Efficiency of adult mouse spermatogonial stem cell colony formation under several culture conditions

Ultrastructural study: in vitro and in vivo differentiation of mice spermatogonial stem cells

Mouse testicular tissue is composed of seminiferous tubules and interstitial tissue. Mammalian spermatogenesis is divided into three stages: spermatocytogenesis (mitotic divisions) in which spermatogonial stem cells (SSCs) turn into spermatocytes, followed by two consecutive meiotic divisions in which spermatocytes form spermatids. Spermatids differentiate into spermatozoa during spermiogenesis. Various factors affect the process of spermatogenesis and the organization of cells in the testis. Any disorder in different stages of spermatogenesis will have negative effects on male fertility. The aim of the current study was to compare the in vitro and in vivo spermatogenesis processes before and after transplantation to azoospermic mice using ultrastructural techniques. In this study, mice were irradiated with single doses of 14 Gy 60Co radiation. SSCs isolated from neonatal mice were cultured in vitro for 1 week and were injected into the seminiferous tubule recipient's mice. Testicular cells of neonatal mice were cultured in the four groups on extracellular matrix-based 3D printing scaffolds. The transplanted testes (8 weeks after transplantation) and cultured testicular cells in vitro (after 3 weeks) were then processed for transmission electron microscopy studies. Our study's findings revealed that the morphology and ultrastructure of testicular cells after transplantation and in vitro culture are similar to those of in vivo spermatogenesis, indicating that spermatogenic cell nature is unaltered in vitro.

Advances of three-dimensional (3D) culture systems for in vitro spermatogenesis

The loss of germ cells and spermatogenic failure in non-obstructive azoospermia are believed to be the main causes of male infertility. Laboratory studies have used in vitro testicular models and different 3-dimensional (3D) culture systems for preservation, proliferation and differentiation of spermatogonial stem cells (SSCs) in recent decades. The establishment of testis-like structures would facilitate the study of drug and toxicity screening, pathological mechanisms and in vitro differentiation of SSCs which resulted in possible treatment of male infertility. The different culture systems using cellular aggregation with self-assembling capability, the use of different natural and synthetic biomaterials and various methods for scaffold fabrication provided a suitable 3D niche for testicular cells development. Recently, 3D culture models have noticeably used in research for their architectural and functional similarities to native microenvironment. In this review article, we briefly investigated the recent 3D culture systems that provided a suitable platform for male fertility preservation through organ culture of testis fragments, proliferation and differentiation of SSCs.

Effects and Mechanisms Activated by Treatment with Cationic, Anionic and Zwitterionic Liposomes on an In Vitro Model of Porcine Pre-Pubertal Sertoli Cells

Liposomes have been successfully used as drug-delivery vehicles, but there are no clinical studies on improved fertility and the few reported experimental studies have been performed in animal models far from humans. The aim of this paper was to study the effects of treatment with cationic, anionic and zwitterionic liposomes on our superior mammalian model of porcine prepubertal Sertoli cells (SCs) to find a carrier of in vitro test drugs for SCs. Porcine pre-pubertal SCs cultures were incubated with different liposomes. Viability, apoptosis/necrosis status (Annexin-V/Propidium iodide assay), immunolocalisation of β-actin, vimentin, the phosphorylated form of AMP-activated protein Kinase (AMPK)α and cell ultrastructure (Transmission Electron Microscopy, TEM) were analysed. Zwitterionic liposomes did not determine changes in the cell cytoplasm. The incubation with anionic and cationic liposomes modified the distribution of actin and vimentin filaments and increased the levels of the phosphorylated form of AMPKα. The Annexin/Propidium Iodide assay suggested an increase in apoptosis. TEM analysis highlighted a cytoplasmic vacuolisation. In conclusion, these preliminary data indicated that zwitterionic liposomes were the best carrier to use in an in vitro study of SCs to understand the effects of molecules or drugs that could have a clinical application in the treatment of certain forms of male infertility.

Co-supplementation of freezing media with trehalose and vitamin C on cell viability and apoptotic gene expression in ovine spermatogonial stem cells

The purpose of this research was to investigate the trehalose and vitamin C (Vit C) co-supplementation of freezing media to create a successful cryopreservation protocol for conservation of ovine spermatogonial stem cells (SSCs). SSCs were cryopreserved and cultured with an essential freezing medium containing 200 mM trehalose, 40 µg/mL Vit C, and a combination of both for 3 weeks. Cell viability, colony number and diameter and mRNA levels of Bax, and Bcl-2 genes were evaluated before and after cryopreservation with quantitative real-time PCR. The results showed that cells cryopreserved in freezing medium containing 200 mM of trehalose plus 40 µg/mL Vit C had considerably greater cell viability than the control group (P<0.0001). Up to the 3rd week of cell culture, supplementation of freezing medium with 200 mM trehalose resulted in significantly lower colonies diameters than in the control group. No significant differences were observed during the 1st to 2nd weeks in colony diameter and number of colonies between cells cryopreserved in the freezing medium containing either Vit C or trehalose compared with the control groups. Following thawing, the mRNA level of Bax in the Vit C + trehalose group was drastically lower than in those treated with trehalose or Vit C only (P<0.0001). High expression of Bcl-2 in the 40 µg/mL Vit C group was recorded in the thawed cells compared to the control group (P<0.0001). These findings indicate that the concomitant use of antioxidants and sugar in the freezing medium can improve the quality and viabi­lity of SSCs after freezing via different mechanisms. Further studies are needed to clarify apoptosis and cell biomarkers in SSCs during freezing and thawing.

