Vascularization of the human intervertebral disc: A scoping review

A suture technique combining annulus fibrosis with posterior longitudinal ligament for lumbar disc herniation under endoscopy

Purpose

To investigate the clinical feasibility, efficacy and safety of a suture technique combining annulus fibrosus with posterior longitudinal ligament under full endoscopy in patients with lumbar disc herniation.

Methods

Retrospective case-control study. A total of 412 patients with lumbar disc herniation treated in our hospital from January 2020 to November 2022 were enrolled and analyzed. There were 208 males and 204 females, aged from 26 to 54 years old(average 39.9 ± 5.1). 208 patients were treated with combining annulus fibrous suture with posterior longitudinal ligament after percutaneous lumbar discectomy(PELD) (observation group)0.204 patients were treated with percutaneous lumbar discectomy(PELD) alone(control group). Operation time, blood loss, Visual Analogue scale(VAS), Oswestry disability index(ODI),Japanese Orthopedic Association(JOA), modified MacNab criteria and imaging examination were used to evaluate.

Results

All the 412 patients successfully completed the surgery. Complete follow-up time was 12-18 months, with an average of 15.2 ± 1.6 months. Postoperative symptoms were all significantly relieved. There was no statistically significant difference in baseline data between groups (P > 0.05). The scores of VAS,ODI and JOA at different postoperative follow-up visits were significantly lower than those before surgery (P < 0.05). There was significant difference in each group before and after surgeries (P < 0.05). The postoperative recurrence rates and reoperation rates between groups were significant different(P < 0.05). According to MacNab, the excellent and good rate was 96.2 % (200/208) in observation group and 90.7 % (185/204) in control group(P < 0.05).

Conclusions

The suture technique combining annulus fibrosus with posterior longitudinal ligament under full endoscopy in patients with lumbar disc herniation has satisfactory short- and mid-term clinical effect,and can effectively reduce postoperative recurrence rate, which is a safe and ideal suture technique for annulus fibrosus rupture.

Clinical trial number

not applicable.

Manipulation of Oxygen Tension in Damaged Regions via Hypoxia-Induced IPN Hydrogel Microspheres for Intervertebral Disc Regeneration

Disruption of low oxygen tension homeostasis during intervertebral disc degeneration inhibits endogenous stem cell viability and function, posing a challenge for endogenous regeneration. Here, to achieve sustained hypoxia manipulation, constructed hypoxia-inducible interpenetrating polymer network (IPN) hydrogel microspheres (HIMS) are constructed by microfluidics to integrate the hypoxic system with a stabilizing network. The IPN is synthesized through a two-step polymerization process, consisting of rapid photo-crosslinked gelatin methacrylate anhydride (GM) polymer I and slow enzyme-crosslinked vanillin-grafted gelatin (GV) polymer II. The enzymatic reaction between GV and laccase is able to create a hypoxic microenvironment to modulate oxygen tension in situ within the injured region. HIMS can reduce microenvironmental oxygen tension by 1/3 and maintain a hypoxic microenvironment for up to 5 days, thereby activating the PI3K/AKT/HIF-1α signaling pathway in endogenous stem cells to promote differentiation into nucleus pulposus-like cells. Additionally, NSC-Exos are loaded onto HIMS to trigger endogenous progenitor/stem cell recruitment and migration. Both in vitro and in vivo assays demonstrate that NSC-Exos@HIMS facilitates stem cell recruitment, targets differentiation, and stimulates extracellular matrix synthesis. Overall, the microspheres established herein provide a novel strategy for manipulating oxygen tension and enhancing endogenous tissue regeneration in injured regions during intervertebral disc degeneration.

NanoCRISPR-assisted biomimetic tissue-equivalent patch regenerates the intervertebral disc by inhibiting endothelial-to-mesenchymal transition

The integrity of the intervertebral disc (IVD), an immune-privileged organ protected by the blood-disc barrier, is compromised following annulus fibrosus (AF) injury. This breach facilitates angiogenesis, immune cell infiltration, and inflammation, accelerating intervertebral disc degeneration (IDD) and resulting in various clinical disorders. Current treatments fail to adequately address biological repair of AF defects and angiogenesis. Single-cell RNA sequencing analyses reveal that vascular endothelial growth factor (VEGF), secreted by IDD-associated fibrochondrocytes, is crucial in promoting angiogenesis by inducing endothelial-to-mesenchymal transition (EndoMT). This study proposes a nano-clustered regularly interspaced short palindromic repeats (CRISPR)-assisted AF patch with an aligned, polydopamine-modified nano-lamellae nanofibrous scaffold that replicates the hierarchical structure of natural AF, providing a conducive microenvironment for AF repair. A zeolitic imidazolate framework-8-based nanoCRISPR system encapsulates the CRISPR/CRISPR-associated protein 9 complex to target and eliminate VEGF-mediated angiogenic factors. In vitro studies demonstrate that the nanoCRISPR-assisted patch can enhance AF cell adhesion and migration, promote extracellular matrix deposition, knock out VEGF expression, and inhibit EndoMT. In vivo studies show its significant efficacy in promoting AF repair, inhibiting abnormal angiogenesis, and delaying IDD progression. This study presents a promising approach for structural and biological AF regeneration, addressing physical and angiogenic barriers in IVD regeneration.

Inflammatory Bowel Disease as a Risk Factor for Complications and Revisions Following Lumbar Discectomy

Study DesignRetrospective cohort study.ObjectivesPatients with IBD are at an increased risk for postoperative complications following surgery. The goal of this study is to investigate if inflammatory bowel disease (IBD) is a risk factor for complications following lumbar discectomy.MethodsWe identified IBD patients who underwent lumbar discectomy for lumbar disc herniation (LDH) and matched to them with controls without IBD in a1:5 ratio. We excluded patients with a history of spinal injury, cancer, infection, trauma, or surgery to remove the digestive tract. We used multivariate logistic regression analyses to compare postoperative outcomes, including 90-day complications, 90-day emergency department visits, and 90-day readmissions. In addition, 2-year re-discectomy rates and a 3-year lumbar fusion rate were compared between the cohorts.ResultsAfter applying the study criteria, we identified 6134 IBD patients with LDH for further analysis. With the exception of dura tears, patients with IBD had significantly higher rates of medical complications, incision-related complications, ED visits, and readmission rates compared to patients without IBD, especially for the 2-year and 3-year rates of disc recurrence and revision surgery.ConclusionsPatients with IBD who underwent lumbar discectomy are at a significantly higher rate of complications. Therefore, spine surgeons and other health care providers should be aware of this higher risk associated with IBD patients and properly treat the patients' IBD before surgery to lower these risks.

Harnessing Thrombospondin-1-Enabled Decellularized Nucleus Pulposus Matrices and Elastin-Like Recombinamers to Rebuild an Avascular Analogue of the Intervertebral Disc

With the degeneration of the intervertebral disc (IVD), the ingrowth of vascular and neural structures occurs. Both nerves and blood vessels engage in the development of inflammation and the onset of discogenic pain. The present study aimed to produce a hierarchical biomaterial capable of inhibiting angiogenesis by emulating the microenvironment of non-degenerated IVDs. To this end, we have incorporated an angiogenesis modulator-thrombospondin-1 (TSP-1) into a three-dimensional (3D) hydrogel network containing decellularized nucleus pulposus (dNPs) and azide-cyclooctyne modified elastin-like recombinamers (ELRs). Following the decellularization of nucleus pulposus (NPs) isolated from bovine tissues, pre-gels (pGs) were assembled based on the acid-pepsin extraction of soluble collagens found in the dNPs. Given the inherent affinity of these macromolecules to TSP-1, which was corroborated by immunohistochemical analysis and FT-IR spectroscopy, the pGs were supplemented with two concentrations of TSP-1. Angiogenesis was evaluated using the chick chorioallantoic membrane (CAM) in vivo model. Conjugation of TSP-1 with the pGs resulted in a synergistic suppression of blood vessel formation. Complexation with the ELRs improved the viscoelastic moduli and the structural stability of the hydrogels, which maintained their hydration and osmolarity properties due to the presence of the dNPs. When placed in direct contact with human primary fibroblasts, the materials displayed high cytocompatibility and tunable degradation rates. Our findings indicate that TSP-1-enabled dNP-derived pGs inhibit angiogenesis in vivo, while the presence of the ELRs aids in improving the mechanical properties of the hydrogels, thus providing a platform for rebuilding an avascular analogue of the healthy IVD.

Engineering extracellular matrix-based hydrogels for intervertebral disc regeneration

Lower back pain (LBP) is a major health concern, especially in older adults. A key aetiological factor is intervertebral disc (IVD) degeneration. It is mediated by dysregulation of extracellular matrix (ECM) and inflammation. In recent years, regenerative therapies have garnered attention for their potential to restore disc function by addressing the underlying biological alterations within the IVD. This review focuses on the comprehensive understanding of the anatomy and physiology of the IVD, highlighting its life cycle from embryonic development, and maturation to degenerative phenotype. We describe current treatments for managing LBP caused by IVD degeneration. This review emphasizes on the recent advancements in hydrogel engineering, highlighting natural, synthetic, and composite hydrogels and their application in ECM-targeted regenerative therapy for IVD degeneration. By exploring innovations in hydrogel technology, including improvements in crosslinking techniques and controlled degradation rates-we discuss how these materials could enhance IVD regeneration and potentially be used for the management of LBP. With their enhanced biomimicry, hydrogel-based ECM mimics offer a promising pathway for developing effective, durable therapies that address the root causes of disc degeneration, providing new hope for individuals living with chronic LBP.

