Small Molecule-Based Strategy Promotes Nucleus Pulposus Specific Differentiation of Adipose-Derived Mesenchymal Stem Cells

Nucleus pulposus cell-derived efficient microcarrier for intervertebral disc tissue engineering

Adipose-derived stem cells (ADSCs) show great potential for the treatment of intervertebral disc (IVD) degeneration. An ideal carrier is necessary to transplant ADSCs into degenerated IVDs without influencing cell function. Nucleus pulposus cells (NPCs) can synthesize and deposit chondroitin sulfate and type II collagen which are NP-specific extracellular matrix (ECM) and can also regulate the NP-specific differentiation of stem cells. Bioscaffolds fabricated based on the ECM synthesis functions of NPCs have possible roles in cell transplantation and differentiation induction, but it has not been studied. In this study, we first aggregated NPCs into pellets, and then, NPC-derived efficient microcarriers (NPCMs) were fabricated by pellet cultivation under specific conditions and optimized decellularization. Thirdly, we evaluated the microstructure, biochemical composition, biostability and cytotoxicity of the NPCMs. Finally, we investigated the NP-specific differentiation of ADSCs induced by the NPCMsin vitroand NP regeneration induced by the ADSC-loaded NPCMs in a rabbit model. The results indicated that the injectable NPCMs retained maximal ECM and minimal cell nucleic acid after optimized decellularization and had good biostability and no cytotoxicity. The NPCMs also promoted the NP-specific differentiation of ADSCsin vitro. In addition, the results of MRI, x-ray, and the structure and ECM content of NP showed that the ADSCs-loaded NPCMs can partly restored the degenerated NPin vivo. Our injectable NPCMs regenerated the degenerated NP and provide a simplified and efficient strategy for treating IVD degeneration.

New strategies for the treatment of intervertebral disc degeneration: cell, exosome, gene, and tissue engineering

Low back pain (LBP) caused by intervertebral disc (IVD) generation (IVDD) has always been an important problem that cannot be ignored. Traditional therapies have many deep-rooted and intractable complications that promote their treatment mode transfer to new therapies. This article mainly summarizes the shortcomings of traditional treatment methods and analyzes the research status and future development direction of IVDD treatment. We outlined the most promising IVDD therapies, including cell, exosome, gene, and tissue engineering therapy, especially tissue engineering therapy, which runs through the whole process of other therapies. In addition, the article focuses on the cellular, animal, and preclinical challenges faced by each therapeutic approach, as well as their respective advantages and disadvantages, to provide better ideas for relieving the IVDD patients' pain through new treatment methods.

Researches on Stem and Progenitor Cells in Intervertebral Discs: An Analysis of the Scientific Landscape

Low back pain (LBP) is a common clinical symptom, and the prevalence is ranged from 60% to 70%. With the deepening of basic research, the development of intervertebral disc regeneration-oriented cell therapy, especially stem and progenitor cells therapy, showed good research prospects and was expected to become new methods of treatment for LBP. Our study is aimed at analyzing the scientific output of stem and progenitor cells in intervertebral discs and at driving future research into new publications. Researches focused on this file were searched from the Science Citation Index Expanded (SCI-E) of the Web of Science (WOS) core collection database and were screened according to inclusion criteria. We evaluated and visualized the results, including annual publications, citations, authors, organizations, countries, research directions, funds, and journals by bibliometric website, VOSviewer, and Citespace softwares on May 27, 2022. A total of 450 original articles and reviews were included, and the overall trend of the number of publications rapidly increased. In worldwide, China and the USA were the leading countries for research production. The retrieved 450 publications received 14322 citations, with an average of 31.83 citations and an H-index of 62. The most high-yield author, organization, country, research directions, funds, and journals were Chen QX from Zhejiang University, Zhejiang University, China, Cell Biology, National Natural Science Foundation of China, and Spine, respectively. Keywords cluster analysis showed the research hotspots in the future, including “human intervertebral disc”, “adipose-derived mesenchymal stem cell”, “intervertebral disc degeneration”, “degenerative disc model”, “nucleus pulposus regeneration”, “human cartilage”, “3d culture”, “shrinkage-free preparation”, and “polylactide disc”. Furthermore, with accumulating evidence demonstrating the role of stem and progenitor cells in intervertebral discs, “microenvironment”, “activation”, “intervertebral disc degeneration”, and “oxidative stress” are becoming the research frontiers and trends.

