Orthobiologic Management Options for Degenerative Disc Disease

Degenerative disc disease (DDD) is a pervasive condition that limits quality of life and burdens economies worldwide. Conventional pharmacological treatments primarily aimed at slowing the progression of degeneration have demonstrated limited long-term efficacy and often do not address the underlying causes of the disease. On the other hand, orthobiologics are regenerative agents derived from the patient's own tissue and represent a promising emerging therapy for degenerative disc disease. This review comprehensively outlines the pathophysiology of DDD, highlighting the inadequacies of existing pharmacological therapies and detailing the potential of orthobiologic approaches. It explores advanced tools such as platelet-rich plasma and mesenchymal stem cells, providing a historical overview of their development within regenerative medicine, from foundational in vitro studies to preclinical animal models. Moreover, the manuscript delves into clinical trials that assess the effectiveness of these therapies in managing DDD. While the current clinical evidence is promising, it remains insufficient for routine clinical adoption due to limitations in study designs. The review emphasizes the need for further research to optimize these therapies for consistent and effective clinical outcomes, potentially revolutionizing the management of DDD and offering renewed hope for patients.

Improved antitumor activity through a tyramidyl maslinic acid derivative. Design and validation as drug-loaded electrospun polymeric nanofibers

Among the most harmful tumors detected in the human body, such as breast, colon, brain or pancreas, breast (BC) and colorectal cancer (CRC) are the first and third most frequent cancer worldwide, respectively. The current existing chemotherapeutic treatments present serious side effects due to their intravenous administration can induce cytotoxicity in healthy cells. Thus, new treatment methods based on drug-loaded polymeric nanofibers (NFs) have gained significant potential for their use in localized cancer chemotherapy. Here, a deep in vitro comparative analysis between maslinic acid (MA) and a tyramine-maslinic acid (TMA) derivative is initially performed. This analysis includes a proliferation, and a cell cycle assay, and a genotoxicity, antiangiogenic and apoptosis study. Then, the TMA derivative has been incorporated into electrospun polymeric NFs obtaining an implantable dressing material with antitumor activity. Two types of patches containing TMA-loaded polymeric NFs of poly(caprolactone) (PCL), and a mixture of polylactic acid/poly(4-vinylpyridine) (PLA/PVP) were fabricated by the electrospinning technique. The characterization of the drug-loaded NFs showed an encapsulation capacity of 0.027 mg TMA/mg PCL and 0.024 mg TMA/mg PLA/PVP. Then, the cytotoxic activity of both polymeric systems was tested in CRC (T84), BC (MCF-7) and a no tumor (L929) cell lines exposed to TMA-loaded NFs and blank NFs for 48 h. Moreover, cell cycle assay, genotoxicity, angiogenesis and apoptosis tests were carried out to study the mechanism of action of TMA. Blank NFs showed no-toxicity in all cell lines tested and both drug-loaded NFs significantly reduced cell proliferation (relative proliferation of ≈44 % and ≈25 % respectively). Therefore, TMA was less genotoxic than maslinic acid (MA), and reduced VEGFA expression in MCF-7 cells (1.32 and 2.12-fold for MA and TMA respectively). These results showed that TMA-loaded NFs could constitute a promising biocompatible and biodegradable nanoplatform for the local treatment of solid tumors such as CRC or BC.

Biomedical applications of silk and its role for intervertebral disc repair

Intervertebral disc (IVD) degeneration (IDD) is the main contributor to chronic low back pain. To date, the present therapies mainly focus on treating the symptoms caused by IDD rather than addressing the problem itself. For this reason, researchers have searched for a suitable biomaterial to repair and/or regenerate the IVD. A promising candidate to fill this gap is silk, which has already been used as a biomaterial for many years. Therefore, this review aims first to elaborate on the different origins from which silk is harvested, the individual composition, and the characteristics of each silk type. Another goal is to enlighten why silk is so suitable as a biomaterial, discuss its functionalization, and how it could be used for tissue engineering purposes. The second part of this review aims to provide an overview of preclinical studies using silk-based biomaterials to repair the inner region of the IVD, the nucleus pulposus (NP), and the IVD's outer area, the annulus fibrosus (AF). Since the NP and the AF differ fundamentally in their structure, different therapeutic approaches are required. Consequently, silk-containing hydrogels have been used mainly to repair the NP, and silk-based scaffolds have been used for the AF. Although most preclinical studies have shown promising results in IVD-related repair and regeneration, their clinical transition is yet to come.

