Identification of Putative Biomarkers for the Early Stage of Porcine Spermatogonial Stem Cells Using Next-Generation Sequencing

Understanding the Underlying Molecular Mechanisms of Meiotic Arrest during In Vitro Spermatogenesis in Rat Prepubertal Testicular Tissue

In vitro spermatogenesis appears to be a promising approach to restore the fertility of childhood cancer survivors. The rat model has proven to be challenging, since germ cell maturation is arrested in organotypic cultures. Here, we report that, despite a meiotic entry, abnormal synaptonemal complexes were found in spermatocytes, and in vitro matured rat prepubertal testicular tissues displayed an immature phenotype. RNA-sequencing analyses highlighted up to 600 differentially expressed genes between in vitro and in vivo conditions, including genes involved in blood-testis barrier (BTB) formation and steroidogenesis. BTB integrity, the expression of two steroidogenic enzymes, and androgen receptors were indeed altered in vitro. Moreover, most of the top 10 predicted upstream regulators of deregulated genes were involved in inflammatory processes or immune cell recruitment. However, none of the three anti-inflammatory molecules tested in this study promoted meiotic progression. By analysing for the first time in vitro matured rat prepubertal testicular tissues at the molecular level, we uncovered the deregulation of several genes and revealed that defective BTB function, altered steroidogenic pathway, and probably inflammation, could be at the origin of meiotic arrest.

Culture of spermatogonial stem cells and use of surrogate sires as a breeding technology to propagate superior genetics in livestock production: A systematic review

Background and Aim:

Spermatogonial stem cells (SSCs) have previously been isolated from animals’ testes, cultured in vitro, and successfully transplanted into compatible recipients. The SSC unique characteristic has potential for exploitation as a reproductive tool and this can be achieved through SSC intratesticular transplantation to surrogate sires. Here, we aimed at comprehensively analyzing published data on in vitro maintenance of SSC isolated from the testes of livestock animals and their applications.

Materials and Methods:

The literature search was performed in PubMed, Science Direct, and Google Scholar electronic databases. Data screening was conducted using Rayyan Intelligent Systematic Review software (https://www.rayyan.ai/). Duplicate papers were excluded from the study. Abstracts were read and relevant full papers were reviewed for data extraction.

Results:

From a total of 4786 full papers screened, data were extracted from 93 relevant papers. Of these, eight papers reported on long-term culture conditions (>1 month) for SSC in different livestock species, 22 papers on short-term cultures (5-15 days), 10 papers on transfection protocols, 18 papers on transplantation using different methods of preparation of livestock recipients, and five papers on donor-derived spermatogenesis.

Conclusion:

Optimization of SSC long-term culture systems has renewed the possibilities of utilization of these cells in gene-editing technologies to develop transgenic animals. Further, the development of genetically deficient recipients in the endogenous germline layer lends to a future possibility for the utilization of germ cell transplantation in livestock systems.

Maca Root (Lepidium meyenii) Extract Increases the Expression of MMP-1 and Stimulates Migration of Triple-Negative Breast Cancer Cells

Maca root (Lepidium meyenii) extract is a worldwide consumed food supplement for sexual dysfunctions, increasing sperm production and its motility, and alleviating menopausal symptoms. Once maca root has a role in cell proliferation and motility, and its consumption may increase along with age, mainly in menopausal women, we aimed to investigate the plant effects on triple-negative breast cancer (TNBC) cell lines. Standardized maca root powdered extract showed significant cytotoxic activity in both MDA-MB-231 and Hs578T cells, and the IC₅₀s were 2000 μg/ml and 3000 μg/ml, respectively. Both cell lines showed an increase in migratory capacity. Using bioinformatics tools, we established genes involved in the metastatic process, CAV1, LAMA4, and MMP-1, and the mRNAs expression was assessed by qPCR. Comparing the treated cells to the negative control, CAV1 presented a decreased expression by 2-fold in MDA-MB-231. LAMA4 presented a decrease by 4-fold in Hs578T cells. MMP-1 showed substantially increase mRNA expression in MDA-MB-231 by 86-fold and in Hs578T by 5-fold. To the best of our knowledge, this is the first study indicating that the human consumption of maca may be dangerous due to the upregulation in MMP-1 expression and the increase in TNBC migrated cells.