Application of stem cells in the repair of intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is a common disease that increases with age, and its occurrence is stressful both psychologically and financially. Stem cell therapy for IDD is emerging. For this therapy, stem cells from different sources have been proven in vitro, in vivo, and in clinical trials to relieve pain and symptoms, reverse the degeneration cascade, delay the aging process, maintain the spine shape, and retain mechanical function. However, further research is needed to explain how stem cells play these roles and what effects they produce in IDD treatment. This review aims to summarize and objectively analyse the current evidence on stem cell therapy for IDD.

Cell sources proposed for nucleus pulposus regeneration

Lower back pain (LBP) occurs in 80% of adults in their lifetime; resulting in LBP being one of the biggest causes of disability worldwide. Chronic LBP has been linked to the degeneration of the intervertebral disc (IVD). The current treatments for chronic back pain only provide alleviation of symptoms through pain relief, tissue removal, or spinal fusion; none of which target regenerating the degenerate IVD. As nucleus pulposus (NP) degeneration is thought to represent a key initiation site of IVD degeneration, cell therapy that specifically targets the restoration of the NP has been reviewed here. A literature search to quantitatively assess all cell types used in NP regeneration was undertaken. With key cell sources: NP cells; annulus fibrosus cells; notochordal cells; chondrocytes; bone marrow mesenchymal stromal cells; adipose-derived stromal cells; and induced pluripotent stem cells extensively analyzed for their regenerative potential of the NP. This review highlights: accessibility; expansion capability in vitro; cell survival in an IVD environment; regenerative potential; and safety for these key potential cell sources. In conclusion, while several potential cell sources have been proposed, iPSC may provide the most promising regenerative potential.

The preconditioning of lithium promotes mesenchymal stem cell-based therapy for the degenerated intervertebral disc via upregulating cellular ROS

Abstract

Adipose-derived stem cell (ADSC) is one of the most widely used candidate cell for intervertebral disc (IVD) degeneration-related disease. However, the poor survival and low differentiation efficacy in stressed host microenvironment limit the therapeutic effects of ADSC-based therapy. The preconditioning has been found effective to boost the proliferation and the functioning of stem cells in varying pathological condition. Lithium is a common anti-depression drug and has been proved effective to enhance stem cell functioning. In this study, the effects of preconditioning using LiCl on the cellular behavior of ADSC was investigated, and specially in a degenerative IVD-like condition.

Method

The cellular toxicity on rat ADSC was assessed by detecting lactate dehydrogenase (LDH) production after treatment with a varying concentration of lithium chloride (LiCl). The proliferative capacity of ADSC was determined by detecting Ki67 expression and the relative cell number of ADSC. Then, the preconditioned ADSC was challenged by a degenerative IVD-like condition. And the cell viability as well as the nucleus pulpous (NP) cell differentiation efficacy of preconditioned ADSC was evaluated by detecting the major marker expression and extracellular matrix (ECM) deposit. The therapeutic effects of preconditioned ADSC were evaluated using an IVD degeneration rat model, and the NP morphology and ECM content were assessed.

Results

A concentration range of 1–10 mmol/L of LiCl was applied in the following study, since a higher concentration of LiCl causes a major cell death (about 40%). The relative cell number was similar between preconditioned groups and the control group after preconditioning. The Ki67 expression was elevated after preconditioning. Consistently, the preconditioned ADSC showed stronger proliferation capacity. Besides, the preconditioned groups exhibit higher expression of NP markers than the control group after NP cell induction. Moreover, the preconditioning of LiCl reduced the cell death and promoted ECM deposits, when challenged with a degenerative IVD-like culture. Mechanically, the preconditioning of LiCl induced an increased cellular reactive oxidative species (ROS) level and activation of ERK1/2, which was found closely related to the enhanced cell survival and ECM deposits after preconditioning. The treatment with preconditioned ADSC showed better therapeutic effects than control ADSC transplantation, with better NP preservation and ECM deposits.

Conclusion

These results suggest that the preconditioning with a medium level of LiCl boosts the cell proliferation and differentiation efficacy under a normal or hostile culture condition via the activation of cellular ROS/ERK axis. It is a promising pre-treatment of ADSC to promote the cell functioning and the following regenerative capacity, with superior therapeutic effects than untreated ADSC transplantation.