CULTURE EXPANDED CANINE MESENCHYMAL STEM-CELLS POSSESS OSTEOCHONDROGENIC POTENTIAL IN-VIVO AND IN-VITRO

Mesenchymal Stem Cells (MSCs) possessing the capacity to differentiate into various cell types such as osteoblasts, chondrocytes, myoblasts, and adipocytes have been previously isolated from the marrow and peri osteum of human, murine, lapine, and avian species, This study documen ts the existence of similar multipotential stem cells in canine marrow , The cells mere isolated from marrow aspirates using a modification o f techniques previously established for human MSCs (hMSCs), and found to possess similar growth and morphological characteristics, as well a s osteochondrogenic potential in vivo and in vitro. On the basis of th ese results, the multipotential cells that were isolated and culture e xpanded are considered to be canine MSCs (cMSCs). The occurrence of cM SCs in the marrow was determined to be one per 2.5 x 10(4) nucleated c ells, After enrichment of the cMSCs by centrifugation on a Percoll cus hion, the cells were cultivated in selected lots of serum, Like the hM SCs, cMSCs grew as colonies in primary culture and on replating, grew as a monolayer culture with very uniform spindle morphology. The popul ation doubling time for these cMSCs was approximately 2 days, The morp hology and the growth kinetics of the cMSCs were retained following re peated passaging, The osteogenic phenotype could be induced in the cMS C cultures hy the addition of a synthetic glucocorticoid, dexamethason e, In these osteogenic cultures, alkaline phosphatase activity was ele vated up to 10-fold, and mineralized matrix production was evident, Wh en cMSCs were loaded onto porous ceramics and implanted in autologous canine or athymic murine hosts, copious amounts of bone and cartilage were formed in the pores of the implants, The MSC-mediated osteogenesi s obtained by the implantation of the various MSC-loaded matrix combin ations is the first evidence of osteogenesis in a canine model by impl antation of culture expanded autologous stem cells, The identification and isolation of cMSCs now makes it feasible to pursue preclinical mo dels of bone and cartilage regeneration in canine hosts. (C) 1997 Else vier Science Inc.