PPAR-δ Agonist With Mesenchymal Stem Cells Induces Type II Collagen-Producing Chondrocytes in Human Arthritic Synovial Fluid

PPARδ agonist protects against osteoarthritis by activating AKT/mTOR signaling pathway-mediated autophagy

Osteoarthritis (OA) is the most prevalent degenerative joint disease, and PPARs are involved in its pathogenesis; however, the specific mechanisms by which changes in PPARδ impact the OA pathogenesis yet to be discovered. The purpose of this study was to ascertain how PPARδ affects the onset and development of OA. In vitro, we found that PPARδ activation ameliorated apoptosis and extracellular matrix (ECM) degradation in OA chondrocytes stimulated by IL-1β. In addition, PPARδ activation may modulate AKT/mTOR signaling to partially regulate chondrocyte autophagy and apoptosis. In vivo, injection of PPARδ agonist into the articular cavity improved ECM degradation, apoptosis and autophagy in rats OA models generated by destabilization medial meniscus (DMM), eventually delayed degeneration of articular cartilage. Thus, targeting PPARδ for OA treatment may be a possibility.

Immunomodulatory properties of mesenchymal stromal/stem cells: The link with metabolism

BACKGROUND

Mesenchymal stromal/stem cells (MSCs) are the most promising stem cells for the treatment of multiple inflammatory and immune diseases due to their easy acquisition and potent immuno-regulatory capacities. These immune functions mainly depend on the MSC secretion of soluble factors. Recent studies have shown that the metabolism of MSCs plays critical roles in immunomodulation, which not only provides energy and building blocks for macromolecule synthesis but is also involved in the signaling pathway regulation.

AIM OF REVIEW

A thorough understanding of metabolic regulation in MSC immunomodulatory properties can provide new sights to the enhancement of MSC-based therapy.

KEY SCIENTIFIC CONCEPTS OF REVIEW

MSC immune regulation can be affected by cellular metabolism (glucose, adenosine triphosphate, lipid and amino acid metabolism), which further mediates MSC therapy efficiency in inflammatory and immune diseases. The enhancement of glycolysis of MSCs, such as signaling molecule activation, inflammatory cytokines priming, or environmental control can promote MSC immune functions and therapeutic potential. Besides glucose metabolism, inflammatory stimuli also alter the lipid molecular profile of MSCs, but the direct link with immunomodulatory properties remains to be further explored. Arginine metabolism, glutamine-glutamate metabolism and tryptophan-kynurenine via indoleamine 2,3-dioxygenase (IDO) metabolism all contribute to the immune regulation of MSCs. In addition to the metabolism dictating the MSC immune functions, MSCs also influence the metabolism of immune cells and thus determine their behaviors. However, more direct evidence of the metabolism in MSC immune abilities as well as the underlying mechanism requires to be uncovered.

PPARδ Agonist Promotes Type II Cartilage Formation in a Rabbit Osteochondral Defect Model

Osteoarthritis (OA) is a chronic degenerative joint disease accompanied by an inflammatory milieu that results in painful joints. The pathogenesis of OA is multifactorial, with genetic predisposition, environmental factors, and traumatic injury resulting in the direct or indirect loss of cartilage. The articular cartilage can also be damaged by direct focal traumatic injury. Articular cartilage provides a smooth, deformable bearing surface with a low coefficient of friction, increased contact area, and reduced contact stress. Articular type II hyaline cartilage lines the synovial joints and, when injured, has a limited ability for repair, except for the most superficial layers via diffusion from the synovial fluid, secondary to no blood supply, a complex structure, and a low metabolic rate. Restoring the articular surface can relieve pain and restore function. Although many strategies have been developed to regenerate type II collagen based on the extent of the lesion, surgical treatments are still evolving. The peroxisome proliferator-activated receptor delta (PPARδ) agonist and collagen treatment of mesenchymal stem cells (MSCs) enhance the chondrogenic capacity in vitro. We present a novel technique for cartilage restoration in a rabbit cartilage osteochondral defect model using a PPARδ agonist (GW0742)-infused 3D collagen scaffold to induce type II cartilage from MSCs.

Effect of cell receptors in the pathogenesis of osteoarthritis: Current insights

Osteoarthritis (OA) is a chronic arthritic disease characterized by cartilage degradation, synovial inflammation, and subchondral bone lesions. The studies on the pathogenesis of OA are complex and diverse. The roles of receptors signaling in chondrocyte anabolism, inflammatory factors expression of synovial fibroblast, and angiogenesis in subchondral bone are particularly important for exploring the pathological mechanism of OA and clinical diagnosis and treatment. By reviewing the relevant literature, this article elaborates on the abnormal expression of receptors and the signaling transduction pathways from different pathological changes of OA anatomical components, aiming to provide new research ideas and clinical therapeutic value for OA pathogenesis.

