Isolation and characterization of human spermatogonial stem cells

Enrichment of undifferentiated type a spermatogonia from goat testis using discontinuous percoll density gradient and differential plating

BACKGROUND

The well documented source for adult multipotent stem cells is Spermatogonial Stem Cells (SSCs). They are the foundation of spermatogenesis in the testis throughout adult life by balancing self-renewal and differentiation. The aim of this study was to assess the effect of percoll density gradient and differential plating on enrichment of undifferentiated type A spermatogonia in dissociated cellular suspension of goat testes. Additionally, we evaluated the separated fractions of the gradients in percoll and samples in differential plating at different times for cell number, viability and purification rate of goat SSCs in culture.

METHODS

Testicular cells were successfully isolated from one month old goat testis using two-step enzymatic digestion and followed by two purification protocols, differential plating with different times of culture (3, 4, 5, and 6 hr) and discontinuous percoll density with different gradients (20, 28, 30, and 32%). The difference of percentage of undifferentiated SSCs (PGP9.5 positive) in each method was compared using ANOVA and comparison between the highest percentage of corresponding value between two methods was carried out by t-test using Sigma Stat (ver. 3.5).

RESULTS

The highest PGP9.5 (94.6±0.4) and the lowest c-Kit positive (25.1±0.7) in Percoll method was significantly (p ≤ 0.001) achieved in 32% percoll gradient. While the corresponding rates in differential plating method for the highest PGP9.5 positive cells (81.3±1.1) and lowest c-Kit (17.1±1.4) was achieved after 5 hr culturing (p < 0.001). The enrichment of undifferentiated type A spermatogonia using Percoll was more efficient than differential plating method (p < 0.001).

CONCLUSION

Percoll density gradient and differential plating were efficient and fast methods for enrichment of type A spermatogonial stem cells from goat testes.

Derivation of ES-like cell from neonatal mouse testis cells in autologous sertoli cells co-culture system

BACKGROUND

Spermatogonial stem cell (SSC) is a self-renewing population of male adult stem cell. SSCs have a differentiation potential which are similar to embryonic stem cells. These Embryonic stem like (ES-like) cells can be a potential source for pluripotent cells for stem cell-based therapy.

OBJECTIVE

This study presents an economical and simple co-culture system for pluripotent stem cells generation from neonatal mouse testis Materials and Methods: Isolated testicular cells were cultured in DMEM/F12. Characteristics of the isolated cells and obtained ES-like cell were immune-cytochemically confirmed by examining the presence of PLZF, vimentin, Oct4 and Nanog protein. Expression of the pluripotency and germ-cell specific genes was analyzed by qPCR in derived ES-like colony and SSCs respectively.

RESULTS

The experiment results indicated that our method of obtaining pluripotent ES-like cells from spermatogonial cells (SCs) is simpler than the described methods. ES-like cells were immunopositive for pluripotency markers. ES-like cell qPCR results indicated significant increase in pluripotency genes expression and significant decrease in germ cell-specific genes expression.

CONCLUSION

The results indicated that ES-like cell with pluripotency characteristic were generated from freshly isolated spermatogonial cells. The pluripotent stem cells provide a cellular reservoir usable for regenerative medicine instead of embryonic stem cells. This article extracted from Ph.D. thesis. (Setareh Javanmardi).

Germline stem cells: toward the regeneration of spermatogenesis

Improved therapies for cancer and other conditions have resulted in a growing population of long-term survivors. Infertility is an unfortunate side effect of some cancer therapies that impacts the quality of life of survivors who are in their reproductive or prereproductive years. Some of these patients have the opportunity to preserve their fertility using standard technologies that include sperm, egg, or embryo banking, followed by IVF and/or ET. However, these options are not available to all patients, especially the prepubertal patients who are not yet producing mature gametes. For these patients, there are several stem cell technologies in the research pipeline that may give rise to new fertility options and allow infertile patients to have their own biological children. We will review the role of stem cells in normal spermatogenesis as well as experimental stem cell-based techniques that may have potential to generate or regenerate spermatogenesis and sperm. We will present these technologies in the context of the fertility preservation paradigm, but we anticipate that they will have broad implications for the assisted reproduction field.

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.

