Chia-Lung Wu

Intra-articular delivery of purified mesenchymal stem cells from C57BL/6 or MRL/MpJ superhealer mice prevents posttraumatic arthritis.

Joint injury dramatically enhances the onset of osteoarthritis (OA) and is responsible for an estimated 12% of OA. Posttraumatic arthritis (PTA) is especially common after intra-articular fracture, and no disease-modifying therapies are currently available. We hypothesized that the delivery of mesenchymal stem cells (MSCs) would prevent PTA by altering the balance of inflammation and regeneration after fracture of the mouse knee. Additionally, we examined the hypothesis that MSCs from the MRL/MpJ (MRL) “superhealer” mouse strain would show increased multilineage and therapeutic potentials as compared to those from C57BL/6 (B6) mice, as MRL mice have shown exceptional in vivo regenerative abilities. A highly purified population of MSCs was prospectively isolated from bone marrow using cell surface markers (CD45-/TER119-/PDGFRa+/Sca-1+). B6 MSCs expanded greater than 100,000-fold in 3 weeks when cultured at 2% oxygen and displayed greater adipogenic, osteogenic, and chondrogenic differentiation as compared to MRL MSCs. Mice receiving only a control saline injection after fracture demonstrated PTA after 8 weeks, but the delivery of 10,000 B6 or MRL MSCs to the joint prevented the development of PTA. Cytokine levels in serum and synovial fluid were affected by treatment with stem cells, including elevated systemic interleukin-10 at several time points. The delivery of MSCs did not reduce the degree of synovial inflammation but did show increased bone volume during repair. This study provides evidence that intra-articular stem cell therapy can prevent the development of PTA after fracture and has implications for possible clinical interventions after joint injury before evidence of significant OA.

Dietary fatty acid content regulates wound repair and the pathogenesis of osteoarthritis following joint injury

Objective The mechanisms linking obesity and osteoarthritis (OA) are not fully understood and have been generally attributed to increased weight, rather than metabolic or inflammatory factors. Here, we examined the influence of fatty acids, adipokines, and body weight on OA following joint injury in an obese mouse model. Methods Mice were fed high-fat diets rich in various fatty acids (FA) including saturated FAs (SFAs), ω-6 polyunsaturated FAs (PUFAs), and ω-3 PUFAs. OA was induced by destabilising the medial meniscus. Wound healing was evaluated using an ear punch. OA, synovitis and wound healing were determined histologically, while bone changes were measured using microCT. Activity levels and serum cytokines were measured at various time-points. Multivariate models were performed to elucidate the associations of dietary, metabolic and mechanical factors with OA and wound healing. Results Using weight-matched mice and multivariate models, we found that OA was significantly associated with dietary fatty acid content and serum adipokine levels, but not with body weight. Furthermore, spontaneous activity of the mice was independent of OA development. Small amounts of ω-3 PUFAs (8% by kcal) in a high-fat diet were sufficient to mitigate injury-induced OA, decreasing leptin and resistin levels. ω-3 PUFAs significantly enhanced wound repair, SFAs or ω-6 PUFAs independently increased OA severity, heterotopic ossification and scar tissue formation. Conclusions Our results indicate that with obesity, dietary FA content regulates wound healing and OA severity following joint injury, independent of body weight, supporting the need for further studies of dietary FA supplements as a potential therapeutic approach for OA.

Diet-induced obesity alters the differentiation potential of stem cells isolated from bone marrow, adipose tissue and infrapatellar fat pad: the effects of free fatty acids.

Introduction:Obesity is a major risk factor for several musculoskeletal conditions that are characterized by an imbalance of tissue remodeling. Adult stem cells are closely associated with the remodeling and potential repair of several mesodermally derived tissues such as fat, bone and cartilage. We hypothesized that obesity would alter the frequency, proliferation, multipotency and immunophenotype of adult stem cells from a variety of tissues.Materials and Methods:Bone marrow-derived mesenchymal stem cells (MSCs), subcutaneous adipose-derived stem cells (sqASCs) and infrapatellar fat pad-derived stem cells (IFP cells) were isolated from lean and high-fat diet-induced obese mice, and their cellular properties were examined. To test the hypothesis that changes in stem cell properties were due to the increased systemic levels of free fatty acids (FFAs), we further investigated the effects of FFAs on lean stem cells in vitro.Results:Obese mice showed a trend toward increased prevalence of MSCs and sqASCs in the stromal tissues. While no significant differences in cell proliferation were observed in vitro, the differentiation potential of all types of stem cells was altered by obesity. MSCs from obese mice demonstrated decreased adipogenic, osteogenic and chondrogenic potential. Obese sqASCs and IFP cells showed increased adipogenic and osteogenic differentiation, but decreased chondrogenic ability. Obese MSCs also showed decreased CD105 and increased platelet-derived growth factor receptor α expression, consistent with decreased chondrogenic potential. FFA treatment of lean stem cells significantly altered their multipotency but did not completely recapitulate the properties of obese stem cells.Conclusions:These findings support the hypothesis that obesity alters the properties of adult stem cells in a manner that depends on the cell source. These effects may be regulated in part by increased levels of FFAs, but may involve other obesity-associated cytokines. These findings contribute to our understanding of mesenchymal tissue remodeling with obesity, as well as the development of autologous stem cell therapies for obese patients.

