Assessment of lumbar vertebrae morphology by magnetic resonance imaging in osteoporosis

Sdc4 deletion perturbs intervertebral disc matrix homeostasis and promotes early osteopenia in the aging mouse spine

Syndecan 4 (SDC4), a cell surface heparan sulfate proteoglycan, is known to regulate matrix catabolism by nucleus pulposus cells in an inflammatory milieu. However, the role of SDC4 in the aging spine has never been explored. Here we analyzed the spinal phenotype of Sdc4 global knockout (KO) mice as a function of age. Micro-computed tomography showed that Sdc4 deletion severely reduced vertebral trabecular and cortical bone mass, and biomechanical properties of vertebrae were significantly altered in Sdc4 KO mice. These changes in vertebral bone were likely due to elevated osteoclastic activity. The histological assessment showed subtle phenotypic changes in the intervertebral disc. Imaging-Fourier transform-infrared analyses showed a reduced relative ratio of mature collagen crosslinks in young adult nucleus pulposus (NP) and annulus fibrosus (AF) of KO compared to wildtype discs. Additionally, relative chondroitin sulfate levels increased in the NP compartment of the KO mice. Transcriptomic analysis of NP tissue using CompBio, an AI-based tool showed biological themes associated with prominent dysregulation of heparan sulfate GAG degradation, mitochondria metabolism, autophagy, endoplasmic reticulum (ER)-associated misfolded protein processes and ER to Golgi protein processing. Overall, this study highlights the important role of SDC4 in fine-tuning vertebral bone homeostasis and extracellular matrix homeostasis in the mouse intervertebral disc.

New evidence on the controversy over the correlation between vertebral osteoporosis and intervertebral disc degeneration: a systematic review of relevant animal studies

OBJECTIVE

The effect of vertebral osteoporosis on disc degeneration remains controversial. The aim of this study was to conduct a systematic review and meta-analysis of relevant animal studies to shed more light on the effects and mechanisms of vertebral osteoporosis on disc degeneration and to promote the resolution of the controversy.

METHODS

The PubMed, Cochrane Library, and Embase databases were searched for studies that met the inclusion criteria. Basic information and data were extracted from the included studies and data were analyzed using STATA 15.1 software. This study was registered on INPLASY with the registration number INPLASY202370099 and https://doi.org/10.37766/inplasy2023.7.0099 .

RESULTS

A total of 13 studies were included in our study. Both animals, rats and mice, were covered. Meta-analysis results showed in disc height index (DHI) (P < 0.001), histological score (P < 0.001), number of osteoblasts in the endplate (P = 0.043), number of osteoclasts in the endplate (P < 0.001), type I collagen (P < 0.001), type II collagen (P < 0.001), aggrecan (P < 0.001), recombinant a disintegrin and metalloproteinase with thrombospondin-4 (ADAMTS-4) (P < 0.001), matrix metalloproteinase-1 (MMP-1) (P < 0.001), MMP-3 (P < 0.001), MMP-13 (P < 0.001), the difference between the osteoporosis group and the control group was statistically significant. In terms of disc volume, the difference between the osteoporosis group and the control group was not statistically significant (P = 0.459).

CONCLUSION

Our study shows that vertebral osteoporosis may exacerbate disc degeneration. Abnormal bone remodeling caused by vertebral osteoporosis disrupts the structural integrity of the endplate, leading to impaired nutrient supply to the disc, increased expression of catabolic factors, and decreased levels of type II collagen and aggrecan may be one of the potential mechanisms.

Does vertebral osteoporosis delay or accelerate lumbar disc degeneration? A systematic review

The effect of vertebral osteoporosis on disc degeneration is still debated. The purpose of this study was to provide a systematic review of studies in this area to further reveal the relationship between the two. Relevant studies were searched in electronic databases, and studies were screened according to inclusion and exclusion criteria, and finally, basic information of the included studies was extracted and summarized. This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A total of 34 publications spanning 24 years were included in our study. There were 19 clinical studies, including 12 prospective studies and 7 retrospective studies. Of these, 7 considered vertebral osteoporosis to be positively correlated with disc degeneration, 8 considered them to be negatively correlated, and 4 considered them to be uncorrelated. Two cadaveric studies were included, one considered the two to be negatively correlated and one considered them not to be correlated. Seven animal studies were included, of which five considered a positive correlation between vertebral osteoporosis and disc degeneration and two considered a negative correlation between the two. There were also 6 studies that used anti-osteoporosis drugs for intervention, all of them were animal studies. Five of them concluded that vertebral osteoporosis was positively associated with disc degeneration, and the remaining one concluded that there was no correlation between the two. Our systematic review shows that the majority of studies currently consider an association between vertebral osteoporosis and disc degeneration, but there is still a huge disagreement whether this association is positive or negative. Differences in observation time and follow-up time may be one of the reasons for the disagreement. A large number of clinical and basic studies are still needed in the future to further explore the relationship between the two.