Exploring the role of gut microbiota in intervertebral disc degeneration: insights from bidirectional Mendelian randomization analysis

OBJECTIVE

Although previous studies have indicated a potential association between the gut microbiota and intervertebral disc degeneration (IVDD), the precise nature of this relationship remains unclear. The objective of this study is to further explore the potential causal relationship between gut microbiota and IVDD using a bidirectional Mendelian randomization approach, with the aim of identifying potential microbial characteristics associated with IVDD.

METHODS

Using the data from genome-wide association studies (GWAS) involving 412 gut microbiota species and 227,388 controls and 29,508 cases of IVDD. Inverse variance weighted (IVW) was used as the primary Mendelian randomization (MR) analysis, complemented by weighted median, MR-Egger regression, weighted mode and simple mode methods. Extensive sensitivity analyses were performed to confirm the robustness of the results and to assess heterogeneity and horizontal pleiotropy.

RESULTS

This study revealed a positive genetic predisposition between 6 types of gut microbiota and IVDD through the IVW method, indicating that increased levels of these microbiota may lead to a higher risk of IVDD. Conversely, 6 types of gut microbiota were found to have negative effects on IVDD, suggesting that increased levels of these microbiota may have a protective effect against IVDD. Reverse MR analysis results revealed such possibilities as 1 positive and 5 negative causal relationships between IVDD and gut microbiota. The results of Cochran's Q test, MR-Egger regression, and MR-PRESSO analysis from the bidirectional Mendelian randomization all yielded p-values greater than 0.05, indicating that there is no significant heterogeneity or pleiotropy in the genetic effect analysis between gut microbiota and IVDD.

CONCLUSION

We used a bidirectional Mendelian randomization approach to identify various gut microbiota associated with IVDD. Our findings lay the foundation for further exploration of the pathogenesis and treatment strategies of gut microbiota and IVDD, and provide new possibilities for research on biomarkers of IVDD-related metabolic microbiota.

Regional-Specific Decellularized Meniscus Extracellular Matrix Elastic Nanofiber Aerogels Regulate Meniscal Regeneration and Vascularization

The meniscus is a heterogeneous structure with spatial distribution of cells and vessels. Promoting meniscus healing remains challenging, especially in its avascular inner region. The ideal repair mode shall promote meniscus repair while maintaining local avascularity to prevent pathological changes from vascular invasion. Given the natural biochemical components of native meniscus, decellularized meniscus extracellular matrix (dmECM) shows promise for meniscus repair. Compared to homogeneous dmECM, regional-specific dmECM (RS-dmECM) appears to offer greater potential for constructing heterogeneous meniscus structures. Furthermore, there is currently no study on the effects of RS-dmECM on vascularization. Thus, RS-dmECM is prepared and found dmECM-Outer induced stem cells fibrochondrogenic differentiation, while dmECM-Inner induced the chondrogenic differentiation and inhibited angiogenesis through suppressing the peroxisome proliferators-activated receptors signaling pathway. Subsequently, regional-specific poly(lactic acid)/gelatin/dmECM elastic 3D nanofiber aerogels (PG-dmECM) are fabricated to repair meniscal avascular area defects in a rabbit model. The PG-Outer promotes meniscal fibrocartilage regeneration without a significant effect on vascular invasion. In contrast, the PG-Inner achieves meniscal cartilage regeneration and inhibits vascular invasion. Moreover, the compressive stress can reach 117 kPa, comparable to that of the avascular area. This PG-Inner may have the potential to promote meniscal cartilage regeneration and prevent pathological changes within the avascular area.

New complex cell junctions in and around the intervertebral discs discovered using autoantibodies from patients affected by endemic pemphigus foliaceus in El Bagre, Colombia, South America

BACKGROUND

Traditionally, the intervertebral disks' (IVD) nucleus pulposus (NP) and annulus fibrosus (AF) are considered to have few cellular components and cell junctions. Patients affected by a new variant of endemic pemphigus foliaceus in El Bagre, Colombia, experience back pain in the spinal areas of the lower and upper back. Here, we investigate the reactivity of the patient's autoantibodies to structures in and around the IVDs at the cellular level.

METHODS

We first administered a questionnaire and performed a medical examination. We then tested for autoreactivity against IVDs by indirect immunofluorescence, confocal microscopy, and reflectance confocal microscopy using bovine and human tissues as antigen sources. We tested 45 sera from patients affected by the disease and 45 control sera from the endemic area matched by age, gender, demographics, and work activity.

RESULTS

Most of the patient sera revealed polyclonal antibodies against newly discovered cell junctions in the NP and AF, including their translamellar cross-bridges. Additional reactivities were detected against cell junctions in the spinal cord neurons, paraspinal nerves, blood vessels, anterior and posterior longitudinal ligaments, and paraspinal skeletal muscles. The reactivities of the patient's autoantibodies co-localized with those of commercially available antibodies to desmoplakins I-II, armadillo repeat gene deleted in velo-cardio-facial syndrome, plakophilin-4, and myocardium-enriched zonula occludens-1-associated protein (p < 0.001).

CONCLUSIONS

We discovered novel complex cell junctions in the IVDs using patients' autoantibodies. These discoveries open a new chapter in the knowledge of IVD, representing a breakthrough pertinent to many diseases.

Beyond a ferroptosis inducer: erastin can suppress nutrient deprivation induced cell death in the intervertebral disc

BACKGROUND

Erastin has been found to induce ferroptosis; however, whether erastin may have roles other than ferroptosis inducer in cells is unknown. Nutrient deficiency is one of the major causes of many diseases including intervertebral disc (IVD) degeneration.

PURPOSE

The current study investigates the effect of erastin in nucleus pulposus cells under nutrient deprivation condition.

STUDY DESIGN

Experiment in vitro and ex vivo.

METHODS

The effect of erastin on the cell survival of nucleus pulposus cells was evaluated in fetal bovine serum (FBS) and glucose deprivation condition. RSL3 and ferrostatin-1 were applied to illustrate whether the effect of erastin is ferroptosis dependent. The involvement of solute carrier family 7, membrane 11(SLC7A11), autophagy as well as mechanistic target of rapamycin kinase complex 1(mTORC1) and transcription factor EB (TFEB) were assessed to demonstrate the working mechanism of erastin.

RESULTS

Erastin may induce cell death at the concentration of ≥ 5μM; however, it may protect nucleus pulposus cells against nutrient deprivation induced cell death at lower concentration (0.25-1μM) and the effect of erastin is ferroptosis independent. The mechanism study showed that the effect of erastin may relate to its SCL7A11 regulation, as SCL7A11 knock-down may have the similar effect as erastin. Furthermore, it was also demonstrated that mTORC1-TFEB mediated autophagy was involved in protective effect of erastin.

CONCLUSIONS

Low dose erastin may promote cell survival under nutrient deprivation condition, and its effect is ferroptosis independent; erastin may exert its protective effect through mTORC1-TFEB mediated autophagy regulation.

CLINICAL SIGNIFICANCE

Nutrient deprivation is a major contributor to intervertebral disc degeneration. Our in vitro and ex vivo study showed that low dose of erastin may suppress nutrient deprivation induced cell death in IVD degeneration. Although it was not validated in vivo model due to lack of in vivo nutrient deprivation induced IVD degeneration model currently, this study may still provide a potential therapeutic option for IVD degeneration, which of cause need further validation.

Characterization of bone & cartilage endplate junction in the human lumbar spine: novel ultrastructural insights & association with elemental composition, vascularity and degeneration

OBJECTIVE

Intervertebral disc (IVD)-related pathology is associated with integrity of cartilaginous endplate (CEP), bony endplate (BEP) and their junction. However, ultrastructural details of the CEP, BEP and IVD and their interplay with disc degenerative features such as fissures and calcification are understudied. The current study aimed to ultra structurally explore CEP-BEP junction to IVD features.

METHODS

Fifty-nine lumbar motion segments from 13 male human cadavers (range, 21-80 years of age) were analyzed macroscopically, histologically and through scanning electron microscope. The fissures present in CEP & IVD and gaps at the junction of CEP-BEP & CEP-IVD were measured and correlated with calcification, vascular channels and disc degeneration. Energy-dispersive X-ray analysis (EDX) provided the elemental composition of the CEP, BEP and IVD.

RESULTS

Ultrastructural analysis revealed gaps at the CEP-BEP junction which were occasionally bridged by fine fibrillar adhesions. These junctional gap-width were in significant positive correlation with age (p = 0.001), spinal-level (p = 0.01), severity of disc degeneration (p < 0.001) and IVD calcification (p < 0.001). The vascular channels of BEP around the CEP were in significant positive correlation with age (p = 0.003), junctional gap-width (p < 0.001) & severity of disc degeneration (p < 0.001). EDX distribution of calcium in CEP was also associated significantly with junctional gap-width & vascularity (p = 0.03, p = 0.04, respectively).

CONCLUSION

This is the first study to ultrastructurally assess and map lumbar CEP, BEP and IVD in humans, noting discovery of specific phenotypic patterns of intradiscal calcification, fissures, vascularity and degeneration severity as associated with novel anatomical structures of "adhesion bridges and gaps" which are implicated in marked inflammation and pain.

