P-468 Organotypic culture of testicular tissue from infant boys with cryptorchidism

Study question

Can organotypic culture support the survival and maturation of germ cells and niche-related cells within testicular tissue from infant boys with cryptorchidism?

Summary answer

The testicular structure and the number of germ cells were maintained during organotypic culture, whereas Sertoli cells and peritubular myoid cells (PTMCs) matured.

What is known already

Testicular tissue cryopreservation (TTC) is a strategy to safeguard the fertility of prepubertal boys who face a risk of infertility. Organotypic culture of immature testicular tissue from mice achieved production of spermatozoa. Similarly, the culture of human fetal gonads resulted in the generation of competent spermatids. However , in vitro spermatogenesis by organotypic culture of human prepubertal testicular tissue has not been achieved. It is also unknown whether germ cells as well as its niche-related cells, in testicular tissue from infant boys with cryptorchidism, can maintain and mature under in vitro conditions.

Study design, size, duration

Testicular tissue was cryopreserved from four infant boys with bilateral cryptorchidism undergoing orchidopexy (age range: 0.5-1.4 years), as part of a fertility preservation program. Culture media with and without retinoic acid were tested. Testicular fragments were harvested at 30 days and 60 days after culture and evaluated by histological assessment of tissue structure, germ cell development, and immunohistochemical staining for germ cell and somatic cell markers.

Participants/materials, setting, methods

Cryopreserved-thawed testicular tissue was cut into fragments (1-2 mm3) and placed on top of agarose gel stands and cultured at 34oC with 5% CO2 in Minimum Essential Medium-alpha supplemented with knockout serum replacement, human umbilical cord plasma, Activin A, hormones, growth factors, with or without retinoic acid. Immunohistochemical analyses were performed using germ cell markers (MAGE-A, GAGE, and VASA), Sertoli cell maturation markers (AMH, AR, SOX9), PTMC marker (alpha-SMA).

Main results and the role of chance

Following the 60-day culture, the lumen of the seminiferous tubules had developed. The number of germ cells per tubule remained stable during this period. However, no further germ cell maturation was observed. Germ cells showed different phenotypes of MAGEA, GAGE, and VASA expression with no significant difference in number. The number of SOX9-positive Sertoli cells was significantly increased from 30 days to 60 days of culture (p <0.0001). No difference in AMH expression was observed, while AR expression in Sertoli cells was induced during culture. Alpha-SMA expression was detected in the PTMCs surrounding the seminiferous tubules. The two different culture conditions, with and without retinoic acid in the culture media, did not affect cell survival or maturation.

Limitations, reasons for caution

The small number of testicular biopsies available is a limitation.

Wider implications of the findings

Our organotypic culture conditions support the long-term survival of germ cells in testicular tissue from infant boys with cryptorchidism. Thus, further studies are needed to induce the maturation of germ cells under similar experimental conditions.

Trial registration number

not applicable

O-189 Male fertility restoration by direct transplantation of human infant testicular cells into infertile recipient mouse testis

Study question

Is colonization of human gonocytes and spermatogonial stem cells (SSCs) directly transplanted to seminiferous tubules of busulfan sterilised mice testis during an 8-week period feasible? 

Summary answer

Gonocytes and SSCs from infant boys can settle on the basal membrane and form germline stem cell colonies in the seminiferous tubules of recipient mice.

What is known already

The neonatal or immature animal provides higher populations of gonocytes and/or SSCs than adults, and the number of transplanted donor SSCs directly affects the colonization rate of the recipient testes. Along with SSC transplantation restoring the recipient’s spermatogenesis, donor gonocyte was also reported to be capable of establishing spermatogenesis in rodents.

Study design, size, duration

Transplantation of human testicular cells including gonocytes and SSCs into seminiferous tubules of infertile recipient mice. We included 10 infant testis biopsies from which single-cell suspension was transplanted individually into the seminiferous tubules of 10 immunodeficient mice. The immunodeficient mouse testes were injected with busulfan to deplete germ cells. Four weeks later, we did the xenotransplantation. Then after eight weeks, we collected all mouse testes to do further analysis.

Participants/materials, setting, methods

Testis biopsies were obtained from cryptorchid boys undergoing orchidopexy. After enzymatic digestion of the testis biopsies, dissociated single-cell suspensions were pre-labeled with a green fluorescent dye. Then the single-cell suspensions were transplanted into seminiferous tubules of the infertile recipient mice. Eight weeks later, the presence of gonocytes and SSCs was determined by immunohistochemistry and whole-mount immunofluorescence.

Main results and the role of chance

Without in vitro propagation, naturally enriched human germline stem cells settled on the basal membrane of seminiferous tubules and survived in the mouse testes at least for two months demonstrating that human gonocytes and SSCs were capable of colonizing the recipient mouse seminiferous tubules.

Limitations, reasons for caution

The study samples were from infant boys with undescended testes that were more likely to contain gonocytes. It was not possible to determine which germ-cell type at transplantation resulted in the detected gonocytes and SSC colonies after xenotransplantation. Transplantation of gonocytes may include the potential risk of stem cell-related malignancy.

Wider implications of the findings

Without in vitro propagation, male germline stem cell-based transplantation could provide a relatively safe therapeutic treatment for prepubertal boys with cryptorchidism and boys diagnosed with cancer. This method could also facilitate clinical translation.

Trial registration number

not applicable