3D virtual reconstruction and quantitative assessment of the human intervertebral disc's annulus fibrosus: a DTI tractography study

Qualitative and Quantitative MR Imaging of the Cartilaginous Endplate: A Review

The cartilaginous endplate (CEP) plays a pivotal role in facilitating the supply of nutrients and, transport of metabolic waste, as well as providing mechanical support for the intervertebral disc (IVD). Recent technological advances have led to a surge in MR imaging studies focused on the CEP. This article describes the anatomy and functions of the CEP as well as MRI techniques for both qualitative and quantitative assessment of the CEP. Effective CEP MR imaging sequences require two key features: high spatial resolution and relatively short echo time. High spatial resolution spoiled gradient echo (SPGR) and ultrashort echo time (UTE) sequences, fulfilling these requirements, are the basis for most of the sequences employed in CEP imaging. This article reviews existing sequences for qualitative CEP imaging, such as the fat-suppressed SPGR and UTE, dual-echo subtraction UTE, inversion recovery prepared and fat-suppressed UTE, and dual inversion recovery prepared UTE sequences. These sequences are employed together with other techniques for quantitative CEP imaging, including measurements of T2*, T2, T1, T1ρ, magnetization transfer, perfusion, and diffusion tensor parameters. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 2.

Exploring the correlation between magnetic resonance diffusion tensor imaging (DTI) parameters and aquaporin expression and biochemical composition content in degenerative intervertebral disc nucleus pulposus tissue: a clinical experimental study

OBJECTIVE

This study investigates the correlation between magnetic resonance diffusion tensor imaging (DTI) parameters and biochemical composition in degenerative intervertebral disc nucleus pulposus tissue, offering a potential reference for the clinical diagnosis and efficacy evaluation of intervertebral disc degeneration.

METHODS

Human lumbar intervertebral disc nucleus pulposus tissue samples were collected via full endoscopic minimally invasive surgery. DTI was employed to quantitatively measure fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values in the degenerative nucleus pulposus, examining the relationship between Pfirrmann grading and these DTI parameters. Western blotting was used to detect the expression levels of aquaporin 1 (AQP1) and aquaporin 3 (AQP3) in the degenerative tissue. The glycosaminoglycan (GAG) content was quantified using the dimethylmethylene blue (DMMB) colorimetric assay, and collagen content was assessed with the Sircol soluble collagen assay kit. The relationship between Pfirrmann grading and biochemical composition was also analyzed. Finally, correlation analysis was performed between the FA and ADC values from the human nucleus pulposus tissue and their GAG and collagen contents.

RESULTS

A total of 39 patients (19 males, 20 females) with lumbar disc herniation (LDH), averaging 54.41 years of age, were included. As the degree of Pfirrmann degeneration increased, FA values rose, while ADC values continuously declined. Concurrently, as degeneration progressed, expression of AQP1 and AQP3 proteins decreased, GAG content significantly diminished, and collagen content increased. FA values exhibited a moderate negative correlation with GAG content (r = -0.5974, P < 0.0001) and a strong positive correlation with collagen content (r = 0.8694, P < 0.0001). ADC values showed a moderate positive correlation with GAG content (r = 0.6873, P < 0.0001) and a strong negative correlation with collagen content (r = -0.8502, P < 0.0001).

CONCLUSION

The FA and ADC values derived from magnetic resonance DTI, along with the protein expression levels of AQPs, can reflect the severity of intervertebral disc degeneration to a certain extent. Additionally, the content of glycosaminoglycans and collagen in the nucleus pulposus of the intervertebral disc correlates with the FA and ADC values of the DTI parameters. Therefore, magnetic resonance DTI quantitative imaging provides a means to assess the biochemical composition changes within the intervertebral discs, offering valuable insights for the clinical diagnosis and evaluation of therapeutic efficacy in intervertebral disc degenerative diseases.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR2000041151, Registered on 19 December, 2020, https://www.chictr.org.cn/showproj.html?proj=206119 .

