Weizman, E. | Search bioRxiv

bioRxiv2023

Mesenchymal Stromal Cells regulate human Hematopoietic Stem Cell survival and regeneration via cAMP/PKA pathway

Ionizing radiation (IR) and chemotherapies severely impair hematopoietic stem and progenitor cell (HSPC) function, causing bone marrow failure and secondary malignancies. Mesenchymal stromal cells (MSCs) within the hematopoietic niche support HSPC survival and regeneration, but the underlying pro-survival mechanisms remain incompletely understood. Here, we show that MSCs suppress IR-induced apoptosis in human HSPCs and preserve their regenerative capacity. Transcriptomic analyses identified a robust induction of CREB target genes in HSPCs upon MSC contact, driven by MSC-secreted prostaglandin E2 (PGE2) via cAMP signaling. While MSC-derived PGE2 predominantly protected quiescent HSPCs from IR-induced apoptosis, direct pharmacological elevation of cAMP with Forskolin/IBMX (FSKN/IBMX) effectively shielded both quiescent and cycling HSPCs, significantly enhancing their engraftment and self-renewal. Mechanistically, cAMP pathway activation reduced pro-apoptotic ASPP1 and PUMA expression, elevated p21, and stabilized anti-apoptotic MCL1 and BCL-XL proteins. Collectively, our study uncovers an MSC-driven PGE2/CREB signaling pathway critical for human HSPC regeneration, highlighting pharmacological modulation of this axis as a promising strategy to mitigate DNA damage-induced myelosuppression and improve transplantation outcomes.

cell biology↗

bioRxiv2023

Sedentary behavior may accelerate aging through impact on epigenome and transcriptome: lessons from muscle inactivation in Drosophila larvae

AimThe biological mechanisms linking sedentary lifestyles and metabolic derangements are incompletely understood. Our animal model mimics sedentary behavior during early life, enabling us to explore the associated chromatin epigenetic and transcriptomic landscapes. MethodsDrosophila larvae carrying a temperature-sensitive mutation in the shibire1 (shi) gene were used. shi homozygous mutant larvae undergo instant arrest of muscle contraction at a restrictive temperature (30{degrees}C), without affecting other systems. Both shi and control (y,w) larvae were held at permissive temperature (18{degrees}C), and transferred to restrictive temperature (30{degrees}C) for six hours. Larvae were then dissected, fixed, and double-labeled with antibodies specific for epigenetic marks of chromatin activation (H3K9ac) and repression (H3K27me3), and their fluorescence signal was quantified. In addition, whole genome analysis of RNA-Pol II binding to DNA in muscle-specific inactive, or control larvae was performed using muscle-specific targeted DamID (TaDa) protocol. ResultsInducing muscle inactivity in shi larvae at 300C yielded a significantly higher ratio between chromatin activation and repression, based upon H3K9ac/H3K27me3 signals (p=0.025), relative to all control groups for which this ratio was comparable (p=0.995). Furthermore, muscle inactivation led to altered Pol II binding to 121 out of 2010 genes (6%). The suppressed protein-coding genes included genes associated with longevity, DNA repair, muscle function, and ubiquitin-dependent proteostasis. In addition, a three-fold enrichment of genes coding for lncRNAs was noted in the muscle-inactive larvae. ConclusionInducing muscle inactivation exerted a multi-level impact upon chromatin, triggering an altered epigenetic balance, as well as downregulation of the transcriptional activity of genes essential for muscle function, carbohydrate metabolism, longevity and others. Extrapolating these findings to humans holds promise for establishing a molecular link between sedentary behavior and metabolic diseases.

physiology↗