Proteomic profiling of human plasma and intervertebral disc tissue reveals matrisomal, but not plasma, biomarkers of disc degeneration

BACKGROUND

Intervertebral disc (IVD) degeneration is a common cause of low back pain, and the most symptomatic patients with neural compression need surgical intervention to relieve symptoms. Current techniques used to diagnose IVD degeneration, such as magnetic resonance imaging (MRI), do not detect changes in the tissue extracellular matrix (ECM) as degeneration progresses. Improved techniques, such as a combination of tissue and blood biomarkers, are needed to monitor the progression of IVD degeneration for more effective treatment plans.

METHODS

To identify tissue and blood biomarkers associated with degeneration progression, we histologically graded 35 adult human degenerate IVD tissues and matched plasma from the individuals into two groups: mild degenerate and severe degenerate. Mass spectrometry was utilised to characterise proteomic differences in tissue and plasma between the two groups. Top differentially distributed proteins were further validated using immunohistochemistry and qRT-PCR. Additionally, correlational analyses were conducted to define similarities and differences between tissue and plasma protein changes in individuals with mild and severe IVD degeneration.

RESULTS

Our data revealed that the abundance of 31 proteins was significantly increased in severe degenerated IVD tissues compared to mild. Functional analyses showed that more than 40% of these proteins were matrisome-related, indicating differences in ECM protein composition between severe and mild degenerate IVD tissues. We confirmed adipocyte enhancer-binding protein 1 (AEBP1) as one of the most significantly enriched core matrisome genes and proteins as degeneration progressed. Compared to others, AEBP1 protein levels best distinguished between mild and severe degenerated IVD tissues with an area under the curve score of 0.768 (95% CI: 0.60-0.93). However, we found that protein changes from associated plasma exhibited a weak relationship with histological grading and AEBP1 tissue levels. Given that systemic plasma changes are complex, a larger sample cohort may be required to identify patterns in blood relating to IVD degeneration progression.

CONCLUSIONS

In this study, we have identified AEBP1 as a tissue marker for monitoring the severity of disc degeneration in humans. Further work to link alterations in tissue AEBP1 levels to changes in blood-related proteins will be beneficial for detailed monitoring of IVD degeneration thereby enabling more personalised treatment approaches.

Human molecular mechanisms of discogenic low back pain: A scoping review

The limited understanding of the mechanisms underlying human discogenic low back pain (DLBP) has hampered the development of effective treatments. While there is much research on disc degeneration, the association between degeneration and pain is weak. Therefore, there is an urgent need to identify pain-inducing molecular mechanism to facilitate the development of mechanism-specific therapeutics. This scoping review aims to determine the current knowledge of molecular mechanisms associated with human DLBP. A systematic search on CENTRAL, CINAHL, Citation searching, ClinicalTrials.gov, Embase, Google Scholar, MEDLINE, PsycINFO, PubMed, Scopus, Web of Science, and World Health Organization was performed. Studies with human DLBP as diagnosed by discography or imaging that analyzed human disc tissues and reported pain-related outcomes were included, and those on predominant radicular pain were excluded. The search returned 6012 studies. Most studies did not collect pain-related outcomes. Those that included pain assessment relied on self-report of pain intensity and disability. Six studies qualified for data extraction and synthesis. The main molecular mechanisms associated with DLBP were the expressions of nociceptive neuropeptides and cytokines, particularly TNF-αdue to its strong association with pain outcomes. Activation of NF-κB signaling pathway, alterations in adrenoceptor expressions, and increase in reactive oxygen species (ROS) were also associated with DLBP through regulation of pro-inflammatory factors and pain-related neuropeptides. Current evidence converges to TNF-α, NF-κB signaling, and ROS-induced pro-inflammation. Major weaknesses in the current literature are the focus on degeneration without pain phenotyping, and lack of association of molecular findings with pain outcomes. PERSPECTIVE: This scoping review identified TNF-α, NF-κB signaling, and ROS-induced pro-inflammation as relevant mechanisms of human discogenic low back pain. Major weaknesses in the current literature are the focus on degeneration without pain phenotyping, and lack of association of molecular findings with pain outcomes.

Microplastics in human skeletal tissues: Presence, distribution and health implications

Although microplastics have been detected in human blood, placenta and other tissues. In this study, for the first time, we characterized the presence and variation of microplastic deposition patterns in three human skeletal tissues, namely the bone, cartilage, and intervertebral discs. Forty microplastic fragments were observed in 24 samples from the bone, cartilage, and intervertebral disc, ranging from 25.44 to 407.39 μm in diameter. The deposition abundance of microplastics in the human intervertebral disc (61.1 ± 44.2 particles/g) was higher than those in the bone (22.9 ± 15.7 particles/g) and cartilage tissue (26.4 ± 17.6 particles/g). The average sizes of microplastics in intervertebral discs (159.5 ± 103.8 μm) and bone (138.86 ± 105.67 μm) were larger than that in the cartilage tissue (87.5 ± 30.7 μm). The most frequently identified polymers were polypropylene (35 %), ethylene vinyl acetate copolymer (30 %), and polystyrene (20 %). The in vivo experiment suggested that microplastics invaded the bone, cartilage, and intervertebral discs through blood circulation after 4 weeks of exposure. Serum levels of tumor necrosis factor-α (TNF-α), Type Ⅰ procollagen amino-terminal peptide (PINP), and tartrate-resistant acid phosphatase-5b (TRACP-5b) were elevated compared with those in the control group (p < 0.05). Our study suggests that microplastics invade the bone, cartilage, and intervertebral discs through the blood supply, causing distinct patterns of microplastic accumulation in these regions. Microplastic invasion can affect skeletal health by influencing the expression of inflammatory and bone morphogenetic cytokines. These findings provide insights into investigating the impact of microplastics on human skeletal health.

Sirt1 blocks nucleus pulposus and macrophages crosstalk by inhibiting RelA/Lipocalin 2 axis

Background

Intervertebral disc degeneration (IVDD) stands as a primary pathophysiological driver of low back pain, yet no therapeutic intervention effectively arrests its progression. Evidence shows that certain Sirt1 agonists may confer protective effects on intervertebral discs, but the underlying mechanisms remain unclear. This study aims to delineate the interaction between Sirt1 and the inflammatory microenvironment, offering potential novel avenues for IVDD prevention and treatment.

Methods

In vitro IL-1β-induced nucleus pulposus cells (NPCs) degenerative model and in vivo a mouse annulus fibrosus needle puncture model in Sirt1 transgenic (Sirt1TG) and the same litter WT mice were used to investigate the role of Sirt1 in homeostasis and inflammation. Mechanistic insights were obtained through RNA sequencing, co-immunoprecipitation (Co-IP), luciferase assays, and chromatin immunoprecipitation-(ChIP)-PCR. A co-culture system of Raw264.7 and NPCs was employed to assess the involvement of Lipocalin 2.

Results

Our study demonstrated reduced Sirt1 expression in degenerating human nucleus pulposus (NP) tissue. Both in vitro and in vivo data revealed that NP-specific overexpression of Sirt1 inhibited extracellular matrix degradation and inflammation. Mechanistically, Sirt1 suppressed the acetylation of RelA/p65 at lysine 310 and phosphorylation at serine 536, with the C-terminus of Sirt1 and the RHD-NLS domain of RelA mediating to their interaction. Furthermore, NPCs-derived Lipocalin 2 was identified as a cytokine involved in macrophage chemotaxis and M1 polarization to exacerbate inflammation.

Conclusion

Our work revealed that Sirt1 negatively regulates Lipocalin 2, thereby ameliorating the inflammatory milieu and blocking NPCs and macrophages crosstalk.

The Translational Potential of this Article

This study illuminates the crucial role and molecular mechanisms of Sirt1 in regulating the NP microenvironment. These insights shed light on strategies for the prevention and treatment of IVDD-related herniation and low back pain. By pinpointing specific biological targets, the screening of smallmolecule compounds with significant clinical implications can be facilitated. This translational innovation promises to optimize cells communication within intervertebral disc microenvironment via localized drug delivery, potentially improving patient outcomes and satisfaction following spinal fusion or discectomy surgeries.

Specific plasma biomarker signatures associated with patients undergoing surgery for back pain

BACKGROUND CONTEXT

Intervertebral disc degeneration (IDD) affects numerous people worldwide. The role of inflammation is increasingly recognized but remains incompletely resolved. Peripheral molecules could access neovascularized degenerated discs and contribute to the ongoing pathology.

PURPOSE

To assess a large array of plasma molecules in patients with IDD to identify biomarkers associated with specific spinal pathologies and prognostic biomarkers for the surgery outcome.

DESIGN

Prospective observational study combining clinical data and plasma measures.

PATIENT SAMPLE

Plasma samples were collected just before surgery. Extensive clinical data (age, sex, smoking status, Modic score, glomerular filtration rate, etc.) were extracted from clinical files from 83 patients with IDD undergoing spine surgery.

OUTCOME MEASURES

Recovery 2 months postsurgery as assessed by the treating neurosurgeon.

METHODS

Over 40 biological molecules were measured in patients' plasma using multiplex assays. Statistical analyses were performed to identify associations between biological and clinical characteristics (age, sex, Body Mass Index (BMI), smoking status, herniated disc, radiculopathy, myelopathy, stenosis, MODIC score, etc.) and plasma levels of biological molecules.

RESULTS

Plasma levels of Neurofilament Light chain (NfL) were significantly elevated in patients with myelopathy and spinal stenosis compared to herniated disc. Plasma levels of C- reactive protein (CRP), Neurofilament Light chain (NfL), and Serum Amyloid A (SAA) were negatively associated, while CCL22 levels were positively associated with an efficient recovery 2 months postsurgery.