Neuroinflammation and nociception in intervertebral disc degeneration: a review of precision medicine perspective

Intervertebral disc (IVD) degeneration is a major cause of low back pain (LBP), which results in disability worldwide. However, the pathogenesis of IVD degeneration mediating LBP remains unclear. Current conservative treatments and surgical interventions are both to relieve the symptoms and minimise pain; nevertheless, they are unable to reverse the degeneration. Previous studies have shown that inflammation and nociception markers are important indicators of pain mechanisms in IVD degeneration underlying LBP. As such, multiomics profiling allows the discovery of these target markers to understand the key pathological mechanisms mediating IVD degeneration underpinnings of LBP. This article provides insights into a precision medicine approach for identifying and understanding the pathophysiology of IVD degeneration associated with LPB based on the severity of the disease from early and mild to severe degenerative stages. Molecular profiling of key markers in degenerative IVDs based on patient stratification at early, mild, and severe stages will contribute to the identification of target markers associated with signalling pathways in mediating neuroinflammation, innervation, and nociception underlying painful IVD degeneration. This approach will offer an understanding of establishing personalised clinical strategies tailored to the severity of IVD degeneration for the treatment of LBP.

Diacetoxy-6-gingerdiol protects the extracellular matrix of nucleus pulposus cells and ameliorates intervertebral disc degeneration by inhibiting the IL-1β-mediated NLRP3 pathway

Intervertebral disc degeneration (IDD) is a common cause of low back pain, causing a huge emotional and economic burden on patients and society. Reduction of nucleus pulposus cells (NPC) and extracellular matrix (ECM) is the main feature of IDD, and NPC is the main source of ECM. Thermal apoptosis is a newly discovered form of cell death in recent years that differs significantly from apoptosis in terms of molecular mechanisms and cellular morphological changes. Diacetoxy-6-gingerdiol(D-6-G), a type of gingerol, has anti-inflammatory and antioxidant effects, but whether it has an inhibitory effect on cellular pyroptosis is not clear. Therefore, in the present study, we investigated the effect of D-6-G on the ECM of the nucleus pulposus oblongata under IL-1β treatment, as well as the mechanism of its effect on NLRP3 inflammasome and cellular focal death. In vitro cellular experiments demonstrated that D-6-G could bind to and inhibit the activity of NLRP3 inflammasome, and interestingly, D-6-G could also inhibit cellular pyroptosis and protect the nucleus pulposusry cellular microenvironment by activating the Nrf2/HO-1 axis. In conclusion, we found that D-6-G could inhibit NLRP3 inflammatory vesicle activity as well as cellular pyroptosis in NPCs and protect the ECM, suggesting the potential of D-6-G to delay IDD.

Stimuli-Responsive Delivery Systems for Intervertebral Disc Degeneration

As a major cause of low back pain, intervertebral disc degeneration is an increasingly prevalent chronic disease worldwide that leads to huge annual financial losses. The intervertebral disc consists of the inner nucleus pulposus, outer annulus fibrosus, and sandwiched cartilage endplates. All these factors collectively participate in maintaining the structure and physiological functions of the disc. During the unavoidable degeneration stage, the degenerated discs are surrounded by a harsh microenvironment characterized by acidic, oxidative, inflammatory, and chaotic cytokine expression. Loss of stem cell markers, imbalance of the extracellular matrix, increase in inflammation, sensory hyperinnervation, and vascularization have been considered as the reasons for the progression of intervertebral disc degeneration. The current treatment approaches include conservative therapy and surgery, both of which have drawbacks. Novel stimuli-responsive delivery systems are more promising future therapeutic options than traditional treatments. By combining bioactive agents with specially designed hydrogels, scaffolds, microspheres, and nanoparticles, novel stimuli-responsive delivery systems can realize the targeted and sustained release of drugs, which can both reduce systematic adverse effects and maximize therapeutic efficacy. Trigger factors are categorized into internal (pH, reactive oxygen species, enzymes, etc.) and external stimuli (photo, ultrasound, magnetic, etc.) based on their intrinsic properties. This review systematically summarizes novel stimuli-responsive delivery systems for intervertebral disc degeneration, shedding new light on intervertebral disc therapy.

Research on the role and mechanism of IL-17 in intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is one of the primary causes of low back pain (LBP), which seriously affects patients' quality of life. In recent years, interleukin (IL)-17 has been shown to be highly expressed in the intervertebral disc (IVD) tissues and serum of patients with IDD, and IL-17A has been shown to promote IDD through multiple pathways. We first searched databases such as PubMed, Cochrane, Embase, and Web of Science using the search terms "IL-17 or interleukin 17″ and "intervertebral discs". The search period ranged from the inception of the databases to December 2023. A total of 24 articles were selected after full-text screening. The main conclusion of the clinical studies was that IL-17A levels are significantly increased in the IVD tissues and serum of IDD patients. The results from the in vitro studies indicated that IL-17A can activate signaling pathways such as the NF-κB and MAPK pathways; promote inflammatory responses, extracellular matrix degradation, and angiogenesis; and inhibit autophagy in nucleus pulposus cells. The main finding of the in vivo experiments was that puncture of animal IVDs resulted in elevated levels of IL-17A within the IVD, thereby inducing IDD. Clinical studies, in vitro experiments, and in vivo experiments confirmed that IL-17A is closely related to IDD. Therefore, drugs that target IL-17A may be novel treatments for IDD, providing a new theoretical basis for IDD therapy.

