Biology subjects

Haelterman, N. A.

Publications and source records attributed to Haelterman, N. A..

6 recordsLinked to original sources

bioRxiv2026

Cross-Species Efficacy of Combinatorial Gene Therapy for Osteoarthritis and Correction of Neuro-Inflammatory Pain Mechanisms

Osteoarthritis is a leading cause of chronic pain and disability, which lacks disease-modifying treatment. Given the complex multi-tissue and multifactorial drivers behind disease progression, effective treatments will require simultaneously targeting several mechanisms underlying joint degeneration and pain. Here, we developed and evaluated a combinatorial gene therapy, consisting of a high-capacity adenoviral vector carrying two therapeutic genes to target distinct pathological mechanisms: inflammation (IL-1Ra) and chondrocyte health (PRG4). Intra-articular delivery of this treatment improved functional, structural, and pain outcomes in murine and equine osteoarthritis models. In addition, treatment normalized inflammatory environments in joint tissues, as well as in the dorsal root ganglia (DRG) known to harbor joint-innervating sensory neurons. Moreover, gene therapy reversed OA-induced molecular signatures of neural hyperexcitability, suggesting amelioration of peripheral sensitization. Collectively, these findings support combinatorial gene therapy as a promising treatment for osteoarthritis, while identifying neuroinflammatory signatures for correction of disease progression and pain. One Sentence SummaryA single intra-articular injection of a combinatorial gene therapy slows OA progression and reduces pain in small and large animal models.

systems biology↗

bioRxiv2025

A validated set of neural gene reporter mice and chemical tracers tools for mapping knee innervating neurons

Joint pain is an increasing concern for our aging population, as current therapies to slow joint disease progression or reduce pain are largely ineffective and often carry significant health and dependency risks. Age and joint disease induce changes to all tissues that make up the joint, including the dense neural network that innervates the joint. Several studies have correlated joint innervation changes in diseases such as osteoarthritis or rheumatoid arthritis, but little is known about their respective functional consequences. How subtypes of knee-innervating neurons affect pain experience remains relatively uncharacterized. A few studies focused on a single neural subtype due to the limited availability of validated tools to study joint innervation. To better understand the relationship between aging, joint disease, and pain, systematic characterization of nociceptors and other neural subtypes regulating joint homeostasis and pain is urgently needed. This studys objective was to establish a validated molecular and genetic toolbox for accurate mapping of the neuro-architecture in the murine knee. We screened genetic reporter mice, containing different combinations of Cre and Flp recombinase alleles along with recombinase responsive reporter alleles to either highlight peripheral nociceptors or post-ganglionic sympathetic neurons for their specificity and accuracy in labeling specific neural subtypes in the dorsal root ganglia, sympathetic ganglia, and the knee joint. Additionally, we compared the performance of a series of conventional retrograde tracers for effective labelling of sensory and sympathetic neurons innervating the knee joint. The validated molecular and genetic tools identified in this study will facilitate the creation of comprehensive joint innervation maps in physiological and pathological contexts, setting the stage for identifying the cellular and molecular changes responsible for mediating joint pain, a necessary goal for improved therapeutic interventions. Lay summaryJoint diseases, such as Rheumatoid Arthritis and Osteoarthritis significantly affect the neural landscape in joints, impacting pain, balance, and joint health. Understanding these nerve changes can provide insights into the drivers of joint pain and potential treatments. Our study evaluated genetic and conventional neural tracer tools to visualize and track knee innervating nerve fibers. We found two genetic mouse lines that specifically highlight sensory and sympathetic nerves, making them suitable models for knee joint studies. Additionally, the fluorescent tracer True Blue, effectively marks cell bodies of knee-innervating neurons. These tools will help researchers better understand nerve changes in painful joint pathologies.

neuroscience↗

bioRxiv2025

KneEZ Clear, an Effective Tissue Clearing Protocol to Study Musculoskeletal Tissues in the Mouse