Cartilage-Specific Knockout of the Mechanosensory Ion Channel TRPV4 Decreases Age-Related Osteoarthritis

Osteoarthritis (OA) is a progressive degenerative disease of articular cartilage and surrounding tissues, and is associated with both advanced age and joint injury. Biomechanical factors play a critical role in the onset and progression of OA, yet the mechanisms through which physiologic or pathologic mechanical signals are transduced into a cellular response are not well understood. Defining the role of mechanosensory pathways in cartilage during OA pathogenesis may yield novel strategies or targets for the treatment of OA. The transient receptor potential vanilloid 4 (TRPV4) ion channel transduces mechanical loading of articular cartilage via the generation of intracellular calcium ion transients. Using tissue-specific, inducible Trpv4 gene-targeted mice, we demonstrate that loss of TRPV4-mediated cartilage mechanotransduction in adulthood reduces the severity of aging-associated OA. However, loss of chondrocyte TRPV4 did not prevent OA development following destabilization of the medial meniscus (DMM). These results highlight potentially distinct roles of TRPV4-mediated cartilage mechanotransduction in age-related and post-traumatic OA, and point to a novel disease-modifying strategy to therapeutically target the TRPV4-mediated mechanotransduction pathway for the treatment of aging-associated OA.

Serum and synovial fluid lipidomic profiles predict obesity-associated osteoarthritis, synovitis, and wound repair

High-fat diet-induced obesity is a major risk factor for osteoarthritis (OA) and diminished wound healing. The objective of this study was to determine the associations among serum and synovial fluid lipid levels with OA, synovitis, adipokine levels, and wound healing in a pre-clinical obese mouse model of OA. Male C57BL/6 J mice were fed either a low-fat (10% kcal) or one of three high-fat (HF, 60% kcal) diets rich in saturated fatty acids (SFAs), ω-6 or ω-3 polyunsaturated FAs (PUFAs). OA was induced by destabilization of the medial meniscus. Mice also received an ear punch for evaluating wound healing. Serum and synovial fluid were collected for lipidomic and adipokine analyses. We demonstrated that the serum levels of ω-3 PUFAs were negatively correlated with OA and wound size, but positively correlated with adiponectin levels. In contrast, most ω-6 PUFAs exhibited positive correlations with OA, impaired healing, and inflammatory adipokines. Interestingly, levels of pentadecylic acid (C15:0, an odd-chain SFA) and palmitoleic acid were inversely correlated with joint degradation. This study extends our understanding of the links of FAs with OA, synovitis and wound healing, and reports newly identified serum and synovial fluid FAs as predictive biomarkers of OA in obesity.

Conditional Macrophage Depletion Increases Inflammation and Does Not Inhibit the Development of Osteoarthritis in Obese Macrophage Fas‐Induced Apoptosis–Transgenic Mice

To investigate whether short‐term, systemic depletion of macrophages can mitigate osteoarthritis (OA) following injury in the setting of obesity.

Animal Models of Meniscal Injury in Post-Traumatic Arthritis

The meniscus plays a significant role in maintenance of joint stability and congruence. Injuries to the meniscus often lead to post-traumatic arthritis and joint degeneration. To investigate development of post-traumatic OA and evaluate the chondroprotective effects of the meniscus, various animal models of meniscal injury have been developed. However, selection of an appropriate animal model is crucial in designing a study with translational relevance due to the diverse range of possible m eniscal injury patterns, and anatomical differences between animals and humans. This chapter outlines considerations for selection of a meniscal injury model, describes the injury models that have been investigated, and discusses confounding variables and outcome measures for evaluation of structural and functional changes in the joint following meniscal injury.

Survey of Animal Models in Post-Traumatic Arthritis: Choosing the Right Model to Answer the Right Question

The selection of a model to study post-traumatic arthritis is a challenging and potentially confusing decision. This chapter was added specifically to address questions investigators may have when considering moving their work into an animal model. It is not possible to cover every possible species of animal that could be used. Therefore, this chapter provides a comprehensive review of the various aspects of arthritis after joint injury that can be studied in three commonly used species. This work provides an overview of what assays, information, and data can be available to the investigators. It is important that investigators are certain they will be able to collect data to address their research question before the investigation begins.