Biology subjects

Levin-Zaidman, S.

Publications and source records attributed to Levin-Zaidman, S..

5 recordsLinked to original sources

bioRxiv2026

TLR2-mediated microbial sensing by intestinal stem cells coordinates epithelial antimicrobial defense.

Intestinal regeneration and host defense require adaptation to environmental cues, but the mechanisms underlying this coordination remain unclear. We show that intestinal Lgr5 stem cells act as luminal sensors via apically localized Toll-like receptor 2 (TLR2), enabling direct detection of microbiota-derived signals. We identify apical TLR2 activation as a mechanism of luminal sensing in adult stem cells and show that it controls epithelial differentiation, antimicrobial peptide production, and crypt organization, with a particularly strong influence on Paneth cell maturation. Genetic ablation of constitutive, epithelial, or stem cell-specific TLR2 disrupts these processes, leading to impaired antimicrobial defense and altered epithelial composition. Using germ-free mice and human intestinal organoids, we demonstrate that this pathway is microbiota-dependent and evolutionarily conserved, respectively. These findings support a model in which stem cells act as active integrators of environmental information and suggest a broader principle by which barrier tissues couple microbial sensing to regeneration and host protection.

immunology↗

bioRxiv2025

Specialized Molecular Pathways Drive the Formation of Light-Scattering Assemblies in Leucophores

Pigmentation plays a vital role in the survival of organisms, supporting functions such as camouflage, communication, and mate attraction. In vertebrates, these functions are mediated by specialized pigment cells known as chromatophores of which, uric acid crystal-forming leucophores remain the least understood, with little known about their molecular mechanisms. A key question in pigment cell biology is whether different crystal chemistries require distinct molecular pathways, or whether similar cellular processes drive the formation of diverse crystals. This study was designed to unravel the uncharacterized process of uric acid crystallization in leucophores and compare them to guanine crystal formation in iridophores and pterin formation in xanthophores. The results of our transcriptomic, ultrastructural, and metabolomic analyses, demonstrate that leucophores share molecular pathways with iridophores, particularly those connected to organelle organization and purine metabolism, but express discrete genes involved in uric acid biosynthesis and storage. Additionally, leucophores share intracellular trafficking and pterin biosynthesis genes with xanthophores, suggesting universally conserved processes. Ultrastructural studies reveal star-like fibrous structures in leucosomes, which likely serve as scaffolds for unique one-dimensional uric acid assemblies that radiate from the core and act as efficient light scatterers. These findings provide new insights into leucophore cell biology and the specialized mechanisms driving molecular crystalline assembly, and reveal that while some cellular processes are conserved, the specific chemistry of each crystal type drives the evolution of distinct molecular pathways.

cell biology↗

bioRxiv2024

Elucidating early intestinal stem cell response to bacterial infection

Intestinal stem cells (ISCs) are the regenerative force of the gut epithelium. Lgr5+-ISC have been shown to respond to changes in their microenvironment by coping with different metabolites, adapting to caloric changes, and recovering from injury and inflammation. However, how pathogenic bacteria affect adult stem cell regeneration and, as a consequence, the overall tissue adaption to infection has yet to be explored in depth. Here, we interrogated early Lgr5+ ISC responses to an enteric intracellular pathogen by profiling individual IECs from the mouse small intestine. Utilizing GFP-labeled Salmonella enterica, we isolated intracellular invaded cells to elucidate invasion programs of epithelial cell subsets. In particular, we identified a Salmonella-specific infection signature comprised of antimicrobial peptide (AMP) genes, including the Defensin gene family. Our findings demonstrate that Salmonella enterica targets differentiated Paneth, enterocytes, and stem/progenitor cells at these early stages of infection. In response, a rapid Lg5+ ISC-driven cellular remodeling to enterocyte and Paneth lineages expressing AMP genes is initiated to combat the intruders. Importantly, we uncovered an ISC differentiation program via inflammasome activation to protect the crypt environment, while eliminating infected stem cells from the overall stem cell pool. This novel Lgr5+ stem cell defense mechanism not only protects the gut epithelium from persistent bacterial infection but also promotes tissue regeneration. We propose epithelial remodeling to AMP-secreting cells as a novel innate immune response to handle different gut stresses mediated by Lgr5+ ISCs to maintain organizational principles of gut homeostasis and physiology.

