermatogenesis system has improved the possibility of producing fertile spermatozoa from the cryopreserved testis and has reduced the dependency on transplantation. This review provides an update on various cryopreservation strategies for fertility preservation in males expecting gonadotoxic treatment. It also discusses various methods of assessing and ameliorating cryoinjuries. Newer developments on in vitro spermatogenesis and testicular tissue engineering for in vitro sperm production from cryopreserved SSCs and testicular tissue are also discussed.

The ART of bringing extinction to a freeze - History and future of species conservation, exemplified by rhinos

The ongoing mass extinction of animal species at an unprecedented rate is largely caused by human activities. Progressive habitat destruction and fragmentation is resulting in accelerated loss of biodiversity on a global scale. Over decades, captive breeding programs of non-domestic species were characterized by efforts to optimize species-specific husbandry, to increase studbook-based animal exchange, and to improve enclosure designs. To counter the ongoing dramatic loss of biodiversity, new approaches are warranted. Recently, new ideas, particularly the application of assisted reproduction technologies (ART), have been incorporated into classical zoo breeding programs. These technologies include semen and oocyte collection, artificial insemination, and in-vitro embryo generation. More futuristic ideas of advanced ART (aART) implement recent advances in biotechnology and stem-cell related approaches such as cloning, inner cell mass transfer (ICM), and the stem-cell-associated techniques (SCAT) for the generation of gametes and ultimately embryos of highly endangered species, such as the northern white rhinoceros (Ceratotherium simum cottoni) of which only two female individuals are left. Both, ART and aART greatly depend on and benefit from the rapidly evolving cryopreservation techniques and biobanking not only of genetic, but also of viable cellular materials suitable for the generation of induced pluripotent stem cells (iPSC). The availability of cryopreserved materials bridges gaps in time and space, thereby optimizing the available genetic variability and enhancing the chance to restore viable populations.

Influence of freezing techniques and glycerol-based cryoprotectant combinations on the survival of testicular tissues from adult collared peccaries

The objective of the study was to evaluate the effects of different cryopreservation techniques including glycerol-based cryoprotectant combinations on the structure and viability of testicular tissues from adult collared peccaries. Tissue biopsies (3.0 mm³) from 5 different individuals were allocated to 10 different groups: fresh control; slow freezing (SF), conventional vitrification (CV), or solid-surface vitrification (SSV); each of them using three different combinations of cryoprotectants [dimethyl sulfoxide (DMSO) + ethylene glycol (EG); DMSO + Glycerol; and EG + Glycerol]. After thawing/warming, samples were evaluated for histomorphology, viability, proliferative capacity potential, and DNA integrity. Most effective preservation of testicular histomorphology was achieved using SF and CV with DMSO + EG. However, the use of glycerol-based cryoprotectant combinations increased the occurrence of tubular cell swelling, tubular cell loss and shrinkage from the basal membrane. Cell viability was comparable among cryopreservation methods and cryoprotectant combinations. Regarding cell proliferative capacity, the use of SF with EG + Glycerol and SSV with DMSO + Glycerol impaired the conservation of spermatogonia proliferative potential compared to other treatments. Moreover, CV with DMSO + EG was better than SF with EG + Glycerol for Sertoli cell proliferation potential. Regarding DNA integrity, less damage occurred when using SF with DMSO + EG while more fragmentations were observed when using CV with EG + Glycerol or DMSO + Glycerol as well as SSV with EG + Glycerol or DMSO + Glycerol. In sum, SF and CV appeared to be the most suitable methods for the cryopreservation of adult peccary testicular tissues. Additionally, the use of glycerol-based cryoprotectant combinations did not improve testicular tissues preservation with DMSO + EG being the most efficient option.

