Chemical enhancement in embryo development and stem cell derivation from single blastomeres

Learning Towards Maturation of Defined Feeder-free Pluripotency Culture Systems: Lessons from Conventional Feeder-based Systems

Pluripotent stem cells (PSCs) are widely recognized as one of the most promising types of stem cells for applications in regenerative medicine, tissue engineering, disease modeling, and drug screening. This is due to their unique ability to differentiate into cells from all three germ layers and their capacity for indefinite self-renewal. Initially, PSCs were cultured using animal feeder cells, but these systems presented several limitations, particularly in terms of Good Manufacturing Practices (GMP) regulations. As a result, feeder-free systems were introduced as a safer alternative. However, the precise mechanisms by which feeder cells support pluripotency are not fully understood. More importantly, it has been observed that some aspects of the need for feeder cells like the optimal density and cell type can vary depending on conditions such as the developmental stage of the PSCs, phases of the culture protocol, the method used in culture for induction of pluripotency, and intrinsic variability of PSCs. Thus, gaining a better understanding of the divergent roles and necessity of feeder cells in various conditions would lead to the development of condition-specific defined feeder-free systems that resolve the failure of current feeder-free systems in some conditions. Therefore, this review aims to explore considerable feeder-related issues that can lead to the development of condition-specific feeder-free systems.

Suppression of transforming growth factor β signaling promotes ground state pluripotency from single blastomeres

STUDY QUESTION

Can transforming growth factor β (TGFβ) inhibition promote ground state pluripotency of embryonic stem cells (ESCs) from single blastomeres (SBs) of cleavage embryos in different mouse stains?

SUMMARY ANSWER

Small molecule suppression of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) and TGFβ signaling (designated as R2i) can enhance the generation of mouse ESCs from SBs of different cleavage stage embryos compared with the dual suppression of ERK1/2 and glycogen synthase kinase 3 (GSK3), designated as 2i, regardless of the strain of mouce.

WHAT IS KNOWN ALREADY

It is known that chemical inhibition of TGFβ promotes ground state pluripotency in the generation and sustenance of naïve ES cells from mouse blastocysts compared with the well-known 2i condition. However, the positive effect of this inhibition on mouse ESCs from early embryonic SBs remains obscure.

STUDY DESIGN, SIZE, DURATION

We used 155 cleavage-stage mouse embryos to optimize the culture conditions for blastocyst development. Then, to assess the effects of R2i and 2i on ESC generation from SBs, we cultured isolated SBs in 2i and R2i for 10 days. SBs were replated under the same conditions to produce ESCs. In total, 46 embryos and 321 SBs from two- to eight-cell stages were recovered from NMRI and BALB/c mouse strains and used in this study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Blastomeres from 2- to 8-cell stage mouse embryos were dispersed and individually seeded into a 96-well plates that included mitotically inactivated feeder cells. ESCs were generated in B27N2 defined medium supplemented with R2i or 2i. Randomly selected ESC lines, generated from SBs of each stage, were assessed for pluripotency and germ-line transmission.

MAIN RESULTS AND THE ROLE OF CHANCE

We demonstrated that dual inhibition of ERK1/2 and TGFβ (R2i) enhanced efficient blastocyst development and efficient establishment of ESCs from SB of 2- to 8-cell stage mouse embryos compared with the dual inhibition of ERK1/2 and GSK3 (2i) regardless of the embryonic stage and strain of mice. The proportions of SBs that produced ESC were 50-60 versus 20-30%.

LIMITATIONS, REASONS FOR CAUTION

This study was done with mouse embryos, it is not known whether these findings are transferable to humans.

WIDER IMPLICATIONS OF THE FINDINGS

These findings resulted in an increased efficiency of ESC generation from one biopsied blastomere for autogeneic or allogeneic matched pluripotent cells without the need to destroy viable embryos. The results also provided information about the developmental capacity of early embryonic blastomeres.

STUDY FUNDING/COMPETING INTERESTS

This study was funded by grants provided from Royan Institute, the Iranian Council of Stem Cell Research and Technology and the Iran National Science Foundation. The authors have no conflict of interest to declare.

