Use of Human Embryonic Stem Cell-based Models for Male Reproductive Toxicity Screening

Abstract

Male reproductive toxicity examines harmful effects of various agents on all aspects and developmental stages of the male reproductive system, including germ cell development and spermatogenesis. In developing a model for reproductive toxicity screening it is important to define the developmental stage that this model is going to recreate in vitro and to identify critical molecular targets of this stage. In this review we focus our discussion on the potential for using embryonic stem cell (ESC)-derived models for male reproductive toxicity screening. The rationale for developing novel toxicity models is that despite significant advances in our biological understanding and clinical treatment of infertility, many unresolved cases still remain. This is likely due to our lack of knowledge about environmental influences on the critical stages of gamete development. Many practical and ethical difficulties are associated with the collection of human tissue samples to explore the unknown causes of infertility. Thus, a readily available in vitro model that mimics human gamete development would be an extremely valuable research tool for establishing novel toxicity assays. ESC exhibit a high degree of similarity with primordial germ cells (PGC) at the level of gene expression and molecular signaling. In addition, recent evidence shows that ESC can be differentiated into PGC and spermatids in culture. Multiple lines of evidence point to the differences between mouse and human ESC (hESC). In light of these data, we present the case that hESC are better suited as in vitro toxicity screening models than their mouse counterparts. We then describe some of the most promising hESC-based systems that are used today to model certain aspects of male gamete development and that have a potential to be used for toxicity screening. We conclude by discussing the potential of these existing models in toxicology studies and the possibilities for their improvement in the future.

A roadmap for the development of alternative (non-animal) methods for systemic toxicity testing

“…The obvious potential of combing stem cell methods with Tox-21c approaches was stressed earlier (Chapin and Stedman, 2009). This extends from embryotoxicity to other areas such as male fertility (Krtolica and Giritharan, 2010) and to link toxicity related biomarkers uncovered using hES cells with the PoT concept. However, the vision of Tox-21c is not that a tremendous number of assays in a centralized facility are used for each and every substance.…”

Amniotic fluid stem cell-based models to study the effects of gene mutations and toxicants on male germ cell formation

“…29,[72][73][74] ES cell-based approaches to study germ cell development have been shown to be useful tools for the direct examination of the effects of environmental toxicants on the molecular regulation of human germ cell formation. 30,31 Very recently, we found that mercury and lead can affect the biological properties of human AFS cells. 75 The differentiation of AFS cells into cell of the germ cell lineage would allow to investigate the role of these two toxicants on human male germ cell development, but also to screen additional substances for their toxic potential for spermatogenesis.…”

“…27,28 It is well known that spermatogenesis is a complex biological process, which is particularly sensitive to environmental insults, such as toxicants, 29 and stem cell-based in vitro models have already been used for reproductive toxicity screening. 30,31 …”

Pluripotent stem cells: An in vitro model for nanotoxicity assessments

“…hESC‐based in vitro models have been developed to assess reproductive toxicity based on the genetic and epigenetic changes that occur during germ cell development and to screen the ability of known agents to disrupt germ cell development (Rugg‐Gunn et al ., ). It could be useful to establish an in vitro model to replicate the in vivo development of human male gametes, such as their differentiation into primordial germ cells, generation of spermatogonial stem cells and formation of spermatozoa, to understand and study adverse effects on the male reproductive system (Krtolica & Giritharan, ). The beneficial aspects of stem cells in toxicology and compatibility have promoted the commercialization of hESC‐based in vitro platforms (Pouton & Haynes, ; Sinha, ).…”