Mouse spermatogonial stem cells obtain morphologic and functional characteristics of hematopoietic cells in vivo

Reproductive stage- and season-dependent culture characteristics of enriched caprine male germline stem cells

The present study aims to evaluate season- and reproductive-stage dependent variation in culture characteristics and expression of pluripotency and adhesion markers in caprine-male germline stem cells (cmGSCs). For this, testes from pre-pubertal (4-6 months) and adult (~ 2 years) bucks during non-breeding (July-August; n = 4 each) and breeding (October-November; n = 4 each) seasons were used to isolated testicular cells by two-step enzymatic digestion. After cmGSCs enrichment by multiple methods (differential platting, Percoll density gradient centrifugation, and MACS), cell viability of CD90⁺ cells was assessed before co-cultured onto the Sertoli cell feeder layer up to 3^rd-passage (P-3). The culture characteristics of cmGSCs were compared during primary culture (P-0) and P-3 with different assays [BrdU-assay (proliferation), MTT-assay (senescence), and Cluster-forming activity-assay] and transcript expression analyses by qRT-PCR. Moreover, the co-localization of UCHL-1, CD90, and DBA was examined by a double-immunofluorescence method. In adult bucks, significantly (p < 0.05) higher cell numbers with the ability to proliferate faster and form a greater number of cell clusters, besides up-regulation of pluripotency and adhesion markers expression were observed during the breeding season than the non-breeding season. In contrast, such season-dependent variation was lacking in pre-pubertal bucks. The expression of transcripts during non-breeding seasons was significantly (p < 0.05) higher in pre-pubertal cmGSCs than in adult cells (UCHL-1 = 2.38-folds; CD-90 = 6.66-folds; PLZF = 20.87-folds; ID-4 = 4.75-folds; E-cadherin = 3.89-folds and β1-integrin = 5.70-folds). Overall, the reproductive stage and season affect the population, culture characteristics, and expression of pluripotency and adhesion specific markers in buck testis. These results provide an insight to develop an efficient system for successful cell culture processes targeting cmGSCs.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10616-021-00515-x.

Plasticity of spermatogonial stem cells

There have been significant breakthroughs over the past decade in the development and use of pluripotent stem cells as a potential source of cells for applications in regenerative medicine. It is likely that this methodology will begin to play an important role in human clinical medicine in the years to come. This review describes the plasticity of one type of pluripotent cell, spermatogonial stem cells (SSCs), and their potential therapeutic applications in regenerative medicine and male infertility. Normally, SSCs give rise to sperm when in the testis. However, both human and murine SSCs can give rise to cells with embryonic stem (ES) cell-like characteristics that can be directed to differentiate into tissues of all three embryonic germ layers when placed in an appropriate inductive microenvironment, which is in contrast to other postnatal stem cells. Previous studies have reported that SSCs expressed an intermediate pluripotent phenotype before differentiating into a specific cell type and that extended culture was necessary for this to occur. However, recent studies from our group using a tissue recombination model demonstrated that SSCs differentiated rapidly into another tissue, in this case, prostatic epithelium, without expression of pluripotent ES cell markers before differentiation. These results suggest that SSCs are capable of directly differentiating into other cell types without going through an intermediate ES cell-like stage. Because SSCs do not require reprogramming to achieve a pluripotent state, they are an attractive source of pluripotent cells for use in regenerative medicine.

Stem Cells in Mammalian Gonads

Stem cells have great value in clinical application because of their ability to self-renew and their potential to differentiate into many different cell types. Mammalian gonads, including testes for males and ovaries for females, are composed of germline and somatic cells. In male mammals, spermatogonial stem cells maintain spermatogenesis which occurs continuously in adult testis. Likewise, a growing body of evidence demonstrated that female germline stem cells could be found in mammalian ovaries. Meanwhile, prior studies have shown that somatic stem cells exist in both testes and ovaries. In this chapter, we focus on mammalian gonad stem cells and discuss their characteristics as well as differentiation potentials.

Use of Stirred Suspension Bioreactors for Male Germ Cell Enrichment

Spermatogenesis is a stem cell based system. Both therapeutic and biomedical research applications of spermatogonial stem cells require a large number of cells. However, there are only few germ line stem cells in the testis, contained in the fraction of undifferentiated spermatogonia. The lack of specific markers makes it difficult to isolate these cells. The long term maintenance and proliferation of nonrodent germ cells in culture has so far been met with limited success, partially due to the lack of highly enriched starting populations. Differential plating, which depends on the differential adhesion properties of testicular somatic and germ cells to tissue culture dishes, has been the method of choice for germ cell enrichment, especially for nonrodent germ cells. However, for large animals, this process becomes labor intensive and increases variability due to the need for extensive handling. Here, we describe the use of stirred suspension bioreactors, as a novel system for enriching undifferentiated germ cells from 1-week-old pigs. This method capitalizes on the adherent properties of somatic cells within a controlled environment, thus promoting the enrichment of progenitor cells with minimal handling and variability.