Efficacy of Ficus carica leaf extract on morphological and molecular behavior of mice germ stem cells

Infertility is one of the most prevalent health disorders in reproductive-age males and females. Ficus carica (Fc), an herbal plant, has been used traditionally for the treatment of different diseases such as infertility especially in Iranian folk medicine. This study examined the effects of Fc leaf extract on the proliferation of mice spermatogonial stem cells (SSCs). Phenolic, flavonoid content, major polyphenolic compounds and antioxidant activity of the extract was evaluated respectively by Folin-Ciocateu, aluminum chloride, HPLC and the FRAP and DPPH methods. Testicular cells of neonate mice were extracted and their identity was confirmed using cytokeratin for Sertoli and Oct-4, CDHI and PLZF for SSCs. Effects of Fc (0.0875, 0.175, 0.35, 0.71 and 1.42 mg/ml) was evaluated at third, 7th, 9th and 14th days of culture by colony assay. The expression of the Mvh, GFRα1 and Oct-4 genes and the viability and proliferation of cultured cells was assessed at the end of the culture period. The extract has a rich phenolic and flavonoid content such as Rutin, Psoralen, Bergapten and Caffeoylmalic acid using HPLC analysis. It also had a potent reducing and radical scavenging activity. Morphology of colonies was similar in all groups. Higher viability, proliferation, colony number and diameter of SSCs was seen in the presence of Fc leaf extract in a dose-dependent manner so that higher number and diameter of colonies were observed in two higher doses of 0.71 and 1.42 mg/ml, separately for each time point relative to other groups. The Mvh, Oct-4 and GFRα1 genes expression had no significant differences between groups. It seems that Fc leaf extract not only had no any cytotoxic effects on the viability and proliferation of SSCs but also support their stemness state. So, this culture system can be employed for enrichment of germ stem cells for use in clinical applications.

Leptin promotes proliferation of neonatal mouse stem/progenitor spermatogonia

PURPOSE

To keep and increase spermatogonial stem cell number (SSC) is the only available option for pediatric cancer survivors to maintain fertility. Leptin is secreted by the epididymal white adipose tissue and has receptors on stem/progenitor spermatogonia. The purpose of this study is to demonstrate dose- and time-dependent proliferative effect of leptin on stem/progenitor spermatogonia cultures from prepubertal mice testes.

METHODS

CD90.2 (+) stem/progenitor spermatogonia were isolated from the C57BL/6 mouse testis on postnatal day 6 and placed in culture. The proliferative effect of leptin supplementation was assessed by colony formation (diameter and number), WST proliferation assays, and xCELLigence real-time cell analysis (RTCA) on days 3, 5, and 7 of culture. Expressions of p-ERK1/2, p-STAT3, total STAT3, and p-SHP2 levels were determined by western blot analysis.

RESULTS

Leptin supplementation of 100 ng/ml increased the diameter (p = 0.001) and number (p = 0.01) of colonies in stem/progenitor spermatogonial cultures and caused higher proliferation by WST-1 (p = 0.009) compared with the control on day 7. The EC50 was calculated as 114 ng/ml for leptin by RTCA. Proliferative dose of leptin induced increased expression of p-ERK1/2 (p = 0.009) and p-STAT3 (p = 0.023) on stem/progenitor spermatogonia when compared with the untreated group.

CONCLUSION

The results indicated that leptin supplementation exhibited a dose- and time-dependent proliferative effect on stem/progenitor spermatogonia that was associated with increased expression of ERK1/2 and STAT3 pathways while maintaining their undifferentiated state. This output presents a new agent that may help to expand the stem/progenitor spermatogonia pool from the neonatal testis in order to autotransplant after cancer treatment.

Differentiation of neonate mouse spermatogonial stem cells on three-dimensional agar/polyvinyl alcohol nanofiber scaffold

Electrospun nanofiber matrices sufficiently mimic the structural morphology of natural extracellular matrix. In this study, we aimed to examine the effects of agar/polyvinyl alcohol nanofiber (PVA) scaffold on the proliferation efficiency and differentiation potential of neonate mouse spermatogonial stem cells (SCCs). Testicular cells were isolated from testes of 40 mouse pups and were seeded in: 1) 2D cell culture plates in the absence (2D/-GF) or presence (2D/+GF) of growth factors and 2) onto agar/PVA scaffold in the absence (3D/-GF) or presence (3D/+GF) of growth factors. The cells were subsequently cultured for 4 weeks. First 2 weeks were dedicated to proliferative phase, whereas the next 2 weeks emphasized the differentiation phase. The identity of the SCCs was investigated at different time-points by flow cytometry and quantitative reverse transcription PCR (qRT-PCR) analyses against the germ cell markers, including PLZF, Id-4, Gfrα-1, Tekt-1, and Sycp-3. After 2 weeks of culture, the 3D/+GF group showed the highest percentage of PLZF-positive cells among culture systems (P < 0.05). The expression levels of pre-meiotic markers (Id-4 and Gfrα-1) decreased significantly in all groups, particularly in 3D/+GF group after 28 days of culture. Additionally, the cells in the 3D/+GF group displayed the highest expression of meiotic (Sycp-3) and post-meiotic markers (Tekt-1) 14 days after differentiation induction. Seemingly, the combination of the agar/PVA scaffold and growth factor-supplemented medium synergistically increased the differentiation rate of mouse SSCs into meiotic and post-meiotic cells. Thus, agar/PVA nanofiber scaffolds may have the potential for applications in the restoration of infertility, especially in azoospermic males.