The role of microenvironment in stem cell-based regeneration of intervertebral disc

Regenerative medicine for intervertebral disc (IVD) disease, by utilizing chondrocytes, IVD cells, and stem cells, has progressed to clinical trials in the treatment of back pain, and has been studied in various animal models of disc degeneration in the past decade. Stem cells exist in their natural microenvironment, which provides vital dynamic physical and chemical signals for their survival, proliferation and function. Long-term survival, function and fate of mesenchymal stem cells (MSCs) depend on the microenvironment in which they are transplanted. However, the transplanted MSCs and the endogenous disc cells were influenced by the complicated microenvironment in the degenerating disc with the changes of biochemical and biophysical components. It is important to understand how the MSCs and endogenous disc cells survive and thrive in the harsh microenvironment of the degenerative disc. Furthermore, materials containing stem cells and their natural microenvironment have good clinical effects. However, the implantation of tissue engineering IVD (TE-IVD) cannot provide a complete and dynamic microenvironment for MSCs. IVD graft substitutes may need further improvement to provide the best engineered MSC microenvironment. Additionally, the IVD progenitor cells inside the stem cell niches have been regarded as popular graft cells for IVD regeneration. However, it is still unclear whether actual IVD progenitor cells exist in degenerative spinal conditions. Therefore, the purpose of this review is fourfold: to discuss the presence of endogenous stem cells; to review and summarize the effects of the microenvironment in biological characteristics of MSC, especially those from IVD; to explore the feasibility and prospects of IVD graft substitutes and to elaborate state of the art in the use of MSC transplantation for IVD degeneration in vivo as well as their clinical application.

MSCs-engineered biomimetic PMAA nanomedicines for multiple bioimaging-guided and photothermal-enhanced radiotherapy of NSCLC

Background

The recently developed biomimetic strategy is one of the mostly effective strategies for improving the theranostic efficacy of diverse nanomedicines, because nanoparticles coated with cell membranes can disguise as “self”, evade the surveillance of the immune system, and accumulate to the tumor sites actively.

Results

Herein, we utilized mesenchymal stem cell memabranes (MSCs) to coat polymethacrylic acid (PMAA) nanoparticles loaded with Fe(III) and cypate—an derivative of indocyanine green to fabricate Cyp-PMAA-Fe@MSCs, which featured high stability, desirable tumor-accumulation and intriguing photothermal conversion efficiency both in vitro and in vivo for the treatment of lung cancer. After intravenous administration of Cyp-PMAA-Fe@MSCs and Cyp-PMAA-Fe@RBCs (RBCs, red blood cell membranes) separately into tumor-bearing mice, the fluorescence signal in the MSCs group was 21% stronger than that in the RBCs group at the tumor sites in an in vivo fluorescence imaging system. Correspondingly, the T₁-weighted magnetic resonance imaging (MRI) signal at the tumor site decreased 30% after intravenous injection of Cyp-PMAA-Fe@MSCs. Importantly, the constructed Cyp-PMAA-Fe@MSCs exhibited strong photothermal hyperthermia effect both in vitro and in vivo when exposed to 808 nm laser irradiation, thus it could be used for photothermal therapy. Furthermore, tumors on mice treated with phototermal therapy and radiotherapy shrank 32% more than those treated with only radiotherapy.

Conclusions

These results proved that Cyp-PMAA-Fe@MSCs could realize fluorescence/MRI bimodal imaging, while be used in phototermal-therapy-enhanced radiotherapy, providing desirable nanoplatforms for tumor diagnosis and precise treatment of non-small cell lung cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00823-6.

Tissue Engineering Strategies for Intervertebral Disc Treatment Using Functional Polymers

Intervertebral disc (IVD) is the fibrocartilage between the vertebrae, allowing the spine to move steadily by bearing multidirectional complex loads. Aging or injury usually causes degeneration of IVD, which is one of the main reasons for low back pain prevalent worldwide and reduced quality of life. While various treatment strategies for degenerative IVD have been studied using in vitro studies, animal experiments, and clinical trials, there are unsolved limitations for endogenous regeneration of degenerative IVD. In this respect, several tissue engineering strategies that are based on the cell and scaffolds have been extensively researched with positive outcomes for regeneration of IVD tissues. Scaffolds made of functional polymers and their diverse forms mimicking the macro- and micro-structure of native IVD enhance the biological and mechanical properties of the scaffolds for IVD regeneration. In this review, we discuss diverse morphological and functional polymers and tissue engineering strategies for endogenous regeneration of degenerative IVD. Tissue engineering strategies using functional polymers are promising therapeutics for fundamental and endogenous regeneration of degenerative IVD.

