Dedifferentiation-like reprogramming of degenerative nucleus pulposus cells into notochordal-like cells by defined factors.

The extensive degeneration of functional somatic cells and the depletion of endogenous stem/progenitor populations present significant challenges to tissue regeneration in degenerative diseases. Currently, a cellular reprogramming approach enabling directly generating corresponding progenitor populations from degenerative somatic cells remains elusive. The present study focused on intervertebral disc degeneration (IVDD) and identified a three-factor combination (OCT4, FOXA2, TBXT [OFT]) that could induce the dedifferentiation-like reprogramming of degenerative nucleus pulposus cells (dNPCs) toward induced notochordal-like cells (iNCs). Single-cell transcriptomics dissected the transitions of cell identity during reprogramming. Further, OCT4 was found to directly interact with bromodomain PHD-finger transcription factor to remodel the chromatin during the early phases, which was crucial for initiating this dedifferentiation-like reprogramming. In rat models, intradiscal injection of adeno-associated virus carrying OFT generated iNCs from in situ dNPCs and reversed IVDD. These results collectively present a proof-of-concept for dedifferentiation-like reprogramming of degenerated somatic cells into corresponding progenitors through the development of a factor-based strategy, providing a promising approach for regeneration in degenerative disc diseases.

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.

Swelling-Mediated Mechanical Stimulation Regulates Differentiation of Adipose-Derived Mesenchymal Stem Cells for Intervertebral Disc Repair Using Injectable UCST Microgels.

Mechanical stimulation is an effective approach for controlling stem cell differentiation in tissue engineering. However, its realization in in vivo tissue repair remains challenging since this type of stimulation can hardly be applied to injectable seeding systems. Here, it is presented that swelling of injectable microgels can be transformed to in situ mechanical stimulation via stretching the cells adhered on their surface. Poly(acrylamide-co-acrylic acid) microgels with the upper critical solution temperature property are fabricated using inverse emulsion polymerization and further coated with polydopamine to increase cell adhesion. Adipose-derived mesenchymal stem cells (ADSCs) adhered on the microgels can be omnidirectionally stretched along with the responsive swelling of the microgels, which upregulate TRPV4 and Piezo1 channel proteins and enhance nucleus pulposus (NP)-like differentiation of ADSCs. In vivo experiments reveal that the disc height and extracellular matrix content of NP are promoted after the implantation with the microgels. The findings indicate that swelling-induced mechanical stimulation has great potential for regulating stem cell differentiation during intervertebral disc repair.

An esterase-responsive ibuprofen nano-micelle pre-modified embryo derived nucleus pulposus progenitor cells promote the regeneration of intervertebral disc degeneration.

Stem cell-based transplantation is a promising therapeutic approach for intervertebral disc degeneration (IDD). Current limitations of stem cells include with their insufficient cell source, poor proliferation capacity, low nucleus pulposus (NP)-specific differentiation potential, and inability to avoid pyroptosis caused by the acidic IDD microenvironment after transplantation. To address these challenges, embryo-derived long-term expandable nucleus pulposus progenitor cells (NPPCs) and esterase-responsive ibuprofen nano-micelles (PEG-PIB) were prepared for synergistic transplantation. In this study, we propose a biomaterial pre-modification cell strategy; the PEG-PIB were endocytosed to pre-modify the NPPCs with adaptability in harsh IDD microenvironment through inhibiting pyroptosis. The results indicated that the PEG-PIB pre-modified NPPCs exhibited inhibition of pyroptosis in vitro; their further synergistic transplantation yielded effective functional recovery, histological regeneration, and inhibition of pyroptosis during IDD regeneration. Herein, we offer a novel biomaterial pre-modification cell strategy for synergistic transplantation with promising therapeutic effects in IDD regeneration.

A conductive supramolecular hydrogel creates ideal endogenous niches to promote spinal cord injury repair.

