Platelet rich plasma (PRP) has recently been investigated for use in tissue regeneration studies that seek to utilize the numerous growth factors released from platelet a-granules. This study examined gene expression patterns, DNA, and collagen content of equine flexor digitorum superficialis tendon (SDFT) explants cultured in media consisting of PRP and other blood products. Blood and bone marrow aspirate (BMA) were collected from horses and processed to obtain plasma, PRP, and platelet poor plasma (PPP). IGF-I, TGF-b1, and PDGF-BB were quantified in all blood products using ELISA. Tendons were cultured in explant fashion with blood, plasma, PRP, PPP, or BMA at concentrations of 100%, 50%, or 10% in serum-free DMEM with amino acids. Quantitative RT-PCR for expression of collagen type I (COL1A1), collagen type III (COL3A1), cartilage oligomeric matrix protein (COMP), decorin, matrix metalloproteinase-3 (MMP-3), and matrix metalloproteinase-13 (MMP-13) was performed as were DNA and total soluble collagen assays. TGF-b1 and PDGF-BB concentrations were higher in PRP compared to all other blood products tested. Tendons cultured in 100% PRP showed enhanced gene expression of the matrix molecules COL1A1, COL3A1, and COMP with no concomitant increase in the catabolic molecules MMP-3 and MMP-13. These findings support in vivo investigation of PRP as an autogenous, patient-side treatment for tendonitis. ß

Summary Objective Diminish interleukin-1β (IL-1β) signaling in a model of primary osteoarthritis by RNA interference-based transcript reduction or receptor blockade, and quantify changes incurred on transcript expression of additional mediators. Methods Knees of Hartley guinea pigs were collected at 120 and 180 days of age following injection with viral vectors (N=4/treatment group/date) at 60 days. Two groups received either adeno-associated viral serotype 5 vector containing a knockdown sequence (TV), or adenoviral vector encoding for IL-1 receptor antagonist protein (Ad-IRAP); treatments were contrasted with opposite knees administered corresponding vector controls. A third group evaluated TV relative to saline-only injected knees. Chondropathy and immunohistochemistry findings were compared to untreated guinea pigs. Transcript expression levels in cartilage were calculated using the comparative CT (2−ΔΔCT) method and analyzed by one-way ANOVA with pairwise comparisons using Tukey 95% confidence intervals. Results Vector transduction was confirmed at both harvest dates. TV and Ad-IRAP, relative to vector controls, significantly decreased IL-1β. Inflammatory mediators [tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8), interferon-γ (IFN-γ)], and catabolic matrix metalloproteinase 13 (MMP13) were also decreased, while anabolic transforming growth factor-β1 (TGF-β1) was increased. IL-1β was also decreased by TV versus saline, with a decrease in MMP13 and increase TGF-β1; TNF-α, IL-8, and IFN-γ were transiently increased. Conclusions This work confirmed that a reduction in IL-1β signaling was accomplished by either method, resulting in decreased expression of three inflammatory mediators and one catabolic agent, and increased expression of an anabolic molecule. Thus, evidence is provided that IL-1β serves a role in vivo in spontaneous osteoarthritis and that these translational tools may provide beneficial disease modification.

Objectives The aim of this study was to evaluate the safety and collect pilot data measuring clinical effects of intravenously administered, adipose-derived, culture-expanded, allogeneic mesenchymal stem cells in dogs with elbow osteoarthritis. Materials and Methods Dogs (n = 13) with naturally occurring elbow osteoarthritis received three intravenous doses of allogeneic canine mesenchymal stem cells via an open-label clinical trial. Primary outcome measures collected over a 6-month study period included objective gait analysis, accelerometry, owner questionnaires and joint fluid analysis. Results No acute adverse events were observed following repeated intravenous treatment with allogeneic mesenchymal stem cells. A significant improvement in mean client-specific outcome measure (CSOM) activity score and CSOM behaviour score was observed when pre-treatment values were compared with post-treatment values (day >28). In contrast, mean peak vertical force significantly decreased from baseline to post-treatment (>day 28). Weekly activity counts did not show a significant difference between baseline to post-treatment time points. Synovial fluid biomarkers did not change during treatment, and labelled mesenchymal stem cells were rarely detected in synovial fluid samples collected after mesenchymal stem cell administration. Clinical Significance For dogs with naturally occurring elbow osteoarthritis, intravenous administration of mesenchymal stem cells was clinically well tolerated. While some subjective outcome measures showed significant improvements, objective outcome measures did not confirm similar changes. Further research is needed before intravenous mesenchymal stem cells can be recommended as a treatment for elbow osteoarthritis in dogs.

Clinically healthy, aging dogs have changes in laboratory variables that indicate altered physiologies compared to younger adult animals, including evidence of IRE, inflammation, and potential gastrointestinal bleeding, suggesting a similar trend to that of elderly human beings. Future studies will examine markers of iron metabolism and inflammation in aging dogs.

