Chemonucleolysis combined with dynamic loading for inducing degeneration in bovine caudal intervertebral discs

Backbone breakthroughs: How rodent models are shaping intervertebral disc disease treatment

Intervertebral disc degeneration (IVDD) is a widespread, disabling condition that significantly contributes to the global burden of musculoskeletal disorders. To better understand its underlying mechanisms and explore potential therapeutic strategies, animal models serve as valuable tools for simulating the complicated pathophysiology of IVDD. Rodent models are extensively used due to their genetic similarities to humans, cost-effectiveness, and rapid attainment of maturity. These models enable the study of specific molecular pathways involved in IVDD, such as inflammation, matrix degradation, tissue repair, and disc microenvironment homeostasis. This review provides a comprehensive overview of the current status of rodent models used in IVDD research, highlighting their advantages, limitations, and contributions to our understanding of the disease. Specifically, we discussed various rodent models, including traumatic (such as needle puncture in the lumbar and coccygeal region, nucleotomy, and annulus fibrosus defect), non-traumatic (including compression models, lumbar spine instability, and bipedalism), chemically induced models (chymopapain, chondroitinase ABC), and genetically modified models. These models offer insights into the severity of IVDD under different conditions, such as trauma, aging, and genetics. In conclusion, rodent models remain indispensable tools for advancing our understanding of IVDD mechanisms and therapeutic interventions. Carefully selecting animal species and models can provide valuable insights that guide future clinical research and treatment approaches. Our review aims to leverage these models to identify therapeutic targets and strategies that may ultimately reduce the impact of IVDD on human health. PERSPECTIVE: This review describes the role of rodent models in IVDD, highlighting their utility in unraveling disease mechanisms and evaluating therapeutics. By replicating the complex molecular pathways and conditions of disc disease, like trauma, aging, and genetics, these models aid in identifying future advancements in managing lower back pain.

Degeneration of the nucleus pulposus affects the internal volumetric strains and failure location of adjacent human metastatic vertebral bodies

Intervertebral disc (IVD) degeneration is suspected to affect the distribution of stress and strain near the vertebral endplates and in the underlying bone. This scenario is worsened by the presence of metastatic lesions on the vertebrae (primarily thoracic vertebrae (60-80 %)) which increase the risk of fracture. As such, this study aimed to evaluate the effect of IVD degeneration on the internal volumetric strains and failure modes of human metastatic vertebral bodies. Five human thoracic spinal segments including one vertebra with lytic metastases and one radiologically healthy vertebra (control) were in situ tested in pure compression within a μCT scanner (isotropic voxel size = 39μm). Each specimen was tested in the elastic regime before and after inducing mock IVD degeneration (enzymatic degeneration with collagenase); and at failure after IVD degeneration. The volumetric strain field was measured using a global Digital Volume Correlation approach (BoneDVC). After IVD degeneration, larger maximum (+187 %, P = 0.002, 95 % CI= [-4447, -1209]) and minimum (+174 %, P = 0.002, 95% CI= [1679, 4258]) principal strains were observed in both metastatic and control vertebrae, with peak differences in correspondence of the IVD anulus fibrosus. IVD degeneration caused a transversal fracture pattern in the vertebrae with failure location onset in the middle portion of the vertebral body and in the cortical shell. In conclusion, IVD degeneration was found to be a key factor in determining the failure mode, suggesting the clinical relevance of including IVD level of degeneration to assess patients' risk of spinal instability. STATEMENT OF SIGNIFICANCE: Vertebrae can be affected by pathologies, like bone metastases, while intervertebral discs tend to degenerate during life. Generally, these structures and pathologies are studied separately. In this study, we explored the effects of artificial intervertebral disc degeneration on the mineralised tissues of the vertebrae with metastases. We observed that the induced intervertebral disc degeneration changes the mechanical behaviour of the vertebral trabecular bone. We believe that the findings of this study may influence the scientific community to develop new clinical tools for the prediction of the risk of fracture in vertebrae with spinal metastases, including the degeneration of the intervertebral discs as a parameter.

Papain Injection Creates a Nucleotomy-like Cavity for Testing Gels in Intervertebral Discs

Biomaterials, such as hydrogels, have an increasingly important role in the development of regenerative approaches for the intervertebral disc. Since animal models usually resist biomaterial injection due to high intradiscal pressure, preclinical testing of the biomechanical performance of biomaterials after implantation remains difficult. Papain reduces the intradiscal pressure, creates cavities within the disc, and allows for biomaterial injections. But papain digestion needs time, and cadaver experiments that are limited to 24 h for measuring range of motion (ROM) cannot not be combined with papain digestion just yet. In this study, we successfully demonstrate a new organ culture approach, facilitating papain digestion to create cavities in the disc and the testing of ROM, neutral zone (NZ), and disc height. Papain treatment increased the ROM by up to 109.5%, extended NZ by up to 210.9%, and decreased disc height by 1.96 ± 0.74 mm. A median volume of 0.73 mL hydrogel could be injected after papain treatment, and histology revealed a strong loss of proteoglycans in the remaining nucleus tissue. Papain has the same biomechanical effects as known from nucleotomies or herniations and thus creates a disc model to study such pathologies in vitro. This new model can now be used to test the performance of biomaterials.

Rotation-traction manipulation induced intradiskal pressure changes in cervical spine-an in vitro study

Objective: Evaluate the effect of rotation-traction manipulation on intradiskal pressure in human cervical spine specimen with different force and duration parameters, and compare the intradiskal pressure changes between rotation-traction manipulation and traction. Methods: Seven human cervical spine specimens were included in this study. The intradiskal pressure was measured by miniature pressure sensor implanting in the nucleus pulposus. rotation-traction manipulation and cervical spine traction were simulated using the MTS biomechanical machine. Varied thrust forces (50N, 150N, and 250N) and durations (0.05 s, 0.1 s, and 0.15 s) were applied during rotation-traction manipulation with Intradiscal pressure recorded in the neutral position, rotation-anteflexion position, preloading, and thrusting phases. Futuremore, we documented changes in intradiscal pressure during cervical spine traction with different loading forces (50N, 150N, and 250N). And a comparative analysis was performed to discern the impact on intradiscal pressure between manipulation and traction. Results: Manipulation application induced a significant reduction in intradiscal pressure during preloading and thrusting phases for each cervical intervertebral disc (p < 0.05). When adjusting thrust parameters, a discernible decrease in intradiscal pressure was observed with increasing thrust force, and the variations between different thrust forces were statistically significant (p < 0.05). Conversely, changes in duration did not yield a significant impact on intradiscal pressure (p > 0.05). Additionally, after traction with varying loading forces (50N, 150N, 250N), a noteworthy decrease in intradiscal pressure was observed (p < 0.05). And a comparative analysis revealed that rotation-traction manipulation more markedly reduced intradiscal pressure compared to traction alone (p < 0.05). Conclusion: Both rotation-traction manipulation and cervical spine traction can reduce intradiscal pressure, exhibiting a positive correlation with force. Notably, manipulation elicits more pronounced and immediate decompression effect, contributing a potential biomechanical rationale for its therapeutic efficacy.