The current effective method for treatment of spinal cord injury (SCI) is to reconstruct the biological microenvironment by filling the injured cavity area and increasing neuronal differentiation of neural stem cells (NSCs) to repair SCI. However, the method is characterized by several challenges including irregular wounds, and mechanical and electrical mismatch of the material-tissue interface. In the current study, a unique and facile agarose/gelatin/polypyrrole (Aga/Gel/PPy, AGP3) hydrogel with similar conductivity and modulus as the spinal cord was developed by altering the concentration of Aga and PPy. The gelation occurred through non-covalent interactions, and the physically crosslinked features made the AGP3 hydrogels injectable. In vitro cultures showed that AGP3 hydrogel exhibited excellent biocompatibility, and promoted differentiation of NSCs toward neurons whereas it inhibited over-proliferation of astrocytes. The in vivo implanted AGP3 hydrogel completely covered the tissue defects and reduced injured cavity areas. In vivo studies further showed that the AGP3 hydrogel provided a biocompatible microenvironment for promoting endogenous neurogenesis rather than glial fibrosis formation, resulting in significant functional recovery. RNA sequencing analysis further indicated that AGP3 hydrogel significantly modulated expression of neurogenesis-related genes through intracellular Ca2+ signaling cascades. Overall, this supramolecular strategy produces AGP3 hydrogel that can be used as favorable biomaterials for SCI repair by filling the cavity and imitating the physiological properties of the spinal cord.

Enhancement of nucleus pulposus repair by glycoengineered adipose-derived mesenchymal cells.

Adipose-derived mesenchymal stem cells (ADSCs) are promising candidates for repairing degenerated intervertebral discs through multiple means, including: i. Secretion of bioactive factors to regulate inflammation and, ii. The potential to differentiate into nucleus pulposus (NP)-like cells, which can integrate into host tissues. However, the differentiation ability of ADSCs to NP-like cells is limited, which emphasizes on the need for alternative approaches to regulate cell differentiations. Given that cell functions are influenced by interactions between the extracellular matrix (ECM) and cells, we hypothesize that cell surface modification promotes ADSCs adhesion and differentiation towards NP-like cells. In this study, cell surfaces of ADSCs were functionalized with unnatural sialic acid via metabolic glycoengineering. Subsequently, adhesion abilities of modified cells to three main ECM (laminin, collagen and fibronectin) were compared. The adhesion assay revealed that glycoengineered ADSCs had the highest affinity for collagen, compared to laminin and fibronectin. Moreover, cultures with collagen coated plates enhanced the differentiation of glycoengineered ADSCs to NP-like cells. Metabolic glycoengineering prolonged ADSCs viability. The glycoengineered ADSCs increased the height and elasticity of intervertebral discs, as well as the water content and ECM volumes of nucleus pulposus. In conclusion, metabolic glycoengineering of cell surfaces has a significant role in modulating cell biological functions and promoting NP tissue repair.

Partial reprogramming strategy for intervertebral disc rejuvenation by activating energy switch.

Rejuvenation of nucleus pulposus cells (NPCs) in degenerative discs can reverse intervertebral disc degeneration (IDD). Partial reprogramming is used to rejuvenate aging cells and ameliorate progression of aging tissue to avoiding formation of tumors by classical reprogramming. Understanding the effects and potential mechanisms of partial reprogramming in degenerative discs provides insights for development of new therapies for IDD treatment. The findings of the present study show that partial reprogramming through short-term cyclic expression of Oct-3/4, Sox2, Klf4, and c-Myc (OSKM) inhibits progression of IDD, and significantly reduces senescence related phenotypes in aging NPCs. Mechanistically, short-term induction of OSKM in aging NPCs activates energy metabolism as a "energy switch" by upregulating expression of Hexokinase 2 (HK2) ultimately promoting redistribution of cytoskeleton and restoring the aging state in aging NPCs. These findings indicate that partial reprogramming through short-term induction of OSKM has high therapeutic potential in the treatment of IDD.

Estrogen/ER in anti-tumor immunity regulation to tumor cell and tumor microenvironment.