CONCLUSIONS

Our results show that CRP and CCL22 plasma levels combined with the age of the IDD patient can predict the 2-month postsurgery recovery (Area Under the Curve [AUC]=0.883). Moreover, NfL could become a valuable monitoring tool for patients with spinal cord injuries.

Cervical spine infection arising from chronic paronychia: A case report and review of literature

BACKGROUND

Cervical spine pyogenic infection (CSPI) is a rare and challenging form of spinal infection that is typically caused by pyogenic bacteria and primarily affects the cervical vertebral bodies and surrounding tissues. Given its nonspecific symptoms, such as fever and neck pain, early diagnosis is crucial to prevent severe complications, including spinal cord injury. We report a previously unreported case of acute CSPI arising from chronic paronychia, exploring its diagnostic and therapeutic challenges through a review of the current literature.

CASE SUMMARY

The presented case involved a 15-year-old man with CSPI caused by Staphylococcus aureus, which led to complications including bacteremia and a paronychia-associated abscess. Acute pyogenic infection was initially diagnosed by typical symptoms and blood culture. Fever improved after antibiotic treatment while developing progressive limbs dysfunction. Six days after admission, the patient underwent anterior cervical debridement + autogenous iliac bone graft fusion + plate internal fixation and received 12 weeks of antibiotic treatment after the operation. Re-examination 3 years postoperatively showed that the patient had stable cervical fixation, no significant neck pain or upper limb abnormalities, and normal urinary function.

CONCLUSION

Early imaging findings, laboratory markers, and timely antibiotic treatment are crucial for CSPI management, preventing complications and facilitating recovery.

Alginate vs. Hyaluronic Acid as Carriers for Nucleus Pulposus Cells: A Study on Regenerative Outcomes in Disc Degeneration

Intervertebral disc degeneration is a leading cause of chronic low back pain, affecting millions globally. Regenerative medicine, particularly cell-based therapies, presents a promising therapeutic strategy. This study evaluates the comparative efficacy of two biomaterials-hyaluronic acid (HA) and alginate-as carriers for nucleus pulposus (NP) cell transplantation in a beagle model of induced disc degeneration. NP cells were isolated, cultured, and injected with either HA or alginate into degenerated discs, with saline and non-cell-loaded carriers used as controls. Disc height index, T2-weighted MRI, and histological analyses were conducted over a 12-week follow-up period to assess reparative outcomes. Imaging revealed that both carrier and cell-loaded treatments improved outcomes compared to degenerative controls, with cell-loaded carriers consistently outperforming carrier-only treated discs. Histological assessments supported these findings, showing trends toward extracellular matrix restoration in both treatment groups. While both biomaterials demonstrated reparative potential, HA showed greater consistency in supporting NP cells in promoting disc regeneration. These results underscore HA's potential as a superior carrier for NP cell-based therapies in addressing disc degeneration.

Unveiling the Gut-Disc Axis: How Microbiome Dysbiosis Accelerates Intervertebral Disc Degeneration

The gut microbiome (GM), often referred to as the second genome of the human body, plays a crucial role in various metabolic processes and mediates the development of numerous diseases. Intervertebral disc degeneration (IDD) is an age-related degenerative spinal disease characterized by the loss of disc height, hydration, and integrity, leading to pain and reduced mobility. Although the pathogenesis of IDD is not fully understood, recent studies suggest that dysbiosis of the gut microbiome may accelerate the progression of IDD through multiple mechanisms. This article begins by discussing the potential relationship between GM dysbiosis and human diseases, followed by a comprehensive review of the regulatory mechanisms of GM in skeletal diseases within the gut-disc axis framework. Furthermore, it explores three potential pathways through which GM dysbiosis may mediate the development of IDD: immunomodulation, bacterial translocation and colonization, and the decomposition and absorption of intestinal metabolites. These pathways can disrupt disc cell homeostasis and promote degenerative changes. Finally, this paper summarizes for the first time the potential therapeutic approaches for delaying IDD by targeting the gut-disc axis, providing new insights into the pathogenesis and regenerative repair strategies for IDD.

An anti-senescence hydrogel with pH-responsive drug release for mitigating intervertebral disc degeneration and low back pain

Oxidative stress and aging lead to progressive senescence of nucleus pulposus (NP) cells, resulting in intervertebral disc (IVD) degeneration (IVDD). In some cases, degenerative IVD can further cause low back pain (LBP). Several studies have confirmed that delaying and rejuvenating the senescence of NP cells can attenuate IVDD. However, the relatively closed tissue structure of IVDs presents challenges for the local application of anti-senescence drugs. Here, we prepared an anti-senescence hydrogel by conjugating phenylboronic acid-modified gelatin methacryloyl (GP) with quercetin to alleviate IVDD by removing senescent NP cells. The hydrogel exhibited injectability, biodegradability, prominent biocompatibility and responsive release of quercetin under pathological conditions. In vitro experiments demonstrated that the hydrogel could reduce the expression of senescence markers and restore the metabolic balance in senescent NP cells. In vivo studies validated that a single injection of the hydrogel in situ could maintain IVD tissue structure and alleviate sensitivity to noxious mechanical force in the rat models, indicating a potential therapeutic approach for ameliorating IVDD and LBP. This approach helps prevent potential systemic toxicity associated with systemic administration and reduces the morbidity resulting from repeated injections of free drugs into the IVD, providing a new strategy for IVDD treatment.

The Role of Microvascular Variations in the Process of Intervertebral Disk Degeneration and Its Regulatory Mechanisms: A Literature Review

Microvascular changes are considered key factors in the process of intervertebral disk degeneration (IDD). Microvascular invasion and growth into the nucleus pulposus (NP) and cartilaginous endplates are unfavorable factors that trigger IDD. In contrast, the rich distribution of microvessels in the bony endplates and outer layers of the annulus fibrosus is an important safeguard for the nutrient supply and metabolism of the intervertebral disk (IVD). In particular, the adequate supply of microvessels in the bony endplates is the main source of the nutritional supply for the entire IVD. Microvessels can affect the progression of IDD through a variety of pathways. Many studies have explored the effects of microvessel alterations in the NP, annulus fibrosus, cartilaginous endplates, and bony endplates on the local microenvironment through inflammation, apoptosis, and senescence. Studies also elucidated the important roles of microvessel alterations in the process of IDD, as well as conducted in-depth explorations of cytokines and biologics that can inhibit or promote the ingrowth of microvessels. Therefore, the present manuscript reviews the published literature on the effects of microvascular changes on IVD to summarize the roles of microvessels in IVD and elaborate on the mechanisms of action that promote or inhibit de novo microvessel formation in IVD.

Discogenic Low Back Pain: Anatomic and Pathophysiologic Characterization, Clinical Evaluation, Biomarkers, AI, and Treatment Options

Discogenic low back pain (LBP) is a significant clinical condition arising from degeneration of the intervertebral disc, a common yet complex cause of chronic pain, defined by fissuring in the annulus fibrosus resulting in vascularization of growing granulation tissue and growth of nociceptive nerve fibers along the laceration area. This paper delves into the anatomical and pathophysiological underpinnings of discogenic LBP, emphasizing the role of intervertebral disc degeneration in the onset of pain. The pathogenesis is multifactorial, involving processes like mitochondrial dysfunction, accumulation of advanced glycation end products, and pyroptosis, all contributing to disc degeneration and subsequent pain. Despite its prevalence, diagnosing discogenic LBP is challenging due to the overlapping symptoms with other forms of LBP and the absence of definitive diagnostic criteria. Current diagnostic approaches include clinical evaluations, imaging techniques, and the exploration of potential biomarkers. Treatment strategies range from conservative management, such as physical therapy and pharmacological interventions, to more invasive procedures such as spinal injections and surgery. Emerging therapies targeting molecular pathways involved in disc degeneration are under investigation and hold potential for future clinical application. This paper highlights the necessity of a multidisciplinary approach combining clinical, imaging, and molecular data to enhance the accuracy of diagnosis and the effectiveness of treatment for discogenic LBP, ultimately aiming to improve patient outcomes.

Assessment of Tie2-Rejuvenated Nucleus Pulposus Cell Transplants from Young and Old Patient Sources Demonstrates That Age Still Matters

Cell transplantation is being actively explored as a regenerative therapy for discogenic back pain. This study explored the regenerative potential of Tie2+ nucleus pulposus progenitor cells (NPPCs) from intervertebral disc (IVD) tissues derived from young (<25 years of age) and old (>60 years of age) patient donors. We employed an optimized culture method to maintain Tie2 expression in NP cells from both donor categories. Our study revealed similar Tie2 positivity rates regardless of donor types following cell culture. Nevertheless, clear differences were also found, such as the emergence of significantly higher (3.6-fold) GD2 positivity and reduced (2.7-fold) proliferation potential for older donors compared to young sources. Our results suggest that, despite obtaining a high fraction of Tie2+ NP cells, cells from older donors were already committed to a more mature phenotype. These disparities translated into functional differences, influencing colony formation, extracellular matrix production, and in vivo regenerative potential. This study underscores the importance of considering age-related factors in NPPC-based therapies for disc degeneration. Further investigation into the genetic and epigenetic alterations of Tie2+ NP cells from older donors is crucial for refining regenerative strategies. These findings shed light on Tie2+ NPPCs as a promising cell source for IVD regeneration while emphasizing the need for comprehensive understanding and scalability considerations in culture methods for broader clinical applicability.