Wholemount, 3-dimensional (3D) tissue imaging holds significant promise for analyzing heterogeneous musculoskeletal tissues, such as knee joints, that demand time- and labor-intensive processing using traditional histological methods. Current musculoskeletal clearing protocols rely on either solvent-based tissue clearing, which substantially alters the size and architecture of cleared tissues, possibly compromising downstream quantification and perhaps more importantly reducing signal from endogenous fluorescent reporters, or on expensive and time-consuming hydrogel-based approaches that requires specialized equipment. While aqueous-based clearing overcomes these challenges, there is a clear need for a method that is optimized for clearing musculoskeletal tissues and that can easily be implemented in a standard lab environment. Here, we present KneEZ Clear, a simple, rapid, and flexible aqueous-based method that renders mineralized and non-mineralized tissues of murine knee joints optically transparent. We show that KneEZ Clear, which is based on the EZ Clear method, is highly flexible, demonstrating efficacy in a wide range of murine musculoskeletal tissues including the vertebral column, hindlimb, skull, and teeth. Critically, KneEZ Clear does not require specialized equipment and retains endogenous signal from fluorophores and fluorescent proteins. Additionally, following clearing and wholemount imaging, precious samples can still be processed for subsequent 2D histological analyses for validation or further study. Finally, we show that KneEZ Clear can be applied to samples of disease models to reveal alterations in tissue architecture and homeostasis. The simplicity, versatility, and efficiency of KneEZ Clear for optical clearing of musculoskeletal tissues will accelerate our understanding of cellular interactions and dynamics in homeostasis and disease.

physiology↗

bioRxiv2025

Optimization of Tissue Clearing Methods and Imaging Conditions for 3D Visualization of the Vasculature of the Adult Murine Knee

The vasculature is an essential regulator of tissue oxygenation, metabolism, and immune surveillance under developmental and homeostatic conditions, as well as in regeneration and disease. Within the musculoskeletal system, blood vessels are involved in bone development and resorption, and they also mediate the inflammatory processes that contribute to diseases affecting the joints, including osteoarthritis. Historically, visualization of vascular networks in joints has been limited to conventional histological approaches due to technical limitations and the inherit structure of the skeletal muscle and bones. Recent advances in optical tissue clearing technologies and 3D fluorescence imaging approaches enabling three-dimensional analysis in whole, intact tissues offer an entree to interrogate musculoskeletal development and disease at a cellular resolution. However, these techniques were not originally developed to image hard mineralized tissues, such as the femur and tibias. To circumvent these challenges, we have optimized tissue decalcification conditions and systematically compared aqueous- and solvent-based tissue clearing approaches to establish an optimal pipeline for clearing and imaging of mineralized tissues with superior resolution of the vasculature. Collectively, this work shows that optical clearing and lightsheet microscopy presents a viable method for generating high-resolution images of the murine hindlimb vasculature, with potential applications in aging and disease modeling.

developmental biology↗

bioRxiv2021

Drosophila functional screening of de novo variants in autism uncovers deleterious variants and facilitates discovery of rare neurodevelopmental diseases

Individuals with autism spectrum disorders (ASD) exhibit an increased burden of de novo variants in a broadening range of genes. We functionally tested the effects of ASD missense variants using Drosophila through humanization rescue and overexpression-based strategies. We studied 79 ASD variants in 74 genes identified in the Simons Simplex Collection and found 38% of them caused functional alterations. Moreover, we identified GLRA2 as the cause of a spectrum of neurodevelopmental phenotypes beyond ASD in eight previously undiagnosed subjects. Functional characterization of variants in ASD candidate genes point to conserved neurobiological mechanisms and facilitates gene discovery for rare neurodevelopmental diseases.

genetics↗

bioRxiv2020

Tendon and Motor Phenotypes in the Crtap-/- Mouse Model of Recessive Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is characterized by short stature, skeletal deformities, low bone mass with bone fragility, and motor deficits. A subset of OI patients also present with joint hypermobility; however, the role of tendon/ligament dysfunction in OI pathogenesis is largely unknown. Using the Crtap-/- mouse model of severe, recessive OI, we found that mutant Achilles tendons and patellar ligaments were thinner with increased collagen cross-links and reduced collagen fibril size at 1- and 4-months compared to wildtype. Patellar ligaments from Crtap-/- mice also had fewer progenitors with a concomitant increase in immature cells. RNA-seq analysis of Achilles tendons and patellar ligaments from 1-month Crtap-/- mice revealed dysregulation in matrix gene expression concomitant with predicted alterations in TGF-{beta}, inflammatory, and metabolic signaling. Finally, a series of behavioral tests revealed severe motor impairments and reduced grip strength in 4-month Crtap-/- mice - a phenotype that correlates with the tendon/ligament pathology.

genetics↗