As the essential sexual hormone, estrogen and its receptor has been proved to participate in the regulation of autoimmunity diseases and anti-tumor immunity. The adjustment of tumor immunity is related to the interaction between cancer cells, immune cells and tumor microenvironment, all of which is considered as the potential target in estrogen-induced immune system regulation. However, the specific mechanism of estrogen-induced immunity is poorly understood. Typically, estrogen causes the nuclear localization of estrogen/estrogen receptor complex and alternates the transcription pattern of target genes, leading to the reprogramming of tumor cells and differentiation of immune cells. However, the estrogen-induced non-canonical signal pathway activation is also crucial to the rapid function of estrogen, such as NF-κB, MAPK-ERK, and ß-catenin pathway activation, which has not been totally illuminated. So, the investigation of estrogen modulatory mechanisms in these two manners is vital for the tumor immunity and can provide the potential for endocrine hormone targeted cancer immunotherapy. Here, this review summarized the estrogen-induced canonical and non-canonical signal transduction pathway and aimed to focus on the relationship among estrogen and cancer immunity as well as immune-related tumor microenvironment regulation. Results from these preclinical researches elucidated that the estrogen-target therapy has the application prospect of cancer immunotherapy, which requires the further translational research of these treatment strategies.

Injectable kartogenin and apocynin loaded micelle enhances the alleviation of intervertebral disc degeneration by adipose-derived stem cell.

Cell transplantation has been proved the promising therapeutic effects on intervertebral disc degeneration (IVDD). However, the increased levels of reactive oxygen species (ROS) in the degenerated region will impede the efficiency of human adipose-derived stem cells (human ADSCs) transplantation therapy. It inhibits human ADSCs proliferation, and increases human ADSCs apoptosis. Herein, we firstly devised a novel amphiphilic copolymer PEG-PAPO, which could self-assemble into a nanosized micelle and load lipophilic kartogenin (KGN), as a single complex (PAKM). It was an injectable esterase-responsive micelle, and showed controlled release ability of KGN and apocynin (APO). Oxidative stimulation promoted the esterase activity in human ADSCs, which accelerate degradation of esterase-responsive micelle. Compared its monomer, the PAKM micelle possessed better bioactivities, which were attributed to their synergistic effect. It enhanced the viability, autophagic activation (P62, LC3 II), ECM-related transcription factor (SOX9), and ECM (Collagen II, Aggrecan) maintenance in human ADSCs. Furthermore, it is demonstrated that the injection of PAKM with human ADSCs yielded higher disc height and water content in rats. Therefore, PAKM micelles perform promoting cell survival and differentiation effects, and may be a potential therapeutic agent for IVDD.

A bioactive injectable self-healing anti-inflammatory hydrogel with ultralong extracellular vesicles release synergistically enhances motor functional recovery of spinal cord injury.

The repair and motor functional recovery after spinal cord injury (SCI) remains a worldwide challenge. The inflammatory microenvironment is one of main obstacles on inhibiting the recovery of SCI. Using mesenchymal stem cells (MSCs) derived extracellular vesicles to replace MSCs transplantation and mimic cell paracrine secretions provides a potential strategy for microenvironment regulation. However, the effective preservation and controlled release of extracellular vesicles in the injured spinal cord tissue are still not satisfied. Herein, we fabricated an injectable adhesive anti-inflammatory F127-polycitrate-polyethyleneimine hydrogel (FE) with sustainable and long term extracellular vesicle release (FE@EVs) for improving motor functional recovery after SCI. The orthotopic injection of FE@EVs hydrogel could encapsulate extracellular vesicles on the injured spinal cord, thereby synergistically induce efficient integrated regulation through suppressing fibrotic scar formation, reducing inflammatory reaction, promoting remyelination and axonal regeneration. This study showed that combining extracellular vesicles into bioactive multifunctional hydrogel should have great potential in achieving satisfactory locomotor recovery of central nervous system diseases.

Interpreting the Mechanisms by which Integrins Promote the Differentiation of Mesenchymal Stem Cells and Integrin Application Prospects.

