Spermatogonial stem cells are self-renewal and differentiate into sperm in post-pubertal mammals. There exists a balance between the self-renewal and differentiation in the testes. Spermatogonial stem cells make up only 0.03% of testicular cells in adult mice. These cells maintain sperm production by differentiating after puberty. Therefore, analyzing the expression of genes associated with spermatogenesis is critical for understanding differentiation. The present study aimed to establish the postnatal period of cells in relation to spermatogenesis. To study the expression of differentiated and undifferentiated marker genes in enriched spermatogonial stem cells, in vitro culture was performed and cells from pup (6–8-day-old) and adult (4-months-old) testicular tissues were isolated. As a result, undifferentiated genes, Pax7, Plzf, GFRa1, Etv5 and Bcl6b , were highly increased in cultured spermaotogonial stem cells compared with pup and adult testicular cells. On the other hands, differentiated gene, c-kit was highly increased in adult testicular cells, Also Stra8 gene was highly increased in pup and adult testicular cells. This study provides a better understanding of spermatogenesis-associated gene expression during postnatal periods.

Until today, success in germline cells and tissue cryopreservation is limited mainly due to the poor understanding of the complex physiological processes can lead to cell damage during cryopreservation. Germline cells, from both male and female, have unique ability to differentiate into one or more cell lines and thus it becomes a crucial point to store them in subzero temperature with the minimal damage of their functional properties and maximum recovery of unchanged and viable cells when thawed. In the past three decades, a vast research has been performed using various different animal models which in fact have led to development of new methodologies and optimization of older one. However, successful use of animal model has provided the opportunity in research with human germline cells and tissues preservation, but not in all the cases. Therefore, the use of new cryo-protective chemicals and modified protocols have been often found in different groups of researchers based on the types, physical structures, utility and animal species of the specimens to be cryopreserved. This review discusses about the basics of different types of cryopreservation methodologies and commonly used optimized protocols and cryoprotectants for germline cells and tissues preservation.

Spermatogonial stem cells (SCCs) is foundation for spermatogenesis throughout male adult life because they have ability of self-renewal and differentiation into spermatozoa. Storage of such SSCs is very important to study on male reproduction, which would contribute human male infertility to be treated. However, during cryopreservation, the most cells are damaged by cryoinjury such as apoptosis, necrosis, osmotic stress, oxidative stress and so on. For the reason, in cryopreservation technique, targeting purpose is what cells are stored stably without cryoinjury. The purpose of this study was to develop the cryoprotectant for decrease in cryoinjury of SSCs by using melatonin and necrostatin-1 as additive cryoprotectant. The SSCs with melatonin or necrostatin-1 was frozen for 1 month, and then thawed to evaluate survival, recovery and proliferation rate. The result showed that necrostatin-1 50 mM was significantly greater than DMSO control. Furthermore, we conducted the characterization of cryo-thawed SSCs with necrostatin-1 50 mM to confirm whether the SSCs could maintain the undifferentiated state. As a result, the normal expression of each marker, which is PLZF, GFRa1 and VASA, was observed except for C-kit, meaning that the cells could maintain the undifferentiated state regardless of cryopreservation. Therefore, the result indicates that the cryo-thawed SSCs have ability of proliferation and self-renewal. In conclusion, our finding verifies that cryopreservation of SSC with necrostatin-1 50 mM could be helpful to preserve the SSCs stably, contributing to various studies on male reproduction and infertility treatment

Artificial insemination and embryo transfer is one of the most important factors affecting to the production of fawn from deer nuclear transfer in the field of deer farms. This study* was conducted to establish the production technology of nuclear transfered embryo in deer. For estrus synchronization or superovulation tretments in flower deer and elk, each 10 does were inserted into the vagina for 14 days with CIDR (Pfizer New Zealand Ltd., NZ) for elk and Ring-CIDR (Bioculture Co., Ltd., Korea) for flower deer, and then those inserted devices were removed. The estrus synchronization of each 6 does were induced by the intramuscular injection of PGF2α (25 mg/head) and PG600 (hCG 200IU + PMSG 400IU, Intevet, Holland). Then, the superovulation of each 4 does of flower deer and elk was induced by additional injection of FSH (200 mg/ head) twice with an interval of 24 hours , respectively. Follicular oocytes were collected from each 2 does superovulated after 48 hours since the injection of PG600 and FSH. In the meantime, the ovarian response and the number of the collected ovarian follicles were investigated with the surgical operations. As a result, the average number of the collected ovarian follicles were 8.5 and 9.0 in flower deer and elk, respectively. The ovarian follicles collected from each two does were cultured in vitro for 48 hours with m-DMEM medium, and then the cell fusion was carried out after the nuclear transfer by the antler cell. As a result, 5 out of 18 ovarian follicles collected from 2 elk does were reached on the MII stage, but there was no generation resulting from the nuclear transferred embryos by the antler cell after enucleation. In 2 flower does, 7 out of 17 ovarian follicles were reached to the MII stage, but one of them was developed to parthenogenetic embryo as well despite a case of fusion from the nuclear transferred embryo. Embryos were collected in a surgical way on the 7th day after artificial insemination, numbers of average embryos collected were 2.5 and 3.0 in each 2 flower deer and elk does superovulated, respectively. The collected two embryos were transplanted to each 2 does synchronized. As a result, a head of fawn was produced from only one elk doe, where as a head of fawn were delivered from one out of 4 elk does artificial inseminated. Given these findings, we consider that more or less of problems might have occurred in vitro culture system of ovarian follicles in the production of nuclear transfered deer embryos. In addition, the greatest reason why both the aetificial insemination and embryo transfer failed was considered attributable to stress due to anesthesia and catching.

