Patrat, C. | Search bioRxiv

bioRxiv2023

Characterization and hierarchy of the spermatogonial stem cell compartment in human spermatogenesis by spectral cytometry using a 16-colors panel

About one in six couples experience fertility problems, and male infertility accounts for about half of these cases. Spermatogenesis originates from a small pool of spermatogonial stem cells (SSCs), which are of interest for the treatment of infertility but remain poorly characterized in humans. Using multiparametric spectral flow cytometric analysis with a 16-colours (16-C) panel of cell markers, we identify novel markers of SSCs and provide insights into unravelling and resolving the heterogeneity of the human spermatogonial cells. This 16-C panel of markers allowed the identification of a primitive SSCs state with the {beta}-2M-CD51/61- ITGA6+SSEA4+TSPAN33+THY1+CD9+EPCAMmedCD155+CD148+CD47highCD7high phenotype, with a profile close to the most primitive SSCs states 0 and SSC1-B previously defined by sc-RNAseq approach. The hierarchy of events in the spermatogonial stem cell and progenitor compartment of human spermatogenesis has been delineated. This highlights the importance of a multi-parametric and spectral cytometry approach. The in-depth characterization of testicular cells should help to overcome the lack of stem cell knowledge, that hinders the understanding of the regenerative potential of SSCs, and is a critical parameter for the successful development of new SSCs-based cell therapies.

developmental biology↗

bioRxiv2022

Mechanics of human embryo compaction

The shaping of the human embryo begins with compaction, during which cells come into close contact and form a tighter structure1,2. Assisted reproductive technology (ART) studies suggest that human embryos fail compaction primarily because of defective adhesion3,4. Based on our current understanding of animal morphogenesis5,6, other morphogenetic engines, such as cell contractility, could be involved in shaping the human embryo. However, the molecular, cellular and physical mechanisms driving human embryo morphogenesis remain uncharacterized. Using micropipette aspiration on human embryos donated to research, we have mapped cell surface tensions during compaction. This reveals a 4-fold increase of tension at the cellmedium interface while cell-cell contacts keep a steady tension. Comparison between human and mouse reveals qualitatively similar but quantitively different mechanical strategies, with human embryos being mechanically least efficient. Inhibition of cell contractility and cell-cell adhesion in human embryos reveal that only contractility controls the surface tension responsible for compaction. Interestingly, if both cellular processes are required for compaction, they exhibit distinct mechanical signatures when faulty. Analyzing the mechanical signature of naturally failing embryos, we find evidence that non-compacting embryos or partially compacting embryos with excluded cells have defective contractility. Together, our study reveals that an evolutionarily conserved increase in cell contractility is required to generate the forces driving the first morphogenetic movement shaping the human body.

developmental biology↗