Getting to the Core: Exploring the Embryonic Development from Notochord to Nucleus Pulposus

The intervertebral disc (IVD) is the largest avascular organ of the human body and plays a fundamental role in providing the spine with its unique structural and biomechanical functions. The inner part of the IVD contains the nucleus pulposus (NP), a gel-like tissue characterized by a high content of type II collagen and proteoglycans, which is crucial for the disc's load-bearing and shock-absorbing properties. With aging and IVD degeneration (IDD), the NP gradually loses its physiological characteristics, leading to low back pain and additional sequelae. In contrast to surrounding spinal tissues, the NP presents a distinctive embryonic development since it directly derives from the notochord. This review aims to explore the embryology of the NP, emphasizing the pivotal roles of key transcription factors, which guide the differentiation and maintenance of the NP cellular components from the notochord and surrounding sclerotome. Through an understanding of NP development, we sought to investigate the implications of the critical developmental aspects in IVD-related pathologies, such as IDD and the rare malignant chordomas. Moreover, this review discusses the therapeutic strategies targeting these pathways, including the novel regenerative approaches leveraging insights from NP development and embryology to potentially guide future treatments.

A comprehensive review of cell transplantation and platelet-rich plasma therapy for the treatment of disc degeneration-related back and neck pain: A systematic evidence-based analysis

Low back pain (LBP) and neck pain predominate as the primary causes of disability. Cell- and platelet-rich plasma (PRP) products are potential therapies with clinical trials and reviews promoting their efficacy. Nonetheless, they frequently disregard the clinical significance of reported improvements. In this systematic review, the effectuated improvements in pain, disability, quality of life (QoL), and radiographic images are comprehensively described and scored on their clinical significance. An electronic database literature search was conducted on July 2023 for in-human assessment of cell or PRP products to alleviate discogenic pain. Papers were screened on quantitative pain, disability, QoL, radiographic improvements, and safety outcomes. Risk of bias was assessed through MINORS and Cochrane Source of Bias tools. Reported outcomes were obtained, calculated, and assessed to meet minimal clinically important difference (MCID) standards. From 7623 screened papers, a total of 80 articles met the eligibility criteria, presenting 68 specific studies. These presented at least 1974 treated patients. Overall, cell/PRP injections could alleviate pain and disability, resulting in MCID for pain and disability in up to a 2-year follow-up, similar to those observed in patients undergoing spinal fusion. Included trials predominantly presented high levels of bias, involved heterogeneous study designs, and only a minimal number of randomized controlled trials. Nonetheless, a clear clinically significant impact was observed for cell- and PRP-treated cohorts with overall good safety profiles. These results highlight a strong therapeutic potential but also underline the need for future cost-effectiveness assessments to determine the benefits of cell/PRP treatments.

SOD2 orchestrates redox homeostasis in intervertebral discs: A novel insight into oxidative stress-mediated degeneration and therapeutic potential

Low back pain (LBP) is a pervasive global health concern, primarily associated with intervertebral disc (IVD) degeneration. Although oxidative stress has been shown to contribute to IVD degeneration, the underlying mechanisms remain undetermined. This study aimed to unravel the role of superoxide dismutase 2 (SOD2) in IVD pathogenesis and target oxidative stress to limit IVD degeneration. SOD2 demonstrated a dynamic regulation in surgically excised human IVD tissues, with initial upregulation in moderate degeneration and downregulation in severely degenerated IVDs. Through a comprehensive set of in vitro and in vivo experiments, we found a suggestive association between excessive mitochondrial superoxide, cellular senescence, and matrix degradation in human and mouse IVD cells. We confirmed that aging and mechanical stress, established triggers for IVD degeneration, escalated mitochondrial superoxide levels in mouse models. Critically, chondrocyte-specific Sod2 deficiency accelerated age-related and mechanical stress-induced disc degeneration in mice, and could be attenuated by β-nicotinamide mononucleotide treatment. These revelations underscore the central role of SOD2 in IVD redox balance and unveil potential therapeutic avenues, making SOD2 and mitochondrial superoxide promising targets for effective LBP interventions.

Bioenergetic dysfunction in the pathogenesis of intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is a frequent cause of low back pain and is the most common cause of disability. Treatments for symptomatic IVD degeneration, including conservative treatments such as analgesics, physical therapy, anti-inflammatories and surgeries, are aimed at alleviating neurological symptoms. However, there are no effective treatments to prevent or delay IVD degeneration. Previous studies have identified risk factors for IVD degeneration such as aging, inflammation, genetic factors, mechanical overload, nutrient deprivation and smoking, but metabolic dysfunction has not been highlighted. IVDs are the largest avascular structures in the human body and determine the hypoxic and glycolytic features of nucleus pulposus (NP) cells. Accumulating evidence has demonstrated that intracellular metabolic dysfunction is associated with IVD degeneration, but a comprehensive review is lacking. Here, by reviewing the physiological features of IVDs, pathological processes and metabolic changes associated with IVD degeneration and the functions of metabolic genes in IVDs, we highlight that glycolytic pathway and intact mitochondrial function are essential for IVD homeostasis. In degenerated NPs, glycolysis and mitochondrial function are downregulated. Boosting glycolysis such as HIF1α overexpression protects against IVD degeneration. Moreover, the correlations between metabolic diseases such as diabetes, obesity and IVD degeneration and their underlying molecular mechanisms are discussed. Hyperglycemia in diabetic diseases leads to cell senescence, the senescence-associated phenotype (SASP), apoptosis and catabolism of extracellualr matrix in IVDs. Correcting the global metabolic disorders such as insulin or GLP-1 receptor agonist administration is beneficial for diabetes associated IVD degeneration. Overall, we summarized the recent progress of investigations on metabolic contributions to IVD degeneration and provide a new perspective that correcting metabolic dysfunction may be beneficial for treating IVD degeneration.

Spinal infection caused by Aspergillus flavus in a diabetic: a case report and literature review

Spinal infections, notably those induced by Aspergillus flavus (A. flavus), represent a complex and uncommon clinical challenge. In individuals with diabetes mellitus, the risk is exacerbated due to a compromised immune response and a heightened vulnerability to non-standard pathogens. This case report chronicles the intricate diagnostic and treatment journey of a 59-year-old diabetic patient grappling with a spinal infection attributed to A. flavus. The diagnosis was delayed due to non-specific symptoms and unclear radiological signs. The administration of voriconazole, a targeted antifungal treatment, resulted in a significant clinical and radiological improvement, underscoring its effectiveness in treating such unusual fungal spinal infections; meanwhile, we found that terbinafine hydrochloride also has a similar effect in treating fungal spinal infections. This case underscores the importance of considering fungal causes in spinal infections among diabetic patients and highlights prompt diagnosis and individualized targeted antifungal therapy.

Burst Spinal Cord Stimulation as Compared With L2 Dorsal Root Ganglion Stimulation in Pain Relief for Nonoperated Discogenic Low Back Pain: Analysis of Two Prospective Studies

INTRODUCTION

Chronic discogenic low back pain (CD-LBP) is caused by degenerated disks marked by neural and vascular ingrowth. Spinal cord stimulation (SCS) has been shown to be effective for pain relief in patients who are not responsive to conventional treatments. Previously, the pain-relieving effect of two variations of SCS has been evaluated in CD-LBP: Burst SCS and L2 dorsal root ganglion stimulation (DRGS). The aim of this study is to compare the effectivity in pain relief and pain experience of Burst SCS with that of conventional L2 DRGS in patients with CD-LBP.

MATERIALS AND METHODS

Subjects were implanted with either Burst SCS (n = 14) or L2 DRGS with conventional stimulation (n = 15). Patients completed the numeric pain rating score (NRS) for back pain and Oswestry disability index (ODI) and EuroQoL 5D (EQ-5D) questionnaires at baseline, and at three, six, and 12 months after implantation. Data were compared between time points and between groups.

RESULTS

Both Burst SCS and L2 DRGS significantly decreased NRS, ODI, and EQ-5D scores as compared with baseline. L2 DRGS resulted in significantly lower NRS scores at 12 months and significantly increased EQ-5D scores at six and 12 months.

CONCLUSIONS

Both L2 DRGS and Burst SCS resulted in reduction of pain and disability, and increased quality of life in patients with CD-LBP. L2 DRGS provided significantly increased pain relief and improvement in quality of life when compared with Burst SCS.

CLINICAL TRIAL REGISTRATION

The clinical trial registration numbers for the study are NCT03958604 and NL54405.091.15.

Cartilaginous endplates: A comprehensive review on a neglected structure in intervertebral disc research

The cartilaginous endplates (CEP) are key components of the intervertebral disc (IVD) necessary for sustaining the nutrition of the disc while distributing mechanical loads and preventing the disc from bulging into the adjacent vertebral body. The size, shape, and composition of the CEP are essential in maintaining its function, and degeneration of the CEP is considered a contributor to early IVD degeneration. In addition, the CEP is implicated in Modic changes, which are often associated with low back pain. This review aims to tackle the current knowledge of the CEP regarding its structure, composition, permeability, and mechanical role in a healthy disc, how they change with degeneration, and how they connect to IVD degeneration and low back pain. Additionally, the authors suggest a standardized naming convention regarding the CEP and bony endplate and suggest avoiding the term vertebral endplate. Currently, there is limited data on the CEP itself as reported data is often a combination of CEP and bony endplate, or the CEP is considered as articular cartilage. However, it is clear the CEP is a unique tissue type that differs from articular cartilage, bony endplate, and other IVD tissues. Thus, future research should investigate the CEP separately to fully understand its role in healthy and degenerated IVDs. Further, most IVD regeneration therapies in development failed to address, or even considered the CEP, despite its key role in nutrition and mechanical stability within the IVD. Thus, the CEP should be considered and potentially targeted for future sustainable treatments.

