The effect of bioactive glass ceramics on the expression of bone-related genes and proteins in vitro

Using biodegradable bone substitutes in alveolar ridge augmentation avoids second-site surgery for autograft harvesting. Considerable efforts have been undertaken to develop rapidly resorbable bone substitute materials with a higher degree of biodegradability than tricalcium phosphate (TCP). This study examines the effect of novel biodegradable glass ceramics on the expression of bone-related genes and proteins by human bone-derived cells (HBDC) and compares this behavior with that of TCP. Test materials used were alpha-TCP, a surface-treated glass ceramic GB9N with crystalline phase Ca2KNa(PO4)(2) and a small amount of amorphous silica phosphate; AP40 - a glass ceramic based on crystalline phases of apatite and wollastonite; and a glass ceramic Mg5 composed of 20.6% CaO, 58.5% P2O5, 14.4% Na2O, 4.1% MgO and 2.4% CaF2 (wt%). HBDC were grown on the substrata for 3, 5, 7, 14 and 21 days, counted and probed for various bone-related mRNAs and proteins (type I collagen (Col I), osteocalcin (OC), osteopontin (OP), osteonectin (ON), alkaline phosphatase (ALP) and bone sialoprotein (BSP)). The substrata supported continuous cellular growth for 21 days. By day 21, GB9N had the highest number of HBDC. GB9N induced significantly enhanced expression of Col I, ALP, OP, OC and ON mRNA at 3 days; of OP, OC and ON mRNA and protein at 7 and 14 days; and of ALP, OP and OC mRNA and Col I, ALP, BSP, ON and OP protein at 21 days. Since all novel glass ceramics supported cellular proliferation together with expression of bone-related genes and proteins at least as much as TCP, these ceramics can be regarded as potential bone substitutes. GB9N had the most effect on osteoblastic differentiation, thus suggesting that this material may possess a higher potency to enhance osteogenesis than TCP.