Transmembrane integrin receptors represent a major component of cell-extracellular matrix (ECM) communications that mediate cellular biological activities, including proliferation and differentiation. Stem cells, especially mesenchymal stem cells (MSC), have rapidly emerged as promising therapies for various diseases. Dynamic links exist between extracellular and intracellular environments that profoundly influence the cellular activities via integrin receptors, such as cell morphology transformation and differentiation. Interpreting the roles of integrin receptors in the regulation of MSC differentiation may potentially lead to an amplified therapeutic effect. In this review, we summarize, for the first time, the potential mechanisms by which integrins promote MSC multilineage differentiation, including integrin downstream signaling cascades and the interactions between integrin and ion channels, the cytoskeleton, and nuclear mechanoresponses. Furthermore, we focus on the current state and future prospects of the application of integrins to promote cell differentiation.

Strategies and prospects of effective neural circuits reconstruction after spinal cord injury.

Due to the disconnection of surviving neural elements after spinal cord injury (SCI), such patients had to suffer irreversible loss of motor or sensory function, and thereafter enormous economic and emotional burdens were brought to society and family. Despite many strategies being dealing with SCI, there is still no effective regenerative therapy. To date, significant progress has been made in studies of SCI repair strategies, including gene regulation of neural regeneration, cell or cell-derived exosomes and growth factors transplantation, repair of biomaterials, and neural signal stimulation. The pathophysiology of SCI is complex and multifaceted, and its mechanisms and processes are incompletely understood. Thus, combinatorial therapies have been demonstrated to be more effective, and lead to better neural circuits reconstruction and functional recovery. Combinations of biomaterials, stem cells, growth factors, drugs, and exosomes have been widely developed. However, simply achieving axon regeneration will not spontaneously lead to meaningful functional recovery. Therefore, the formation and remodeling of functional neural circuits also depend on rehabilitation exercises, such as exercise training, electrical stimulation (ES) and Brain-Computer Interfaces (BCIs). In this review, we summarize the recent progress in biological and engineering strategies for reconstructing neural circuits and promoting functional recovery after SCI, and emphasize current challenges and future directions.

Allogenic γδ T cell and tumor cell fused vaccine for enhanced immunotherapeutic efficacy of osteosarcoma.

Human γδ T cells have displayed their potential in cancer immunity through efficient tumor killing activities. Besides, they are also known for their capacity of antigen presentation. How to improve γδ T cells' immunotherapeutic effect as the cell vaccine is still a great challenge. Herein, we explore the human γδ T cells and tumor cell fused vaccine for enhanced immunotherapeutic efficacy of osteosarcoma. The fusion cell vaccine was prepared by chemical fusion between human γδ T cells and inactive osteosarcoma Saos-2 cells. The fusion process was confirmed by microscopy observation, and flow cytometry analysis further validated the antigen presenting functions of the fusion cells. Moreover, the immunotherapeutic potential of the fusion cells was then verified via cytotoxicity assay and cytokine release detection. Our study provided novel immunotherapeutic strategy for patients with osteosarcoma, which merits further practice in the near future.

Transplantation Strategies for Spinal Cord Injury Based on Microenvironment Modulation.

Spinal cord injury (SCI) is different from peripheral nerve injury; it results in devastating and permanent damage to the spine, leading to severe motor, sensory and autonomic dysfunction. SCI produces a complex microenvironment that can result in hemorrhage, inflammation and scar formation. Not only does it significantly limit regeneration, but it also challenges a multitude of transplantation strategies. In order to promote regeneration, researchers have recently begun to focus their attention on strategies that manipulate the complicated microenvironment produced by SCI. And some have achieved great therapeutic effects. Hence, reconstructing an appropriate microenvironment after transplantation could be a potential therapeutic solution for SCI. In this review, first, we aim to summarize the influential compositions of the microenvironment and their different effects on regeneration. Second, we highlight recent research that used various transplantation strategies to modulate different microenvironments produced by SCI in order to improve regeneration. Finally, we discuss future transplantation strategies regarding SCI.

An injectable recombinant human milk fat globule-epidermal growth factor 8-loaded copolymer system for spinal cord injury reduces inflammation through NF-κB and neuronal cell death.