CD14 is a unique membrane marker of porcine spermatogonial stem cells, regulating their differentiation

Molecular markers of spermatogonia are necessary for studies on spermatogonial stem cells (SSCs) and improving our understanding of molecular and cellular biology of spermatogenesis. Although studies of germ cell surface marker have been extensively conducted in the testes of rodents, these markers have not been well studied in domestic animals. We aimed to determine the expression pattern of cluster of differentiation 14 (CD14) in developing porcine testes and cultured porcine SSCs (pSSCs), as well as its role in pSSC colony formation. Interestingly, expression of CD14 was observed in porcine testes with PGP9.5-positive undifferentiated spermatogonia at all developmental stages. In addition, in vitro cultured pSSCs expressed CD14 and showed successful colony formation, as determined by fluorescence-activated cell sorting and flow cytometry. PKH26 dye-stained CD14-positive cells transplants were performed into the testes of recipient mice, which were depleted of both testicular germ and somatic cells from immunodeficiency mice and were shown to colonise the recipient testes. Moreover, a colony-forming assay showed that the development of pSSC colonies was disrupted by a high concentration of lipopolysaccharide. These studies indicated that CD14 is surface marker of early spermatogonia in developing porcine testes and in pSSCs, suggesting a role for CD14 in porcine spermatogenesis.

Expression patterns and role of SDF-1/CXCR4 axis in boar spermatogonial stem cells

The signaling of chemokine stromal cell-derived factor (SDF)-1 and its receptor C-X-C motif chemokine receptor 4 (CXCR4) is involved in the cellular proliferation, survival, and migration of various cell types. Although SDF-1/CXCR4 has been implicated in the maintenance of the spermatogonial population during mouse testis development, their expression patterns and functions in boar testis remain unclear. In the present study, the expression pattern of SDF-1 and CXCR4 was determined during pre-pubertal and post-pubertal stage boar testes and in vitro cultured porcine spermatogonial stem cells (pSSCs). The role of these proteins in colony formation in cultured pSSCs was also investigated. Interestingly, SDF-1 expression was observed in PGP 9.5-positve spermatogonia in all developing stages of boar testis; however, CXCR4 expression was only detected in spermatogonia from 5-day-old boar testis. In addition, SDF-1 and CXCR4 expression was observed in cultured pSSCs from 5-day-old boar testes, and inhibition of the CXCR4 receptor signaling pathway by AMD3100 significantly decreased the colony formation of pSSCs. These results suggest that SDF-1 and CXCR4 are useful markers for detecting stage-specific spermatogonia in boar testis. Our results reveal the role of the SDF-1/CXCR4 axis in pSSC in vitro culture.

Species-specific expression of phosphoglycerate kinase 2 (PGK2) in the developing porcine testis

Whereas stage-specific markers for spermatogonial cells have been well investigated in mouse, the specific markers of germ cells in the testis of domestic animals have not been well defined. Phosphoglycerate kinase (PGK), an enzyme that converts 1,3-bisphosphoglycerate and adenosine diphosphate to 3-phosphoglycerate and adenosine triphosphate, has two isozymes: PGK1 and PGK2. In mouse, PGK1 exists only during the early stages of spermatogenesis, and PGK2 is then expressed during the pachytene spermatocyte stage. In this study, we investigated the localization of PGK2 in the developing porcine testis, and compared the similarities and differences in its expression with that of the PGK2 in mouse. The PGK2 protein was found to be exclusively expressed in spermatids of the adult mouse testis, whereas PGK2-positive cells were observed in the prepubertal and postpubertal testes of pigs. Based on this result, we examined the expression of PGK2 in in vitro-cultured porcine undifferentiated spermatogonia and found it to be maintained in the cultured cells. To verify this result and identify the spermatogonial stem cell-like potential in recipient testes, PKH26 dye-stained PGK2-positive cells were transplanted into the testes of busulfan-treated immunodeficient mouse that had been depleted of both testicular germ cells and somatic cells. The transplanted cells colonized the recipient testis at 8 weeks post transplantation, and fluorescence microscopy identified the cells in the basement membranes of the seminiferous tubules of the injected mouse. Taken together, our results suggest that PGK2 is expressed differently in the testes of mouse and pigs according to developmental stage. This finding should contribute to the study of spermatogenesis and the production of transgenic domestic animals through in vitro spermatogonial sperm cell culture.