Precision medicine strategies for spinal degenerative diseases: Injectable biomaterials with in situ repair and regeneration

Structural design and biomechanical analysis of a combined titanium and polyetheretherketone cage based on PE-PLIF fusion

In lumbar spinal fusion, the titanium cage tends to cause stress shielding due to their high elastic modulus, which can lead to degenerative lesions in adjacent spinal segments. Furthermore, polyetheretherketone (PEEK) cages have certain material characteristics that do not promote bone ingrowth and fusion stability. In this study, a new cage was designed, and its biomechanical performance in percutaneous endoscopic posterior lumbar interbody fusion (PE-PLIF) was analyzed using the finite element (FE) method. A complete model of the L4-L5 lumbar spine was established, and static and harmonic vibration FE analysis models were developed based on it. The biomechanical properties of titanium, PEEK, and combined cage in PE-PLIF fusion were compared. The strain capacity of the combined fusion increased by 9.5% when compared to the titanium fusion. The surgical model under the combined fusion reduces the L5 endplate stress by 12% in the forward flexion condition and the fusion stress by 17% in the vibration condition compared to the model supported by the titanium fusion, and the differences in screw stress and mobility among the three models are not significant in multiple conditions. Consequently, the combined cage demonstrates a certain reduction in the stress-shielding effect when compared to the titanium cage; it has better fusion effect and provides theoretical support and guidance for the design of the clinical fusion cage.

Effects of circulating inflammatory proteins on spinal degenerative diseases: Evidence from genetic correlations and Mendelian randomization study

Background

Numerous investigations have suggested links between circulating inflammatory proteins (CIPs) and spinal degenerative diseases (SDDs), but causality has not been proven. This study used Mendelian randomization (MR) to investigate the causal associations between 91 CIPs and cervical spondylosis (CS), prolapsed disc/slipped disc (PD/SD), spinal canal stenosis (SCS), and spondylolisthesis/spondylolysis.

Methods

Genetic variants data for CIPs and SDDs were obtained from the genome-wide association studies (GWAS) database. We used inverse variance weighted (IVW) as the primary method, analyzing the validity and robustness of the results through pleiotropy and heterogeneity tests and performing reverse MR analysis to test for reverse causality.

Results

The IVW results with Bonferroni correction indicated that beta-nerve growth factor (β-NGF), C-X-C motif chemokine 6 (CXCL6), and interleukin-6 (IL-6) can increase the risk of CS. Fibroblast growth factor 19 (FGF19), sulfotransferase 1A1 (SULT1A1), and tumor necrosis factor-beta (TNF-β) can increase PD/SD risk, whereas urokinase-type plasminogen activator (u-PA) can decrease the risk of PD/SD. FGF19 and TNF can increase SCS risk. STAM binding protein (STAMBP) and T-cell surface glycoprotein CD6 isoform (CD6 isoform) can increase the risk of spondylolisthesis/spondylolysis, whereas monocyte chemoattractant protein 2 (MCP2) and latency-associated peptide transforming growth factor beta 1 (LAP-TGF-β1) can decrease spondylolisthesis/spondylolysis risk.

Conclusions

MR analysis indicated the causal associations between multiple genetically predicted CIPs and the risk of four SDDs (CS, PD/SD, SCS, and spondylolisthesis/spondylolysis). This study provides reliable genetic evidence for in-depth exploration of the involvement of CIPs in the pathogenic mechanism of SDDs and provides novel potential targets for SDDs.

Nano-Micron Combined Hydrogel Microspheres: Novel Answer for Minimal Invasive Biomedical Applications

Hydrogels, key in biomedical research for their hydrophilicity and versatility, have evolved with hydrogel microspheres (HMs) of micron-scale dimensions, enhancing their role in minimally invasive therapeutic delivery, tissue repair, and regeneration. The recent emergence of nanomaterials has ushered in a revolutionary transformation in the biomedical field, which demonstrates tremendous potential in targeted therapies, biological imaging, and disease diagnostics. Consequently, the integration of advanced nanotechnology promises to trigger a new revolution in the realm of hydrogels. HMs loaded with nanomaterials combine the advantages of both hydrogels and nanomaterials, which enables multifaceted functionalities such as efficient drug delivery, sustained release, targeted therapy, biological lubrication, biochemical detection, medical imaging, biosensing monitoring, and micro-robotics. Here, this review comprehensively expounds upon commonly used nanomaterials and their classifications. Then, it provides comprehensive insights into the raw materials and preparation methods of HMs. Besides, the common strategies employed to achieve nano-micron combinations are summarized, and the latest applications of these advanced nano-micron combined HMs in the biomedical field are elucidated. Finally, valuable insights into the future design and development of nano-micron combined HMs are provided.