Spinal cord injury (SCI) is a common disease and a major cause of paralysis, carrying much burden around the world. Despite the progress made with growth factors therapy, the response rate of acute SCI treatment still remains unsatisfactory, due largely to complex and severe inflammatory reactions. Herein, we prepare a MFG-E8-loaded copolymer system-based anti-inflammation therapy for SCI treatment. It is shown that the MFG-E8-loaded copolymer system can decrease pro-inflammatory cytokine expression and neuron death. In a rat model of crush-caused SCI, the copolymer system shows significant therapeutic efficacy by ameliorating inflammation, decreasing fibrotic scar, promoting myelin regeneration and suppressing overall SCI severity.

Scar Tissue-Targeting Polymer Micelle for Spinal Cord Injury Treatment.

Spinal cord injury (SCI) is a devastating disorder, leading to permanent motor and sensory deficit. Despite recent advances in neurosciences, the treatment efficacy on SCI patients remains unsatisfactory, mainly due to the poor accumulation, short retention, and lack of controlled release of therapeutics in lesion tissue. Herein, an injured spinal cord targeting prodrug polymer micelle is built. An esterase-responsive bond is used to link apocynin (APO) monomer, because of the enhanced esterase activity found in microglia cells after activation, which ensures a controlled degradation of APO prodrug (Allyloxypolyethyleneglycol-b-poly [2-(((4-acetyl-2-methoxyphenoxy)carbonyl)oxy)ethyl methacrylate], APEG-PAPO or PAPO) by activated microglia cells. A scar tissue-homing peptide (cysteine-alanine-glutamine-lysine, CAQK) is introduced to the PAPO to endow the polymer micelle the lesion tissue-targeting ability. As a result, this CAQK-modified prodrug micelle (cPAM) exhibits an improved accumulation and prolonged retention in lesion tissue compared to the control micelle. The cPAM also leads to superior tissue protection and sustained motor function recovery than the control groups in a mouse model of SCI. In conclusion, the cPAM induces an effective treatment of SCI by the lesion tissue specific delivery of the prodrug polymer via its robust scar binding effect, making the scar tissue a drug releasing platform for sustained treatment of SCI.

Stem Cell Transplantation: A Promising Therapy for Spinal Cord Injury.

Spinal Cord Injury (SCI) causes irreversible functional loss of the affected population. The incidence of SCI keeps increasing, resulting in huge burden on the society. The pathogenesis of SCI involves neuron death and exotic reaction, which could impede neuron regeneration. In clinic, the limited regenerative capacity of endogenous cells after SCI is a major problem. Recent studies have demonstrated that a variety of stem cells such as induced Pluripotent Stem Cells (iPSCs), Embryonic Stem Cells (ESCs), Mesenchymal Stem Cells (MSCs) and Neural Progenitor Cells (NPCs) /Neural Stem Cells (NSCs) have therapeutic potential for SCI. However, the efficacy and safety of these stem cellbased therapy for SCI remain controversial. In this review, we introduce the pathogenesis of SCI, summarize the current status of the application of these stem cells in SCI repair, and discuss possible mechanisms responsible for functional recovery of SCI after stem cell transplantation. Finally, we highlight several areas for further exploitation of stem cells as a promising regenerative therapy of SCI.

Bioactive Elastic Scaffolds Loaded with Neural Stem Cells Promote Rapid Spinal Cord Regeneration.

Despite decades of research, spinal cord injury (SCI) still causes irreparable damage to the human body. Key challenges that hinder the regeneration and extension of neurons following SCI must be overcome, including the overexpressed glial scar formation and strong inflammatory responses in lesion tissue. Transplantation of neural stem cells (NSCs) represents a promising therapeutic method due to its beneficial roles like growth factor secretion and anti-inflammation. However, NSCs usually differentiate into astrocytes, which is considered as one potential limitation of current NSC therapy. Herein, we fabricate an elastic poly(sebacoyl diglyceride) (PSeD) scaffold to mimic the mechanical properties of the natural spinal cord. The PSeD scaffold is coated with poly(sebacoyl diglyceride)-isoleucine-lysine-valine-alanine-valine-serine (PSeD-IKVAVS) to create a bioactive interface. The core point of this topic is divided into two parts. First, PSeD is a bioelastomer and its mechanical properties are similar to those of the natural spinal cord. This feature reduces the direct stimulation to the spinal cord tissue by the elastomer and then reduces the immune response or resistance caused by the host spinal cord tissue. Second, the IKVAVS peptide modifies PSeD to create a bioactive interface to support NSC growth and differentiation. In the in vivo study, the number of CD68-positive macrophages decreased in the PSeD-IKVAVS/NSC group compared to that in the SCI group (20% vs 60%). The low inflammation induced by the scaffold was beneficial to NSCs, resulting in increased locomotor recovery, as indicated by the increased Basso-Beattie-Bresnahan score (5, the average score in the PSeD-IKVAVS/NSC group, vs 2, the average score in the SCI group). Based on the above two characteristics, a PSeD-IKVAVS bioelastomer is fabricated, which provides a beneficial and bioactive microenvironment for NSCs after transplantation.