Pharmaceutical therapeutics for articular regeneration and restoration: state-of-the-art technology for screening small molecular drugs

Articular cartilage damage caused by sports injury or osteoarthritis (OA) has gained increased attention as a worldwide health burden. Pharmaceutical treatments are considered cost-effective means of promoting cartilage regeneration, but are limited by their inability to generate sufficient functional chondrocytes and modify disease progression. Small molecular chemical compounds are an abundant source of new pharmaceutical therapeutics for cartilage regeneration, as they have advantages in design, fabrication, and application, and, when used in combination, act as powerful tools for manipulating cellular fate. In this review, we present current achievements in the development of small molecular drugs for cartilage regeneration, particularly in the fields of chondrocyte generation and reversion of chondrocyte degenerative phenotypes. Several clinically or preclinically available small molecules, which have been shown to facilitate chondrogenesis, chondrocyte dedifferentiation, and cellular reprogramming, and subsequently ameliorate cartilage degeneration by targeting inflammation, matrix degradation, metabolism, and epigenetics, are summarized. Notably, this review introduces essential parameters for high-throughput screening strategies, including models of different chondrogenic cell sources, phenotype readout methodologies, and transferable advanced systems from other fields. Overall, this review provides new insights into future pharmaceutical therapies for cartilage regeneration.

A review on the wide range applications of hyaluronic acid as a promising rejuvenating biomacromolecule in the treatments of bone related diseases

Hyaluronic acid (HA) is a multifunctional high molecular weight polysaccharide produced by synoviocytes, fibroblasts, and chondrocytes, and is naturally found in many tissues and fluids, and more abundantly in articular cartilage and synovial fluid. Naturally occurring HA is thought to participate in many biological processes, such as regulation of cell adhesion and cell motility, manipulation of cell differentiation and proliferation, and providing mechanical properties to tissues (Girish and Kemparaju, 2007). Due to its excellent physicochemical properties such as high viscosity, elasticity, biodegradability, biocompatibility, nontoxicity, and nonimmunogenicity, HA based formulations have a wide range of applications and serves as a promising rejuvenating biomacromolecule in biomedical applications. In recent decades, HA is currently a popular topic, and has been widely used in bone related diseases for its remarkable efficacy in articular cartilage lubrication, analgesia, anti-inflammation, immunomodulatory, chondroprotection, anti-cancer and etc. Moreover, the safety and tolerability of HA based formulations have also been well-documented for treatment of various types of bone related diseases (Chen et al., 2018). This review gives a deep understanding on the special benefits and provides a mechanism-based rationale for the use of HA in bone related diseases conditions with special reference to osteoarthritis (OA), rheumatoid arthritis (RA), bone metastatic cancers.

PPAR-δ agonist affects adipo-chondrogenic differentiation of human mesenchymal stem cells through the expression of PPAR-γ

Introduction

Peroxisome proliferator–activated receptor (PPAR) subfamily play an important role in chondrogenesis. Previous study has reported that mixture of GW0742 (PPAR-δ agonist), hyaluronic acid (HA) and mesenchymal stem cells (MSCs) enhance chondrogenesis. The purpose of this study is to compare with efficacies of commercially available HA and demonstrate correlation of PPAR-γ and PPAR-δ.

Methods

In this experimental study, MSCs were cultured with chondrogenic media and clinical HA gels (Euflexxa®, Synvisc®, Orthovisc® and Supartz®) using micormass culture method. Expression of type Ⅰ, Ⅱ collagen and matrix metalloprotease-13 (MMP-13) was measured by immunoblotting. MSCs were cultured with chondrogenic media and/or HA and/or GW0742 and/or rosiglitazone (PPAR-γ agonist) and/or human osteoarthritis synovial fluid. Immunoblotting was used to measure expression of type Ⅱ collagen and PPAR-γ. To identify the effective dose for chondrogenesis and adipogenesis, either 0.1, 1, 5 or 10 μM of rosiglitazone was added to MSCs in chondrogenic media or adipogenic media.

Results

Clinical HA gels inhibited expression of type Ⅰ collagen and enhanced the expression of MMP-13. Type Ⅱ collagen expression was significantly elevated in all treatment groups except Supartz®. GW0742 decreased the expression of PPAR-γ with/without inflammation condition. Rosiglitazone enhanced adipogenesis in a dose-dependent manner and enhanced the expression of type Ⅱ collagen under inflammation condition. Otherwise, the expression of type Ⅱ collagen and formation of chondrocyte spheroids showed a dose-dependent manner with a peak at 1 μM of rosiglitazone.

