Linda A. Dahlgren

EFFECT OF ADIPOSE-DERIVED NUCLEATED CELL FRACTIONS ON TENDON REPAIR IN HORSES WITH COLLAGENASE-INDUCED TENDINITIS

OBJECTIVE To assess the potential of adipose-derived nucleated cell (ADNC) fractions to improve tendon repair in horses with collagenase-induced tendinitis. ANIMALS 8 horses. PROCEDURES Collagenase was used to induce tendinitis in the superficial digital flexor tendon of 1 forelimb in each horse. Four horses were treated by injection of autogenous ADNC fractions, and 4 control horses were injected with PBS solution. Healing was compared by weekly ultrasonographic evaluation. Horses were euthanatized at 6 weeks. Gross and histologic evaluation of tendon structure, fiber alignment, and collagen typing were used to define tendon architecture. Biochemical and molecular analyses of collagen, DNA, and proteoglycan and gene expression of collagen type I and type III, decorin, cartilage oligomeric matrix protein (COMP), and insulin-like growth factor-I were performed. RESULTS Ultrasonography revealed no difference in rate or quality of repair between groups. Histologic evaluation revealed a significant improvement in tendon fiber architecture; reductions in vascularity, inflammatory cell infiltrate, and collagen type III formation; and improvements in tendon fiber density and alignment in ADNC-treated tendons. Repair sites did not differ in DNA, proteoglycan, or total collagen content. Gene expression of collagen type I and type III in treated and control tendons were similar. Gene expression of COMP was significantly increased in ADNC-injected tendons. CONCLUSIONS AND CLINICAL RELEVANCE ADNC injection improved tendon organization in treated tendons. Although biochemical and molecular differences were less profound, tendons appeared architecturally improved after ADNC injection, which was corroborated by improved tendon COMP expression. Use of ADNC in horses with tendinitis appears warranted.

Insulin-like growth factor-I improves cellular and molecular aspects of healing in a collagenase-induced model of flexor tendinitis

Flexor tendinitis is a common and debilitating injury of elite and recreational athletes. Healing may be improved through intratendinous injection of insulin‐like growth factor‐I (IGF‐I), which has been shown in vitro to stimulate mitogenesis and enhance tendon matrix production. This study investigated the effects of intratendinous injection of IGF‐I on tendon healing in an equine model of flexor tendinitis. Collagenase‐induced lesions were created in the tensile region of the flexor digitorum superficialis tendon of both forelimbs of eight horses. Treated tendons were injected with 2 μg rhIGF‐I intralesionally every other day for 10 injections, while controls received 0.9% NaCl. Tendon fiber deposition and organization were evaluated serially using ultrasonography throughout the 8 week trial period. Following euthanasia, the tendons were harvested and DNA, hydroxyproline, and glycosaminoglycan content determined, mechanical strength and stiffness evaluated, gene expression and spatial arrangement of collagen types I and III assessed by northern blot and in situ hybridization, and tendon fiber architecture assessed by polarized light microscopy. Local soft tissue swelling was reduced in the IGF‐I treated limbs. Similarly, lesion size in IGF‐I treated tendons was smaller 3 and 4 weeks after initiation of treatment. Cell proliferation and collagen content of the IGF‐I treated tendons were increased compared to controls. Mechanically, IGF‐I treated tendons showed a trend toward increased stiffness compared to saline treated controls. Considered together with the decreased soft tissue swelling and improved sonographic healing, these data support the potential use of intralesional IGF‐I for treatment of debilitating tendon injuries.

In vitro effects of three equimolar concentrations of methylprednisolone acetate, triamcinolone acetonide, and isoflupredone acetate on equine articular tissue cocultures in an inflammatory environment

OBJECTIVE To compare the effects of 3 equimolar concentrations of methylprednisolone acetate (MPA), triamcinolone acetonide (TA), and isoflupredone acetate (IPA) on equine articular tissue cocultures in an inflammatory environment. SAMPLE Synovial and osteochondral explants from the femoropatellar joints of 6 equine cadavers (age, 2 to 11 years) without evidence of musculoskeletal disease. PROCEDURES From each cadaver, synovial and osteochondral explants were harvested from 1 femoropatellar joint to create cocultures. Cocultures were incubated for 96 hours with (positive control) or without (negative control) interleukin (IL)-1β (10 ng/mL) or with IL-1β and MPA, TA, or IPA at a concentration of 10-4, 10-7, or 10-10M. Culture medium samples were collected from each coculture after 48 and 96 hours of incubation. Concentrations of prostaglandin E2, matrix metalloproteinase-13, lactate dehydrogenase, and glycosaminoglycan were determined and compared among treatments at each time. RESULTS In general, low concentrations (10-7 and 10-10M) of MPA, TA, and IPA mitigated the inflammatory and catabolic (as determined by prostaglandin E2 and matrix metalloproteinase-13 quantification, respectively) effects of IL-1β in cocultures to a greater extent than the high (10-4M) concentration. Mean culture medium lactate dehydrogenase concentration for the 10-4M IPA treatment was significantly greater than that for the positive control at both times, which was suggestive of cytotoxicosis. Mean culture medium glycosaminoglycan concentration did not differ significantly. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the in vitro effects of IPA and MPA were similar to those of TA at clinically relevant concentrations (10-7 and 10-10M).