Treatment Effects of Intra-Articular Allogenic Mesenchymal Stem Cell Secretome in an Equine Model of Joint Inflammation.

Background: Allogenic mesenchymal stem cell (MSC) secretome is a novel intra-articular therapeutic that has shown promise in in vitro and small animal models and warrants further investigation. Objectives: To investigate if intra-articular allogenic MSC-secretome has anti-inflammatory effects using an equine model of joint inflammation. Study Design: Randomized positively and negatively controlled experimental study. Method: In phase 1, joint inflammation was induced bilaterally in radiocarpal joints of eight horses by injecting 0.25 ng lipopolysaccharide (LPS). After 2 h, the secretome of INFy and TNFα stimulated allogeneic equine MSCs was injected in one randomly assigned joint, while the contralateral joint was injected with medium (negative control). Clinical parameters (composite welfare scores, joint effusion, joint circumference) were recorded, and synovial fluid samples were analyzed for biomarkers (total protein, WBCC; eicosanoid mediators, CCL2; TNFα; MMP; GAGs; C2C; CPII) at fixed post-injection hours (PIH 0, 8, 24, 72, and 168 h). The effects of time and treatment on clinical and synovial fluid parameters and the presence of time-treatment interactions were evaluated. For phase 2, allogeneic MSC-secretome vs. allogeneic equine MSCs (positive control) was tested using a similar methodology. Results: In phase 1, the joint circumference was significantly (p < 0.05) lower in the MSC-secretome treated group compared to the medium control group at PIH 24, and significantly higher peak synovial GAG values were noted at PIH 24 (p < 0.001). In phase 2, no significant differences were noted between the treatment effects of MSC-secretome and MSCs. Main Limitations: This study is a controlled experimental study and therefore cannot fully reflect natural joint disease. In phase 2, two therapeutics are directly compared and there is no negative control. Conclusions: In this model of joint inflammation, intra-articular MSC-secretome injection had some clinical anti-inflammatory effects. An effect on cartilage metabolism, evident as a rise in GAG levels was also noted, although it is unclear whether this could be considered a beneficial or detrimental effect. When directly comparing MSC-secretome to MSCs in this model results were comparable, indicating that MSC-secretome could be a viable off-the-shelf alternative to MSC treatment.

MSC encapsulation in alginate microcapsules prolongs survival after intra-articular injection, a longitudinal in vivo cell and bead integrity tracking study.

Mesenchymal stem cells (MSC) are promising candidates for use as a biological therapeutic. Since locally injected MSC disappear within a few weeks, we hypothesize that efficacy of MSC can be enhanced by prolonging their presence. Previously, encapsulation in alginate was suggested as a suitable approach for this purpose. We found no differences between the two alginate types, alginate high in mannuronic acid (High M) and alginate high in guluronic acid (High G), regarding MSC viability, MSC immunomodulatory capability, or retention of capsule integrity after subcutaneous implantation in immune competent rats. High G proved to be more suitable for production of injectable beads. Firefly luciferase-expressing rat MSC were used to track MSC viability. Encapsulation in high G alginate prolonged the presence of metabolically active allogenic MSC in immune competent rats with monoiodoacetate-induced osteoarthritis for at least 8 weeks. Encapsulation of human MSC for local treatment by intra-articular injection did not significantly influence the effect on pain, synovial inflammation, or cartilage damage in this disease model. MSC encapsulation in alginate allows for an injectable approach which prolongs the presence of viable cells subcutaneously or in an osteoarthritic joint. Further fine tuning of alginate formulation and effective dosage for might be required in order to improve therapeutic efficacy depending on the target disease. Graphical Abstract.

Intra-articular Injections of Platelet-Rich Plasma Releasate Reduce Pain and Synovial Inflammation in a Mouse Model of Osteoarthritis.

BACKGROUND: Osteoarthritis (OA) is a degenerative joint disease leading to pain and disability for which no curative treatment exists. A promising biological treatment for OA is intra-articular administration of platelet-rich plasma (PRP). PRP injections in OA joints can relieve pain, although the exact working mechanism is unclear. PURPOSE: To examine the effects of PRP releasate (PRPr) on pain, cartilage damage, and synovial inflammation in a mouse OA model. STUDY DESIGN: Controlled laboratory study. METHODS: OA was induced unilaterally in the knees of male mice (n = 36) by 2 intra-articular injections of collagenase at days -7 and -5. At day 0, pain was measured by registering weight distribution on the hindlimbs, after which mice were randomly divided into 2 groups. Mice received 3 intra-articular injections of PRP or saline in the affected knee. Seven mice per group were euthanized at day 5 for assessment of early synovial inflammation and cartilage damage. Pain in the remaining mice was registered for a total of 3 weeks. These mice were euthanized at day 21 for assessment of cartilage damage and synovial inflammation on histological evaluation. Antibodies against iNOS, CD163, and CD206 were used to identify different subtypes of macrophages in the synovial membrane. RESULTS: Mice in the PRPr group increased the distribution of weight on the affected joint in 2 consecutive weeks after the start of the treatment ( P < .05), whereas mice in the saline group did not. At day 21, PRPr-injected knees had a thinner synovial membrane ( P < .05) and a trend toward less cartilage damage in the lateral joint compartment ( P = .053) than saline-injected knees. OA knees treated with saline showed less anti-inflammatory (CD206+ and CD163+) cells at day 5 than healthy knees, an observation that was not made in the PRPr-treated group. A higher level of pain at day 7 was associated with a thicker synovial membrane at day 21. The presence of CD206+ cells was negatively associated with synovial membrane thickness. CONCLUSION: In a murine OA model, multiple PRPr injections reduced pain and synovial thickness, possibly through modulation of macrophage subtypes. CLINICAL RELEVANCE: PRPr injections in early OA or shortly after joint trauma can reduce pain and synovial inflammation and may inhibit OA development in patients.