Stepwise reduction of bony density in patients induces a higher risk of annular tears by deteriorating the local biomechanical environment

BACKGROUND CONTEXT

The relationship between osteoporosis and intervertebral disc degeneration (IDD) remains unclear. Considering that annular tear is the primary phenotype of IDD in the lumbar spine, the deteriorating local biomechanical environment may be the main trigger for annular tears.

PURPOSE

To investigate whether poor bone mineral density (BMD) in the vertebral bodies may increase the risk of annular tears via the degradation of the local biomechanical environment.

STUDY DESIGN

This study was a retrospective investigation with relevant numerical mechanical simulations.

PATIENT SAMPLE

A total of 64 patients with low back pain (LBP) and the most severe IDD in the L4-L5 motion segment were enrolled.

OUTCOME MEASURES

Annulus integration status was assessed using diffusion tensor fibre tractography (DTT). Hounsfield unit (HU) values of adjacent vertebral bodies were employed to determine BMD. Numerical simulations were conducted to compute stress values in the annulus of models with different BMDs and body positions.

METHODS

The clinical data of the 64 patients with low back pain were collected retrospectively. The BMD of the vertebral bodies was measured using the HU values, and the annulus integration status was determined according to DTT. The data of the patients with and without annular tears were compared, and regression analysis was used to identify the independent risk factors for annular tears. Furthermore, finite element models of the L4-L5 motion segment were constructed and validated, followed by estimating the maximum stress on the post and postlateral interfaces between the superior and inferior bony endplates (BEPs) and the annulus.

RESULTS

Patients with lower HU values in their vertebral bodies had significantly higher incidence rates of annular tears, with decreased HU values being an independent risk factor for annular tears. Moreover, increased stress on the BEP-annulus interfaces was associated with a stepwise reduction of bony density (ie, elastic modulus) in the numerical models.

CONCLUSIONS

The stepwise reduction of bony density in patients results in a higher risk of annular tears by deteriorating the local biomechanical environment. Thus, osteoporosis should be considered to be a potential risk factor for IDD biomechanically.

Comprehensive analysis of gene expression profiles of annulus fibrosus subtypes and hub genes in intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) has been considered a major cause of low back pain. Therefore, further molecular subtypes of IVDD and identification of potential critical genes are urgently needed. First, consensus clustering was used to classify patients with IVDD into two subtypes and key module genes for subtyping were identified using weighted gene co-expression network analysis (WGCNA). Then, key module genes for the disease were identified by WGCNA. Subsequently, SVM and GLM were used to identify hub genes. Based on the above genes, a nomogram was constructed to predict the subtypes of IVDD. Finally, we find that ROM1 is lowered in IVDD and is linked to various cancer prognoses. The present work offers innovative diagnostic and therapeutic biomarkers for molecular subtypes of IVDD.

Future of low back pain: unravelling IVD components and MSCs' potential

Low back pain (LBP) mainly emerges from intervertebral disc (IVD) degeneration. However, the failing mechanism of IVD ́s components, like the annulus fibrosus (AF) and nucleus pulposus (NP), leading to IVD degeneration/herniation is still poorly understood. Moreover, the specific role of cellular populations and molecular pathways involved in the inflammatory process associated with IVD herniation remains to be highlighted. The limited knowledge of inflammation associated with the initial steps of herniation and the lack of suitable models to mimic human IVD ́s complexity are some of the reasons for that. It has become essential to enhance the knowledge of cellular and molecular key players for AF and NP cells during inflammatory-driven degeneration. Due to unique properties of immunomodulation and pluripotency, mesenchymal stem cells (MSCs) have attained diverse recognition in this field of bone and cartilage regeneration. MSCs therapy has been particularly valuable in facilitating repair of damaged tissues and may benefit in mitigating inflammation' degenerative events. Therefore, this review article conducts comprehensive research to further understand the intertwine between the mechanisms of action of IVD components and therapeutic potential of MSCs, exploring their characteristics, how to optimize their use and establish them safely in distinct settings for LPB treatment.