Positioning regulation of organelle network via Chinese microneedle

The organelle network is a key factor in the repair and regeneration of lesion. However, effectively intervening in the organelle network which has complex interaction mechanisms is challenging. In this study, on the basis of electromagnetic laws, we constructed a biomaterial-based physical/chemical restraint device. This device was designed to jointly constrain electrical and biological factors in a conductive screw-threaded microneedle (ST-needle) system, identifying dual positioning regulation of the organelle network. The unique physical properties of this system could accurately locate the lesion and restrict the current path to the lesion cells through electromagnetic laws, and dynamic Van der Waals forces were activated to release functionalized hydrogel microspheres. Subsequently, the mitochondria-endoplasmic reticulum (ER) complex was synergistically targeted by increasing mitochondrial ATP supply to the ER via electrical stimulation and by blocking calcium current from the ER to the mitochondria using microspheres, and then the life activity of the lesion cells was effectively restored.

Injectable smart stimuli-responsive hydrogels: pioneering advancements in biomedical applications

Hydrogels have established their significance as prominent biomaterials within the realm of biomedical research. However, injectable hydrogels have garnered greater attention compared with their conventional counterparts due to their excellent minimally invasive nature and adaptive behavior post-injection. With the rapid advancement of emerging chemistry and deepened understanding of biological processes, contemporary injectable hydrogels have been endowed with an "intelligent" capacity to respond to various endogenous/exogenous stimuli (such as temperature, pH, light and magnetic field). This innovation has spearheaded revolutionary transformations across fields such as tissue engineering repair, controlled drug delivery, disease-responsive therapies, and beyond. In this review, we comprehensively expound upon the raw materials (including natural and synthetic materials) and injectable principles of these advanced hydrogels, concurrently providing a detailed discussion of the prevalent strategies for conferring stimulus responsiveness. Finally, we elucidate the latest applications of these injectable "smart" stimuli-responsive hydrogels in the biomedical domain, offering insights into their prospects.

Dual-Setting Bone Cement Based On Magnesium Phosphate Modified with Glycol Methacrylate Designed for Biomedical Applications

Magnesium phosphate cement (MPC) is a suitable alternative for the currently used calcium phosphates, owing to beneficial properties like favorable resorption rate, fast hardening, and higher compressive strength. However, due to insufficient mechanical properties and high brittleness, further improvement is still expected. In this paper, we reported the preparation of a novel type of dual-setting cement based on MPC with poly(2-hydroxyethyl methacrylate) (pHEMA). The aim of our study was to evaluate the effect of HEMA addition, especially its concentration and premix time, on the selected properties of the composite. Several beneficial effects were found: better formability, shortened setting time, and improvement of mechanical strengths. The developed cements were hardening in ∼16-21 min, consisted of well-crystallized phases and polymerized HEMA, had porosity between ∼2-11%, degraded slowly by ∼0.1-4%/18 days, their wettability was ∼20-30°, they showed compressive and bending strength between ∼45-73 and 13-20 MPa, respectively, and, finally, their Young's Modulus was close to ∼2.5-3.0 GPa. The results showed that the optimal cement composition is MPC+15%HEMA and 4 min of polymer premixing time. Overall, our research suggested that this developed cement may be used in various biomedical applications.

Risk factors of epidural hematoma in patients undergoing spinal surgery: a meta-analysis of 29 cohort studies

OBJECTIVE

The authors conducted this meta-analysis to identify risk factors for spinal epidural haematoma (SEH) among patients following spinal surgery.

METHODS

The authors systematically searched Pub: Med, Embase, and the Cochrane Library for articles that reported risk factors associated with the development of SEH in patients undergoing spinal surgery from inception to 2 July 2022. The pooled odds ratio (OR) was estimated using a random-effects model for each investigated factor. The evidence of observational studies was classified as high quality (Class I), moderate quality (Class II or III) and low quality (Class IV) based on sample size, Egger's P value and between-study heterogeneity. In addition, subgroup analyses stratified by study baseline characteristics and leave-one-out sensitivity analyses were performed to explore the potential sources of heterogeneity and the stability of the results.

RESULTS

Of 21 791 articles screened, 29 unique cohort studies comprising 150 252 patients were included in the data synthesis. Studies with high-quality evidence showed that older patients (≥60 years) (OR, 1.35; 95% CI, 1.03-1.77) were at higher risk for SEH. Studies with moderate-quality evidence suggested that patients with a BMI greater than or equal to 25 kg/m² (OR, 1.39; 95% CI, 1.10-1.76), hypertension (OR, 1.67; 95% CI, 1.28-2.17), and diabetes (OR, 1.25; 95% CI, 1.01-1.55) and those undergoing revision surgery (OR, 1.92; 95% CI, 1.15-3.25) and multilevel procedures (OR, 5.20; 95% CI, 2.89-9.37) were at higher risk for SEH. Meta-analysis revealed no association between tobacco use, operative time, anticoagulant use or American Society of Anesthesiologists (ASA) classification and SEH.

CONCLUSIONS

Obvious risk factors for SEH include four patient-related risk factors, including older age, obesity, hypertension and diabetes, and two surgery-related risk factors, including revision surgery and multilevel procedures. These findings, however, must be interpreted with caution because most of these risk factors had small effect sizes. Nonetheless, they may help clinicians identify high-risk patients to improve prognosis.