ABBREVIATIONS

2D: two dimentional; 3D: three dimentional; bFGF: basic fibroblast growth factor; BMP-4: bone morphogenetic protein 4; DMEM: Dulbecco's modified Eagle's medium; ECM: extracellular matrix; FCS: fetal calf serum; FTIR: Fourier-transform infrared spectroscopy; GDNF: glial cell line-derived neurotrophic factor; GF: growth factors; Gfrα-1, GDNF family co-receptor α1; Id-4, Inhibitor of DNA Binding 4; MTT: methylthiazoltetrazolium; PLZF: promyelocytic leukemia zinc finger; PVA: polyvinyl alcohol; qRT-PCR: quantitative reverse transcription PCR; RA: retinoic acid; SACS: soft agar culture system; SD: standard deviation; SEM: scanning electron microscope; SSCs: spermatogonial stem cells; Sycp-3, Synaptonemal complex protein 3; Tekt-1, Tektin 1.

Differential role of r-met-hu G-CSF on male reproductive function and development in prepubertal domestic mammals

The understanding of mammalian spermatogenesis niche factors active during sexual development may be leveraged to impact reproduction in farm animals. The aim of this study was to evaluate the effects of r-met-hu/G-CSF (filgrastim) on prepubertal sexual development of guinea pigs (Cavia porcellus) and ram lambs (Ovis aries). Individuals of both species were administered r-met-hu/G-CSF daily for 4 days. During and after administration protocols, testicular function and development were assessed through hematological responses, hormonal profiles (gonadotropins, testosterone and cortisol) testicular morphometry and germ cell kinetics. As expected, r-met-hu/G-CSF acutely mobilized white-lineage blood cells in both species. LH was increased by r-met-hu/G-CSF in guinea pigs (P<0.01) but T remained unchanged. In ram lambs gonadotropins and T increased in dose-response fashion (P<0.01) while cortisol values were stable and similar in treated and control animals (P>0.05). In guinea pigs there were no differences in testicular weights and volumes 2-mo after r-met-hu/G-CSF application (P>0.05). However, ram lambs showed a dose-response effect regarding testis weight (P<0.05). 66.66% of ram lambs had initial testes not yet in meiosis or starting the first spermatogenic wave. After 60-days only 25% of control animals were pubertal while all treated animals (1140-μg) had reached puberty. We propose an integrated hypothesis that G-CSF can stimulate spermatogenesis through two possible ways. 1) r-met-hu/G-CSF may go through the brain blood barrier and once there it can stimulate GnRH-neurons to release GnRH with the subsequent release of gonadotrophins. 2) a local testicular effect through stimulation of steroidogenesis that enhances spermiogenesis via testosterone production and a direct stimulation over spermatogonial stem cells self-renewal. In conclusion, this study shows that r-met-hu/G-CSF differentially affects prepubertal sexual development in hystricomorpha and ovine species, a relevant fact to consider when designing methods to hasten sexual developmental in mammalian species.

In vitro culture of spermatogonial stem cells isolated from adult alpaca (Vicugna pacos) testes analysed with Dolichos biflorus by flow cytometry

Spermatogonial stem cell (SSC) is known for its self-renewal capacity. We have studied the in vitro proliferation of isolated SSC from adult alpaca (Vicugna pacos) testes. A total of 107 samples were evaluated of which 31 were evaluated at baseline, 36 were cultivated in DMEM and 40 in STEMPRO media. Half of the cultivated samples was analysed after 14 days, and the rest after 21 days. Round cell subpopulations were identified with FITC-DBA by flow cytometry: strongly positive DBA (sDBA+) as SSC, weakly positive DBA (wDBA+) as in early differentiation and negative DBA as differentiated. At the beginning, 4.16% of the cells were SSC, 37.61% wDBA+ while 54.12% were DBA-. After 14 days, 42.28% of SSC, 44.68% wDBA+ and 11.07% DBA- were found in DMEM while 47.09% of SSC, 32.57% wDBA+ and 18.48% DBA- in STEMPRO. After 21 days 38.66% were SSC, 52.78% wDBA and 7.65% DBA- in DMEM and on STEMPRO media 47.92% SSC, 44.20% wDBA+, 4.93% DBA-. There is a significant difference between the number of initial and SSC cultivated, as well as between DBA- (p < 0.05), while there is no significant difference between the wDBA+ (p > 0.05). Our results suggest that both culture media are appropriate for the in vitro proliferation of alpacas SSC.