Multidrug-eluting bi-layered microparticle-mesh scaffolds for musculoskeletal tissue regeneration

Stem cell-based tissue engineering necessitates the development of a biocompatible scaffold, as a structural support, that provides a continuous supply of bioactive molecules for specific lineage differentiation. While incorporating bioactive molecules within a scaffold to improve stem cell differentiation has been reported in the literature, there is minimal evidence of any scaffold that can deliver a customized concoction of both hydrophobic and hydrophilic bioactive molecules to induce in situ lineage differentiation without any external supplements. In this study, we established a bioactive, drug-eluting bi-layered microparticle-mesh scaffold (BMMS) using the electrospinning technique. This BMMS was co-encapsulated with hydrophobic dexamethasone (in the mesh), hydrophilic ascorbic acid and β-glycerophosphate or proline (in the microparticles). We hypothesized that a sustained-releasing BMMS can direct in situ specific lineage differentiation of MSCs (e.g. osteogenic and chondrogenic) in a minimally supplemented culture environment into musculoskeletal tissues. The characterization of this BMMS revealed good encapsulation efficiencies of the bioactive molecules with sustained-releasing capabilities. The release kinetics of each drug was further analyzed using mathematical drug-releasing models. These scaffolds were subsequently shown to have potential for osteogenic or chondrogenic lineage differentiation from mesenchymal stem cells (MSCs) in a minimally supplemented culture medium.

Differentiation of MSC and annulus fibrosus cells on genetically engineered silk fleece-membrane-composites enriched for GDF-6 or TGF-β3

Intervertebral disc (IVD) repair is a high-priority topic in our active and increasingly ageing society. Since a high number of people are affected by low back pain treatment options that are able to restore the biological function of the IVD are highly warranted. Here, we investigated whether the feasibility of genetically engineered (GE)-silk from Bombyx mori containing specific growth factors to precondition human bone-marrow derived mesenchymal stem cells (hMSC) or to activate differentiated human annulus fibrosus cells (hAFC) prior transplantation or for direct repair on the IVD. Here, we tested the hypothesis that GE-silk fleece can thrive human hMSC towards an IVD-like phenotype. We aimed to demonstrate a possible translational application of good manufacturing practice (GMP)-compliant GE-silk scaffolds in IVD repair and regeneration. GE-silk with growth and differentiation factor 6 (GDF-6-silk) or transforming growth factor β3 (TGF-β3, TGF-β3-silk) and untreated silk (cSilk) were investigated by DNA content, cell activity assay and glycosaminoglycan (GAG) content and their differentiation potential by qPCR analysis. We found that all silk types demonstrated a very high biocompatibility for both cell types, that is, hMSC and hAFC, as revealed by cell activity, and DNA proliferation assay. Further, analyzing qPCR of marker genes revealed a trend to differentiation toward an NP-like phenotype looking at the Aggrecan/Collagen 2 ratio which was around 10:1. Our results support the conclusion that our GE-silk scaffold treatment approach can thrive hMSC towards a more IVD-like phenotype or can maintain the phenotype of native hAFC. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1324-1333, 2018.

Transplantation of Hypoxic-Preconditioned Bone Mesenchymal Stem Cells Retards Intervertebral Disc Degeneration via Enhancing Implanted Cell Survival and Migration in Rats

Objective

Special hypoxic and hypertonic microenvironment in intervertebral discs (IVDs) decreases the treatment effect of cell transplantation. We investigated the hypothesis that hypoxic preconditioning (HP) could improve the therapeutic effect of bone mesenchymal stem cells (BMSCs) to IVD degeneration.

Methods

BMSCs from green fluorescent protein-transgenic rats were pretreated with cobalt chloride (CoCl₂, 100 μM, 24 h) for hypoxic conditions in vitro. Apoptosis (related pathways of caspase-3 and bcl-2) and migration (related pathways of HIF-1α and CXCR4) were detected in BMSCs. In vivo, BMSCs and HP BMSCs (H-BMSCs) were injected into the rat model of IVD degeneration. The IVD height, survival, migration, and differentiation of transplanted BMSCs and matrix protein expression (collagen II, aggrecan, and MMP-13) were tested.

