Matrix-mediated retention of in vitro osteogenic differentiation potential and in vivo bone-forming capacity by human adult bone marrow-derived mesenchymal stem cells during ex vivo expansion

Mesenchymal stem cells (MSCs) represent an attractive cell source for tissue engineering applications, since they are readily isolated from adult bone marrow and have the ability to differentiate along multiple mesenchymal lineages, including osteogenic. Currently, utilization of MSCs for bone tissue engineering is limited because of the attenuation of their osteogenic differentiation potential and in vivo bone-forming capacity following ex vivo expansion on conventional tissue culture plastic (TCP). Previously, we demonstrated that a denatured type I collagen (DC) matrix promotes the maintenance of MSC in vitro osteogenic differentiation potential during ex vivo expansion in contrast to TCP. In this study, we further demonstrate that the maintenance of MSC osteogenic differentiation potential is primarily due to the ability of DC matrix to influence the retention of early passage osteogenic functions in late passage (LP) cells during ex vivo expansion, in contrast to solely enhancing attenuated LP cellular functions during osteogenic differentiation. Serum-associated factors played a significant role in influencing the retention of MSC osteogenic differentiation potential during expansion on the DC matrix. Significantly, the results show that although LP cells expanded ex vivo on TCP highly attentuate their in vivo bone-forming capacity, the expansion of MSCs on DC matrix preserves this ability as determined by histological, histomorphometric, and bone mineral density evaluations of MSC-seeded hydroxyapatite/tricalcium phosphate scaffolds following an 8-week implantation period within a heterotopic muscle pouch model. These findings provide further insight into the importance of matrix-mediated effects on MSC function and selective factors important in this process. (c) 2006 Wiley Periodicals, Inc.