Long Term Liver Engraftment of Functional Hepatocytes Obtained from Germline Cell-Derived Pluripotent Stem Cells

One of the major hurdles in liver gene and cell therapy is availability of ex vivo-expanded hepatocytes. Pluripotent stem cells are an attractive alternative. Here, we show that hepatocyte precursors can be isolated from male germline cell-derived pluripotent stem cells (GPSCs) using the hepatoblast marker, Liv2, and induced to differentiate into hepatocytes in vitro. These cells expressed hepatic-specific genes and were functional as demonstrated by their ability to secrete albumin and produce urea. When transplanted in the liver parenchyma of partially hepatectomised mice, Liv2-sorted cells showed regional and heterogeneous engraftment in the injected lobe. Moreover, approximately 50% of Y chromosome-positive, GPSC-derived cells were found in the female livers, in the region of engraftment, even one month after cell injection. This is the first study showing that Liv2-sorted GPSCs-derived hepatocytes can undergo long lasting engraftment in the mouse liver. Thus, GPSCs might offer promise for regenerative medicine.

Optimization of the conditions of isolation and culture of dairy goat male germline stem cells (mGSC)

Male germline stem cells (mGSC) reside in the basement of seminiferous tubules of the testis and have the capacity of self-renewal and differentiation into sperm throughout the life of animals. Reports on mice and human mGSC have demonstrated that mGSC are an unlimited resource of pluripotent stem cells for sperm production. The conditions of isolation and culture of mouse and human mGSC are well developed; however, the systematic culture conditions of dairy goat mGSC are still deficient although there have been several reports of successful cultures. With the present research, several key elements of isolation and culture of dairy goat mGSC have been determined. Details for the conditions of isolation of dairy testicular spermatogonium cells were optimized, and effects of several extracellular matrix types, ages of dairy goat, and cytokines on enrichment and culture of mGSC were compared. Biological characteristics of the cells were also evaluated by RT-PCR and immunofluorescent staining. The results indicated there is one kind of enzyme cocktail (CTHD (1mg/ml collagenase, 10μg/ml DNase, 1mg/ml hyaluronidase and 1mg/ml trypsin) combined TD (0.25% trypsin and 10mg/ml DNaseI)) that can be used to successfully isolate dairy goat testicular spermatogonium cells efficiently; and fibronectin as well as laminin were efficient extracellular matrix to enrich mGSC among the extracellular matrix types evaluated. Age of dairy goat clearly influenced the cultures of dairy goat mGSC with the efficiency of establishment of an mGSC line being greater if the age of the dairy goat is younger. Some cytokines e.g. BIO (A GSK3 inhibitor, 6-bromoindirubin-3'-oxime) and basic fibroblast growth factor (bFGF) acted positively on the maintenance of proliferation and pluripotency of mGSC. Leukemia inhibitory factor (LIF) might, however, inhibit the proliferation of dairy goat mGSC. These cultured mGSC maintained similar characteristics as mouse and human mGSC. These results provide an efficient system to isolate and culture of dairy goat mGSC.

Treatment with chicken-egg-white or whole-egg extracts maintains and enhances the survival and differentiation of spleen cells

The identification of egg extracts with the ability to maintain and enhance the survival and differentiation of cells would be widely useful in cellular biology research. In this study, we compared the different abilities of spleen cells to survive and differentiate in vivo after permeabilization by five different types of egg extracts. Five types of egg extracts were prepared. The spleen cells from male GFP-transgenic mice were permeabilized by the extracts for 30 min, cultured for 12 days, and then transfused into irradiated female mice. At varying days after transplantation, the percentage of GFP-expressing surviving spleen cells was detected in the peripheral blood by flow cytometry. At 120 days after transplantation, bone marrow cells from the female mice were analyzed for the presence of cells containing the Y chromosome. Surviving GFP-positive spleen cells that had been permeabilized with either chicken-egg-white or whole-egg extracts could be detected in the female mice after transplantation. A lower percentage of GFP-positive cells was also detected after permeabilization by the other extracts tested, and no GFP-positive cells were found in the female mouse transfused with spleen cells permeabilized with Hank's Buffered Salt Solution (HBSS) as a control. At 120 days after transplantation, the percentage of cells containing a Y chromosome in the bone marrow positively correlated with the percentage of GFP-positive cells in the peripheral blood. After permeabilization by chicken-egg-white or whole-egg extracts, spleen cells demonstrated significantly enhanced survival and differentiation functions compared with the spleen cells treated with the other egg extracts tested. These results show that chicken-egg-white and whole-egg extracts have roles in maintaining and enhancing the survival and differentiation of spleen cells. Therefore, these two types of extracts may be of future use in maintaining the function of stem cells.