Porcine spermatogonial stem cells (SSCs) prefer three-dimensional (3D) culture systems to 2D ones for the maintenance of self-renewal. Of the many 3D culture systems, agar-based hydrogels are candidates for supporting porcine SSC self-renewal, and there are various types of agar powder that can be used. In this study, we sought to identify an agar-based 3D hydrogel system that exhibited strong efficacy in the maintenance of porcine SSC self-renewal. First, 3D hydrogels with different mechanics were prepared with various concentrations of Bacto agar, lysogeny broth (LB) agar, and agarose powder, and the 3D hydrogel with the strongest alkaline phosphatase (AP) activity and greatest increase in colony size was identified for the different types of agar powder. Second, among the porcine SSCs cultured in the different 3D hydrogels, we analyzed the colony formation, morphology, and size; AP activity; and transcription and translation of porcine SSC-related genes, and these were compared to determine the optimal 3D hydrogel system for the maintenance of porcine SSC self-renewal. We found that 0.6% (w/v) Bacto agar-, 1% (w/v) LB agar-, and 0.2% (w/v) agarose-based 3D hydrogels showed the strongest maintenance of AP activity and the most pronounced increase in colony size in the culture of porcine SSCs. Moreover, among these hydrogels, the strongest transcription and translation of porcine SSC-related genes and largest colony size were detected in porcine SSCs cultured in the 0.2% (w/v) agarose-based 3D hydrogel, whereas there were no significant differences in colony formation and morphology. These results demonstrate that the 0.2% (w/v) agarose-based 3D hydrogel can be effectively used for the maintenance of porcine SSC self-renewal.

Generally, fate of spematogonial stem cells (SSCs) can be determined specifically by microenvironments enclosed with various extracellular matrix (ECM) components and integrins recognizing directly ECM proteins play an pivotal role in transporting ECM-derived signals into cytoplasm, resulting in inducing a variety of biological functions such as cell attachment, self-renewal and differentiation. However, to date, studies on type of integrins expressed on the undifferentiated SSCs remain unclear. Therefore, we tried to investigate systematically what kind of integrin subunits are expressed transcriptionally or translationally in the SSCs derived from testis of hybrid B6CBAF1 mouse. For these, isolation of SSCs from testis were conducted by magnetic activated cell sorting (MACS) using Thy1 antibody. Subsequently, transcriptional and translational level of integrin α and β subunits in the isolated SSCs were measured by real-time PCR and fluorescene immunoassay, respectively. As the results, transcriptional levels of genes encoding total 25 integrin subunits were quantified, and integrin α4, α6, α7, α9, αV, αL and αE and integrin β1, β5 showed higher expression levels than other subunits. By contrast, integrin α3, α5, α 10 and α11 and integrin β2, β3, β4, β7 were weakly transcribed. When translational levels of the integrin α subunits showing high transcription level (α4, α6, α7, α9, αV αL, and αE) were measured, integrin α6, α7, α9, αV and αL were higher than integrin α4 and αE. In case of integrin β subunit, β1 evaluated more expression than β5. From these results, we speculate that the undifferentiated SSCs derived from hybrid B6CBAF1 mouse may express integrin α4β1, α6β1, α7β1, α9β1, αVβ1 and/or αVβ5 on plasma membrane. Moreover, this information will greatly contribute to constructing non-cellular niche supporting self-renewal of SSCs in the future.