Embryonic stem cell derived germ cells induce spermatogenesis after transplantation into the testes of an adult mouse azoospermia model

The present study aimed to: (i) identify the exogenous factors that allow in vitro differentiation of mouse spermatogonial stem cells (SSCs) from embryonic stem cells (ESCs); (ii) evaluate the effects of Sertoli cells in SSC enrichment; and (iii) assess the success of transplantation using in vitro differentiated SSCs in a mouse busulfan-treated azoospermia model. A 1-day-old embryoid body (EB) received 5 ng/ml of bone morphogenetic protein 4 (BMP4) for 4 days, 3 µM retinoic acid (RA) in a SIM mouse embryo-derived thioguanine and ouabain resistant (STO) co-culture system for 7 days, and was subsequently co-cultured for 2 days with Sertoli cells in the presence or absence of a leukaemia inhibitory factor (LIF), basic fibroblast growth factor (bFGF) and RA composition, and in the presence of these factors in simple culture medium. Higher viability, proliferation and germ cell gene expression were seen in the presence of the LIF, bFGF and RA composition, on top of Sertoli cells. Immunocytochemistry results showed higher CDH1 expression in this group. Sertoli co-culture had no effects on SSC proliferation. Eight weeks after transplantation, injected cells were observed at the base of the seminiferous tubules and in the recipient testes. The number of spermatogonia and the mass of the testes were higher in transplanted testes relative to the control group. It seems that transplantation of these cells can be useful in infertility treatment.

Effects of different Sertoli cell types on the maintenance of adult spermatogonial stem cells in vitro

Spermatongonial stem cells (SSCs) are unique testis cells that are able to proliferate, differentiate, and transmit genetic information to the next generation. However, the effect of different Sertoli cell types on the expression of specific SSC genes is not yet well understood. In this study, we compare the in vitro effect of adult Sertoli cells, embryonic Sertoli cells, and TM4 (a Sertoli cell line) as feeder layers on the expression of SSC genes. SSCs were isolated from the testis of adult male mice and purified by differential plating. Following enrichment, SSCs were cultivated for 1 and 2 wk in the presence of various feeders. The expression of SSC-specific genes (Mvh, ZBTB, and c-kit) was evaluated by real-time polymerase chain reaction. Our results revealed that expression of the specific SSC genes was significantly higher in the embryonic Sertoli cells after 1 and 2 wk compared to the adult Sertoli cells and the TM4 group. Our finding suggest that co-culturing of SSCs with embryonic Sertoli cells is helpful for in vitro cultivation of SSCs and might improve the self-renewal of these stem cells.

Generation of Mouse Spermatogonial Stem-Cell-Colonies in A Non-Adherent Culture

OBJECTIVE

The properties of self-renewal and division in spermatogonial stem cells (SSCs) support spermatogenesis. There is a number of reported methods for in vitro SSC culture systems. The development of a culture system that effectively supports isolation and selfrenewal of germline stem cells (GSCs) is of tremendous benefit for clinical trials, experimental research, and as potential treatment for male infertility. The current study aims to consider the cultivation and behavior of GSCs in a non-adherent culture system.

MATERIALS AND METHODS

In this experimental study, we cultured testicular cells from neonatal mice in agarose coated plates in the presence of Dulbecco's modified Eagle's medium (DMEM) medium (CTRL group), 10% fetal bovine serum (FBS)+DMEM (10% group), and growth factor (G group) that contained 2% FBS, glial cell-derived neurotrophic factor (GDNF), epidermal growth factor (EGF), and fibroblast growth factor (FGF). Mouse spermatogonial stem-like colonies were isolated approximately 3 weeks after digestion of the testis tissue. After passages 2-3, the identity of the mouse spermatogonial stem-like cells was confirmed by immunocytochemistry, reverse transcription-polymerase chain reaction (RT-PCR), and flow cytometry against the germ cell markers α6, β1, c-Kit, Thy-1, c-Ret, Plzf, and Oct4. The statistical significance between mean values in different groups was determined by one-way analysis of variance (ANOVA).

RESULTS

We observed spermatogonial stem-like colonies in the G and 10% groups, but not the CTRL group. Immunocytochemistry, flow cytometry, and RT-PCR confirmed expressions of germ cell markers in these cells. In the spermatogonial stem-like cells, we observed a significant expression (P<0.05) of germ cell markers in the G and 10% groups versus the testis cells (T). Their proliferative and apoptotic activities were examined by Ki67 and PI/annexin V-FITC. Alkaline phosphatase assay showed that mouse spermato- gonial stem-like colonies were partially positive.

CONCLUSION

A non-adherent culture system could provide a favorable method for in vitro short-term culture of spermatogonial stem-like cell colonies.

In vitro effects of date palm (Phoenix dactylifera L.) pollen on colonization of neonate mouse spermatogonial stem cells

ETHNOPHARMACOLOGICAL RELEVANCE

Date palm (Phoenix dactylifera L.) pollen (DPP) is widely used as a folk remedy for male infertility treatment, and has well known medicinal effects.

