Summary Reasons for performing study Biological treatments for osteoarthritis (OA) are an important component of disease control. Understanding the expression of catabolic and anabolic genes during osteoarthritis progression should help to identify the major mediators of the disease. Objective To compare the cytokine and anabolic marker concentrations in synovium, synovial fluid, and cartilage between normal and osteoarthritic joints. Methods Equine carpi from horses age 2–11 years were used. Tissues were harvested at the time of surgery or euthanasia, and RNA was isolated for RT-PCR analysis. Tumor necrosis factor alpha (TNFα), interleukin-1beta (IL-1β), aggrecanase 1 (ADAMTS-4), aggrecanase 2 (ADAMTS-5), matrix metalloproteinase-13 (MMP-13), interleukin 17 (IL-17), and collagen I alpha 1(Col-1) expression was determined in synovium. TNFα, IL-1β, ADAMTS-4, ADAMTS-5, MMP-13, IL-17, collagen IIB (Col-2B), and aggrecan expression was determined in cartilage. TNFα concentration in the synovial fluid was determined by enzyme-linked immunosorbent assay (ELISA). Results Expression of TNFα, ADAMTS-5, and MMP-13 was significantly increased in synovial tissue from OA joints. Synovial membrane IL-1β abundance showed only moderate elevations in OA, without reaching significant levels. Cytokine expression was increased in OA cartilage samples, particularly for TNFα (p=0.0007), IL-1β (p<0.0001), ADAMTS-4 (p=0.0011), and MMP-13 (p<0.0001). Collagen type I expression was significantly increased in synovial tissues from OA groups. Collagen type II message was diminished in mild and moderate stages of OA, but rebounded to significant elevations in severely degenerate joints. Conversely, aggrecan levels significantly declined in all OA cartilage groups (p<0.001). Synovial fluid TNFα peptide concentration was significantly increased in severe OA cases (p=0.021). Conclusion TNFα was significantly increased in all degrees of equine OA, and was abundantly expressed in synovial membrane and cartilage. Similarly, IL-1β was overexpressed in OA cartilage, but not to a significant extent in synovium. ADAMTS-4 was more abundant in OA cartilage while ADAMTS-5 predominated in OA synovium. IL-17 expression was not observed in osteoarthritic equine synovium nor cartilage. Potential relevance Control of TNFα should be considered further as a target in the treatment of OA. ADAMTS-4 may be the primary aggrecanase causing cartilage breakdown in OA.

BackgroundAs the search for an immune privileged allogeneic donor mesenchymal stem cell (MSC) line continues in equine medicine, the characterization of the cells between different sources becomes important. Our research seeks to more clearly define the MSC marker expression of different equine MSC donors.MethodsThe bone marrow-derived MSCs from two equine breeds and different blood donor-types were compared over successive culture passages to determine the differential expression of important antigens. Eighteen Thoroughbreds and 18 Standardbreds, including 8 blood donor (erythrocyte Aa, Ca, and Qa antigen negative) horses, were evaluated. Bone marrow was taken from each horse for isolation and culture of MSCs. Samples from passages 2, 4, 6, and 8 were labelled and evaluated by flow cytometry. The cell surface expression of CD11a/18, CD44, CD90 and MHC class II antigens were assessed. Trilineage assays for differentiation into adipogenic, chondrogenic and osteogenic lines were performed to verify characterization of the cells as MSCs.FindingsThere were significant differences in mesenchymal stem cell marker expression between breeds and blood antigen-type groups over time. Standardbred horses showed a significantly lower expression of MHC class II than did Thoroughbred horses at passages 2, 4 and 6. CD90 was significantly higher in universal blood donor Standardbreds as compared to non-blood donor Standardbreds over all time points. All MSC samples showed high expression of CD44 and low expression of CD11a/18.ConclusionsUniversal blood donor- type Standardbred MSCs from passages 2–4 show the most ideal antigen expression pattern of the horses and passages that we characterized for use as a single treatment of donor bone marrow-derived MSCs. Further work is needed to determine the significance of this differential expression along with the effect of the expression of MHC I on equine bone marrow-derived MSCs.

Expression of ADAMDEC1, GRP94, HCST, hUNC-93A, and RRM2 was differentially regulated in peripheral WBCs obtained from horses with experimentally induced osteoarthritis. Gene expression of ADAMDEC1, hUNC-93A, and RRM2 in peripheral WBCs has the potential for use as a diagnostic aid for osteoarthritis in horses.

Despite significant immunosuppressive activity, allogeneic mesenchymal stromal cells (MSCs) carry an inherent risk of immune rejection when transferred into a recipient. In naïve recipients, this immune response is initially driven by the innate immune system, an immediate reaction to the foreign cells, and later, the adaptive immune system, a delayed response that causes cell death due to recognition of specific alloantigens by host cells and antibodies. This review describes the actions of MSCs to both suppress and activate the different arms of the immune system. We then review the survival and effectiveness of the currently used allogeneic MSC treatments.