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8. The DNA damage response is required for oocyte cyst breakdown and follicle formation in mice

Author

Martínez Marchal, Ana, Huang, Yan, Guillot-Ferriols, Maria Teresa, Ferrer-Roda, Mònica, Guixé, Anna, Garcia-Caldés, Montserrat, Roig, Ignasi, Martínez Marchal, Ana, Huang, Yan, Guillot-Ferriols, Maria Teresa, Ferrer-Roda, Mònica, Guixé, Anna, Garcia-Caldés, Montserrat, and Roig, Ignasi

Abstract

Altres ajuts: AMM was supported by a PIF fellowship from Universitat Autònoma de Barcelona (B16P0048), Mammalian oogonia proliferate without completing cytokinesis, forming cysts. Within these, oocytes differentiate and initiate meiosis, promoting double-strand break (DSBs) formation, which are repaired by homologous recombination (HR) causing the pairing and synapsis of the homologs. Errors in these processes activate checkpoint mechanisms, leading to apoptosis. At the end of prophase I, in contrast with what is observed in spermatocytes, oocytes accumulate unrepaired DSBs. Simultaneously to the cyst breakdown, there is a massive oocyte death, which has been proposed to be necessary to enable the individualization of the oocytes to form follicles. Based upon all the above-mentioned information, we hypothesize that the apparently inefficient HR occurring in the oocytes may be a requirement to first eliminate most of the oocytes and enable cyst breakdown and follicle formation. To test this idea, we compared perinatal ovaries from control and mutant mice for the effector kinase of the DNA Damage Response (DDR), CHK2. We found that CHK2 is required to eliminate ~50% of the fetal oocyte population. Nevertheless, the number of oocytes and follicles found in Chk2- mutant ovaries three days after birth was equivalent to that of the controls. These data revealed the existence of another mechanism capable of eliminating oocytes. In vitro inhibition of CHK1 rescued the oocyte number in Chk2 -/- mice, implying that CHK1 regulates postnatal oocyte death. Moreover, we found that CHK1 and CHK2 functions are required for the timely breakdown of the cyst and to form follicles. Thus, we uncovered a novel CHK1 function in regulating the oocyte population in mice. Based upon these data, we propose that the CHK1- and CHK2-dependent DDR controls the number of oocytes and is required to properly break down oocyte cysts and form follicles in mammals. In mammals, female fertility is limited by the number of germ cells, i.e., the oocytes, females are born with. These oocytes associate with

Published
2020

10. Piezoelectric Stimulation Induces Osteogenesis in Mesenchymal Stem Cells Cultured on Electroactive Two-Dimensional Substrates.

Author

Guillot-Ferriols M, Costa CM, Correia DM, Rodríguez-Hernández JC, Tsimbouri PM, Lanceros-Méndez S, Dalby MJ, Gómez Ribelles JL, and Gallego-Ferrer G

Abstract

Physical cues have been shown to be effective in inducing osteogenic differentiation of mesenchymal stem cells (MSCs). Here, we propose piezoelectric stimulation as a potential osteogenic cue mimicking the electroactive properties of bone's extracellular matrix. When combined with a magnetostrictive component, piezoelectric polymers can be used for MSC stimulation by applying an external magnetic field. The deformation of the magnetostrictive component produces a deformation in the polymer matrix, generating a change in the surface charge that induces an electric field that can be transmitted to the cells. Cell adhesion, cytoskeleton changes, and metabolomics are the first evidence of MSC osteoblastogenesis and can be used to study initial MSC response to this kind of stimulation. In the current study, poly(vinylidene) fluoride (PVDF) piezoelectric films with and without cobalt ferrite oxide (CFO) crystallized from the melt in the presence of the ionic liquid 1-butyl-3-methyl-imidazolium chloride ([Bmim][Cl]) were produced. [Bmim][Cl] allowed the production of the β-phase, the most electroactive phase, even without CFO. After ionic liquid removal, PVDF and PVDF-CFO films presented high percentages of the β-phase and similar crystalline content. Incorporating CFO nanoparticles was effective, allowing the electromechanical stimulation of MSCs by applying a magnetic field with a bioreactor. Before stimulation, the initial response of MSCs was characterized in static conditions, showing that the produced films were biocompatible and noncytotoxic, allowing MSC adhesion and proliferation in the short term. Stimulation experiments revealed that MSCs electromechanically stimulated for 3 days in PVDF-CFO supports showed longer focal adhesions and decreased vimentin cytoskeletal density, both signals of early osteogenic differentiation. Furthermore, they rearranged their energy metabolism toward an osteogenic phenotype after 7 days of culture under the same stimulation. The results prove that MSCs respond to electromechanical stimulation by osteogenic differentiation., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Published
2024
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