Conclusions

PPAR-γ has a considerable anti-inflammatory effect and a strong pro-adipogenic effect, which inhibits the chondrogenic effect. PPAR-γ is related with PPAR-δ and shows a chondrogenic effect at lower concentrations. And clinical HA gels shows various efficacy of chondrogenesis. This study suggested that PPAR-γ and PPAR-δ are key regulatory factors of chondrogenesis.

A natural supplement formula reduces anti-oxidative stress and enhances osteo-chondrogenic differentiation potential in mesenchymal stem cells

There is great interest in using natural supplements to treat various medical conditions. In this study, we evaluated the anti-oxidative and stem cell differentiation effects of a mixture of vitamin D, Lactobacillus rhamnosus, ginger, curcumin, and Boswellia extract. The calcein acetoxymethyl assay after H₂O₂ treatment showed that combined natural supplement had an anti-oxidative effect. NS-J also increased calcium deposition, as shown by Alizarin Red S staining, indicating bone formation activity. The contents of type II collagen and glycosaminoglycans, which are biomarkers of cartilage, were higher in mesenchymal stem cells treated with combined natural supplement than in cells treated with individual ingredients of the formula. In mesenchymal stem cells treated with human osteoarthritis synovial fluids, combined natural supplement enhanced the expression of type II collagen and PPAR-δ, overcoming the anti-chondrogenic effect of inflammatory conditions. Combined natural supplement also inhibited Oil Red O staining in cells, which indicates inhibited adipogenesis. Thus, combined natural supplement, a formula comprising vitamin D, Lactobacillus rhamnosus, ginger, curcumin and Boswellia extract, reduced oxidative stress, enhanced osteogenesis and chondrogenesis, and inhibited adipogenesis in mesenchymal stem cells to a greater extent than the individual ingredients, indicating synergistic interaction. In addition, combined natural supplement increased the expression PPAR-δ, suggesting that these effects correlate with the PPAR-δ pathway.

A natural supplement formula reduces anti-oxidative stress and enhances osteo-chondrogenic differentiation potential in mesenchymal stem cells

There is great interest in using natural supplements to treat various medical conditions. In this study, we evaluated the anti-oxidative and stem cell differentiation effects of a mixture of vitamin D, Lactobacillus rhamnosus, ginger, curcumin, and Boswellia extract. The calcein acetoxymethyl assay after H₂O₂ treatment showed that combined natural supplement had an anti-oxidative effect. NS-J also increased calcium deposition, as shown by Alizarin Red S staining, indicating bone formation activity. The contents of type II collagen and glycosaminoglycans, which are biomarkers of cartilage, were higher in mesenchymal stem cells treated with combined natural supplement than in cells treated with individual ingredients of the formula. In mesenchymal stem cells treated with human osteoarthritis synovial fluids, combined natural supplement enhanced the expression of type II collagen and PPAR-δ, overcoming the anti-chondrogenic effect of inflammatory conditions. Combined natural supplement also inhibited Oil Red O staining in cells, which indicates inhibited adipogenesis. Thus, combined natural supplement, a formula comprising vitamin D, Lactobacillus rhamnosus, ginger, curcumin and Boswellia extract, reduced oxidative stress, enhanced osteogenesis and chondrogenesis, and inhibited adipogenesis in mesenchymal stem cells to a greater extent than the individual ingredients, indicating synergistic interaction. In addition, combined natural supplement increased the expression PPAR-δ, suggesting that these effects correlate with the PPAR-δ pathway.

Improving Cell Therapy Survival and Anabolism in Harsh Musculoskeletal Disease Environments

Cell therapies are an up and coming technology in orthopedic medicine that has the potential to provide regenerative treatments for musculoskeletal disease. Despite numerous cell therapies showing preclinical success for common musculoskeletal indications of disc degeneration and osteoarthritis, there have been mixed results when testing these therapies in humans during clinical trials. A theory behind the mixed success of these cell therapies is that the harsh microenvironments of the disc and knee they are entering inhibit their anabolism and survival. Therefore, there is much ongoing research looking into how to improve the survival and anabolism of cell therapies within these musculoskeletal disease environments. This includes research into improving cell function under specific microenvironmental conditions known to exist in the intervertebral disc (IVD) and knee environment such as hypoxia, low-nutrient conditions, hyperosmolarity, acidity, and inflammation. This research also includes improving differentiation of cells into desired native cell phenotypes to better enhance their survival and anabolism in the knee and IVD. This review highlights the effects of specific musculoskeletal microenvironmental challenges on cell therapies and what research is being done to overcome these challenges. Impact statement While there has been significant clinical interest in using cell therapies for musculoskeletal pathologies in the knee and intervertebral disc, cell therapy clinical trials have had mixed outcomes. The information presented in this review includes the environmental challenges (i.e., acidic pH, inflammation, hyperosmolarity, hypoxia, and low nutrition) that cell therapies experience in these pathological musculoskeletal environments. This review summarizes studies that describe various approaches to improving the therapeutic capability of cell therapies in these harsh environments. The result is an overview of what approaches can be targeted and/or combined to develop a more consistent cell therapy for musculoskeletal pathologies.