Ultrasound-guided disc pain induction test for diagnosis of discogenic lumbar pain: a cross-sectional study

BACKGROUND

Several methods can be used to diagnose discogenic pain, but only discoblock can diagnose discogenic pain definitively. This study aimed to examine the usefulness of an ultrasound-guided disc pain induction test for a simple and accurate diagnosis of the culprit lesion.

METHODS

We included 41 patients with lumbar pain in whom pain was induced by an ultrasound-guided disc pain induction test. All patients had confirmed pain at L1/2 to L5/S1 based on an ultrasound-guided disc pain induction test and underwent X-ray photography and magnetic resonance imaging. Seventeen patients who required injection due to severe pain underwent discoblock procedures for discs with the most intense pain, and visual analogue scale (VAS) scores were obtained before and after the procedure for these patients. We analysed the association between painful discs and radiological findings.

RESULTS

Pain induction was noted in a total of 65 discs, and the pain was induced in 23 patients in only one disc. All patients had disc degeneration of Pfirrmann classification grade 1 or higher, with more significant disc degeneration in painful discs than in painless discs. There was no significant relationship between the presence or absence of pain and Modic type. The average VAS measurements improved significantly from 9.5 (pre-procedure) to 2.5 (post-procedure). These results suggest that the most painful discs were the causes of discogenic lumbar pain.

CONCLUSIONS

Our ultrasound-guided disc pain induction test may help diagnose disc degeneration and identify culprit lesions, even when multiple discs exhibit findings of degeneration.

Inducing Angiogenesis in the Nucleus Pulposus

Bone morphogenetic protein (BMP) gene delivery to Lewis rat lumbar intervertebral discs (IVDs) drives bone formation anterior and external to the IVD, suggesting the IVD is inhospitable to osteogenesis. This study was designed to determine if IVD destruction with a proteoglycanase, and/or generating an IVD blood supply by gene delivery of an angiogenic growth factor, could render the IVD permissive to intra-discal BMP-driven osteogenesis and fusion. Surgical intra-discal delivery of naïve or gene-programmed cells (BMP2/BMP7 co-expressing or VEGF165 expressing) +/- purified chondroitinase-ABC (chABC) in all permutations was performed between lumbar 4/5 and L5/6 vertebrae, and radiographic, histology, and biomechanics endpoints were collected. Follow-up anti-sFlt Western blotting was performed. BMP and VEGF/BMP treatments had the highest stiffness, bone production and fusion. Bone was induced anterior to the IVD, and was not intra-discal from any treatment. chABC impaired BMP-driven osteogenesis, decreased histological staining for IVD proteoglycans, and made the IVD permissive to angiogenesis. A soluble fragment of VEGF Receptor-1 (sFlt) was liberated from the IVD matrix by incubation with chABC, suggesting dysregulation of the sFlt matrix attachment is a possible mechanism for the chABC-mediated IVD angiogenesis we observed. Based on these results, the IVD can be manipulated to foster vascular invasion, and by extension, possibly osteogenesis.

The Role of Sex Hormones in Degenerative Disc Disease

STUDY DESIGN

Narrative review.

OBJECTIVES

The purpose of this review is to outline the role of sex hormones, particularly estrogen, in the pathogenesis of degenerative disc disease (DDD).

METHODS

A narrative review of studies discussing sex hormones and intervertebral disc (IVD) degeneration was conducted through a search of bibliographic databases to identify various mechanisms involved in effectuating DDD.

RESULTS

Estrogen-deficient states negatively impact various aspects of IVD function. These internal hormone environments reflect routine changes that commonly arise with physiologic aging and can compromise IVD structural integrity through a host of processes. Additionally, allosteric molecules such as micro-RNAs (mi-RNAs) and G protein-coupled estrogen receptors (GPER) antagonists can bind to estrogen receptors and inhibit protective downstream effects with estrogen receptor signaling. Furthermore, cursory studies have observed chondrogenic effects with testosterone supplementation, although the specific mechanism remains unclear.

CONCLUSIONS

Regulation of sex hormones, namely estrogen and testosterone, significantly impacts the structural integrity and function of IVDs. Uncovering underlying interactions driving these regulatory processes can facilitate development of novel, clinical therapies to treat DDD.

Development and Degeneration of the Intervertebral Disc-Insights from Across Species

Back pain caused by intervertebral disc (IVD) degeneration has a major socio-economic impact in humans, yet historically has received minimal attention in species other than humans, mice and dogs. However, a general growing interest in this unique organ prompted the expansion of IVD research in rats, rabbits, cats, horses, monkeys, and cows, further illuminating the complex nature of the organ in both healthy and degenerative states. Application of recent biotechnological advancements, including single cell RNA sequencing and complex data analysis methods has begun to explain the shifting inflammatory signaling, variation in cellular subpopulations, differential gene expression, mechanical loading, and metabolic stresses which contribute to age and stress related degeneration of the IVD. This increase in IVD research across species introduces a need for chronicling IVD advancements and tissue biomarkers both within and between species. Here we provide a comprehensive review of recent single cell RNA sequencing data alongside existing case reports and histo/morphological data to highlight the cellular complexity and metabolic challenges of this unique organ that is of structural importance for all vertebrates.

Gut microbiota and intervertebral disc degeneration: a bidirectional two-sample Mendelian randomization study

BACKGROUND

Although previous studies have suggested a close association between gut microbiota (GM) and intervertebral disc degeneration (IVDD), the causal relationship between them remains unclear. Hence, we thoroughly investigate their causal relationship by means of a two-sample Mendelian randomization (MR) study, aiming to determine the impact of gut microbiota on the risk of developing intervertebral disc degeneration.

METHODS

Summary data from genome-wide association studies of GM (the MiBioGen) and IVDD (the FinnGen biobank) have been acquired. The inverse variance weighted (IVW) method was utilized as the primary MR analysis approach. Weighted median, MR-Egger regression, weighted mode, and simple mode were used as supplements. The Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) and MR-Egger regression were performed to assess horizontal pleiotropy. Cochran's Q test evaluated heterogeneity. Leave-one-out sensitivity analysis was further conducted to determine the reliability of the causal relationship. A reverse MR analysis was conducted to assess potential reverse causation.

RESULTS

We identified nine gut microbial taxa that were causally associated with IVDD (P < 0.05). Following the Benjamini-Hochberg corrected test, the association between the phylum Bacteroidetes and a higher risk of IVDD remained significant (IVW FDR-corrected P = 0.0365). The results of the Cochrane Q test did not indicate heterogeneity (P > 0.05). Additionally, both the MR-Egger intercept test and the MR-PRESSO global test revealed that our results were not influenced by horizontal pleiotropy (P > 0.05). Furthermore, the leave-one-out analysis substantiated the reliability of the causal relationship. In the reverse analysis, no evidence was found to suggest that IVDD has an impact on the gut microbiota.

CONCLUSION

Our results validate the potential causal impact of particular GM taxa on IVDD, thus providing fresh insights into the gut microbiota-mediated mechanism of IVDD and laying the groundwork for further research into targeted preventive measures.

Investigation of the Mitigation of DMSO-Induced Cytotoxicity by Hyaluronic Acid following Cryopreservation of Human Nucleus Pulposus Cells

To develop an off-the-shelf therapeutic product for intervertebral disc (IVD) repair using nucleus pulposus cells (NPCs), it is beneficial to mitigate dimethyl sulfoxide (DMSO)-induced cytotoxicity caused by intracellular reactive oxygen species (ROS). Hyaluronic acid (HA) has been shown to protect chondrocytes against ROS. Therefore, we examined the potential of HA on mitigating DMSO-induced cytotoxicity for the enhancement of NPC therapy. Human NPC cryopreserved in DMSO solutions were thawed, mixed with equal amounts of EDTA-PBS (Group E) or HA (Group H), and incubated for 3-5 h. After incubation, DMSO was removed, and the cells were cultured for 5 days. Thereafter, we examined cell viability, cell proliferation rates, Tie2 positivity (a marker of NP progenitor cells), and the estimated numbers of Tie2 positive cells. Fluorescence intensity of DHE and MitoSOX staining, as indicators for oxidative stress, were evaluated by flow cytometry. Group H showed higher rates of cell proliferation and Tie2 expressing cells with a trend toward suppression of oxidative stress compared to Group E. Thus, HA treatment appears to suppress ROS induced by DMSO. These results highlight the ability of HA to maintain NPC functionalities, suggesting that mixing HA at the time of transplantation may be useful in the development of off-the-shelf NPC products.

