Selective synthesis of bone morphogenetic proteins-1, -3, -4 and bone sialoprotein may be important for osteoinduction by Saos-2 cells.
An ability to induce new bone formation at a required site would represent a considerable advance in bone repair and tissue engineering. It has been shown that the healing of critical-size bone defects in rats can be augmented by extracts of Saos-2 cells. These human osteosarcoma cells uniquely contain a bone-inducing activity, whereas other human osteosarcoma cells, e.g., U-2 OS cells, cannot replicate the osteoinductive capacity. To understand the necessary components of the Saos-2 bone-inducing activity, this study compared osteoinductive Saos-2 cells with non-osteoinductive U-2 OS cells with respect to the synthesis of bone morphogenetic proteins (BMPs)-1, -2, -3, -4, -5, -6, and -7 and the non-collagenous matrix proteins bone sialoprotein (BSP), osteonectin (ON), osteopontin (OPN), and osteocalcin (OC). The main differences were abundant synthesis of BMP-1/tolloid, BMP-3, -4, and BSP by Saos-2 cells, but absence or reduced synthesis in U-2 OS cells. BMP-2 and -7 were present in low amounts in both cell types, while BMP-5 and -6 were more abundant in U-2 OS cells, suggesting that these BMPs were of lesser importance for the osteoinductivity of Saos-2 cells. However, a relatively high expression of BMP-3 and -4, together with BMP-1/tolloid, may be important for the osteoinductive capacity of Saos-2 cells. The inability of U2-OS cells to induce bone, despite expressing most of the BMPs, may be due to an insufficiency of tolloid, BMP-3 or -4, BSP, and/or other unknown factors. A better understanding of the necessary components of the Saos-2 cell bone-inducing agent may, in future, lead to clinically useful Saos-2 cell products for bone repair and tissue engineering.
Anderson
H Clarke
HC
Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS 66160, USA.
Reynolds
Paul R
PR
Hsu
Howard H T
HH
Missana
Lilliana
L
Masuhara
Kensaku
K
Moylan
Paul E
PE
Roach
Helmtrude I
HI
D000818:Animals; D001857:Bone Matrix / Q000737:chemistry; D019485:Bone Morphogenetic Proteins / Q000096:biosynthesis*; D001842:Bone and Bones / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D017690:Cell Transplantation; D016895:Culture Media, Serum-Free; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D015675:Osteocalcin / Q000378:metabolism; D010012:Osteogenesis / Q000502:physiology*; D015676:Osteonectin / Q000378:metabolism; D012516:Osteosarcoma; D012795:Sialoglycoproteins / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured
D019485:Bone Morphogenetic Proteins; D016895:Culture Media, Serum-Free; D015676:Osteonectin; D012795:Sialoglycoproteins; D015675:Osteocalcin