AIM OF THE STUDY

This study aimed to determine the in vitro effects of DPP on the efficiency of neonate mouse spermatogonial stem cells (SSCs) proliferation.

MATERIAL AND METHODS

Sertoli and SSCs were isolated from 6 to 10-days-old mouse testes, and their identity was confirmed using immunocytochemistry against cytokeratin for sertoli cells and PLZF, Oct-4 and CDH-1 for SSCs. Isolated testicular cells were cultured in the absence or presence of 0.06, 0.25 and 0.62mg/ml concentrations of DPP aqueous extract for 2 weeks. The number and diameter of SSC colonies were assessed during third, 7th, 9th and 14th day of culture, and the expression of the Mvh, GFRα-1 and Oct-4 was evaluated using quantitative PCR at the end of the culture period. The significance of the data was analyzed using ANOVA and paired samples t-test and Tukey and Bonferroni test as post hoc tests at the level of p≤0.05.

RESULTS

Pattern assay of colony formation showed that SSCs numbers increased in the present of 0.62mg/ml concentration of DPP extract with higher slop relative to other groups (P <0.05). Colony diameters had no significant difference between groups in 3th, 7th, 9th and 14th days after culture. The Mvh and Oct-4 genes expression had no significant difference between groups, while GFRα1 expression was increased significantly in cells treated with 0.06mg/ml concentration relative to other groups (P<0.05).

CONCLUSION

It seems that co-culture of SSCs with sertoli sells in the presence of low doses of DPP can increase SSCs proliferation and keep their stemness state, while higher concentrations can differentiate the treated cells.

Spermatogenesis: The Commitment to Meiosis

Mammalian spermatogenesis requires a stem cell pool, a period of amplification of cell numbers, the completion of reduction division to haploid cells (meiosis), and the morphological transformation of the haploid cells into spermatozoa (spermiogenesis). The net result of these processes is the production of massive numbers of spermatozoa over the reproductive lifetime of the animal. One study that utilized homogenization-resistant spermatids as the standard determined that human daily sperm production (dsp) was at 45 million per day per testis (60). For each human that means ∼1,000 sperm are produced per second. A key to this level of gamete production is the organization and architecture of the mammalian testes that results in continuous sperm production. The seemingly complex repetitious relationship of cells termed the "cycle of the seminiferous epithelium" is driven by the continuous commitment of undifferentiated spermatogonia to meiosis and the period of time required to form spermatozoa. This commitment termed the A to A1 transition requires the action of retinoic acid (RA) on the undifferentiated spermatogonia or prospermatogonia. In stages VII to IX of the cycle of the seminiferous epithelium, Sertoli cells and germ cells are influenced by pulses of RA. These pulses of RA move along the seminiferous tubules coincident with the spermatogenic wave, presumably undergoing constant synthesis and degradation. The RA pulse then serves as a trigger to commit undifferentiated progenitor cells to the rigidly timed pathway into meiosis and spermatid differentiation.

Models of in vitro spermatogenesis

Understanding the mechanisms that lead to the differentiation of male germ cells from their spermatogonial stem cells through meiosis to give rise to mature haploid spermatozoa has been a major quest for many decades. Unlike most other cell types this differentiation process is more or less completely dependent upon the cells being located within the strongly structured niche provided by mature Sertoli cells within an intact seminiferous epithelium. While much new information is currently being obtained through the application and description of relevant gene mutations, there is still a considerable need for in vitro models with which to explore the mechanisms involved. Not only are systems of in vitro spermatogenesis important for understanding the basic science, they have marked pragmatic value in offering ex vivo systems for the artificial maturation of immature germ cells from male infertility patients, as well as providing opportunities for the transgenic manipulation of male germ cells. In this review, we have summarized literature relating to simplistic culturing of germ cells, co-cultures of germ cells with other cell types, especially with Sertoli cells, cultures of seminiferous tubule fragments, and briefly mention the opportunities of xenografting larger testicular pieces. The majority of methods are successful in allowing the differentiation of small steps in the progress of spermatogonia to spermatozoa; few tolerate the chromosomal reduction division through meiosis, and even fewer seem able to complete the complex morphogenesis which results in freely swimming spermatozoa. However, recent progress with complex culture environments, such as 3-d matrices, suggest that possibly success is now not too far away.

Establishment and characterization of an ovarian cell line from Southern catfish (Silurus meridionalis)

An ovarian cell line was successfully developed from the juvenile ovary of Southern catfish (SCO1) (Silurus meridionalis), which was designated as SCO1. The cell line multiplied preferentially in L-15 medium with 15 % fetal bovine serum at 28 °C for more than 70 passages over a period of 420 days. SCO1 showed fibroblast-like morphology and predominantly retained a diploid karyotype of 58 chromosomes. From the gene expression patterns, SCO1 showed a characteristic of ovarian granulosa cells. After the cells were transfected with the green fluorescent protein expression vector, bright fluorescent signals could be observed in approximately 30 % cells. This cell line may be valuable for the evaluation of endocrine disruptors and studying interactions between somatic cells and germ cells.

