Design, synthesis, imaging, and biomechanics of a softness-gradient hydrogel nucleus pulposus prosthesis in a canine lumbar spine model

Lomber Disk Hernisinde Disk Restorasyon Hidrojel İmplant (Gelstixtm) Kullandığımız Hastalarda Sonuçlar: Retrospektif Kohort Çalışması

Introduction: The aim of this study is evaluting the results of disc restoration hidrogel implanted (GelstixTM) lomber disc hernia patients. Material-Method: Patients suffered from chronic back pain diagnosed lumber disc hernia who were admitted to Firat University Algology Clinic and treated with disc restoration hidrogel between January 2013 – January 2014 were evaluated. Cases were evaluated for demografic characteristics, magnetic resistance imaging findings, preoperative and postoperative VAS, complications, side effects and patients satisfaction after prosedure. Results: Of the operated 62 patients were 25 male (40,3%) and 37 female (59,7%). Mean age of all patients was 49,18±14,18 years, mean age of female patients was 50,81±13,37 years and mean age of male patients was 46,76±15,27 years. Mean duration of pain in female and male patients was 37,81±37,92 months and 25,36±33,58 months, respectively. Preoperative and postoperatif VAS scores of female and male patients were 8,24±1,09 and 7,88±1,01 and 3,56±2,11 and 3,76±2,17, respectively. Of the 62 patients suffered from 16 right leg pain (25,8%), 20 left leg pain (32,3%), 26 bilateral lower limb pain (41,9%). Of 62 patients 31 had no additional disorders (50%), 12 had cardiac disorders (19,4%), 3 had (4,8%) respiratory disorders, 7 had endocrine disorders (11,3%), 4 had both endocrine and cardiac disorders (6,5%), 2 had both cardiac and respiratory disorders (3,2%), 1 had both endocrine and respiratory disorders (1,6%), and 2 had both endocrine, cardiac and respiratory disorders (3,2%). Of the 62 patients 25 had bulging (40,3%), 5 had protrusion (8,1%), 4 had narrowed neural foramen (6,5%), 18 had bulging +narrowed neural foramen (29%), 3 had narrowed neural foramen + protrusion (4,8%) and 7 had bulging + protrusion (11,3%). Thirteen patients hadn’t had previous therapy (20,97%), transforaminal steroid injection was applied to 29 patients (46,77%) and medical threapy (such as NSAID, miyorelactants) was applied to 20 (32,26%). Levels of complaints were 2 at L2-L3 (3,2%), 17 at L3-L4 (27,4%), 28 at L4-L5 (45,2%) and 15 at L5-S1 (24,2%). Without L2-L3 level other operated levels had significant difference between preropeative VAS scores and postoperative VAS scores. The number of unsatissfied patients was 9 (14,5%), moderated satisfied patients number 16(25,8%),good satisfied patients number was 16 (25,8%), and perfectly satisfied patients number was 21 (33,9%). Conclusion: Disc restoration hidrogel is a safe minimal invasive technique with satisfactory results, low complication rates and low side effect risk especially in young and middle aged patients.

Advances in Tissue Engineering for Disc Repair

Intervertebral disc (IVD) degeneration is a leading cause of chronic low back pain (LBP) that results in serious disability and significant economic burden. IVD degeneration alters the disc structure and spine biomechanics, resulting in subsequent structural changes throughout the spine. Currently, treatments of chronic LBP due to IVD degeneration include conservative treatments, such as pain medication and physiotherapy, and surgical treatments, such as removal of herniated disc without or with spinal fusion. However, none of these treatments can completely restore a degenerated disc and its function. Thus, although the exact pathogenesis of disc degeneration remains unclear, there are studies examining the effectiveness of biological approaches, such as growth factor injection, gene therapy, and cell transplantation, in promoting IVD regeneration. Furthermore, tissue engineering using a combination of cell transplantation and biomaterials has emerged as a promising new approach for repair or restoration of degenerated discs. The main purpose of this review was to provide an overview of the current status of tissue engineering applications for IVD regenerative therapy by performing literature searches using PubMed. Significant advances in tissue engineering have opened the door to a new generation of regenerative therapies for the treatment of chronic discogenic LBP.

