Trends in Biotechnology
ReviewPossibilities in Germ Cell Research: An Engineering Insight
Section snippets
Call for Engineering Approaches in Germ Cell Research
It is now well understood that GCs can generate a new body. However, current knowledge of the diverse mechanisms involved in GC development is still in its infancy. This is mainly because there are low numbers of GCs, especially during embryonic development, and the analysis of these cells is tricky. Even minor damage to GCs during their developmental stage can cause infertility, which is a major medical problem that affects 10–15% of couples worldwide [1]. Accordingly, differentiation of PSCs
Male Germ Line Development
How are GCs created in the testis? The answer lies in embryonic development. Mammalian development commences with fertilization that results in the formation of zygote. Zygotes have the ability to build a body by sequential cell fate decisions. In the first cell fate resolution, the inner cell mass (ICM), which produces the future body, becomes set apart from the trophectoderm (TE), developing into extra embryonic tissues. During the second cell fate decision, the epiblast is separated from
Spermatogenesis Niche
In the spermatogenesis niche (Figure 2), seminiferous tubules comprising Sertoli cells (SCs) serve as somatic cells that support GCs during their developmental journey from spermatogonial stem cells (SSCs) to the spermatids. GC–SC contacts support spermatogenesis and enable spermatogonia to attach to the SCs and receive signals necessary for their survival, proliferation, translocation, and differentiation. The number and type of cell junctions are dynamic during this development: occluding
Artificial Niche to Support In Vitro Spermatogenesis
There are dynamic contacts between SSCs and/or PGCLCs in SCs during spermatogenesis. Cell–cell contacts in testes are involved in both cellular localization in the niche and signaling events, which provide adhesion for withstanding mechanical forces 38, 39. Of note, cytoskeleton dynamics and homeostatic pressure exert mechanical forces on the cell–cell contacts [40]. In turn, such a mechanical microenvironment affects important aspects of cell behavior, including migration, proliferation, and
Gradient Pattern of GDNF during Spermatogenesis
A growth factor immobilization strategy can extend the availability of these agents, allowing for spatial control and reducing the amount of growth factor required, resulting in decreased cost and increased efficiency [42]. In addition, surface-immobilized growth factors have a higher bioactivity, which will result in more cell and tissue responses. Last but not least, the multivalency of immobilized growth factors provides a high local concentration of these factors on the biomaterial surface
Screen the Response of PGCLCs to Different Microenvironments
In essence, micropatterned platforms are robotically synthesized growth factor microarrays on a cell-repellent surface. Micropatterning technologies allow for investigating the spatiotemporal aspects of a microenvironment for the regulation of cell behavior [46]. We propose microcontact printing as a way to generate large numbers of islands on a surface where each island represents a microenvironment with different combinations of growth factors (GDNF, FGF, and SCF) and CAMs. Subsequent seeding
Mimicking the Dynamic Process of Spermatogenesis
Microfluidics provides a platform for the sophisticated high-throughput manipulation of small volumes of fluids on a submillimetre scale [50]. This multidisciplinary technology provides a way to fabricate miniaturized and inexpensive [51] devices. This technology can be exploited for investigating high-throughput intercellular communications on a chip [50] and for improving biological research in general [52]. Microfluidic platforms are particularly useful when time-dependent processes are to
Inducing Meiosis in PGCLCs Using Nanostructured Carriers
Low water solubility and a short half-life might hinder the delivery of biomolecules to the target cells [58]. To overcome these challenges, nanoparticles are practical options for intracellular transport and the timely controlled release of biomolecules (Figure 4A). Intracellular delivery of biomolecules can both reduce adverse effects and enhance the amount of necessary biomolecules [59]. Researchers used nanoparticles to deliver anticancer drugs [60] and immunomodulatory compounds 61, 62
Efficient Germ Cell Induction
Currently, in the most efficient protocol [3], PGCLCs are produced in an aggregate-based system. Thus, a 3D differentiation method may provide a more reliable environment for the generation of PGCLCs. However, the 3D approach represents challenges for the homogenous delivery of growth factors by cells in the aggregates [65]. Scanning electron microscopy analysis has shown that secretion of ECM by cells produces a time-dependent shell around the embryonic bodies that significantly reduces the
Concluding Remarks and Future Perspectives
Despite decades of research in the GC area, there are still several controversial challenges in the field (see Outstanding Questions). By contrast, advanced therapies for infertility require the production of GCs and the provision of healthy gametes in the laboratory. To that end, cell- and tissue-engineering approaches have demonstrated promising candidates. Figure 5 illustrates recent fabricated platforms (environments) that could be utilized to advance GC studies. Coupling these approaches
Acknowledgments
This work was supported by a grant provided from Royan Institute, Iranian Council of Stem Cell Research and Technology, the Iran National Science Foundation (INSF).
Glossary
- Epigenetic
- heritable changes in gene expression that that are not related to DNA sequences. It can be result from changes in DNA methylation or histone modifications (e.g., methylation or demethylation of lysine amino acids, K, of histones). Epigenetic changes cause alterations in phenotype without alterations of the genotype.
- Extracellular matrix (ECM)
- a noncellular structure that is secreted by cells in a tissue. The ECM functions as scaffold and is also involved in signaling events.
- Gastrulation
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A comparison between BMP4 and SB4 in inducing germ line gene expression pattern during embryonic stem cells differentiation
2022, DifferentiationCitation Excerpt :Indeed, BMP4 plays the key role in germ line induction during embryo development. Recently, pluripotent stem cells (PSCs) have been introduced as an unlimited source of germ cells for provision of healthy gametes for infertile couples (Esfandiari et al., 2015; Sabour and Schöler, 2012). In this regard, researchers successfully reconstituted germ cell development from PSCs using BMP4 as a major inducer (Hayashi et al., 2011, 2012).
Short time exposure to low concentration of zinc oxide nanoparticles up-regulates self-renewal and spermatogenesis-related gene expression
2020, International Journal of Biochemistry and Cell BiologyCitation Excerpt :The results of studies have shown that these ZnO NPs had cytotoxic effects on human spermatozoa (Barkhordari et al., 2013), and Sertoli and Leydig cells of the mouse testis (Bara and Kaul, 2018; Deepa et al., 2019; Han et al., 2016). Male reproduction and fertility is based on spermatogenesis - a well-regulated, complex process that occurs in the seminiferous tubules of testes as a result of communications between spermatogonia and supporting somatic cells (Sertoli cells) (Esfandiari et al., 2015). Spermatogonial stem cells (SSCs) reside on the basement membrane of seminiferous tubules and are responsible for spermatogenesis and male fertility (Kubota and Brinster, 2018).
Basic and Clinical Approaches for Fertility Preservation and Restoration in Cancer Patients
2018, Trends in BiotechnologyCitation Excerpt :Especially, meiosis and later steps of gamete formation are tightly regulated by the niche and thus, a better understanding of the fine regulation of the human gonadal niche is mandatory for the improvement of in vitro spermatogenesis, iPSC differentiation, and even transdifferentiation [108]. In this regard, bioengineering technologies such as the application of extracellular-matrix-based hydrogels to form scaffolds, or the use of microfluidics and nanoparticles to improve the delivery of growth factors, may also provide support for mimicking the gonadal niche and achieving the maturation of in vitro-derived germ cells (reviewed in [109–111]). Nevertheless, due to the essential role of gametes to transmit genetic and epigenetic information between generations, assessment of safety and functionality of in vitro generated gametes is mandatory prior to their possible clinical translation.
Application of microscope in cell culture experiment of biomaterials in vitro
2020, Acta Microscopica