Small leucine-rich proteoglycans inhibit CNS regeneration by modifying the structural and mechanical properties of the lesion environment

Mechanisms of cardiomyopathy in duchenne muscular dystrophy: A study using pluripotent stem cells derived from patients with severe and mild motor impairment

Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder marked by progressive muscle degeneration and early cardiac involvement, with cardiac dysfunction as a major contributor to mortality. However, the molecular mechanisms underlying DMD-associated cardiac dysfunction remain unclear. This study aimed to elucidate these mechanisms and identify gene expression patterns associated with disease progression. Induced pluripotent stem cells (iPSCs) were derived from two patients with DMD exhibiting severe and mild motor impairment and differentiated into cardiomyocytes (iPSC-CMs). The resulting iPSC-CMs expressed myocardial markers, with genetic analysis confirmed dystrophin deficiency in DMD iPSC-CMs. Transcriptomic analysis revealed distinct gene expression profiles, with severe DMD iPSC-CMs exhibiting upregulation of the positive regulation of the transmembrane receptor protein serine/threonine kinase signaling pathway, leading to reduced proliferation, while mild DMD iPSC-CMs showed increased PI3K-Akt signaling and metabolic activity. Severe DMD iPSC-CMs also displayed more pronounced arrhythmicity, with significant correlation between dilated cardiomyopathy signaling changes and heart rate differences. This study establishes an iPSC-CM model for DMD cardiomyopathy, revealing altered gene expression and signaling pathways involved in cardiac dysfunction. Although non-allelic effects and unquantified differentiation efficiency may impact interpretation, these findings highlight key molecular alterations and offer potential therapeutic targets to improve cardiac outcomes in DMD.

Fecal microbiota transplantation promotes functional recovery in mice with spinal cord injury by modulating the spinal cord microenvironment

BACKGROUND

spinal cord injury (SCI) disrupts the gut microbiota, worsening the injury's impact. Fecal microbiota transplantation (FMT) is increasingly recognized as a promising strategy to improve neural function post-SCI, yet its precise mechanisms are still far from clear. The present study aims to elucidate how FMT influences motor function recovery and its underlying mechanisms utilizing a SCI mouse model.

METHODS

Mice with SCI received FMT from healthy donors. We used 16 S rRNA amplicon sequencing to analyze the alterations of gut microbes. Pathological alterations in the spinal cord tissue, including neuronal survival, axonal regeneration, cell proliferation, and neuroinflammation, were assessed among experimental groups. Additionally, RNA sequencing (RNA-seq) was used to explore alterations in relevant signaling pathways.

RESULTS

Significant shifts in gut microbiota composition following SCI were observed through 16 S rRNA analysis. On day 7 post-SCI, the FMT group exhibited a significantly higher diversity of gut microbiota compared to the ABX group, with the composition in the FMT group more closely resembling that of healthy mice. FMT promoted neuronal survival and axonal regeneration, leading to notable improvements in motor function compared to control mice. Immunofluorescence staining showed increased neuronal survival, alleviated extracellular matrix (ECM) deposition, diminished glial scar formation, and reduced inflammation in FMT-treated mice. RNA-seq analysis indicated that FMT induced transcriptomic changes associated with material metabolism, ECM remodeling, and anti-inflammatory responses.

CONCLUSIONS

FMT restored gut microbiota balance in SCI mice, mitigated inflammation, and promoted ECM remodeling, establishing an optimal environment for neural recovery. These findings demonstrated that FMT may represent a valuable approach to enhance functional recovery following SCI.

Correction: Microglia are essential for tissue contraction in wound closure after brain injury in zebrafish larvae

Although in humans, the brain fails to heal after an injury, young zebrafish are able to restore tissue structural integrity in less than 24 h, thanks to the mechanical action of microglia.