Spermatogenesis is a series of complex processes that produce spermatozoa in male testis and it occurs through consecutive cell divisions and differentiation of germ cells (Russell et al., 1990). This process is initiated by a small number of spermatogonial stem cells (SSCs) that are only two or three per 104 testis cells in mouse case, and finally gives rise to many functional spermatozoa. Similar to the characteristics found in other adult stem cells, SSCs have the capability of self‐renewal and differentiation (Meistrich and van Beek, 1993). SSCs that have these two capabilities are the source of maintaining male postnatal fertility for lifetime. SSCs that exist inside the male testis maintain the numerical equilibrium through self‐renew after birth and they are the only germ‐line stem cell that can transfer the genetic information to the next generation through spermatogenesis. Therefore, when genetic modification is performed at the SSC stage, it can produce transgenic offspring in the next generation as well as germ‐line modification so that it can deliver the transformed character stably to the descendants. Past studies regarding the SSC had been dependent on morphological observations due to the absence of a marker system that can distinguish the SSCs. Brinster et al. (1994) published a groundbreaking turning point in identifying characteristics of SSC by developing SSC transplantation technique (Brinster and Avarbock, 1994; Brinster and Zimmermann, 1994). Utilizing the SSC transplantation technique, the self‐renew and production capability of differentiated tissue derived from transplanted SSC within the recipient’s seminiferous tubule can be directly analyzed. The biological activity of SSCs can also be investigated objectively by the SSC transplantation technique. Since the advent of the SSC transplantation technique, there have been a lot of progresses in the biological field of SSC. Recently, the enrichment technique of SSCs using FACS and specific surface marker, in vitro culture, and genetic modification techniques of SSCs have been developed in rodents. These techniques have potential to enhance the practical applications of SSCs. Characterization and development of useful technique for SSCs are now extending to livestock species.

Spermatogonial stem cells(SSCs) only are responsible for the generation of progeny and for the transmission of genetic information to the next generation in male. Other in vitro studies have cultured SSCs for proliferation, differentiation, and genetic modification in mouse and rat. Currently, information regarding in vitro culture of porcine Germline Stem Cell(GSC) such as gonocyte or SSC is limited and is in need of further studies. Therefore, in this study, we report development of a successful culture system for gonocytes of neonatal porcine testes. Testis cells were extracted from 10～14-day-old pigs. These cells were harvested using enzymatic digestion, and the harvested cells were purified with combination of percoll, laminin, and gelatin selection techniques. The most effective culture system of porcine gonocytes was established through trial experiments which made a comparison between different feeder cells, medium, serum concentrations, temperatures, and O2 tensions. Taken together, the optimal condition was established using C166 or Mouse Embryonic Fibroblast(MEF) feeder cell, Rat Serum Free Medium(RSFM), 0% serum concentration, 37℃ temperature, and O2 20% tension. Although we discovered the optimal culture condition for proliferation of porcine gonocytes, the gonocyte colonies ceased to expand after one month. These results suggest inadequate acquirement of ingredients essential for long term culture of porcine GSCs. Consequently, further study should be conducted to establish a successful long-term culture system for porcine GSCs by introducing various growth factors or nutrients.

The current study was designed to evaluate the effects of the reactive oxygen species (ROS) generated with a xanthine (X) and xanthine oxidase system (XO) on sperm function and DNA fragmentation in porcine spermatozoa. ROS were produced by a combination of 1,000 μM X and 50 mU/ml XO. The ROS scavengers such as superoxide dismutase (SOD) (200 U/ml) and catalase (CAT) (500 U/ml) were also tested. Spermatozoa were incubated for 2 hours in BWW medium with a combination of X-XO supplemented with or without antioxidants at 37℃ under 5% CO2 incubator. Ca-ionophore-induced acrosome reaction, the proportion of swollen spermatozoa under hypo-osmotic condition, malondialdehyde formation for the analysis of lipid peroxidation, and the proportion of DNA fragmentation were determined after 2 hours incubation. The action of ROS on porcine spermatozoa resulted in decreased Ca-ionophore-induced acrosome reaction and membrane integrity, increased the formation of malondialdehyde, and the proportion of sperm with DNA fragmentation(p<0.05). The toxic effects caused by ROS were completely alleviated by CAT in terms of sperm function and characteristics, however SOD did not serve the same scavenger effect as CAT. To conclude, the ROS can cause significant damage to porcine sperm functions and characteristics, which can be minimized by the use of antioxidants.