Results

H-BMSCs could extensively decrease IVD degeneration by increasing IVD height and collagen II and aggrecan expressions when compared with BMSCs. Significantly, more GFP-positive BMSCs were observed in the nucleus pulposus and annulus fibrosus regions of IVD. HP could significantly decrease BMSC apoptosis (activating bcl-2 and inhibiting caspase-3) and improve BMSC migration (increasing HIF-1α and CXCR4) in vitro.

Conclusion

HP could significantly enhance the capacity of BMSCs to repair DDD by increasing the survival and migration of implanted cells and increasing matrix protein expression.

Strategies in regenerative medicine for intervertebral disc repair using mesenchymal stem cells and bioscaffolds

The intervertebral disc (IVD) is a major weight bearing structure that undergoes degenerative changes with aging limiting its ability to dissipate axial spinal loading in an efficient manner resulting in the generation of low back pain. Low back pain is a number one global musculoskeletal disorder with massive socioeconomic impact. The WHO has nominated development of mesenchymal stem cells and bioscaffolds to promote IVD repair as primary research objectives. There is a clear imperative for the development of strategies to effectively treat IVD defects. Early preclinical studies with mesenchymal stem cells in canine and ovine models have yielded impressive results in IVD repair. Combinatorial therapeutic approaches encompassing biomaterial and cell-based therapies promise significant breakthroughs in IVD repair in the near future.

Stem Cell Approaches to Intervertebral Disc Regeneration: Obstacles from the Disc Microenvironment

Intervertebral disc (IVD) degeneration results in segmental instability and irritates neural compressive symptoms, such as low back pain and motor deficiency. The transplanting of stem cell into degenerative discs has attracted increasing clinical attention, as a new and proven approach to alleviating disc degeneration and to relieving discogenic pains. Aside from supplementation with stem cells, the IVD itself already contains a pool of stem and progenitor cells. Since the resident disc stem cells are incapable of reversing the pathologic changes that occur during aging and disc degeneration, it has been debated as to whether transplanted stem cells are capable of providing an efficient and durable therapeutic effect, even though there have been positive outcomes in both animal models and in clinical trials. This review aims to decipher the interactions between the stem cell and the disc microenvironment. Within their new niches in the IVD, the exogenous stem cell shows metabolic adaptation to the low-glucose supply, hypoxia, and compressive loadings, but demonstrates little tolerance to the disc-like acidity and hypertonicity. Similarly, the survival of endogenous stem cells is threatened as well by the harsh disc microenvironment, which may exhaust the stem cell resources and restrict the self-repair capacity of a degenerating IVD. To eliminate the intrinsic obstacles within the stressful disc niches, stem cells should be delivered with an injectable scaffold that provides both survival and mechanical support. Quick healing or concretion of the injection injuries, which minimizes stem cell leakage and disturbance to disc homeostasis, is of equal importance toward achieving efficient stem cell-based disc regeneration.

Stem cell therapy for intervertebral disk regeneration

Intervertebral disk degeneration has been considered an irreversible process characterized by a decrease in cell viability, attenuation of proteoglycan and type II collagen synthesis, and dehydration of nucleus pulposus. Stem cell therapy specifically addresses the degenerative process and offers a potentially effective treatment modality. Current preclinical studies show that mesenchymal stem cells have the capacity to repair degenerative disks by differentiation toward chondrocyte-like cells, which produce proteoglycans and type II collagen. There has been evidence that mesenchymal stem cell transplantation into the intervertebral disk increases the intradiskal magnetic resonance imaging T2 signal intensity, increases the disk height, and decreases the degenerative grade in animal models. Appropriate selection of cell carriers/matrix is important because it may prevent cell leakage into the spinal canal and provide an environment that facilitates cell proliferation and differentiation. Although human cell therapy trials for degenerative disk disease are on the horizon, potential issues might arise. The authors hereby review the current state of regenerative cell therapy in degenerative disk disease, with emphasis in cell source, techniques for cellular expansion, induction, transplantation, potential benefit, and risks of the use of this novel medical armamentarium in the treatment of degenerative disk disease.