Nucleus high intensity in the T2-weighted MRI is a potential predictor of annulus tear in cervical injured patients: a case comparative study

BACKGROUND

Segmental fusion operations assume paramount significance for individuals afflicted by full layers of annulus tears as they avert the perils of rapid disc degeneration and segmental instability. Structures with high signal intensity in the T2-weighted MRI can predict potential damage to the injured segment. Since local structures are shortly related biomechanically, this may be an effective predictor for annulus tears.

METHODS

A retrospective analysis of the clinical data of 57 patients afflicted by cervical injuries and subjected to single-segment ACDF has been performed in this study. The surgeon performed intraoperative exploration to assess the integration status of the annulus. The signal intensity of the prevertebral space, nucleus, and injured vertebral bodies were judged in the T2-weighted imaging data. Regression analyses identified independent predictors for annulus tears, and the area under the receiver operating characteristic curve (AUC) was computed to evaluate the predictive performance of potential independent predictors.

RESULTS

The occurrence of nucleus high intensity was significantly higher among individuals with annulus tears, and the nucleus high intensity was deemed an independent predictor for determining the presence of intraoperative visible annulus tears in patients with cervical injuries. AUC for nucleus high intensity was calculated as 0.717, with a corresponding p-value less than 0.05.

CONCLUSIONS

In the realm of diagnosing annulus tears in injured cervical patients, nucleus high intensity in the T2-weighted MRI emerges as a promising predictive factor. Notably, this applies specifically to patients devoid of fracture and visible annulus tears in their MRI scans. Such positive outcomes should be regarded as prospective indications for ACDF.

Discogenic Low Back Pain: Anatomy, Pathophysiology and Treatments of Intervertebral Disc Degeneration

Intervertebral disc (IVD) degeneration is a major contributing factor for discogenic low back pain (LBP), causing a significant global disability. The IVD consists of an inner core proteoglycan-rich nucleus pulposus (NP) and outer lamellae collagen-rich annulus fibrosus (AF) and is confined by a cartilage end plate (CEP), providing structural support and shock absorption against mechanical loads. Changes to degenerative cascades in the IVD cause dysfunction and instability in the lumbar spine. Various treatments include pharmacological, rehabilitation or surgical interventions that aim to relieve pain; however, these modalities do not halt the pathologic events of disc degeneration or promote tissue regeneration. Loss of stem and progenitor markers, imbalance of the extracellular matrix (ECM), increase of inflammation, sensory hyperinnervation and vascularization, and associated signaling pathways have been identified as the onset and progression of disc degeneration. To better understand the pain originating from IVD, our review focuses on the anatomy of IVD and the pathophysiology of disc degeneration that contribute to the development of discogenic pain. We highlight the key mechanisms and associated signaling pathways underlying disc degeneration causing discogenic back pain, current clinical treatments, clinical perspective and directions of future therapies. Our review comprehensively provides a better understanding of healthy IVD and degenerative events of the IVD associated with discogenic pain, which helps to model painful disc degeneration as a therapeutic platform and to identify signaling pathways as therapeutic targets for the future treatment of discogenic pain.

Effects of Different Parameter Settings for 3D Data Smoothing and Mesh Simplification on Near Real-Time 3D Reconstruction of High Resolution Bioceramic Bone Void Filling Medical Images

Three-dimensional reconstruction plays a vital role in assisting doctors and surgeons in diagnosing the healing progress of bone defects. Common three-dimensional reconstruction methods include surface and volume rendering. As the focus is on the shape of the bone, this study omits the volume rendering methods. Many improvements have been made to surface rendering methods like Marching Cubes and Marching Tetrahedra, but not many on working towards real-time or near real-time surface rendering for large medical images and studying the effects of different parameter settings for the improvements. Hence, this study attempts near real-time surface rendering for large medical images. Different parameter values are experimented on to study their effect on reconstruction accuracy, reconstruction and rendering time, and the number of vertices and faces. The proposed improvement involving three-dimensional data smoothing with convolution kernel Gaussian size 5 and mesh simplification reduction factor of 0.1 is the best parameter value combination for achieving a good balance between high reconstruction accuracy, low total execution time, and a low number of vertices and faces. It has successfully increased reconstruction accuracy by 0.0235%, decreased the total execution time by 69.81%, and decreased the number of vertices and faces by 86.57% and 86.61%, respectively.