본 연구는 돼지에 있어서 정원줄기세포를 포함하는 정소세포를 recipient 돼지의 정소 내로 이식할 수 있는 기법을 개발하기 위하여 시행되었다. 공여세포는 10~14일령의 돼지로부터 채취된 정소에서 효소처리법을 이용하여 회수하였고, recipient의 정소 내로 이식하기 전 형광 마커(PHK26)로 표지하였다. 외과적 수술을 통하여 recipient 돼지부터 정소를 꺼낸 후 초음파 기기와 이식 장치를 이용하여 형광표지된 공여세포를 recipient 정소의 세정관 내로 이식하였다. 14주령의 recipient 정소에 5~7ml 의 공여 세포부유액을 주입하여 정소 내 50% 이상의 세정관 내로 새포부유액의 주입이 가능하였고, 세포부유액이 주입된 세정관 내에서 형광표지된 정소세포들이 고루 이식되어짐이 관찰되었다. 본 연구에서 개발한 이식 기법을 이용하여 효율적인 정소세포의 이식이 가능함에 따라 향후 돼지 정원줄기세포의 연구 및 활용법 개발에 획기적인 돌파구가 마련될 것으로 기대된다.

The aim of this study was to enhance the proliferation efficiency of spermatogonial stem cells (SSCs). In order to improve the proliferation efficiency, we investigated new factors that promote the proliferation of SSCs using in vitro culture method with natural plant extracts. Germ cell populations containing SSCs were collected 6- to 8-days-old from C57BL/6-TG-EGFP (C57GFP) mice and SSCs were isolated from the collected cells via magnetic-activated cell sorting (MACS). Since then, SSCs were cultured for a week with culture medium containing natural plant extracts at concentration of 0.1, 1, and 10 μg/mL. After a week of culture, we looked for an increase, especially a dose-dependent increase, in the number of cells compared to that of the control group. A dose-dependent increase, in the number of cells was observed in the Petasides japonicus-treated groups. Furthermore, we carried out repeated experiment that is process consisting of selection and additional segmentation to explore new factors for activating SSCs at the molecular level. As a results, Petasides japonicus butanol fraction significantly increased the proliferation rate of SSCs in a dose-dependent manner among Petasides japonicus fraction samples. We identified normal expression level of PLZF in SSCs cultured with plant extracts using immunocytochemistry method. Furthermore, we also carried out qRT-PCR and identified normal expression level of Lhx1 and GFRα1. The finding of this study could contribute to improvement of proliferation and activation for SSCs, using culture method with natural plant extracts.

Spermatogonial stem cells (SSCs) possess the unique capacity of self-renewal and differentiation and thereby can transmit genetic information to the next generation. Combination with techniques such as isolation, culture, preservation, and transplantation of the SSC has facilitated the efficient method for production of transgenic animals, and preservation of livestock and endangered species. The purpose of this study was to genetically modify enriched populations of pre-pubertal germ cells using lentiviral transduction and to develop an efficient in vitro culture system and cryopreservation technique for bovine SSCs. To maximize the efficiency of genetic modification of bovine SSCs, effective enrichment techniques need to be developed. Selection of bovine SSCs using a combination of laminin and gelatin was resulted in a 8-fold enrichment. Selected cells were then transduced using a lentiviral vector containing the transgene for the enhanced green fluorescent protein. Transduction efficiency was 17%. Next, to enhance the efficiency of proliferation for in vitro culture, the effects of various culture conditions and growth factors on bovine cell proliferation were evaluated. Based on the results, we developed the optimal culture conditions [2× rat sertum free medium (rSFM) containing 0.1% FBS together with GDNF, GFRα1, bFGF, EGF, LIF, and CSF-1] for maintaining bovine SSCs over 3 months without any alteration of stem cell characteristics and functions. Also, to develop an effective cryopreservation technique for bovine SSCs, the effects of different freezing methods and various cryoprotective agents were tested. The recovery rate, and proliferation capacity of bovine SSCs were significantly greater for germ cells frozen using tissue freezing methods compared to cell freezing methods. Cryopreservation in the presence of 200 mM trehalose resulted in significantly greater recovery rate, and proliferation capacity of germ cells compared to control. As a results, cryopreservation using tissue freezing methods in the presence of 200 mM trehalose is an efficient cryopreservation protocol for bovine SSCs. Collectively, these findings can serve as a model for comprehensively understanding the biology of SSCs and the factors that regulate male fertility. Furthermore, results of this study will be integral for the continued refinement of techniques to manipulate bovine SSCs.