Osteocalcin expression in collagen scaffolds. Human mesenchymal stem cells cultured on C-GAG, XC-GAG, MC-GAG, and XMC-GAG scaffolds in osteogenic medium were subjected with quantitative real-time RT-PCR (QPCR) for osteocalcin expression. Transcript fold changes from time zero are reported. C-GAG, collagen-glycosaminoglycan scaffold; MC-GAG, mineralized collagen-glycosaminoglycan scaffold; RT-PCR, reverse-transcriptase-polymerase chain reaction; XC-GAG, cross-linked collagen-glycosaminoglycan scaffold; XMC-GAG, cross-linked mineralized collagen-glycosaminoglycan scaffold.