Osteogenic protein 1 does not stimulate a regenerative effect in cultured human degenerated nucleus pulposus tissue

Human 3D nucleus pulposus microtissue model to evaluate the potential of pre-conditioned nasal chondrocytes for the repair of degenerated intervertebral disc

Introduction: An in vitro model that appropriately recapitulates the degenerative disc disease (DDD) microenvironment is needed to explore clinically relevant cell-based therapeutic strategies for early-stage degenerative disc disease. We developed an advanced 3D nucleus pulposus (NP) microtissues (µT) model generated with cells isolated from human degenerating NP tissue (Pfirrmann grade: 2-3), which were exposed to hypoxia, low glucose, acidity and low-grade inflammation. This model was then used to test the performance of nasal chondrocytes (NC) suspension or spheroids (NCS) after pre-conditioning with drugs known to exert anti-inflammatory or anabolic activities. Methods: NPµTs were formed by i) spheroids generated with NP cells (NPS) alone or in combination with ii) NCS or iii) NC suspension and cultured in healthy or degenerative disc disease condition. Anti-inflammatory and anabolic drugs (amiloride, celecoxib, metformin, IL-1Ra, GDF-5) were used for pre-conditioning of NC/NCS. The effects of pre-conditioning were tested in 2D, 3D, and degenerative NPµT model. Histological, biochemical, and gene expression analysis were performed to assess matrix content (glycosaminoglycans, type I and II collagen), production and release of inflammatory/catabolic factors (IL-6, IL-8, MMP-3, MMP-13) and cell viability (cleaved caspase 3). Results: The degenerative NPµT contained less glycosaminoglycans, collagens, and released higher levels of IL-8 compared to the healthy NPµT. In the degenerative NPµT, NCS performed superior compared to NC cell suspension but still showed lower viability. Among the different compounds tested, only IL-1Ra pre-conditioning inhibited the expression of inflammatory/catabolic mediators and promoted glycosaminoglycan accumulation in NC/NCS in DDD microenvironment. In degenerative NPµT model, preconditioning of NCS with IL-1Ra also provided superior anti-inflammatory/catabolic activity compared to non-preconditioned NCS. Conclusion: The degenerative NPµT model is suitable to study the responses of therapeutic cells to microenvironment mimicking early-stage degenerative disc disease. In particular, we showed that NC in spheroidal organization as compared to NC cell suspension exhibited superior regenerative performance and that IL-1Ra pre-conditioning of NCS could further improve their ability to counteract inflammation/catabolism and support new matrix production within harsh degenerative disc disease microenvironment. Studies in an orthotopic in vivo model are necessary to assess the clinical relevance of our findings in the context of IVD repair.

New Hope for Treating Intervertebral Disc Degeneration: Microsphere-Based Delivery System

Intervertebral disc (IVD) degeneration (IVDD) has been considered the dominant factor in low back pain (LBP), and its etiological mechanisms are complex and not yet fully elucidated. To date, the treatment of IVDD has mainly focused on relieving clinical symptoms and cannot fundamentally solve the problem. Recently, a novel microsphere-based therapeutic strategy has held promise for IVD regeneration and has yielded encouraging results with in vitro experiments and animal models. With excellent injectability, biocompatibility, and biodegradability, this microsphere carrier allows for targeted delivery and controlled release of drugs, gene regulatory sequences, and other bioactive substances and supports cell implantation and directed differentiation, aiming to improve the disease state of IVD at the source. This review discusses the possible mechanisms of IVDD and the limitations of current therapies, focusing on the application of microsphere delivery systems in IVDD, including targeted delivery of active substances and drugs, cellular therapy, and gene therapy, and attempts to provide a new understanding for the treatment of IVDD.

Regulating the fate of stem cells for regenerating the intervertebral disc degeneration

Lower back pain is a leading cause of disability and is one of the reasons for the substantial socioeconomic burden. The etiology of intervertebral disc (IVD) degeneration is complicated, and its mechanism is still not completely understood. Factors such as aging, systemic inflammation, biochemical mediators, toxic environmental factors, physical injuries, and genetic factors are involved in the progression of its pathophysiology. Currently, no therapy for restoring degenerated IVD is available except pain management, reduced physical activities, and surgical intervention. Therefore, it is imperative to establish regenerative medicine-based approaches to heal and repair the injured disc, repopulate the cell types to retain water content, synthesize extracellular matrix, and strengthen the disc to restore normal spine flexion. Cellular therapy has gained attention for IVD management as an alternative therapeutic option. In this review, we present an overview of the anatomical and molecular structure and the surrounding pathophysiology of the IVD. Modern therapeutic approaches, including proteins and growth factors, cellular and gene therapy, and cell fate regulators are reviewed. Similarly, small molecules that modulate the fate of stem cells for their differentiation into chondrocytes and notochordal cell types are highlighted.

"Old Drugs, New Tricks" - Local controlled drug release systems for treatment of degenerative joint disease

Osteoarthritis (OA) and chronic low back pain (CLBP) caused by intervertebral disc (IVD) degeneration are joint diseases that have become major causes for loss of quality of life worldwide. Despite the unmet need, effective treatments other than invasive, and often ineffective, surgery are lacking. Systemic administration of drugs entails suboptimal local drug exposure in the articular joint and IVD. This review provides an overview of the potency of biomaterial-based drug delivery systems as novel treatment modality, with a focus on the biological effects of drug release systems that have reached translation at the level of in vivo models and relevant ex vivo models. These studies have shown encouraging results of biomaterial-based local delivery of several types of drugs, mostly inhibitors of inflammatory cytokines or other degenerative factors. Prevention of inflammation and degeneration and pain relief was achieved, although mainly in small animal models, with interventions applied at an early disease stage. Less convincing data were obtained with the delivery of regenerative factors. Multidisciplinary efforts towards tackling the discord between in vitro and in vivo release, combined with adaptations in the regulatory landscape may be needed to enhance safe and expeditious introduction of more and more effective controlled release-based treatments with the OA and CLBP patients.