Enhancing cell migration in shape-memory alginate–collagen composite scaffolds: In vitro and ex vivo assessment for intervertebral disc repair

Lower lumbar disc disorders pose a significant problem in an aging society with substantial socioeconomic consequences. Both inner tissue (nucleus pulposus) and outer tissue (annulus fibrosus) of the intervertebral disc are affected by such debilitating disorders and can lead to disc herniation and lower back pain. In this study, we developed an alginate–collagen composite porous scaffold with shape-memory properties to fill defects occurring in annulus fibrosus tissue of degenerated intervertebral discs, which has the potential to be administered using minimal invasive surgery. In the first part of this work, we assessed how collagen incorporation on preformed alginate scaffolds influences the physical properties of the final composite scaffold. We also evaluated the ability of annulus fibrosus cells to attach, migrate, and proliferate on the composite alginate–collagen scaffolds compared to control scaffolds (alginate only). In vitro experiments, performed in intervertebral disc-like microenvironmental conditions (low glucose and low oxygen concentrations), revealed that for alginate only scaffolds, annulus fibrosus cells agglomerated in clusters with limited infiltration and migration capacity. In comparison, for alginate–collagen scaffolds, annulus fibrosus cells readily attached and colonized constructs, while preserving their typical fibroblastic-like cell morphology with spreading behavior and intense cytoskeleton expression. In a second part of this study, we investigated the effects of alginate–collagen scaffold when seeded with bone marrow derived mesenchymal stem cells. In vitro, we observed that alginate–collagen porous scaffolds supported cell proliferation and extracellular matrix deposition (collagen type I), with secretion amplified by the local release of transforming growth factor-β3. In addition, when cultured in ex vivo organ defect model, alginate–collagen scaffolds maintained viability of transplanted mesenchymal stem cells for up to 5 weeks. Taken together, these findings illustrate the advantages of incorporating collagen as a means to enhance cell migration and proliferation in porous scaffolds which could be used to augment tissue repair strategies.

Stemming the Degeneration: IVD Stem Cells and Stem Cell Regenerative Therapy for Degenerative Disc Disease

The intervertebral disc (IVD) is immensely important for the integrity of vertebral column function. The highly specialized IVD functions to confer flexibility and tensile strength to the spine and endures various types of biomechanical force. Degenerative disc disease (DDD) is a prevalent musculoskeletal disorder and is the major cause of low back pain and includes the more severe degenerative lumbar scoliosis, disc herniation and spinal stenosis. DDD is a multifactorial disorder whereby an imbalance of anabolic and catabolic factors, or alterations to cellular composition, or biophysical stimuli and genetic background can all play a role in its genesis. However, our comprehension of IVD formation and theetiology of disc degeneration (DD) are far from being complete, hampering efforts to formulate appropriate therapies to tackle DD. Knowledge of the stem cells and various techniques to manipulate and direct them to particular fates have been promising in adopting a stem-cell based regenerative approach to DD. Moreover, new evidence on the residence of stem/progenitor cells within particular IVD niches has emerged holding promise for future therapeutic applications. Existing issues pertaining to current therapeutic approaches are also covered in this review.

The challenge and advancement of annulus fibrosus tissue engineering

BACKGROUND

Intervertebral disc degeneration, a main cause of back pain, is an endemic problem and a big economic burden for the health care system. Current treatments are symptom relieving but do not address underlying problems-biological and structural deterioration of the disc. Tissue engineering is an emerging approach for the treatment of intervertebral disc degeneration since it restores the functionality of native tissues. Although numerous studies have focused on the nucleus pulposus tissue engineering and achieved successes in laboratory settings, disc tissue engineering without annulus fibrosus for the end stage of disc degeneration is deemed to fail. The purpose of this article is to review the advancement of annulus fibrosus tissue engineering.

MATERIAL AND METHODS

Relevant articles regarding annulus fibrosus tissue engineering were identified in PubMed and Medline databases.

RESULTS

The ideal strategy for disc regeneration is to restore the function and integrity of the disc by using biomaterials, native matrices, growth factors, and cells that producing matrices. In the past decades there are tremendous advancement in annulus fibrosus tissue engineering including cell biology, biomaterials, and whole disc replacement. The recent promising results on whole disc tissue engineering-a composite of annulus fibrosus and nucleus pulposus-make the tissue engineering approach more appealing.

CONCLUSION

Despite the promising results in disc tissue engineering, there is still much work to be done regarding the clinical application.