immunology↗

bioRxiv2022

Kynurenic acid, a key L-tryptophan-derived metabolite, protects the heart from an ischemic damage

BackgroundRenal injury induces major changes in plasma and cardiac metabolites. We sought to identify a key metabolite that may affect cardiac mitochondria following an acute kidney injury (AKI) that may be harnessed to protect the heart following an acute ischemic event. Methods and ResultsMetabolomics profiling of cardiac lysates and plasma samples derived from rats that underwent AKI 1 or 7 days earlier by 5/6 nephrectomy versus sham-operated controls was performed. We detected only 26 differential metabolites in both heart and plasma samples at the two selected time points, relative to sham. Out of which, kynurenic acid (kynurenate, KYNA) seemed most relevant. Interestingly, KYNA given at 10 mM concentration significantly rescued the viability of H9C2 cardiac myoblast cells grown under anoxic conditions and largely improved their mitochondrial structure and function as determined by flow cytometry and cell staining with MitoTracker dyes. Moreover, KYNA diluted in the drinking water of animals induced with an acute myocardial infarction, highly enhanced their cardiac recovery according to echocardiography and histopathology. Conclusion and translational aspectKYNA may represent a key metabolite absorbed by the heart following AKI. This metabolite can enhance cardiac cell viability following an ischemic event in a mechanism that is mediated, at least in part, by the protection of the cardiac mitochondria. A short-term administration of KYNA may be highly beneficial in the treatment of the acute phase of kidney disease in order to attenuate progression to CRS and in ischemic cardiac conditions to reduce ischemic myocardial damage. HighlightsO_LIThe levels of the L-Tryptophan-derived metabolite, Kynurenic acid (KYNA), are significantly elevated in the heart and the plasma of animals induced with an acute kidney disease. C_LIO_LIKYNA rescues the viability of cardiac cells from an ischemic damage both in vitro and in vivo. C_LIO_LIKYNA can protect the structure & function of cardiac mitochondria in H9C2 cardiomyoblast cells upon exposure to anoxia. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=140 HEIGHT=200 SRC="FIGDIR/small/492275v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@f2a49aorg.highwire.dtl.DTLVardef@14a501org.highwire.dtl.DTLVardef@15d016aorg.highwire.dtl.DTLVardef@10800e7_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2021

Neonatal enthesis healing involves non-inflammatory formation of acellular scar through ECM secretion by resident cells

Wound healing is a well-orchestrated process that typically recruits the immune and vascular systems to restore the structure and function of the injured tissue. Injuries to the enthesis, a hypocellular and avascular tissue, often result in fibrotic scar formation and loss of mechanical properties, thereby severely affecting musculoskeletal function and life quality. This raises questions about the healing capabilities of the enthesis. Here, we established an injury model to the Achilles entheses of neonatal mice to study the possibility that at an early age, the enthesis can heal more effectively. Histology and immunohistochemistry analyses revealed an atypical process that did not involve inflammation or angiogenesis. Instead, neonatal enthesis healing was mediated by secretion of collagen types I and II by resident cells, which formed a permanent hypocellular and avascular scar. Transmission electron microscopy showed that the cellular response to injury, including ER stress, autophagy and cell death, varied between the tendon and cartilage ends of the enthesis. Single-molecule in situ hybridization, immunostaining, and TUNEL assays verified these differences. Finally, gait analysis showed that these processes effectively restored function of the injured leg. Collectively, these findings reveal a novel healing mechanism in neonatal entheses, whereby local ECM secretion by resident cells forms an acellular ECM deposit in the absence of inflammation markers, allowing gait restoration. These insights into the healing mechanism of a complex transitional tissue may lead to new therapeutic strategies for adult enthesis injuries.

molecular biology↗