Injectable Self-Setting Ternary Calcium-Based Bone Cement Promotes Bone Repair

Bone defects, especially large ones, are clinically difficult to treat. The development of new bone repair materials exhibits broad application prospects in the clinical treatment of trauma. Bioceramics are considered to be one of the most promising biomaterials owing to their good biocompatibility and bone conductivity. In this study, a self-curing bone repair material having a controlled degradation rate was prepared by mixing calcium citrate, calcium hydrogen phosphate, and semi-hydrated calcium sulfate in varying proportions, and its properties were comprehensively evaluated. In vitro cell experiments and RNA sequencing showed that the composite cement activated PI3K/Akt and MAPK/Erk signaling pathways to promote osteogenesis by promoting the proliferation and osteoblastic differentiation of mesenchymal stem cells. In a rat model with femoral condyle defects, the composite bone cement showed excellent bone repair effect and promoted bone regeneration. The injectable properties of the composite cement further improved its practical applicability, and it can be applied in bone repair, especially in the repair of irregular bone defects, to achieve superior healing.

Research progress in decellularized extracellular matrix hydrogels for intervertebral disc degeneration

As one of the most common clinical disorders, low back pain (LBP) influences patient quality of life and causes substantial social and economic burdens. Many factors can result in LBP, the most common of which is intervertebral disc degeneration (IDD). The progression of IDD cannot be alleviated by conservative or surgical treatments, and gene therapy, growth factor therapy, and cell therapy have their own limitations. Recently, research on the use of hydrogel biomaterials for the treatment of IDD has garnered great interest, and satisfactory treatment results have been achieved. This article describes the classification of hydrogels, the methods of decellularized extracellular matrix (dECM) production and the various types of gel formation. The current research on dECM hydrogels for the treatment of IDD is described in detail in this article. First, an overview of the material sources, decellularization methods, and gel formation methods is given. The focus is on research performed over the last three years, which mainly consists of bovine and porcine NP tissues, while for decellularization methods, combinations of several approaches are primarily used. dECM hydrogels have significantly improved mechanical properties after the polymers are cross-linked. The main effects of these gels include induction of stem cell differentiation to intervertebral disc (IVD) cells, good mechanical properties to restore IVD height after polymer cross-linking, and slow release of exosomes. Finally, the challenges and problems still faced by dECM hydrogels for the treatment of IDD are summarised, and potential solutions are proposed. This paper is the first to summarise the research on dECM hydrogels for the treatment of IDD and aims to provide a theoretical reference for subsequent studies.

A Pre-clinical Standard Operating Procedure for Evaluating Orthobiologics in an In Vivo Rat Spinal Fusion Model

The rat animal model is a cost effective and reliable model used in spinal pre-clinical research. Complications from various surgical procedures in humans often arise that were based on these pre-clinical animal models. Therefore safe and efficacious pre-clinical animal models are needed to establish continuity into clinical trials. A Standard Operating Procedure (SOP) is a validated method that allows researchers to safely and carefully replicate previously successful surgical techniques. Thus, the aim of this study is to describe in detail the procedures involved in a common rat bilateral posterolateral intertransverse spinal fusion SOP used to test the efficacy and safety different orthobiologics using a collagen-soaked sponge as an orthobiologic carrier. Only two orthobiologics are currently FDA approved for spinal fusion surgery which include recombinant bone morphogenetic protein 2 (rhBMP-2), and I-FACTOR. While there are many additional orthobiologics currently being tested, one way to show their safety profile and gain FDA approval, is to use well established pre-clinical animal models. A preoperative, intraoperative, and postoperative surgical setup including specific anesthesia and euthanasia protocols are outlined. Furthermore, we describe different postoperative methods used to validate the spinal fusion SOP, which include μCT analysis, histopathology, biomechanical testing, and blood analysis. This SOP can help increase validity, transparency, efficacy, and reproducibly in future rat spinal fusion surgery procedures.

The role of oxidative stress in intervertebral disc cellular senescence

With the aggravation of social aging and the increase in work intensity, the prevalence of spinal degenerative diseases caused by intervertebral disc degeneration(IDD)has increased yearly, which has driven a heavy economic burden on patients and society. It is well known that IDD is associated with cell damage and degradation of the extracellular matrix. In recent years, it has been found that IDD is induced by various mechanisms (e.g., genetic, mechanical, and exposure). Increasing evidence shows that oxidative stress is a vital activation mechanism of IDD. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) could regulate matrix metabolism, proinflammatory phenotype, apoptosis, autophagy, and aging of intervertebral disc cells. However, up to now, our understanding of a series of pathophysiological mechanisms of oxidative stress involved in the occurrence, development, and treatment of IDD is still limited. In this review, we discussed the oxidative stress through its mechanisms in accelerating IDD and some antioxidant treatment measures for IDD.