Bhadouria, N. | bioRxiv Science

bioRxiv2023

Lumbar endplate microfracture injury induces Modic-like changes, intervertebral disc degeneration and spinal cord sensitization-An In Vivo Rat Model

BACKGROUND CONTEXT: Endplate (EP) injury plays critical roles in painful IVD degeneration since Modic changes (MCs) are highly associated with pain. Models of EP microfracture that progress to painful conditions are needed to better understand pathophysiological mechanisms and screen therapeutics. PURPOSE: Establish in vivo rat lumbar EP microfracture model with painful phenotype. STUDY DESIGN/SETTING: In vivo rat study to characterize EP-injury model with characterization of IVD degeneration, vertebral bone marrow remodeling, spinal cord sensitization, and pain-related behaviors. METHODS: EP-driven degeneration was induced in 5-month-old male Sprague-Dawley rats L4-5 and L5-6 IVDs through the proximal vertebral body injury with intradiscal injections of TNF (n=7) or PBS (n=6), compared to Sham (surgery without EP-injury, n=6). The EP-driven model was assessed for IVD height, histological degeneration, pain-like behaviors (hindpaw von Frey and forepaw grip test), lumbar spine MRI and CT analyses, and spinal cord substance P (SubP). RESULTS: EP injuries induced IVD degeneration with decreased IVD height and MRI T2 values. EP injury with PBS and TNF both showed MC type1-like changes on T1 and T2-weighted MRI, trabecular bone remodeling on CT, and damage in cartilage EP adjacent to the injury. EP injuries caused significantly decreased paw withdrawal threshold and reduced grip forces, suggesting increased pain sensitivity and axial spinal discomfort. Spinal cord dorsal horn SubP was significantly increased, indicating spinal cord sensitization. CONCLUSIONS: EP microfracture can induce crosstalk between vertebral bone marrow, IVD and spinal cord with chronic pain-like conditions. CLINICAL SIGNIFICANCE: This rat EP microfracture model of IVD degeneration was validated to induce MC-like changes and pain-like behaviors that we hope will be useful to screen therapies and improve treatment for EP-drive pain.

pathology↗

bioRxiv2021

Raloxifene reduces sex- and age-related intervertebral disc degeneration in mice by estrogen signaling

Estrogen agonist raloxifene is an FDA-approved treatment for osteoporosis in postmenopausal women that may also be a promising prophylactic for painful intervertebral disc (IVD) degeneration. Here, we hypothesized that raloxifene would augment IVD structure and reduce neurokinin-1 (substance P) in young and old mice by stimulating estrogen signaling. 2.5 month (male and female) and 22.5 month (female) C57Bl/6J mice were subcutaneously injected with raloxifene hydrochloride (5x/week, 6week, n=7-9/grp). Next, to determine the impact of estrogen-deficiency to IVD structure and substance P, female mice were ovariectomized (OVX) at 4mo and tissues from OVX and sham-operated mice were harvested at 6mo (n=5-6/grp). First, compared to male IVD, female IVD expressed less col2 and osterix transcription, early markers of IVD degeneration. Irrespective of sex, raloxifene increased the transcriptional expression for extracellular matrix anabolism, proliferation, notochordal cells (vs chondrocyte-like cells) and estrogen signaling in young IVD. Next, we determined that biological sex and aging each induced structural features of lumbar IVD degeneration. Therapeutically, injection of raloxifene countered these features by increasing IVD height in young mice, preventing mild sex-related IVD degeneration in young female mice and partially reversing age-related IVD degeneration in old female mice. Further, estrogen agonist raloxifene upregulated er- protein and downregulated substance P protein in young and old IVD. By contrast, estrogen-deficiency by OVX increased IVD degeneration and substance P protein in IVD cells. Similarly, substance P protein in vertebral osteocytes was upregulated in females relative to males and by estrogen-deficiency and downregulated by raloxifene. Overall, raloxifene augmented IVD structure and reduced substance P expression in young and old female murine IVD, whereas estrogen-deficiency increased substance P in the spine. These data suggest that raloxifene may potentially relieve painful IVD degeneration in postmenopausal women induced by biological sex, estrogen-deficiency and advanced age. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=71 SRC="FIGDIR/small/449482v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@87c74borg.highwire.dtl.DTLVardef@2d2bf8org.highwire.dtl.DTLVardef@1a1e365org.highwire.dtl.DTLVardef@15803e7_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract Injection of raloxifene promotes IVD health by engaging estrogen and Wnt signaling to promote cell proliferation and IVD structure. Differential estrogen signaling by raloxifene and ovariectomy regulated nerve signaling protein substance P in the spine. Raloxifene may also bind water to collagen to promote hydration. Acan: aggrecan, AF: annulus fibrosus, NC: notochordal cell, NP: nucleus pulposus C_FIG

bioengineering↗