Maintenance of potential spermatogonial stem cells in vitro by GDNF treatment in a chondrichthyan model (Scyliorhinus canicula L.)

Previous work in dogfish, Scyliorhinus canicula, has identified the testicular germinative area as the spermatogonial stem cell niche. In the present study, an in vitro co-culture system of spermatogonia and somatic cells from the germinative area was developed. Long-term maintenance of spermatogonia has been successful, and addition of GDNF has promoted the development of clones of spermatogonia expressing stem cell characteristics such as alkaline phosphatase activity and has allowed maintenance of self-renewal in spermatogonia for at least 5 mo under culture conditions, notably by decreasing cell apoptosis. Furthermore, clones of spermatogonia expressed the receptor of GDNF, GFRalpha1, which is consistent with the effect of GDNF on cells despite the lack of identification of a GDNF sequence in the dogfish's transcriptome. However, a sequence homologous to artemin has been identified, and in silico analysis supports the hypothesis that artemin could replace GDNF in the germinative area in dogfish. This study, as the first report on long-term in vitro maintenance of spermatogonia in a chondrichthyan species, suggests that the GFRalpha1 signaling function in self-renewal of spermatogonial stem cells is probably conserved in gnathostomes.

In vitro culture and characterization of spermatogonial stem cells on Sertoli cell feeder layer in goat (Capra hircus)

PURPOSE

To develop an efficient protocol for isolation, purification and long-term culture of spermatogonial stem cell (SSC) in goat.

METHODS

The isolation of SSC was performed by testicular disaggregation by enzymatic digestion using collagenase IV, trypsin and DNase I. Further SSCs were enriched using Percoll density gradient centrifugation. The purity of SSCs was assessed by immunocytochemistry (ICC) using α6 integrin. The SSCs were co-cultured on Sertoli cell feeder layer. The SSC colonies were characterized by studying the expression of SSC specific markers (viz., α6 integrin and PLZF) using ICC. The abundance of mRNAs encoding the markers of SSC (viz., β1 integrin and Oct-4) and Sertoli cells (viz., vimentin) was also assayed using quantitative real-time PCR (qPCR).

RESULTS

The viability of isolated testicular cells was > 90 % and the Percoll density gradient method resulted in 3.65 folds enrichment with a purity of 82.5 %. Co-culturing of SSCs with Sertoli cell feeder layer allowed the maintenance of stable SSC colonies even after one and half months of culture. The results of ICC analysis showed the expression of α6 integrin and PLZF in almost all the SSC colonies. qPCR analysis revealed a differential expression of mRNAs encoding β1 integrin, Oct-4 and vimentin markers.

CONCLUSION

Results of this study demonstrate a simple enzymatic digestion and Percoll density gradient method for isolation and enrichment of SSCs, and suitability of Sertoli cell feeder layer for long term in vitro culture of SSC in goats. Results also suggest the possible application of non-caprine antibodies against SSC specific markers for the identification and subsequent assessment of SSCs in goats.

Effects of extracellular matrices and lectin Dolichos biflorus agglutinin on cell adhesion and self-renewal of bovine gonocytes cultured in vitro

Surface molecules of primitive male germ cells, gonocytes, are essential components for regulating cell adhesion and maintaining self-renewal in mammalian species. In domestic animals, the stage-specific glycan epitope α-N-acetylgalactosamine (GalNAc) is recognised by the lectin Dolichos biflorus agglutinin (DBA) and is found on the surface of gonocytes and spermatogonia. Gonocytes from bovine testis formed mouse embryonic stem-like cell colonies on plates that had been coated with DBA or extracellular matrix (ECM) components, such as gelatin (GN), laminin (LN) and poly-L-lysine (PLL). The number of colonies on the DBA-coated plate was significantly higher than that on the GN-, LN- and PLL-coated plates. Pretreating gonocytes with DBA to neutralise the terminal GalNAc residues strongly suppressed colony formation. Furthermore, expression of a germ cell-specific gene and pluripotency-related transcription factors was increased considerably on the DBA-coated plates. These results suggest that the GalNAc residues on gonocytes can recognise precoated DBA on plates and the resulting GalNAc–DBA complexes support germ cell and stem cell potentials of gonocytes in vitro. These glycan complexes, through the GalNAc epitope, may provide a suitable microenvironment for the adhesion and cell proliferation of gonocytes in culture.

The effects of poly L-lactic acid nanofiber scaffold on mouse spermatogonial stem cell culture

INTRODUCTION

A 3D-nanofiber scaffold acts in a similar way to the extracellular matrix (ECM)/basement membrane that enhances the proliferation and self-renewal of stem cells. The goal of the present study was to investigate the effects of a poly L-lactic acid (PLLA) nanofiber scaffold on frozen-thawed neonate mouse spermatogonial stem cells (SSCs) and testis tissues.

