This study evaluated chondrogenesis of mesenchymal progenitor stem cells (MSCs) cultured initially under pre-confluent monolayer conditions exposed to transforming growth factor-81 (TGF-Pl ), and subsequently in three-dimensional cultures containing insulin-like growth factor I (IGF-I). Bone marrow aspirates and chondrocytes were obtained from horses and cultured in monolayer with 0 or 5 ng of TGF-P1 per ml of medium for 6 days. TGIF-81 treated and untreated cultures were distributed to threedimensional fibrin disks containing 0 or 100 ng of IGF-I per ml of medium to establish four treatment groups. After 13 days, cultures were assessed by toluidine blue staining, collagen types I and I1 in situ hybridization and immunohistochemistry, proteoglycan production by [35S]-s~ilfate incorporation, and disk DNA content by fluorometry. Mesenchymal cells in monolayer cultures treated with TGF-81 actively proliferated for the first 4 days, developed cellular rounding, and formed cell clusters. Treated MSC cultures had a two-fold increase in medium proteoglycan content. Pretreatment of MSCs with TGF-81 followed by exposure of cells to IGF-I in three-dimensional culture significantly increased the formation of markers of chondrocytic flmction including disk proteoglycan content and procollagen type I1 mRNA production. However, proteoglycan and procollagen type I1 production by MSC's remained lower than parallel chondrocyte cultures. MSC pretreatment with TGF-P1 without sequential IGF-I was less effective in initiating expression of markers of chondrogenesis. This study indicates that although MSC differentiation was less than complete when compared to mature chondrocytes, chondrogenesis was observed in IGF-I supplemented cultures, particularly when used in concert with TGF-81 pretreatment. 0 9001 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.

Results suggest that TGF-beta1 enhances chondrogenic differentiation of bone marrow-derived MSC in a dose-dependent manner.

Cooling the foot could decrease enzymatic reactions associated with laminitis, and warming could increase local perfusion when desired.

A 9-year-old pregnant mare was referred for evaluation of a nonhealing wound of 8 weeks' duration on the lateral aspect of the left forelimb. A soft tissue mass encircled the proximal two thirds of the metacarpus; radiography revealed a moderate periosteal reaction affecting metacarpal bone i.v. Histologic and immunohistochemical examinations revealed eosinophilic granulomatous inflammation and Pythium sp in the soft tissues. The mare was treated for 12 days with antimicrobials, medicated wound dressings, debridement, and i.v. administration of sodium iodide; radiography revealed progression of the bone lesions. The mare was treated by regional arterial perfusion with miconazole and excision of affected soft tissues and the distal two thirds of metacarpal bone i.v. The mare recovered without complications and gave birth to a healthy foal. Regional perfusion of antifungal agents provides high concentrations in soft and osseous tissues and permits use of low dosages of agents administered by other routes, which reduces cost, adverse effects, and teratogenic effects.

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