Dogs with low CHr values often have evidence of inflammation, but low CHr did not reliably predict Fe deficiency. Additional diagnostic tests are needed to differentiate true and functional iron deficiency.

Skeletal muscle dysfunction, articular cartilage degeneration, and bone loss occur essentially in parallel during aging. Mechanisms contributing to this systemic musculoskeletal decline remain incompletely understood, limiting progress toward developing effective therapeutics. Because the progression of human musculoskeletal aging is slow, researchers rely on rodent models to identify mechanisms and test interventions. The Dunkin Hartley guinea pig is an outbred strain that begins developing primary osteoarthritis by 4 months of age with a progression and pathology similar to aging humans. The purpose of this study was to determine if skeletal muscle remodeling during the progression of osteoarthritis in these guinea pigs resembles musculoskeletal aging in humans. We compared Dunkin Hartley guinea pigs to Strain 13 guinea pigs, which develop osteoarthritis much later in the lifespan. We measured myofiber type and size, muscle density, and long-term fractional protein synthesis rates of the gastrocnemius and soleus muscles in 5, 9, and 15-month-old guinea pigs. There was an age-related decline in skeletal muscle density, a greater proportion of smaller myofibers, and a decline in type II concomitant with a rise in type I myofibers in the gastrocnemius muscles from Dunkin Hartley guinea pigs only. These changes were accompanied by age-related declines in myofibrillar and mitochondrial protein synthesis in the gastrocnemius and soleus. Collectively, these findings suggest Dunkin Hartley guinea pigs experience myofiber remodeling alongside the progression of osteoarthritis, consistent with human musculoskeletal aging. Thus, Dunkin Hartley guinea pigs may be a model to advance discovery and therapeutic development for human musculoskeletal aging.

Summary Objective To provide a comprehensive immunohistochemical (IHC) map of the temporal expression and tissue distribution of interleukin-1β (IL-1β) through progression of osteoarthritis (OA) in two strains of guinea pigs with varying propensity for spontaneous knee joint disease. Methods OA-prone Hartley and OA-resistant Strain 13 guinea pigs were collected at 60, 120, 180, 240, 360, and 480 days of age (N=4 animals per strain per date). IHC was performed on whole joint preparations; the distribution of IL-1β expression on coronal sections was mapped, semi-quantitatively scored, and correlated to OA grade using Mankin criteria with guinea pig-specific modifications. OA and IHC indices were compared among times and between strains using the Kruskal-Wallis one-way analysis of variance by ranks followed by Dunn's post test. Results OA indices for both strains increased from 60 to 480 days of age; a statistically higher score (p≤0.01) was found in Hartley animals at 180, 240, 360, and 480 days. At 60 days of age, IL-1β expression was detected in cartilage, menisci, synovium, and subchondral bone in both strains. Persistent and statistically increased (p<0.05) IL-1β expression was found in these same tissues in Hartley animals at 120 and 180 days, while Strain 13 animals demonstrated a significant reduction in positive immunostaining. Statistical differences in IHC indices between strains beyond 240 days of age were restricted to synovium (days 240 and 480) and subchondral bone (days 360 and 480). Conclusions As expected, histologic OA proceeded in an accelerated manner in Hartley animals relative to Strain 13 animals. The OA-prone strain did not demonstrate reduced IL-1β expression during adult maturity as occurred in the OA-resistant strain, and this persistent expression may have corresponded to early incidence of OA. Future interventional studies are warranted to explore whether dysregulation of IL-1β expression may contribute to premature onset of spontaneous disease in the Hartley guinea pig.

A computer-aided gait analysis system was used to contrast two guinea pig strains with differing propensity for osteoarthritis (OA), with/without administration of a nonsteroidal anti-inflammatory drug. Walking speed and static/dynamic gait parameters were determined at baseline. Flunixin meglumine was given and animals were evaluated 4, 24, and 72 hours after treatment. Body weight was compared using unpaired t-tests. Knee joints were histologically evaluated using species-specific criteria; indices were analyzed using one-way ANOVA, Kruskal-Wallis test, followed by Dunn's multiple comparisons. A generalized linear model followed by Tukey's posttests juxtaposed gait parameters; walking speed was a covariate for other outcome measures. Body weight was not different between strains; OA-prone animals demonstrated more progressive chondropathy. At baseline, OA-prone animals had slower walking speeds, narrower hind limb bases of support, shorter stride lengths, and slower limb swing speeds relative to OA-resistant animals. These differences were not detected 4 or 24 hours after treatment. By 72 hours, OA-prone animals had returned to baseline values. These findings indicate a distinct voluntary gait pattern in a rodent model of bilateral primary OA, modification of which may allow rapid screening of novel therapies. Flunixin meglumine temporarily permitted OA-prone animals to move in a manner that was analogous to OA-resistant animals.