The root of reduced fertility in aged women and possible therapentic options: current status and future perspects

It is well known that maternal ageing not only causes increased spontaneous abortion and reduced fertility, but it is also a high genetic disease risk. Although assisted reproductive technologies (ARTs) have been widely used to treat infertility, the overall success is still low. The main reasons for age-related changes include reduced follicle number, compromised oocyte quality especially aneuploidy, altered reproductive endocrinology, and increased reproductive tract defect. Various approaches for improving or treating infertility in aged women including controlled ovarian hyperstimulation with intrauterine insemination (IUI), IVF/ICSI-ET, ovarian reserve testing, preimplantation genetic diagnosis and screening (PGD/PGS), oocyte selection and donation, oocyte and ovary tissue cryopreservation before ageing, miscarriage prevention, and caloric restriction are summarized in this review. Future potential reproductive techniques for infertile older women including oocyte and zygote micromanipulations, derivation of oocytes from germ stem cells, ES cells, and iPS cells, as well as through bone marrow transplantation are discussed.

Mouse and human pluripotent stem cells and the means of their myogenic differentiation

Pluripotent stem cells, such as embryonic stem cells and induced pluripotent stem cells, are an important tool in the studies focusing at the differentiation of various cell types, including skeletal myoblasts. They are also considered as a source of the cells that due to their pluripotent character and availability could be turned into any required tissue and then used in future in regenerative medicine. However, the methods of the derivation of some of cell types from pluripotent cells still need to be perfected. This chapter summarizes the history and current advancements in the derivation and testing of pluripotent stem cells-derived skeletal myoblasts. It focuses at the in vitro methods allowing the differentiation of stem cells grown in monolayer or propagated as embryoid bodies, and also at in vivo tests allowing the verification of the functionality of obtained skeletal myoblasts.

Simple and efficient derivation of mouse embryonic stem cell lines using differentiation inhibitors or proliferation stimulators

The inhibition of endogenous differentiation-inducing signaling or the enhancement of growth capacity and viability of preimplantation embryos, via 2i (PD0325901 and CHIR99021), dramatically improves the establishment of mouse embryonic stem cells (mESCs). Using adrenocorticotropic hormone fragments 1-24 (ACTH 1-24), which enhances survival and/or proliferation of mESCs, also increases the derivation of mESCs from single blastomeres significantly. The CHIR99021 pathway and the proposed ACTH pathway are likely different. Therefore, this study aimed to assess the synergetic effects of 2i and ACTH 1-24 on derivation of mESCs. Results in the present study demonstrate that germline-transmitted mESCs could be efficiently derived from ICR and C57BL/6J at 0.5-4.5 days postcoitum denuded zygotes to blastocysts or isolated blastomeres of 2-8-cell embryos and cultured in 10 μL droplets with human foreskin fibroblast (Hs68) or STO (a mouse embryonic fibroblast line) feeders and in knockout serum replacement (KSR) ESC medium containing 2i or ACTH 1-24. The overall success rates for C57BL/6J and ICR were 56.2% when cultured in 2i+ACTH 1-24, 26.6% in 2i, 6.7% in ACTH 1-24, and 4.8% in KSR ESC medium. These results imply that CHIR99021 and ACTH 1-24 are synergistically enhancing the establishment of mESCs. The proposed protocol also demonstrates a highly efficient and reproducible method, has a simple layout, is easy to apply, and could be used as an alternative method for routinely establishing mESC lines.

Effects of melanocortins on fetal development

Melanocortins, adrenocorticotropic hormone (ACTH) and α-, β-, and γ-melanocyte-stimulating hormone (MSH) are produced in the placenta and secreted into embryos/fetuses. ACTH concentrations are higher in fetal plasma than in maternal plasma and peak at mid-gestation in rats, whereas ACTH production starts in the anterior lobe of the fetal pituitary at later stages. Melanocortin receptors (MC1-5R), receptors for ACTH and α-, β- and γ-MSH, are expressed in various adult organs. The specific function of these receptors has been well examined in the hypothalamic-pituitary-adrenocortical (HPA) axis and the HPA axis-like network in the skin, and anti-inflammatory effects for white blood cells have also been investigated. MC2R and/or MC5R are also expressed in the testis, lung, kidney, adrenal, liver, pancreas, brain and blood cells at different stages in mouse and rat embryos/fetuses. Melanocortins in embryos and fetuses promote maturation of the HPA axis and also contribute to the development of lung, testis, brain and blood cells. Recently, a unique ACTH function was revealed in fetuses: placental ACTH, which is secreted by the maternal leukemia inhibitory factor (LIF), and induces LIF secretion from fetal nucleated red blood cells. Finally, the maternal LIF-placental ACTH-fetal LIF signal relay regulates the LIF level and promotes neurogenesis in fetuses, which suggests that ACTH acts as a signal transducer or effector for fetal development in the maternal-fetal signal pathway.