METHODS

The isolated spermatogonial cells were divided into six culture groups: (1) fresh spermatogonial cells, (2) fresh spermatogonial cells seeded onto PLLA, (3) frozen-thawed spermatogonial cells, (4) frozen-thawed spermatogonial cells seeded onto PLLA, (5) spermatogonial cells obtained from frozen-thawed testis tissue, and (6) spermatogonial cells obtained from frozen-thawed testis tissue seeded onto PLLA. Spermatogonial cells and testis fragments were cryopreserved and cultured for 3 weeks. Cluster assay was performed during the culture. The presence of spermatogonial cells in the culture was determined by a reverse transcriptase polymerase chain reaction for spermatogonial markers (Oct4, GFRα-1, PLZF, Mvh(VASA), Itgα6, and Itgβ1), as well as the ultrastructural study of cell clusters and SSCs transplantation to a recipient azoospermic mouse. The significance of the data was analyzed using the repeated measures and analysis of variance.

RESULTS

The findings indicated that the spermatogonial cells seeded on PLLA significantly increased in vitro spermatogonial cell cluster formations in comparison with the control groups (culture of SSCs not seeded on PLLA) (P≤0.001). The viability rate for the frozen cells after thawing was 63.00% ± 3.56%. This number decreased significantly (40.00% ± 0.82%) in spermatogonial cells obtained from the frozen-thawed testis tissue. Both groups, however, showed in vitro cluster formation. Although the expression of spermatogonial markers was maintained after 3 weeks of culture, there was a significant downregulation for some spermatogonial genes in the experimental groups compared with those of the control groups. Furthermore, transplantation assay and transmission electron microscopy studies suggested the presence of SSCs among the cultured cells.

CONCLUSION

Although PLLA can increase the in vitro cluster formation of neonate fresh and frozen-thawed spermatogonial cells, it may also cause them to differentiate during cultivation. The study therefore has implications for SSCs proliferation and germ cell differentiation in vitro.

THY1 as a reliable marker for enrichment of undifferentiated spermatogonia in the goat

Spermatogonial stem cells are unique cells of testes that can restore fertility upon transplantation into recipient testes. However, use of suitable markers for enrichment of these cells have important potential application. THY1, is an established conserved marker of spermatogonial stem cells in bovine, rodents, and primates, but there is no information available in goats. After three rounds of enzymatic digestion of prepubertal goat testicular tissues, undifferentiated spermatogonia positive for THY1 were isolated by magnetic-activated cell sorting and were used for immunocytochemistry, real-time polymerase chain reaction analysis for gene expression, protein expression, and transplantation into recipient mice. Immunocytochemical analyses showed that significantly higher percentage of THY1(+) cells were positive for PLZF and VASA when compared with unselected population. This result for PLZF was further confirmed at the protein level. Real-time polymerase chain reaction analysis revealed that expression of THY1, PLZF, VASA, BCL6B, and UCHL1 as SCCs characteristic genes in THY1(+) cells was significantly higher than in the initial population. Finally, transplantation of PKH26-labeled cells revealed that THY1(+) cells had higher capacity for colony formation when compared with unselected cells. In conclusion, the results provide indications that THY1 surface marker can be reliably used for enrichment of undifferentiated spermatogonial in the goats.

An improved protocol for isolation and culturing of mouse spermatogonial stem cells

Spermatogonial stem cells (SSCs) represent a unique testicular cell type that has the capacity for proliferating, differentiating, and transmitting genetic information. This particular cell type is a strong focus of stem cell research, with isolation and maintenance of SSCs as an important issue. Therefore, we attempted to optimize SSCs handling and to analyze different media and feeder layers, such as adult and embryonic Sertoli cells. The expression patterns of SSC-specific proteins (α6 and β1 integrins, Stra8, and DAZL) and restoration of spermatogenesis were chosen as parameters to demonstrate the efficacy of the protocol. SSCs were isolated from testes of 3- to 6-day-old mice using a magnetic activated cell-sorting system and Thy-1 antibody. After enrichment, SSCs were cultured for 7 days with different media and feeder layers. Then, SSCs were transplanted to recipient mice. Culturing on adult and embryonic Sertoli cells and in the presence of different growth factors [glial cell line-derived neurotrophic factor (GDNF), GDNF family receptor α1 (GFR-α1), and basic fibroblast growth factor (bFGF) resulted in an undifferentiated SSC phenotype with typical stem cell characteristics observed in vivo. The established co-culture model could help to improve the recovery and quality of stem cell preparation of mammalian testis.

Proliferation of small number of human spermatogonial stem cells obtained from azoospermic patients

PURPOSE

This study aims to proliferate spermatogonial stem cells (SSCs) and compare the in-vitro effects of laminin and growth factors on the proliferation of adult human SSC.

METHODS

Isolated testicular cells were cultured in DMEM supplemented with 5 % fetal calf serum (FCS). During the culture, enriched spermatogonial cells were treated with a combination of glial cell line-derived neurotrophic factor (GDNF), basic fibroblast growth factor (bFGF), epidermal growth factor (EGF) and mouse leukemia inhibitory factor (LIF) in the presence or absence of human placental laminin-coated dishes. Cluster assay was performed during culture. Presence of spermatogonia was determined by an ultrastructural study of the cell clusters, reverse transcription polymerase chain reaction (RT-PCR) for spermatogonial markers and xenotransplantation to the testes of busulfan-treated recipient mice. Statistical significance between mean values was determined using statistical ANOVA tests.