Comparison of biomechanical studies of disc repair devices based on a systematic review

BACKGROUND CONTEXT

A variety of solutions have been suggested as candidates for the repair of the annulus fibrosis (AF), with the ability to withstand physiological loads of paramount importance.

PURPOSE

The objective of our study was to capture the scope of biomechanical test models of AF repairs. We hypothesized that common test parameters would emerge.

STUDY DESIGN

Systematic Review METHODS: PubMed and EMBASE databases were searched for studies in English including the keywords "disc repair AND animal models," "disc repair AND cadaver spines," "intervertebral disc AND biomechanics," and "disc repair AND biomechanics." This list was further limited to those studies which included biomechanical results from annular repair in animal or human spinal segments from the cervical, thoracic, lumbar and/or coccygeal (tail) segments. For each study, the method used to measure the biomechanical property and biomechanical test results were documented.

RESULTS

A total of 2,607 articles were included within our initial analysis. Twenty-two articles met our inclusion criteria. Significant variability in terms of species tested, measurements used to quantify annular repair strength, and the method/direction/magnitude that forces were applied to a repaired annulus were found. Bovine intervertebral disc was most commonly used model (6 of 22 studies) and the most common mechanical property reported was the force required for failure of the disc repair device (15 tests).

CONCLUSIONS

Our hypothesis was rejected; no common features were identified across AF biomechanical models and as a result it was not possible to compare results of preclinical testing of annular repair devices. Our analysis suggests that a standardized biomechanical model that can be repeatably executed across multiple laboratories is required for the mechanical screening of candidates for AF repair.

CLINICAL SIGNIFICANCE

This literature review provides a summary of preclinical testing of annular repair devices for clinicians to properly evaluate the safety/efficacy of developing technology designed to repair annular defects after disc herniations.

Safety of intradiscal injection and biocompatibility of polyester amide microspheres in a canine model predisposed to intervertebral disc degeneration

Repair of degenerated intervertebral discs (IVD) might be established via intradiscal delivery of biologic therapies. Polyester amide polymers (PEA) were evaluated for in vitro cytotoxicity and in vivo biocompatibility, and thereafter intradiscal application of PEA microspheres (PEAMs) in a canine model predisposed to IVD degeneration at long-term (6 months) follow-up. PEA extracts did not induce cytotoxicity in mouse fibroblast cells (microscopy and XTT assay), while a slight foreign body reaction was demonstrated by histopathology after intramuscular implantation in rabbits. Intradiscal injection of a volume of 40 µL through 26 and 27G needles induced no degenerative changes in acanine model susceptible to IVD disease. Although sham-injected IVDs showed increased CAV1 expression compared with noninjected IVDs, which may indicate increased cell senescence, these findings were not supported by immunohistochemistry, biomolecular analysis of genes related to apoptosis, biochemical and histopathological results. PEAM-injected IVDs showed significantly higher BAX/BCL2 ratio vs sham-injected IVDs suggestive of an anti-apoptotic effect of the PEAMs. These findings were not supported by other analyses (clinical signs, disc height index, T2 values, biomolecular and biochemical analyses, and IVD histopathology). PEAs showed a good cytocompatibility and biocompatibility. PEAMs are considered safe sustained release systems for intradiscal delivery of biological treatments. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 707-714, 2017.

Tissue Engineering a Biological Repair Strategy for Lumbar Disc Herniation

The intervertebral disc is a critical part of the intersegmental soft tissue of the spinal column, providing flexibility and mobility, while absorbing large complex loads. Spinal disease, including disc herniation and degeneration, may be a significant contributor to low back pain. Clinically, disc herniations are treated with both nonoperative and operative methods. Operative treatment for disc herniation includes removal of the herniated material when neural compression occurs. While this strategy may have short-term advantages over nonoperative methods, the remaining disc material is not addressed and surgery for mild degeneration may have limited long-term advantage over nonoperative methods. Furthermore, disc herniation and surgery significantly alter the mechanical function of the disc joint, which may contribute to progression of degeneration in surrounding tissues. We reviewed recent advances in tissue engineering and regenerative medicine strategies that may have a significant impact on disc herniation repair. Our review on tissue engineering strategies focuses on cell-based and inductive methods, each commonly combined with material-based approaches. An ideal clinically relevant biological repair strategy will significantly reduce pain and repair and restore flexibility and motion of the spine.