Single-cell transcriptomics reveals heterogeneity and intercellular crosstalk in human intervertebral disc degeneration

The complexity of the human intervertebral disc (IVD) has hindered the elucidation of the microenvironment and mechanisms underlying IVD degeneration (IVDD). Here we determined the landscapes of nucleus pulposus (NP), annulus fibrosus (AF), and immunocytes in human IVD by scRNA-seq. Six NP subclusters and seven AF subclusters were identified, whose functional differences and distribution during different stages of degeneration (Pfirrmann I-V) were investigated. We found MCAM⁺ progenitor in AF, as well as CD24⁺ progenitor and MKI67⁺ progenitor in NP, forming a lineage trajectory from CD24⁺/MKI67⁺ progenitors to EffectorNP_⅓ during IVDD. There is a significant increase in monocyte/macrophage (Mφ) in degenerated IVDs (p = 0.044), with Mφ-SPP1 exclusively found in IVDD but not healthy IVDs. Further analyses of the intercellular crosstalk network revealed interactions between major subpopulations and changes in the microenvironment during IVDD. Our results elucidated the unique characteristics of IVDD, thereby shedding light on therapeutic strategies.

Defining the Patient with Lumbar Discogenic Pain: Real-World Implications for Diagnosis and Effective Clinical Management

There is an enormous body of literature that has identified the intervertebral disc as a potent pain generator. However, with regard to lumbar degenerative disc disease, the specific diagnostic criteria lack clarity and fail to capture the primary components which include axial midline low back pain with or without non-radicular/non-sciatic referred leg pain in a sclerotomal distribution. In fact, there is no specific ICD-10-CM diagnostic code to classify and define discogenic pain as a unique source of pain distinct from other recognized sources of chronic low back pain including facetogenic, neurocompressive including herniation and/or stenosis, sacroiliac, vertebrogenic, and psychogenic. All of these other sources have well-defined ICD-10-CM codes. Corresponding codes for discogenic pain remain absent from the diagnostic coding vernacular. The International Society for the Advancement of Spine Surgery (ISASS) has proposed a modernization of ICD-10-CM codes to specifically define pain associated with lumbar and lumbosacral degenerative disc disease. The proposed codes would also allow the pain to be characterized by location: lumbar region only, leg only, or both. Successful implementation of these codes would benefit both physicians and payers in distinguishing, tracking, and improving algorithms and treatments for discogenic pain associated with intervertebral disc degeneration.

Correlations of Disc Tissue Pathological Changes With Pfirrmann Grade in Patients With Disc Herniation Treated With Microdiscectomy

BACKGROUND

To reveal whether pathological disc changes (vascularization, inflammation, disc aging and senescence as assessed with immunohistopathological CD34, CD68, brachyury and P53 staining densities respectively) are associated with the extent of disease (Pfirrmann grade) and lumbar radicular pain in patients with lumbar disc herniation. We selectively included a homogenous group of 32 patients (16 males and 16 females) with single-level sequestered discs who had disease stages between Pfirrmann grades I to IV and excluded patients with the complete collapse of the disc space to determine histopathological correlations of the disease more precisely.

MATERIALS AND METHODS

Pathological assessments were performed on surgically excised disc specimens stored in a -80°C refrigerator. Preoperative and postoperative pain intensities were determined with visual analog scales (VASs). Pfirrmann disc degeneration grades were determined on routine T2-weighted magnetic resonance imaging (MRI).

RESULTS

Stainings were especially observed with CD34 and CD68, which positively correlated with each other and Pfirrmann grading but not with VAS scores or patients' age. Weak nuclear staining with brachyury was observed in 50% of patients and did not correlate with disease features. Focal weak staining with P53 was only seen in the disc specimen of two patients.

CONCLUSIONS

In the pathogenesis of disc disease, inflammation may trigger angiogenesis. The subsequent aberrant increase of oxygen perfusion in the disc cartilage may cause further damage, as the disc tissue is adapted to hypoxia. This vicious cycle of inflammation and angiogenesis may be a future innovative therapeutic target for chronic degenerative disc disease.

Comprehensive narrative review on the analysis of outcomes from cell transplantation clinical trials for discogenic low back pain

Background

Intervertebral disc (IVD) degeneration is one of the primary causes of low back pain (LBP) and despite a prominent prevalence, present treatment options remain inadequate for a large portion of LBP patients. New developments in regenerative therapeutics offer potentially powerful medical tools to modify this pathology, with specific focus on (stem) cell transplantations. Multiple clinical trials have since reported overall beneficial outcomes favoring cell therapy. Nonetheless, the significance of these improvements is often not (clearly) discussed. As such, this narrative review aims to summarize the significance of the reported improvements from human clinical trials on IVD-targeted cell therapy.

Methods

Through a comprehensive narrative review we discuss the improvements in pain, disability, quality of life, and imaging modalities and reported adverse events following cell therapy for discogenic pain.

Results

Most clinical trials were able to report clear and significant improvements in pain and disability outcomes. Imaging and quality of life improvements however were not as clearly reported but did present some enhancements for a select number of patients. Finally, whether cell therapy can outperform placebo treatment remains intangible.

Conclusions

Our review highlights the clinical significance of observed trends in pain and disability improvement. Nevertheless, reporting quality was found unsatisfactory and large-scale randomized controlled studies remain small in number. Future studies and articles should put more emphasis on improvements in imaging modalities and compare outcomes to (placebo) control groups to fully elucidate the efficacy and safety of cellular therapeutics against LBP.

Evaluating Nonoperative Treatment for Low Back Pain in the Presence of Modic Changes: A Systematic Review

OBJECTIVE

The objective of this study was to summarize and assess the current literature evaluating nonoperative treatments for patients with Modic changes (MCs) and low back pain (LBP).

METHODS

A systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The PubMed database was searched from its inception until May 1, 2022 for studies evaluating MC and clinical outcomes. Key findings, treatment details, and patient information were extracted from included studies. Study quality was assessed using the Newcastle-Ottawa Scale.

RESULTS

Eighteen studies were included in this review, encompassing a total of 2452 patients, 1713 of whom displayed baseline MC. Seventy-eight percent of studies were high quality. Of included studies, 2 evaluated antibiotics, 5 evaluated steroid injections, 6 evaluated conservative therapies, and 5 evaluated other treatment modalities. Antibiotics and bisphosphonates improved treatment in patients with MC. Patients with MC without disc herniation benefited from conservative therapy, while those with Type I Modic changes and disc herniation experienced poorer improvement. Significant variability exists in reported outcomes following steroid injections.

CONCLUSIONS

Nonoperative therapy may provide patients with MC with significant benefits. Patients may benefit from therapies not traditionally utilized for LBP such as antibiotics or bisphosphonates, but conservative therapy is not recommended for patients with concomitant MC and disc herniation. The large variation in follow-up times and outcome measures contributes to significant heterogeneity in studies and inability to predict long-term patient outcomes. More long-term studies are needed to assess nonoperative treatments for LBP in patients with MC.

Intervertebral disc degeneration and osteoarthritis: a common molecular disease spectrum

Intervertebral disc degeneration (IDD) and osteoarthritis (OA) affecting the facet joint of the spine are biomechanically interdependent, typically occur in tandem, and have considerable epidemiological and pathophysiological overlap. Historically, the distinctions between these degenerative diseases have been emphasized. Therefore, research in the two fields often occurs independently without adequate consideration of the co-dependence of the two sites, which reside within the same functional spinal unit. Emerging evidence from animal models of spine degeneration highlight the interdependence of IDD and facet joint OA, warranting a review of the parallels between these two degenerative phenomena for the benefit of both clinicians and research scientists. This Review discusses the pathophysiological aspects of IDD and OA, with an emphasis on tissue, cellular and molecular pathways of degeneration. Although the intervertebral disc and synovial facet joint are biologically distinct structures that are amenable to reductive scientific consideration, substantial overlap exists between the molecular pathways and processes of degeneration (including cartilage destruction, extracellular matrix degeneration and osteophyte formation) that occur at these sites. Thus, researchers, clinicians, advocates and policy-makers should consider viewing the burden and management of spinal degeneration holistically as part of the OA disease continuum.

Homing of vertebral-delivered mesenchymal stromal cells for degenerative intervertebral discs repair - an in vivo proof-of-concept study

Introduction

Cell transplantation shows promising results for intervertebral disc (IVD) repair, however, contemporary strategies present concerns regarding needle puncture damage, cell retention, and straining the limited nutrient availability. Mesenchymal stromal cell (MSC) homing is a natural mechanism of long-distance cellular migration to sites of damage and regeneration. Previous ex vivo studies have confirmed the potential of MSC to migrate over the endplate and enhance IVD-matrix production. In this study, we aimed to exploit this mechanism to engender IVD repair in a rat disc degeneration model.

Methods

Female Sprague Dawley rats were subjected to coccygeal disc degeneration through nucleus pulposus (NP) aspiration. In part 1; MSC or saline was transplanted into the vertebrae neighboring healthy or degenerative IVD subjected to irradiation or left untouched, and the ability to maintain the IVD integrity for 2 and 4 weeks was assessed by disc height index (DHI) and histology. For part 2, ubiquitously GFP expressing MSC were transplanted either intradiscally or vertebrally, and regenerative outcomes were compared at days 1, 5, and 14 post-transplantation. Moreover, the homing potential from vertebrae to IVD of the GFP+ MSC was assessed through cryosection mediated immunohistochemistry.

Results

Part 1 of the study revealed significantly improved maintenance of DHI for IVD vertebrally receiving MSC. Moreover, histological observations revealed a trend of IVD integrity maintenance. Part 2 of the study highlighted the enhanced DHI and matrix integrity for discs receiving MSC vertebrally compared with intradiscal injection. Moreover, GFP rates highlighted MSC migration and integration in the IVD at similar rates as the intradiscally treated cohort.