Synovium-Derived Mesenchymal Stem/Stromal Cells and their Promise for Cartilage Regeneration

Adult tissues are reservoirs of rare populations of cells known as mesenchymal stem/stromal cells (MSCs) that have tissue-regenerating features retained from embryonic development. As well as building up the musculoskeletal system in early life, MSCs also replenish and repair tissues in adult life, such as bone, cartilage, muscle, and adipose tissue. Cells that show regenerative features at least in vitro have been identified from several connective tissues. Bone marrow and adipose tissue are the most well recognized sources of MSCs that are already used widely in clinical practice. Regenerative medicine aims to exploit MSCs and their tissue regeneration even though the underlying mechanisms for their beneficial effects are largely unknown. Despite many studies that have used various tissue-derived MSCs, the most effective tissue source for orthopedic procedures still remains to be identified. Another question that needs to be addressed is how to evaluate autologous MSCs (i.e., patient derived). Previous studies have suggested the features of bone-marrow-derived MSCs can differ widely between individuals, and can be changed in particular in patients suffering from some forms of degenerative disorder, such as osteoarthritis. The synovium is a thin membrane that protects the synovial joints, and it is a rich source of MSCs that show great potential for regenerative medicine. Here, we review synovium-derived MSCs from reports on basic and clinical studies. We discuss their potential to treat cartilage defects caused by either degeneration or trauma, and what needs to be done in further research toward their better exploitation for joint regeneration.

HBXIP activates the PPARδ/NF-κB feedback loop resulting in cell proliferation

Hepatitis B X-interacting protein (HBXIP, also termed as LAMTOR5) plays a crucial role in regulation of cancer progression, while the mechanism is still unclear. Here we found that HBXIP increased the expression of PPARδ (peroxisome proliferator-activated receptor-δ) in gene and protein levels of SW480 or HT-29 colonic cancer cells. Chromatin immunoprecipitation and luciferase reporter assays showed that HBXIP occupied the core promoter (−1079/−239 nt) regions of PPARδ and that HBXIP activated the transcription activity of PPARδ in an NF-κB (p65)-dependent manner. Moreover, Co-immunoprecipitation and immunofluorescence analysis showed that HBXIP bound to NF-κB/p65 in the cells. Interestingly, we found that PPARδ could conversely increase the expression of NF-κB/p65 through activating its transcription activity. In addition, the clinical observations showed that both HBXIP and PPARδ were highly expressed in colonic carcinoma, and HBXIP expression was positively associated with that of PPARδ in the clinical specimen. Importantly, HBXIP expression levels were positively correlated with the clinical pathological parameters including lymph node metastasis and advanced TNM stage. These findings suggest that HBXIP served as a co-activator to activate the positive feedback regulations of NF-κB/PPARδ, which promoted the fast proliferation of the colonic cancer cells. Therapeutically, HBXIP may serve as a potential drug target of colonic cancer cells.

miR-33a hinders the differentiation of adipose mesenchymal stem cells towards urothelial cells in an inductive condition by targeting β‑catenin and TGFR

Tissue engineering technology offers an appealing approach for tissue reconstruction of the urothelium. Adipose-derived mesenchymal stem cells (ADSCs) represent an abundant source for tissue engineering applications. However, ASCs primarily possess mesoderm lineage differentiation potential. It is difficult to induce differentiation of ASCs towards urothelial cells that are derived from the endoderm, although a recent findings have reported that a conditioned medium may drive ADSCs towards differentiation into the urothelium phenotype. In the present study, human ADSCs were isolated from abdominal adipose tissues and incubated in this conditioned medium for indicated time periods. Western blotting showed that protein expression levels of urothelial specific marks, including CK7, CK20 and UPIII, were increased after seven days' incubation, but immunofluorescence microscopy determined that cells with CK7 and UPIII staining were scarce, which suggested a low-efficiency for the differentiation. Prolonging the incubation time did not further increase CK20 and UPIII expression. Furthermore, miR-33a expression was increased with ADSC differentiation. Using synthetic miRNAs to mimic or inhibit the action of miR-33a revealed that miR-33a hinders the differentiation of ADSCs towards urothelial cells. Furthermore, luciferase reporter assay confirmed that β-catenin and transforming growth factor-β receptor (TGFR) are targets of miR-33a. Inhibition of miR-33a expression increased β-catenin and TGFR expression and improved the efficiency of ADSCs towards differentiation into the urothelium phenotype. The present novel finding suggests that miR-33 may be an important target in tissue engineering and regenerative medicine for urothelium repair.