Establishment and in vitro culture of porcine spermatogonial germ cells in low temperature culture conditions

The objective of this study was to establish a porcine spermatogonial germ cell (pSGC) line and develop an in vitro culture system. Isolated total testicular cells (TTCs) from 5-day-old porcine testes were primary cultured at 31, 34, and 37°C. Although the time of colony appearance was delayed at 31°C, strong alkaline phosphatase staining, expressions of pluripotency marker genes such as OCT4, NANOG, and THY1, and the gene expressions of the undifferentiated germ cell markers PLZF and protein gene product 9.5 (PGP9.5) were identified compared to 34 and 37°C. Cell cycle analysis for both pSGC and feeder cells at the three temperatures revealed that more pSGCs were in the G2/M phase at 31°C than 37°C at the subculture stage. In vitro, pSGCs could stably maintain undifferentiated germ cell and stem cell characteristics for over 60days during culture at 31°C. Xenotransplantation of pSGCs to immune deficient mice demonstrated a successful colonization and localization on the seminiferous tubule basement membrane in the recipient testes. In conclusion, pSGCs from neonatal porcine were successfully established and cultured for long periods under a low temperature culture environment in vitro.

Expression of stem cell markers: OCT4, KIT, ITGA6, and ITGB1 in the male germinal epithelium

Efforts have been made for the isolation and characterization of human stem spermatogonia (SG) which would be of major interest for fertility preservation in oncologic patients. We evaluated the expression of mammalian SG stem cell markers, KIT, OCT4, integrin alpha 6 (ITGA6), and integrin beta 1 (ITGB1) as possible indicators for the isolation of those cells in humans. Two different types of SG were individually isolated by micromanipulation from testicular biopsies of men with conserved spermatogenesis. Expression of mRNA showed the absence of KIT and ITGB1 markers in SG. By immunocytochemistry (IC), protein expression for KIT and integrins revealed two types of SG populations, negative (type-1) and positive (type-2). By immunohistochemistry (IH), protein expression for KIT and ITGB1 also revealed two kinds of SG populations, negative (SG A-dark) and positive (SG A-pale). Results suggest that in humans it may be possible to obtain pure populations of stem SG by using negative KIT((-))/ITGB1((-)) sorting.

Discrimination between lung homeostatic and injury-induced epithelial progenitor subsets by cell-density properties

Stem/progenitor cells and their lineage derivatives are often identified by patterns and intensity of cell clusters of differentiation presentation. However, the cell biochemical façade can prove to be elusive, transient, and subject to interlaboratory disparities. To enhance current methods of lung stem cell isolation and identification and to investigate biophysical changes, which occur during homeostasis and in response to acute lung injury, we separated cells on a discontinuous density gradient, of 1.025-1.074 g/cm(3), and characterized the eluted lineages. At homeostasis, surfactant protein-C (SFTPC)-expressing cells of the alveolar type (AT)-2 lineage possessed average densities ≥1.039 g/cm(3) and aquaporin-5 producing AT1 cells equilibrated at densities <1.039 g/cm(3). While 0.74%±0.32% of lung cells were determined proliferating or postmitotic by BrdU nucleotide uptake, 73% of CD49f-, 72% of c-KIT-, and 61% of SCA-1-positive cells (putative alveolar progenitor lineage markers) showed densities ≤1.039 g/cm(3). CD49f/EpCAM(hi) progenitors, as well as c-KIT(pos)/CD45(neg) cells, could be enriched at the 1.039 g/cm(3) interface. Following acute bleomycin-induced injury, the frequency of BrdU-incorporating cells rose to 0.92%±0.36% and density could largely explain cell-lineage distribution. Specifically, a decline in the density of mitotic/postmitotic SFTPC-positive cells to ≤1.029 g/cm(3), in conjunction with an increase in CD45-positive, and proliferating CD45 and c-KIT cells in the heaviest fraction (≥1.074 g/cm(3)) were observed. These data attest to the generation of AT2 cells from low-density precursors and emphasize a relationship between cell density and molecular expression following injury, expanding on our current understanding of lung and progenitor cell dynamics.

Characterization and in vitro culture of putative spermatogonial stem cells derived from feline testicular tissue

Spermatogonial stem cells (SSCs) function to regulate the balance of self-renewal and differentiation of male gametes. SSCs have been successfully isolated and cultured in vitro in several species, but not in feline. Therefore, in this study, we aimed to culture and characterize feline SSCs. In experiment 1, testes (n=5) from different pubertal domestic cats were cryosectioned and fluorescently immunolabeled to examine the expression of SSC (GFRα-1), differentiated spermatogonium (c-kit) and germ cell (DDX-4) markers. In experiments 2 and 3, testicular cells were digested and subsequently cultured in vitro. The resultant presumptive SSC colonies were then collected for SSC identification (experiment 2), or further cultured in vitro on feeder cells (experiment 3). Morphology, gene expression and immunofluorescence were used to identify the SSCs. Experiment 1 demonstrated that varying types of spermatogenic cells existed and expressed different germ cell/SSC markers. A rare population of putative SSCs located at the basement membrane of the seminiferous tubules was specifically identified by co-expression of GFRα-1 and DDX-4. Following enzymatic digestion, grape-like colonies formed by 13-15 days of culture. These colonies expressed GFRA1 and ZBTB16, but did not express KIT. Although we successfully isolated and cultured feline SSCs in vitro, the SSCs could only be maintained for 57 days. In conclusion, this study demonstrates, for the first time, that putative SSCs from testes of pubertal domestic cats can be isolated and cultured in vitro. These cells exhibited SSC morphology and expressed SSC-specific genes. However, long-term culture of these putative SSCs was compromised.