Conclusion

Vertebrally transplanted MSC had a beneficial effect on the degenerative cascade in their neighboring IVD, and thus potentially present an alternative administration strategy. Further investigation will be needed to determine the long-term effects, elucidate the role of cellular homing versus paracrine signaling, and validate our observations on a large animal model.

Harmonization and standardization of nucleus pulposus cell extraction and culture methods

Background

In vitro studies using nucleus pulposus (NP) cells are commonly used to investigate disc cell biology and pathogenesis, or to aid in the development of new therapies. However, lab-to-lab variability jeopardizes the much-needed progress in the field. Here, an international group of spine scientists collaborated to standardize extraction and expansion techniques for NP cells to reduce variability, improve comparability between labs and improve utilization of funding and resources.

Methods

The most commonly applied methods for NP cell extraction, expansion, and re-differentiation were identified using a questionnaire to research groups worldwide. NP cell extraction methods from rat, rabbit, pig, dog, cow, and human NP tissue were experimentally assessed. Expansion and re-differentiation media and techniques were also investigated.

Results

Recommended protocols are provided for extraction, expansion, and re-differentiation of NP cells from common species utilized for NP cell culture.

Conclusions

This international, multilab and multispecies study identified cell extraction methods for greater cell yield and fewer gene expression changes by applying species-specific pronase usage, 60-100 U/ml collagenase for shorter durations. Recommendations for NP cell expansion, passage number, and many factors driving successful cell culture in different species are also addressed to support harmonization, rigor, and cross-lab comparisons on NP cells worldwide.

A prospective study of BurstDR™ spinal cord stimulation for non-operated discogenic low back pain

INTRODUCTION

Chronic discogenic low back pain (CD-LBP) is caused by degeneration of the disc due to trauma to the annulus or by unprovoked degeneration, resulting in chronic pain. Spinal cord stimulation (SCS) employing the BurstDR™ waveform has been shown to be an effective treatment in a variety of chronic pain conditions. The aim of this prospective case study was to determine the effect of BurstDR™ SCS on pain relief, disability, and patient satisfaction in a population with CD-LBP.

METHODS

Seventeen subjects with CD-LBP received a SCS trial with BurstDR™ stimulation. Patients with >50% pain relief after a trial period of 2 weeks were permanently implanted (n = 15). Patients then rated LBP and leg pain using the numeric rating scale (NRS), Oswestry disability index (ODI), patient global impression of change (PGIC), EQ-5D quality of life, and painDETECT for neuropathic pain at baseline following trial, 3, 6, and 12 months after permanent implantation.

RESULTS

Treatment with BurstDR™ SCS resulted in significant reduction of LBP as the NRS was reduced from 71.7 ± 7.3 at baseline to 42.5 ± 18.1 at 12 months. Average pain relief at 12 months was 42.5%. In patients with leg pain (n = 8), pain was significantly reduced from 66.9 ± 8.2 to 11.7 ± 10.4 at 12 months. PainDETECT scores for neuropathic pain significantly reduced from 18.9 ± 4.8 at baseline, and 14.8 ± 3.2 at 12 months. Baseline ODI score significantly reduced from 41.2 ± 12.8 to 25.8 ± 8.6 at 12 months. PGIC scores remained low from 2.6 ± 1.6 at 3 months, 2.5 ± 1.0 at 6 months, and 2.5 ± 1.3 at 12 months. EQ-5D-5L rates remained constant from baseline 56.10 ± 23.9 to 68.6 ± 12.9 at 12 months.

CONCLUSION

BurstDR™ SCS resulted in significant reduction of back pain, leg pain, and quality of life in patients with CD-LBP and decreased the level of disability and generated positive patient satisfaction scores.

Macrophages and Intervertebral Disc Degeneration

The intervertebral disc (IVD) aids in motion and acts to absorb energy transmitted to the spine. With little inherent regenerative capacity, degeneration of the intervertebral disc results in intervertebral disc disease, which contributes to low back pain and significant disability in many individuals. Increasing evidence suggests that IVD degeneration is a disease of the whole joint that is associated with significant inflammation. Moreover, studies show elevated macrophage accumulation within the IVD with increasing levels of disease severity; however, we still need to understand the roles, be they causative or consequential, of macrophages during the degenerative process. In this narrative review, we discuss hallmarks of IVD degeneration, showcase evidence of macrophage involvement during disc degeneration, and explore burgeoning research aimed at understanding the molecular pathways regulating macrophage functions during intervertebral disc degeneration.

Ozone in the adjunct medical treatment. The round personality of a molecule with hormetic properties

Ozone, an allotrope of oxygen, is enjoying an increasing interest in the setting and management of the medical adjunct treatment, which is called, maybe too simplistically, "ozone therapy". Ozone is not a medicine, so the word therapy does not properly fit this gaseous molecule. Like many natural compounds, for example plant flavonoids, even ozone interacts with aryl hydrocarbon receptors (AhRs) and, at low doses, it works according to the paradoxical mechanism of hormesis, involving mitochondria (mitohormesis). Ozone, in the hormetic range, exerts cell protective functions via the Nrf2-mediated activation of the anti-oxidant system, then leading to anti-inflammatory effects, also via the triggering of low doses of 4-HNE. Moreover, its interaction with plasma and lipids forms reactive oxygen species (ROS) and lipoperoxides (LPOs), generally called ozonides, which are enabled to rule the major molecular actions of ozone in the cell. Ozone behaves as a bioregulator, by activating a wide population of reactive intermediates, which usually target mitochondria and their turnover/biogenesis, often leading to a pleiotropic spectrum of actions and behaving as a tuner of the fundamental mechanisms of survival in the cell. In this sense, ozone can be considered a novelty in the medical sciences and in the clinical approach to pharmacology and medical therapy, due to its ability to target complex regulatory systems and not simple receptors.

Update on the roles of macrophages in the degeneration and repair process of intervertebral discs

Intervertebral disc (IVD) degeneration is the common cause of lumbar degenerative diseases, causing severe social and economic burden. The process of IVD degeneration involves a complex of pathologic changes on both extracellular matrix degradation and resident cell apoptosis. In recent years, there is increasing evidence that macrophages play vital roles during the damage and repair process of IVD degeneration. Nevertheless, the interactions between macrophages and IVD are not well understood, even if the IVD has long been regarded as the immune privileged site. Therefore, this review mainly focuses on the progress and obstacles of studies investigating the blood supply, immune response and especially macrophages during the IVD degeneration process.

Single-cell RNA sequencing reveals resident progenitor and vascularization-associated cell subpopulations in rat annulus fibrosus

Background

One of the main causes of low back pain is intervertebral disc degeneration (IDD). Annulus fibrosus (AF) is important for the integrity and functions of the intervertebral disc (IVD). However, the resident functional cell components such as progenitors and vascularization-associated cells in AF are yet to be fully identified.

Purpose

Identification of functional AF cell subpopulations including resident progenitors and vascularization-associated cells.

Methods

In this study, the single-cell RNA sequencing data of rat IVDs from a public database were analyzed using Seurat for cell clustering, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) for functional analysis, StemID for stem cell identification, Monocle and RNA velocity for pseudotime differentiation trajectory validation, single-cell regulatory network inference and clustering (SCENIC) for gene regulatory network (GRN) analysis, and CellChat for cell-cell interaction analysis. Immunostaining on normal and degenerated rat IVDs, as well as human AF, was used for validations.

Results

From the data analysis, seven AF cell clusters were identified, including two newly discovered functional clusters, the Grem1 ⁺ subpopulation and the Lum ⁺ ​subpopulation. The Grem1 ⁺ subpopulation had progenitor characteristics, while the Lum ⁺ ​subpopulation was associated with vascularization during IDD. The GRN analysis showed that Sox9 and Id1 were among the key regulators in the Grem1 ⁺ subpopulation, and Nr2f2 and Creb5 could be responsible for the vascularization function in the Lum ⁺ ​subpopulation. Cell-cell interaction analysis revealed highly regulated cellular communications between these cells, and multiple signaling networks including PDGF and MIF signaling pathways were involved in the interactions.

Conclusions

Our results revealed two new functional AF cell subpopulations, with stemness and vascularization induction potential, respectively.

The Translational potential of this article

These findings complement our knowledge about IVDs, especially the AF, and in return provide potential cell source and regulation targets for IDD treatment and tissue repair. The existence of the cell subpopulations was also validated in human AF, which strengthen the clinical relevance of the findings.

An in-depth analysis of the immunomodulatory mechanisms of intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is the pathological basis of disc herniation, spinal stenosis, and other related diseases, and the lower back pain it produces lays a heavy financial burden on individuals and society. Thus, it is essential to comprehend IVDD's pathophysiology. Numerous factors, such as inflammatory factors, oxidative stress, apoptosis, matrix metalloproteinases, are linked to IVDD pathogenesis. Despite the fact that many researches has provided explanations for the pathophysiology of IVDD, these studies are typically singular, restricted, and isolated, expound only on one or two components, and do not systematically analyze and summarize the numerous influencing elements. In addition, we discovered that the incidence of many chronic diseases in the field of orthopedics may be thoroughly and systematically defined in terms of immunological systems. In order to provide a theoretical foundation for an in-depth understanding of the pathological process of IVDD and the formulation of more effective prevention and treatment measures, this review provides a comprehensive and systematic account of the pathogenesis of IVDD from the physical to the molecular barriers of the intervertebral disc, from the nucleus pulposus tissue to the cellular to the immune-molecular level.