Comparative insight into the regenerative mechanisms of the adult brain in zebrafish and mouse: highlighting the importance of the immune system and inflammation in successful regeneration

Regeneration, the complex process of restoring damaged or absent cells, tissues, and organs, varies considerably between species. The zebrafish is a remarkable model organism for its impressive regenerative abilities, particularly in organs such as the heart, fin, retina, spinal cord, and brain. Unlike mammals, zebrafish can regenerate with limited or absent scarring, a phenomenon closely linked to the activation of stem cells and immune cells. This review examines the unique roles played by the immune response and inflammation in zebrafish and mouse during regeneration, highlighting the cellular and molecular mechanisms behind their divergent regenerative capacities. By focusing on zebrafish telencephalic regeneration and comparing it to that of the rodents, this review highlights the importance of a well-controlled, acute, and non-persistent immune response in zebrafish, which promotes an environment conducive to regeneration. The knowledge gained from understanding the mechanisms of zebrafish regeneration holds great promises for the treatment of human neurodegenerative diseases and brain damage (stroke and traumatic brain injuries), as well as for the advancement of regenerative medicine approaches.

Single-cell analysis of innate spinal cord regeneration identifies intersecting modes of neuronal repair

Adult zebrafish have an innate ability to recover from severe spinal cord injury. Here, we report a comprehensive single nuclear RNA sequencing atlas that spans 6 weeks of regeneration. We identify cooperative roles for adult neurogenesis and neuronal plasticity during spinal cord repair. Neurogenesis of glutamatergic and GABAergic neurons restores the excitatory/inhibitory balance after injury. In addition, a transient population of injury-responsive neurons (iNeurons) show elevated plasticity 1 week post-injury. We found iNeurons are injury-surviving neurons that acquire a neuroblast-like gene expression signature after injury. CRISPR/Cas9 mutagenesis showed iNeurons are required for functional recovery and employ vesicular trafficking as an essential mechanism that underlies neuronal plasticity. This study provides a comprehensive resource of the cells and mechanisms that direct spinal cord regeneration and establishes zebrafish as a model of plasticity-driven neural repair.

Estimation of the mass density of biological matter from refractive index measurements

The quantification of physical properties of biological matter gives rise to novel ways of understanding functional mechanisms. One of the basic biophysical properties is the mass density (MD). It affects the dynamics in sub-cellular compartments and plays a major role in defining the opto-acoustical properties of cells and tissues. As such, the MD can be connected to the refractive index (RI) via the well known Lorentz-Lorenz relation, which takes into account the polarizability of matter. However, computing the MD based on RI measurements poses a challenge, as it requires detailed knowledge of the biochemical composition of the sample. Here we propose a methodology on how to account for assumptions about the biochemical composition of the sample and respective RI measurements. To this aim, we employ the Biot mixing rule of RIs alongside the assumption of volume additivity to find an approximate relation of MD and RI. We use Monte-Carlo simulations and Gaussian propagation of uncertainty to obtain approximate analytical solutions for the respective uncertainties of MD and RI. We validate this approach by applying it to a set of well-characterized complex mixtures given by bovine milk and intralipid emulsion and employ it to estimate the MD of living zebrafish (Danio rerio) larvae trunk tissue. Our results illustrate the importance of implementing this methodology not only for MD estimations but for many other related biophysical problems, such as mechanical measurements using Brillouin microscopy and transient optical coherence elastography.

Lumican, a Multifunctional Cell Instructive Biomarker Proteoglycan Has Novel Roles as a Marker of the Hypercoagulative State of Long Covid Disease

This study has reviewed the many roles of lumican as a biomarker of tissue pathology in health and disease. Lumican is a structure regulatory proteoglycan of collagen-rich tissues, with cell instructive properties through interactions with a number of cell surface receptors in tissue repair, thereby regulating cell proliferation, differentiation, inflammation and the innate and humoral immune systems to combat infection. The exponential increase in publications in the last decade dealing with lumican testify to its role as a pleiotropic biomarker regulatory protein. Recent findings show lumican has novel roles as a biomarker of the hypercoagulative state that occurs in SARS CoV-2 infections; thus, it may also prove useful in the delineation of the complex tissue changes that characterize COVID-19 disease. Lumican may be useful as a prognostic and diagnostic biomarker of long COVID disease and its sequelae.