Biocompatibility and intradiscal application of a thermoreversible celecoxib-loaded poly-N-isopropylacrylamide MgFe-layered double hydroxide hydrogel in a canine model

Introduction

Chronic low back pain due to intervertebral disc (IVD) degeneration is associated with increased levels of inflammatory mediators. Current medical treatment consists of oral anti-inflammatory drugs to alleviate pain. In this study, the efficacy and safety of a novel thermoreversible poly-N-isopropylacrylamide MgFe-layered double hydroxide (pNIPAAM MgFe-LDH) hydrogel was evaluated for intradiscal controlled delivery of the selective cyclooxygenase (COX) 2 inhibitor and anti-inflammatory drug celecoxib (CXB).

Methods

Degradation, release behavior, and the ability of a CXB-loaded pNIPAAM MgFe-LDH hydrogel to suppress prostaglandin E₂ (PGE₂) levels in a controlled manner in the presence of a proinflammatory stimulus (TNF-α) were evaluated in vitro. Biocompatibility was evaluated histologically after subcutaneous injection in mice. Safety of intradiscal application of the loaded and unloaded hydrogels was studied in a canine model of spontaneous mild IVD degeneration by histological, biomolecular, and biochemical evaluation. After the hydrogel was shown to be biocompatible and safe, an in vivo dose–response study was performed in order to determine safety and efficacy of the pNIPAAM MgFe-LDH hydrogel for intradiscal controlled delivery of CXB.

Results

CXB release correlated to hydrogel degradation in vitro. Furthermore, controlled release from CXB-loaded hydrogels was demonstrated to suppress PGE₂ levels in the presence of TNF-α. The hydrogel was shown to exhibit a good biocompatibility upon subcutaneous injection in mice. Upon intradiscal injection in a canine model, the hydrogel exhibited excellent biocompatibility based on histological evaluation of the treated IVDs. Gene expression and biochemical analyses supported the finding that no substantial negative effects of the hydrogel were observed. Safety of application was further confirmed by the absence of clinical symptoms, IVD herniation or progression of degeneration. Controlled release of CXB resulted in a nonsignificant maximal inhibition (approximately 35 %) of PGE₂ levels in the mildly degenerated canine IVDs.

Conclusions

In conclusion, this study showed biocompatibility and safe intradiscal application of an MgFe LDH-pNIPAAM hydrogel. Controlled release of CXB resulted in only limited inhibition of PGE₂ in this model with mild IVD degeneration, and further studies should concentrate on application of controlled release from this type of hydrogel in animal models with more severe IVD degeneration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0727-x) contains supplementary material, which is available to authorized users.

Developments in intervertebral disc disease research: pathophysiology, mechanobiology, and therapeutics

Low back pain is a leading cause of disability worldwide and the second most common cause of physician visits. There are many causes of back pain, and among them, disc herniation and intervertebral disc degeneration are the most common diagnoses and targets for intervention. Currently, clinical treatment outcomes are not strongly correlated with diagnoses, emphasizing the importance for characterizing more completely the mechanisms of degeneration and their relationships with symptoms. This review covers recent studies elucidating cellular and molecular changes associated with disc mechanobiology, as it relates to degeneration and regeneration. Specifically, we review findings on the biochemical changes in disc diseases, including cytokines, chemokines, and proteases; advancements in disc disease diagnostics using imaging modalities; updates on studies examining the response of the intervertebral disc to injury; and recent developments in repair strategies, including cell-based repair, biomaterials, and tissue engineering. Findings on the effects of the omega-6 fatty acid, linoleic acid, on nucleus pulposus tissue engineering are presented. Studies described in this review provide greater insights into the pathogenesis of disc degeneration and may define new paradigms for early or differential diagnostics of degeneration using new techniques such as systemic biomarkers. In addition, research on the mechanobiology of disease enriches the development of therapeutics for disc repair, with potential to diminish pain and disability associated with disc degeneration.