The Biomechanics and Biology of the Spinal Degenerative Cascade

Stimuli-Responsive Delivery Systems for Intervertebral Disc Degeneration

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

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

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

Strong association of type 2 diabetes with degenerative lumbar spine disorders

Tantalizing connections between type 2 diabetes and degenerative lumbar spine disorders have become increasingly evident. However, the association of type 2 diabetes with degenerative lumbar spine disorders remains unclear. We sought to clarify the association between type 2 diabetes and lumbar spine disorders using nationwide data in Korea. Furthermore, we explored the association of diabetes with the prevalence of spinal procedures. The data in this study was obtained from Korean health claim database. Between 2016 and 2019, totals of 479,680 diabetes and 479,680 age- and sex-matched control subjects were enrolled. Patients with diabetes had more likely to have degenerative lumbar spine disorders and spinal procedures than controls. Using multivariate-adjusted analysis, patients with diabetes were at increased risk of being concomitantly affected by lumbar disc disorder [adjusted odds ratio 1.11 (95% confidence interval 1.10-1.12)], lumbar spondylotic radiculopathy [1.12 (1.11-1.13)], spondylolisthesis [1.05 (1.02-1.08)] and spinal stenosis [1.16 (1.15-1.18)], compared to controls. Furthermore, diabetic patients had an increased risk of undergoing lumbar spinal injection [1.13 (1.12-1.14)], laminectomy [1.19 (1.15-1.23)], and fusion surgery [1.35 (1.29-1.42)]. We demonstrated that type 2 diabetes was significantly associated with lumbar spine disorders and frequent spinal procedures. Our results suggest diabetes as a predisposing factor for lumbar spine disorders.

mild® Lumbar Decompression for the Treatment of Lumbar Spinal Stenosis

More than 1.2 million people are undergoing treatment for lumbar spinal stenosis (LSS) in the United States. Yet, therapeutic options for these patients are limited to either conservative treatments or highly invasive surgeries. A new image-guided interlaminar decompression procedure, mild®, offers significant relief for many of these patients by debulking dorsal element hypertrophy while preserving structural stability. mild can be performed without general anesthesia and offers a short recovery period. A meta-analysis of four clinical patient series from multiple institutions in the United States evaluated over 250 patients for safety and clinical efficacy of the mild procedure. Clinical efficacy was evaluated at baseline and at three-month follow-up using validated patient reported outcomes (PRO) instruments including the ten-point Visual Analog Scale (VAS) and the Oswestry Disability Index (ODI). Acute safety and patient outcomes was compared to the Spine Patient Outcomes Research Trial (SPORT). No device or procedure-related serious adverse events (SAEs) have been recorded with the mild procedure. Outcome metrics for patients treated with mild demonstrated statistically significant symptomatic improvement over baseline. When compared to open surgery, mild efficacy results compare favorably, and complication rates are much lower. mild is a safe and effective procedure that decompresses LSS in a minimally invasive manner while preserving the structural stability of the spine.

Akt/PKB isoforms expression in the human lumbar herniated disc: correlation with clinical and MRI findings

Intervertebral disc (IVD) degeneration suggests a complex process influenced by genetics, lifestyle and biomechanics, which accounts for the development of low back pain (LBP) and lumbar radiculopathy, a major cause of musculoskeletal disability in humans. The family of Akt/PKB kinases is a principal mediator in the signal transduction pathways, which contribute to transcriptional regulation, cell growth, proliferation, apoptosis, and survival ability. The purpose of this study was to evaluate the transcriptional profile of the AKT family genes in human herniated discs and the involvement of the PI3K-Akt signaling pathway in human IVD degeneration. Real-time PCR analysis was used to assess the mRNA expression pattern of the three Akt/PKB isoforms in 63 herniated and 10 control disc specimens. Our results showed a significant positive correlation between AKT1 and AKT3 mRNA in herniated discs suggesting a synergistic action between these isoforms in disc herniation. Interestingly, AKT2 mRNA was up-regulated in patients with acute pain during the first 12 months, indicating that AKT2 transcriptional activation may be associated with acute rather than chronic inflammation and phagocytosis. Finally, Akt1/PKB transcription presented a stepwise activation as disc herniation deteriorated. Our findings provide evidence on the transcriptional activation of the Akt/PKB pathway indicating that it is involved in lumbar disc degeneration. There is need for further studies to elucidate the exact role and down-stream signaling action of Akt/PKB isoforms in the pathogenesis of lumbar disc herniation.