TRA-1-60+, SSEA-4+, POU5F1+, SOX2+, NANOG+ Clones of Pluripotent Stem Cells in the Embryonal Carcinomas of the Testes

INTRODUCTION

Cancer of the testes is currently the most frequent neoplasm and a leading cause of morbidity in men 15-35 years of age. Its incidence is increasing. Embryonal carcinoma is its most malignant form, which either may be resistant or may develop resistance to therapies, which results in relapses. Cancer stem cells are hypothesized to be drivers of these phenomena.

SPECIFIC AIM

The specific aim of this work was identification and isolation of spectra of single, living cancer stem cells, which were acquired directly from the patients' biopsies, followed by testing of their pluripotency.

PATIENTS METHODS

Biopsies were obtained from the patients with the clinical and histological diagnoses of the primary, pure embryonal carcinomas of the testes. The magnetic and fluorescent antibodies were genetically engineered. The SSEA-4 and TRA-1-60 cell surface display was analyzed by multiphoton fluorescence spectroscopy (MPFS), flow cytometry (FCM), immunoblotting (IB), nuclear magnetic resonance spectroscopy (NMRS), energy dispersive x-ray spectroscopy (EDXS), and total reflection x-ray spectroscopy (TRXFS). The single, living cells were isolated by magnetic or fluorescent sorting followed by their clonal expansion. The OCT4A, SOX2, and NANOG genes' transcripts were analyzed by qRTPCR and the products by IB and MPFS.

RESULTS

The clones of cells, with the strong surface display of TRA-1-60 and SSEA-4, were identified and isolated directly from the biopsies acquired from the patients diagnosed with the pure embryonal carcinomas of the testes. These cells demonstrated high levels of transcription and translation of the pluripotency genes: OCT4A, SOX2, and NANOG. They formed embryoid bodies, which differentiated into ectoderm, mesoderm, and endoderm.

CONCLUSION

In the pure embryonal carcinomas of the testes, acquired directly from the patients, we identified, isolated with high viability and selectivity, and profiled the clones of the pluripotent stem cells. These results may help in explaining therapy-resistance and relapses of these neoplasms, as well as, in designing targeted, personalized therapy.

In vitro Culture of Human Testicular Stem Cells on Feeder-Free Condition

BACKGROUND

Spermatogonial stem cells are subpopulation of spermatogonial cells in testis tissue that support beginning and maintenance of spermatogenesis. Ubiquitin carboxy-terminal hydrolase L1 (UCHL1) could be a specific marker for identification of spermatogonial stem cells including spermatogonial sperm cells (SSCs) in testis tissue and during the culture; therefore we undertook this study to culture these human testicular stem cells (hTSCs) in vitro and approved the presence of human testicular stem cells (hTSCs) by UCHL1, also known as PGP9.5.

METHODS

Enzymatic digestion of human testicular biopsies was done by collagenase IV (4 mg/ml) and trypsin (0.25%). Differential plating of testicular cells in DMEM/F12 and 10% FBS was applied for 16 hr. Floating cells were collected and transferred onto laminin-coated plates with Stem-Pro 34 media supplemented with growth factors of GDNF, bFGF, EGF and LIF to support self-renewal divisions; testicular stem cell clusters were passaged every 14 days for two months. Spermatogonial cells propagation was studied through Expression of UCHL1 in testis tissue and the entire testicular stem cell culture.

RESULTS

Testicular stem cell clusters from 10 patients with obstructive azoospermia were cultured on laminin-coated plates and subsequently propagated for two months. The average of harvested viable cells was approximately 89.6%. UCHL1 was expressed as specific marker in testicular stem cells entire the culture.

CONCLUSION

Human testicular stem cells could be obtained from human testicular tissue by a simple digestion, culturing and propagation method for long-term in vitro conditions. Propagation of these cells approved by specific marker UCHL1, during the culture period.

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.