PubMed · 16266077
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Fred H Geisler. 2005. Bone graft extenders.. https://doi.org/10.3171/spi.2005.3.4.0332
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With the growing number of bone-related traumas and the limitations of traditional bone repair, alternative methods of bone management must be investigated. Demineralized bone matrix protein (DBX) has been used to reconstruct bone. DBX, a type of demineralized bone matrix, is a combination of several different proteins including osteogenic protein-1 (OP-1). Osteogenic protein-1 or Bone Morphogenic Protein-7 (BMP-7) was the first BMP approved for clinical use in the United States. Previous studies have shown that proliferation of osteoblasts (bone forming cells) was stimulated by OP-1. However, the effects of DBM and OP-1 at the cellular level have not been clearly defined. MG-63 osteosarcoma cells were utilized as a model and subsequently plated onto 24 well tissue culture plates at a density of 1x 10(5) ml/well. Cells were exposed to different concentrations of DBX demineralized bone matrix and OP-1 for periods of 24, 48, and 72 hours and compared with untreated controls. After each incubation period, cell morphology, cell damage, cell number, and protein concentrations were determined. Results indicate a significant increase in cell number at 72 hours in cells treated with 30% (5.66 x 10(5)) and 100% (6.3 x 10(5)) DBX treated groups when compared with the control (1.4 x 10(5)). OP-1 results do not indicate a significant increase in cell number at the 24 and 48 hour treatment phases when compared with the control (p > 0.05), however, results do show a statistically significant difference (approximately twofold, p < 0.05) between the control cells (1.9 x 10(4)) and those cells treated with low (3.9 x 10(4)) and high (4.1 x 10(4)) concentrations of OP-1 at the 72 hour time phase. The increases in cell number indicate that both DBX and OP-1 are effective in stimulating cell growth. When comparing the results of the DBX treatments with those of the OP-1 treatments, the cells treated with DBX showed a more substantial increase in bone cell proliferation after treatment than those cells treated with OP-1. This does suggest that DBX provides the most effective treatment for bone cell proliferation. Closer evaluation of the morphology especially the changes occurring at the nuclear level need to be addressed in future studies.
OBJECTIVE: The Wnt family of secreted proteins, their receptors (Fzd proteins) and antagonists (secreted Fzd-related proteins, or Sfrp) regulate chondrocyte differentiation and chrondrogenesis during embryonic development. Here, the hypothesis that the Wnt regulatory network contributes to chondrocyte differentiation of post-natal cells was tested in an in vitro model of chondroinduction by demineralized bone powder (DBP). DESIGN: Human dermal fibroblasts (hDFs) were cultured in porous, three-dimensional (3D) collagen sponges with or without chondroinductive DBP. In some experiments, lithium chloride (LiCl), an agonist of the Wnt/beta-catenin signaling pathway, was added to the culture media. Sponges were cultured for intervals (0.5-21 days) before processing for molecular, histologic, and biochemical analyses. Expression of wnt, fzd, and sfrp genes was characterized by semi-quantitative RT-PCR. Fibroblasts' contacts with DBP were documented by histology. Accumulation of proteoglycan in extracellular matrix was evaluated by histology (metachromasia in toluidine blue-stained sections) and quantitative immunoassay (chondroitin 4-sulfate ELISA). RESULTS: Expression of 15 wnt, fzd, and sfrp family members was detected in hDFs by RT-PCR. A subset of those genes (wnt2b, wnt5b, wnt10b, fzd6, fzd7) showed altered expression in hDFs exposed to DBP for 3 days. wnt and fzd gene expression was not altered before hDFs contacted the DBP within the collagen sponge. Human DFs cultured in plain collagen sponges and treated with LiCl accumulated significantly more metachromatic matrix than NaCl-treated controls on day 10, and showed a trend towards increased matrix chondroitin-4 sulfate content. CONCLUSIONS: These data suggest that changes in Wnt signaling contribute to chondroinduction of post-natal fibroblasts by DBP. This is the first evidence that Wnt components, which are essential regulators of pre-natal chondrocyte differentiation, may also influence post-natal chondrocyte differentiation induced by DBP.
Osteoinductivity of demineralized bone matrix has been attributed to bone morphogenetic proteins (BMP). Other growth factors, including insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta1 (TGF-beta1), have also been detected in demineralized bone matrix. Success of bone graft substitutes containing demineralized bone matrix has been assumed to be closely associated with osteoinductivity of the demineralized bone matrix. Because of differences in bone characteristics between donors and tissue banks, confirmation and measurement of osteoinductivity may play a crucial role in predicting the success of the bone graft substitute. In the current studies, BMP-2, BMP-4, TGF-beta1, and IGF-1 were measured in demineralized bone matrix. A strong association was noted between BMP-2 and TGF-beta1 levels. A strong association was also found between BMP-2 and new bone formation in an ectopic nude rat model.