RESULTS

The findings indicated that the addition of GDNF, bFGF, EGF and LIF on laminin-coated dishes significantly increased in-vitro spermatogonial cell cluster formation in comparison with the control group (p ≤ 0.001). The expression of spermatogonial markers was maintained throughout the culture period. Furthermore, a transplantation experiment showed the presence of SSC among the cultured cells. In addition, a transmission electron microscopy (TEM) study suggested the presence of spermatogonial cells of typical morphology among the cluster cells.

CONCLUSIONS

It can be concluded that human SSCs obtained from non-obstructive azoospermic (NOA) patients had the ability to self-renew in the culture system. This system can be used for the propagation of a small number of these cells from small biopsies.

Isolation and characterization of human spermatogonial stem cells

BACKGROUND

To isolate and characterization of human spermatogonial stem cells from stem spermatogonium.

METHODS

The disassociation of spermatogonial stem cells (SSCs) were performed using enzymatic digestion of type I collagenase and trypsin. The SSCs were isolated by using Percoll density gradient centrifugation, followed by differential surface-attachment method. Octamer-4(OCT4)-positive SSC cells were further identified using immunofluorescence staining and flow cytometry technques. The purity of the human SSCs was also determined, and a co-culture system for SSCs and Sertoli cells was established.

RESULTS

The cell viability was 91.07% for the suspension of human spermatogonial stem cells dissociated using a two-step enzymatic digestion process. The cells isolated from Percoll density gradient coupled with differential surface-attachement purification were OCT4 positive, indicating the cells were human spermatogonial stem cells. The purity of isolated human spermatogonial stem cells was 86.7% as assessed by flow cytometry. The isolated SSCs were shown to form stable human spermatogonial stem cell colonies on the feeder layer of the Sertoli cells.

CONCLUSIONS

The two-step enzyme digestion (by type I collagenase and trypsin) process is an economical, simple and reproducible technique for isolating human spermatogonial stem cells. With little contamination and less cell damage, this method facilitates isolated human spermatogonial stem cells to form a stable cell colony on the supporting cell layer.

In vitro colonization of human spermatogonia stem cells: effect of patient's clinical characteristics and testicular histologic findings

OBJECTIVE

To evaluate the effect of the demographic/clinical characteristics of patients and testicular histologic findings on the in vitro colonization of human spermatogonial stem cells (SSCs). In vitro isolation and proliferation of human SSCs has emerged as a suitable method for the enrichment of spermatogonia germ cells.

METHODS

SSCs were isolated from the testicular biopsies of 47 infertile men with nonobstructive azoospermia and co-cultured with a Sertoli cell monolayer. Age, infertility duration, medical/surgical history, testicular size, and testicular histologic findings were recorded. The patients were divided into 2 groups according to the growth/no growth of human SSC colonies in culture. As the main outcome measure, the number and diameter of germ cell-derived colonies were compared between 2 groups in days 8, 13, and 18 after cultivation with respect to the recorded parameters.

RESULTS

No difference was found between the 2 groups regarding the demographic/clinical parameters. Maturation arrest at the premeiotic spermatogonia stage was present in a considerably greater proportion in the group with growth of human SSC colonies compared with the group without growth of human SSC colonies (14 [45.1%] of 31 versus 3 [18.7%] of 16; P < .001) on days 8, 13, and 18 after culture. Maturation arrest at premeiotic SSCs was associated with a greater number and larger diameter of germ cell colonies compared with the maturation arrest at primary spermatocyte and secondary spermatocyte/spermatid stages (P < .001).

CONCLUSION

Infertile men with testicular histologic findings of maturation arrest at the premeiotic spermatogonia stage were seemingly the most appropriate candidates for testicular biopsy and in vitro propagation of human SSCs, regardless of their demographic/clinical characteristics.

Comparison of colony formation in adult mouse spermatogonial stem cells developed in Sertoli and STO coculture systems

This study aimed to compare the in vitro effects of coculture with Sertoli and SIM mouse embryo-derived thioguanine- and ouabain-resistant (STO) feeder layer cells on the efficiency of adult mouse spermatogonial stem cells (SSCs) colony formation. Sertoli and SSCs were isolated from testes, and their identity was confirmed using immunocytochemistry against Oct4, CDH1, PLZF and C-kit for SSCs and vimentin for Sertoli cells. SSCs were cultured in a simple culture system (control group) and on top of the Sertoli and STO feeder layers for 2 weeks. The number and diameter of colonies were evaluated during third, 7th, 10th and 14th day of culture, and the expression of the Oct-4, α6 and β1 integrins was assessed using quantitative RT-PCR. Significant differences were observed between the three groups, separately for each time (P < 0.05), with higher mean in number and diameter for Sertoli cells (P < 0.05). The results of RT-PCR showed higher gene expression of β1 integrin in Sertoli group, but no significant differences were observed in Oct-4 and α6 integrin gene expression among the three groups. Based the on the optimal effect of Seroli cells on the colony formation of SSCs, it is suggested to use these cells for better colonisation of SSCs.