Embryo production by intracytoplasmic injection of sperm retrieved from neonatal testicular tissue of Agu pigs after cryopreservation and grafting into nude mice

The Agu is the only indigenous pig breed in Japan but its population is very small. In order to estimate the efficacy of testicular xenografting for the conservation of Agu pigs, we investigated whether neonatal testicular fragments would acquire the capacity to produce sperm after they had been cryopreserved and grafted into nude mice. Although on day 180 (day 0 = xenografting), grafts showed a low proportion of seminiferous tubule cross-sections containing sperm (0.1 ± 0.1%, mean ± SEM for four mice), the proportion reached 36.9 ± 16.7% (n = 4 mice) by day 240. When single sperm obtained on day 240 was injected into individual porcine oocytes, 28.2% of the oocytes were found to contain one male and one female pronuclei with the second polar body. Moreover, the blastocyst formation rate after injection of the xenogeneic sperm was 28.4%, whereas that in the absence of sperm injection (attributable to parthenogenesis) was 13.3%. These findings suggest that more than half of the blastocysts resulted from fertilization. Thus, testicular xenografting could assist the conservation of Agu pigs by salvaging germ cells present in neonatal testes even after cryopreservation.

Cryopreservation and Culture of Testicular Tissues: An Essential Tool for Biodiversity Preservation

Systematic cryo-banking of reproductive tissues could enhance reproductive management and ensure sustainability of rare mammalian genotypes. Testicular tissues contain a vast number of germ cells, including at early stages (spermatogonia and spermatocytes), that can potentially develop into viable spermatozoa after grafting or culture in vitro, and the resulting sperm cells then can be used for assisted reproductive techniques. The objective of this review was to describe current advances, limitations, and perspectives related to the use of testicular tissue preservation as a strategy for the conservation of male fertility. Testes can be obtained from mature or prepubertal individuals, immediately postmortem or by orchiectomy, but testicular biopsies could also be an alternative to collect samples from living individuals. Testicular fragments can be then cryopreserved by using slow or ultra-rapid freezing, or even vitrification methods. The composition of cryopreservation media can vary according to species-specific characteristics, especially regarding the cryoprotectant type and concentration. Finally, spermatozoa have been usually obtained after xenografting of testicular fragments into severely immunodeficient mice, while this method still has to be optimized after in vitro culture conditions.

Developmental ability of oocytes retrieved from Meishan neonatal ovarian tissue grafted into nude mice

Ovarian xenografting makes it possible to obtain oocytes with fertilization ability from immature pigs of Western breeds. In this study, we applied these methods to the Meishan, an indigenous Chinese pig breed, and investigated the developmental competence of oocytes grown in their neonatal tissue after grafting into nude mice. First, mice harboring neonatal ovarian tissue were infused with follicle stimulating hormone (FSH) (62.5 U/ml) for 13 days starting at 10, 30, and 60 days after vaginal opening (D10‐, D30‐, and D60‐FSH groups, respectively). Development of antral follicles and their oocytes was most enhanced in the D60‐FSH group. For the next step, we examined the in vitro maturation ability of the oocytes recovered from host mice after infusion with FSH at a dose of 62.5 U/ml or 125 U/ml (FSH‐62.5 or ‐125 group) for 13 days starting at 60 days after vaginal opening. Many more oocytes with maturation ability were obtained from the FSH‐125 group. The FSH‐125 mature oocytes were fertilized in vitro, as shown by formation of male and female pronuclei, but did not reach the blastocyst stage. These results indicate that Meishan neonatal ovaries are able to produce oocytes with fertilization ability after being grafted into nude mice.

Embryo production by intracytoplasmic injection of sperm retrieved from Meishan neonatal testicular tissue cryopreserved and grafted into nude mice

Testicular xenografting, combined with cryopreservation can assist conservation of the genetic diversity of indigenous pigs by salvaging germ cells from their neonatal testes. Using Meishan male piglets as an example, we examined whether testicular tissue would acquire the ability to produce sperm after cryopreservation and grafting into nude mice (MS group). For comparison, testicular tissue from neonatal Western crossbreed male piglets was used (WC group). Sixty days after xenografting (day 0 = grafting), MS grafts had already developed seminiferous tubules containing sperm, whereas in the WC grafts, sperm first appeared on day 120. The proportion of tubules containing spermatids and sperm was higher in the MS group than in the WC group between days 90 and 120. Moreover, in vitro‐matured porcine oocytes injected with a single sperm obtained from the MS group on day 180 developed to the blastocyst stage. The blastocyst formation rate after injection of the xenogeneic sperm was 14.6%, whereas the ratio in the absence of such injection (attributable to parthenogenesis) was 6.7%. Thus, cryopreserved Meishan testicular tissue acquired spermatogenic activity in host mice 60 days earlier than Western crossbreed tissue. Such xenogeneic sperm are likely capable of generating blastocysts in vitro.