An injectable heparin-Laponite hydrogel bridge FGF4 for spinal cord injury by stabilizing microtubule and improving mitochondrial function.

Rationale: Spinal cord injury (SCI) remains a critical clinical challenge. The controlled release of FGF4, a novel neuroprotective factor, from a versatile Laponite hydrogel to the injured site was a promising strategy to promote axon regeneration and motor functional recovery after SCI. Methods: Characterization of Laponite, Laponite/Heparin (Lap/Hep) and Laponite/Heparin loaded with FGF4 (Lap/Hep@FGF4) hydrogels were measured by rheometer. Multiple comprehensive evaluations were used to detect motor functional recovery and the axonal rehabilitation after Lap/Hep@FGF4 treatment in vivo (SCI rat model). Moreover, microtubule dynamic and energy transportation, which regulated axonal regeneration was evaluated by Lap/Hep@FGF4 gel in vitro (primary neuron). Results: FGF4 released from Lap/Hep gel locally achieves strong protection and regeneration after SCI. The Lap/Hep@FGF4 group revealed remarkable motor functional recovery and axonal regrowth after SCI through suppressing inflammatory reaction, increasing remyelination and reducing glial/fibrotic scars. Furthermore, the underlying mechanism of axonal rehabilitation were demonstrated via enhancing microtubule stability and regulating mitochondrial localization after Lap/Hep@FGF4 treatment. Conclusion: This promising sustained release system provides a synergistic effective approach to enhance recovery after SCI underlying a novel mechanism of axonal rehabilitation, and shows a translational prospect for the clinical treatment of SCI.

Intradiscal Injection of Induced Pluripotent Stem Cell-Derived Nucleus Pulposus-Like Cell-Seeded Polymeric Microspheres Promotes Rat Disc Regeneration.

BACKGROUND: Cell replacement therapy is an attractive alternative for treating degenerated intervertebral discs (IVDs), which are related to the reduction of nucleus pulposus-like cells (NP-lCs) and the loss of the extracellular matrix. Induced pluripotent stem cells (iPSCs) which resemble embryonic stem cells are considered to be a potential resource for restoring NP-lCs and disc homeostasis. Here, we proposed an efficient two-step differentiation protocol of human iPSCs into NP-lCs and continuously tested their in vivo ability to regenerate IVDs. METHODS: A polymeric gelatin microsphere (GM) was generated for sustained release of growth and differentiation factor-5 (GDF-5) and as a cell delivery vehicle of NP-lCs. By injecting NP-lC-seeded GDF-5-loaded GMs into the rat coccygeal intervertebral discs, the disc height and water content were examined with the molybdenum target radiographic imaging test and magnetic resonance imaging examination. Histology and immunohistochemistry results were shown with H&E, S-O-Fast Green, and immunohistochemistry staining. RESULTS: We demonstrated that the injection of NP-lC-seeded GDF-5-loaded GMs could reverse IDD in a rat model. The imaging examination indicated that disc height recovered and water content increased. Histology and immunohistochemistry results indicated that the NP cells as well as their extracellular matrix were partially restored. CONCLUSIONS: The results suggest that NP-lC-seeded GDF-5-loaded GMs could partially regenerate degenerated intervertebral discs after transplantation into rat coccygeal intervertebral discs. Our study will help develop a promising method of stem cell-based therapy for IDD.