Intervertebral Disc Nucleus Repair: Hype or Hope?

Chronic back pain is a common disability, which is often accredited to intervertebral disc degeneration. Gold standard interventions such as spinal fusion, which are mainly designed to mechanically seal the defect, frequently fail to restore the native biomechanics. Moreover, artificial implants have limited success as a repair strategy, as they do not alter the underlying disease and fail to promote tissue integration and subsequent native biomechanics. The reported high rates of spinal fusion and artificial disc implant failure have pushed intervertebral disc degeneration research in recent years towards repair strategies. Intervertebral disc repair utilizing principles of tissue engineering should theoretically be successful, overcoming the inadequacies of artificial implants. For instance, advances in the development of scaffolds aided with cells and growth factors have opened up new possibilities for repair strategies. However, none has reached the stage of clinical trials in humans. In this review, we describe the hitches encountered in the musculoskeletal field and summarize recent advances in designing tissue-engineered constructs for promoting nucleus pulposus repair. Additionally, the review focuses on the effect of biomaterial aided with cells and growth factors on achieving effective functional reparative potency, highlighting the ways to enhance the efficacy of these treatments.

Leaping the hurdles in developing regenerative treatments for the intervertebral disc from preclinical to clinical

Chronic back and neck pain is a prevalent disability, often caused by degeneration of the intervertebral disc. Because current treatments for this condition are less than satisfactory, a great deal of effort is being applied to develop new solutions, including regenerative strategies. However, the path from initial promising idea to clinical use is fraught with many hurdles to overcome. Many of the keys to success are not necessarily linked to science or innovation. Successful translation to clinic will also rely on planning and awareness of the hurdles. It will be essential to plan your entire path to clinic from the outset and to do this with a multidisciplinary team. Take advice early on regulatory aspects and focus on generating the proof required to satisfy regulatory approval. Scientific demonstration and societal benefits are important, but translation cannot occur without involving commercial parties, which are instrumental to support expensive clinical trials. This will only be possible when intellectual property can be protected sufficiently to support a business model. In this manner, commercial, societal, medical, and scientific partners can work together to ultimately improve patient health. Based on literature surveys and experiences of the co-authors, this opinion paper presents this pathway, highlights the most prominent issues and hopefully will aid in your own translational endeavors.

Treatment of chronic low back pain - new approaches on the horizon

Back pain is the second leading cause of disability among American adults and is currently treated either with conservative therapy or interventional pain procedures. However, the question that remains is whether we, as physicians, have adequate therapeutic options to offer to the patients who suffer from chronic low back pain but fail both conservative therapy and interventional pain procedures before they consider surgical options such as discectomy, disc arthroplasty, or spinal fusion. The purpose of this article is to review the potential novel therapies that are on the horizon for the treatment of chronic low back pain. We discuss medications that are currently in use through different phases of clinical trials (I–III) for the treatment of low back pain. In this review, we discuss revisiting the concept of chemonucleolysis using chymopapain, as the first drug in an intradiscal injection to reduce herniated disc size, and newer intradiscal therapies, including collagenase, chondroitinase, matrix metalloproteinases, and ethanol gel. We also review an intravenous glial cell-derived neurotrophic growth factor called artemin, which may repair sensory nerves compressed by herniated discs. Another new drug in development for low back pain without radiculopathy is a subcutaneous monoclonal antibody acting as nerve growth factor called tanezumab. Finally, we discuss how platelet-rich plasma and stem cells are being studied for the treatment of low back pain. We believe that with these new therapeutic options, we can bridge the current gap between conservative/interventional procedures and surgeries in patients with chronic back pain.

An Inflammatory Nucleus Pulposus Tissue Culture Model to Test Molecular Regenerative Therapies: Validation with Epigallocatechin 3-Gallate

Organ cultures are practical tools to investigate regenerative strategies for the intervertebral disc. However, most existing organ culture systems induce severe tissue degradation with only limited representation of the in vivo processes. The objective of this study was to develop a space- and cost-efficient tissue culture model, which represents degenerative processes of the nucleus pulposus (NP). Intact bovine NPs were cultured in a previously developed system using Dyneema jackets. Degenerative changes in the NP tissue were induced either by the direct injection of chondroitinase ABC (1-20 U/mL) or by the diffusion of interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) (both 100 ng/mL) from the culture media. Extracellular matrix composition (collagens, proteoglycans, water, and DNA) and the expression of inflammatory and catabolic genes were analyzed. The anti-inflammatory and anti-catabolic compound epigallocatechin 3-gallate (EGCG, 10 µM) was employed to assess the relevance of the degenerative NP model. Although a single injection of chondroitinase ABC reduced the proteoglycan content in the NPs, it did not activate cellular responses. On the other hand, IL-1β and TNF-α significantly increased the mRNA expression of inflammatory mediators IL-6, IL-8, inducible nitric oxide synthase (iNOS), prostaglandin-endoperoxide synthase 2 (PTGS2) and matrix metalloproteinases (MMP1, MMP3, and MMP13). The cytokine-induced gene expression in the NPs was ameliorated with EGCG. This study provides a proof of concept that inflammatory NP cultures, with appropriate containment, can be useful for the discovery and evaluation of molecular therapeutic strategies against early degenerative disc disease.