Spermatogenesis is initiated from spermatogonial stem cells (SSCs) that has an ability of self-renewal and unipotency to generate differentiating germ cells. The objective of this study is to develop the simple method for derivation of SSCs using non-sorting of both spermatogonia and feeder cells. Simply uncapsulated mouse testes were treated with enzymes followed by surgical mincing, and single cells were cultured in stempro-34TM cell culture media at 37℃. After 5 days of culture, aciniform of SSC colony was observed, and showed a strong alkaline phosphatase activity. Molecular characterization of mouse SSCs showed that most of the mouse SSC markers such as integrin α6 and β1, CD9 and Stra8. In addition, pluripotency embryonic stem cell (ESC) marker Oct4 were expressed, however Sox2 expression was lowered. Interestingly, expression of SSC markers such as Vasa, Dazl and PLZF were stronger than mouse ESC (mESC). This data suggest that generated mouse SSCs (mSSCs) in this study has at least similar biomarkers expression to mESC and mSSCs derived from other study. Immunocytochemistry using whole mSSC colony also confirmed that mSSCs generated from this study expressed SSC specific biomarkers such as c-kit, Thy1, Vasa and Dazl. In conclusion, mSSCs from 5 days old mouse testes were successfully established without sorting of spermatogonia, and this cells expressed both mESC and SSC specific biomarkers. This simple derivation method for mSSCs may facilitate the study of spermatogenesis.

Althogh Spermatogonial stem cells (SSCs) are widely studied in mice, study of pig SSCs is not sufficient for the isolation, long-term culture, and characterization. To identify the effect of growth factor in cultured pig SSC, newly generated pSSCs like cell from neonatal 5days porcine testis were cultured and investigated for the pSSCs like cell formation. Glial derived neurotrophic gactor (GDNF), fibroblast growth factor (FGF), leukemia inhibitory factor (LIF), and epidermal growth factor (EGF) were applied to culture media to identify the pSSC like cell growth and stem cell formation. The criteria for the determining of stem cell characters, morphology, number of colonies, putative stem cell marker were analysed by microspic, polymerase chain reaction (PCR) and immunocytochemistry (ICC) methods. Most of the pSSCs like cells were formed approximately 100 μm size with sphere shape. Most of the feeder cells were highly dependent on FGF that feeder cells were not stably attached on plate without FGF and colony formation of pSSC was not observed consequently. Immunocyto chemistry data revealed that this cells expressed the ubiquitin-C-terminal hydrolase 1 (UCHL-1, PGP9.5) and Dolichos Biflorus Agglutinin (DBA) in addition of 20 ng/ml EGF, 10 ng/ml FGF, 10 ng/ml GDNF, 10 U3/ml LIF. In addition, Alkaline Phosphatase ()was positive in all period of culture. This study suggest that various growth factorsinp SSC culture system is important to regulate and maintain the pSSC. In conculsion, although the precise role of growth factor in pSSC proliferation need to be clarified, combination of growth factor might be critical in order to derivation and proliferation of neonatal pSSCs and spermatogenesis.

The HMG box containing protein (HBP) has a high mobility group domain and involved in the regulation of proliferation and differentiation of tissues. We screened HBP2 in glioblastoma using Suppression Subtractive Hybridization (SSH) and isolated human spermatogonial stem cell‐like cells (hSSC‐like cells) derived from patients of nonobstructive azoospermia (NOA). Expression of HBP2 was analyzed by RT‐PCR in undifferentiated stem cells (human Embryonic Stem Cells, hSSC‐like cells 2P) and spontaneous differentiated stem cells (hSSC‐like cells 4P). It was overexpressed in hESC and hSSC‐like cells 2P but not in hSSC‐like cells 4P. Also, the expression level of HBP2 was downregulated in colon tumor tissues compared to normal tissues. Specifically in synchronized WI‐38 cells, HBP2 was highly upregulated until the G1 phase of the cell cycle and gradually decreased during the S phase. Our results suggest that HBP2 was downregulated during the spontaneous differentiation of hSSC‐like cells. HBP2 was differently expressed in colon tissues and was related to G1‐progression in WI‐38 cells. It may play a role in the maintenance of an undifferentiated hSSC‐like cell state and transits from G1 to S in WI‐38 cells. This research was important that it identified a biomarker for an undifferentiated state of hSSC‐like cells and characterized its involvement to arrest during cell cycle in colon cancer.

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.