The Relationship Between Bone Mineral Density and Lumbar Disc Herniation in Postmenopausal Women

INTRODUCTION

In previous studies, the relationship between BMD (bone mineral density) and LDH (lumbar disc herniation) has been investigated in young people, except for postmenopausal women. The aim of this study was to evaluate this association in postmenopausal women.

METHODS

A cross-sectional analysis of 545 consecutive postmenopausal women was performed at a single center. The study included patients aged 45 to 85 with low back pain. Age, weight, height, L1-L4 BMD, L1-L4 T-score, L1-L4 Z-score, femoral neck BMD, femoral neck T-score, and femoral neck Z-score of patients were collected. MRI scans were assessed for the diagnosis of LDH. To explore the impact of the number of herniated segments, patients with LDH were further divided into single-level and multi-level LDH groups.

RESULTS

Five hundred and thirteen postmenopausal women were included in the final analysis. The mean age of the patients was 61.3±8.6 years in the LDH group and 58.4±7.8 years in the non-LDH group (p=0.001). The LDH group had higher lumbar (p<0.001) and femoral neck (p<0.05) BMD, T, and Z-scores than the non-LDH group. In binary logistic regression analysis, age, lumbar, and femoral neck BMD were significantly associated with LDH (p<0.001, p=0.03, and p=0.040, respectively). Patients with multi-level herniation had significantly higher rates of obesity (BMI ≥30) compared to patients with single-level herniation (58.0% vs. 47.0%; p=0.031). However, in terms of obesity rates, the LDH group and the non-LDH group were statistically similar (53.9% vs. 54.2%; p=0.961). There was no association between the single and multi-level herniation groups in terms of L1-4 and femoral neck BMD (p=0.760 and 0.435, respectively).

CONCLUSION

Higher lumbar bone mineral density and higher femoral neck bone mineral densities were found to be associated with lumber disc herniation in postmenopausal women with low back pain. These results suggest that bone mineral density assessment may be useful in clinical practice to determine which patients are at higher risk of lumbar disc herniation.

Assessment of Lumbar Vertebrae Morphology by Computed Tomography in Older Adults with Osteoporosis

BACKGROUND

Hounsfield units (HU) values derived from computerized tomography (CT) have been used in diagnosis for osteoporosis in the lumbar spine.

OBJECTIVE

This study aimed to identify anatomical dimensions of lumbar vertebrae on CT images, which were different between older normal, osteopenic and osteoporotic subjects.

METHODS

This prospective pilot study enrolled 79 older adults. Based on CT measurements of lumbar vertebrae in HU, participants were classified into three groups: normal (HU > 109), osteopenia (HU: 94-108), and osteoporosis (HU < 93). Altogether, 42 anatomical variables of lumbar vertebrae, L2, L3, L4, and L5, were measured in each participant by CT, including 24 parameters measurable by MRI or plain X-ray, and 18 parameters measurable by MRI only.

RESULTS

Among the morphological measurements also measurable by MRI and plain X-ray, the length upper curve, 50% and 75% of L5, length upper with cortex of L4, length center of cortex of L3, as well as width upper curve 75% of L2, were significantly different between the three groups (p= 0.008, 0.007, 0.035, 0.036, and 0.003 respectively). Among the morphological measurements also measurable by MRI, only width upper cortex 75% of L5 and width lower cortex 25% of L3 were significantly different between the three groups (p= 0.031 and 0.020, respectively).

CONCLUSION

Seven CT morphological measurements may be used as "reference standard" CT measurements for preliminarily diagnosing osteoporosis and osteopenia in older adults.

Estrogen Deficiency Exacerbates Intervertebral Disc Degeneration Induced by Spinal Instability in Rats

STUDY DESIGN

An experimental animal study of osteoporosis (OP) and intervertebral disc degeneration (IDD).

OBJECTIVE

The aim of this study was to clarify the effects of estrogen deficiency and supplement on cervical IDD induced by bilateral facetectomy in rats.

SUMMARY OF BACKGROUND DATA

The relationship between IDD and OP is still controversy with the wide prevalence in aged people.

METHODS

Seventy-two Sprague-Dawley female rats were randomly divided into ovariectomy (OVX) group, facet joints resection of C4-6 (FR), FR-OVX group, estrogen replacement therapy (ERT, based on the FR-OVX group) group, and sham group. Specimens of C4-6 segment were harvested at 12 and 24 weeks. The microstructures of C5 vertebrae, vertebral endplate lesions and calcification, and IDD of C5/6 disc were evaluated by micro-computed tomography (micro-CT) and histology. The protein and gene levels of aggrecan, Col2α1, matrix metalloprotease (MMP)-3, and MMP-13 in the C5/6 and C4/5 discs were measured.

RESULTS

Microstructures of C5 vertebral body were weakened significantly after ovariectomy, while restored effectively with estradiol supplementation. The facetectomy led to significant IDD, and the IDD was aggravated when combined with OVX. The IDD of the ERT group was alleviated effectively and similar to that of the FR group in intervertebral disc height, vertebral endplate lesions and calcification, and disc degeneration scores. In addition, the estrogen supplement maintained the extracellular matrix by decreasing MMP-3 and MMP-13, and increasing aggrecan and Col2α1 expression.

CONCLUSION

The present study demonstrated that estrogen deficiency exacerbated IDD induced by spinal instability, while estrogen supplementation alleviated the progression of disc degeneration related to osteoporosis.

LEVEL OF EVIDENCE

N/A.

Repression of let-7b-5p prevents the development of multifidus muscle dysfunction by promoting vitamin D accumulation via upregulation of electron transfer flavoprotein alpha subunit in a rat model of multifidus muscle injury

Multifidus muscle dysfunction is associated with the multifidus muscle injury (MMI), which ultimately result in the low-back pain. Increasing evidence shows that microRNAs (miRs) may be involved in multifidus muscle dysfunction. In this study, we tested the hypothesis that downregulation of let-7b-5p may inhibit the multifidus muscle dysfunction development and progression. The target prediction program and luciferase activity determination confirmed electron transfer flavoprotein alpha subunit (ETFA) as a direct target gene of let-7b-5p. To study the mechanisms and functions of let-7b-5p in relation to ETFA in MMI progression, we prepared rats with experimental MMI, and a lentivirus-based packaging system was designed to upregulate expressions of let-7b-5p, and downregulate the expression of ETFA. ETFA was identified as a target gene of let-7b-5p. Older age, a longer duration of pain, and higher visual analog scale and Oswestry disability index scores for the patients with chronic low-back pain were linked to a more severe degree of degenerative muscle atrophy and fatty infiltration. Increased expression of let-7b-5p and decreased expression of ETFA and vitamin D receptor (VDR) were positively correlated with multifidus muscle dysfunction. Downregulated let-7b-5p could inhibit infiltration of collagen fibers, reverse the ultrastructural changes of multifidus muscle, and induce the VDR expression, thereby repair the MMI. The results provided a potential basis for let-7b-5p that could support targeted intervention in multifidus muscle dysfunction. Collectively, this study confirmed that downregulation of let-7b-5p has a potential inhibitory effect on the development of the function of the musculus myocytes by upregulating ETFA.

Animal models for glucocorticoid-induced postmenopausal osteoporosis: An updated review

Glucocorticoid-induced postmenopausal osteoporosis is a severe osteoporosis, with high risk of major osteoporotic fractures. This severe osteoporosis urges more extensive and deeper basic study, in which suitable animal models are indispensable. However, no relevant review is available introducing this model systematically. Based on the recent studies on GI-PMOP, this brief review introduces the GI-PMOP animal model in terms of its establishment, evaluation of bone mass and discuss its molecular mechanism. Rat, rabbit and sheep with their respective merits were chosen. Both direct and indirect evaluation of bone mass help to understand the bone metabolism under different intervention. The crucial signaling pathways, miRNAs, osteogenic- or adipogenic- related factors and estrogen level may be the predominant contributors to the development of glucocorticoid-induced postmenopausal osteoporosis.

Relevant Anatomic and Morphological Measurements of the Rat Spine: Considerations for Rodent Models of Human Spine Trauma

STUDY DESIGN

Basic science study measuring anatomical features of the cervical and lumbar spine in rat with normalized comparison with the human.

OBJECTIVE

The goal of this study is to comprehensively compare the rat and human cervical and lumbar spines to investigate whether the rat is an appropriate model for spine biomechanics investigations.

SUMMARY OF BACKGROUND DATA

Animal models have been used for a long time to investigate the effects of trauma, degenerative changes, and mechanical loading on the structure and function of the spine. Comparative studies have reported some mechanical properties and/or anatomical dimensions of the spine to be similar between various species. However, those studies are largely limited to the lumbar spine, and a comprehensive comparison of the rat and human spines is lacking.

METHODS

Spines were harvested from male Holtzman rats (n = 5) and were scanned using micro- computed tomography and digitally rendered in 3 dimensions to quantify the spinal bony anatomy, including the lateral width and anteroposterior depth of the vertebra, vertebral body, and spinal canal, as well as the vertebral body and intervertebral disc heights. Normalized measurements of the vertebra, vertebral body, and spinal canal of the rat were computed and compared with corresponding measurements from the literature for the human in the cervical and lumbar spinal regions.

RESULTS

The vertebral dimensions of the rat spine vary more between spinal levels than in humans. Rat vertebrae are more slender than human vertebrae, but the width-to-depth axial aspect ratios are very similar in both species in both the cervical and lumbar regions, especially for the spinal canal.

CONCLUSION

The similar spinal morphology in the axial plane between rats and humans supports using the rat spine as an appropriate surrogate for modeling axial and shear loading of the human spine.