Stimulation of bone collagenase synthesis by mouse fibrosarcoma in resorbing bone in vitro culture.

Fragments of transplantable mouse fibrosarcoma, co-cultured with 5-day-old mouse calvaria, stimulated bone to synthesize and/or release collagenase (～0.6 units/ml) into the culture medium, whereas the tumour alone neither released nor synthesized collagenase.     

The effect of fluoride pretreatment and ascorbic acid on bone growth in tissue culture

The addition of ascorbic acid to tissue culture media was found to increase the collagen and mineral content of bones grown in vitro both effects resulting apparently from an increased rate of collagen synthesis. Ascorbic acid also increased the solubility of the bone collagen, possibly by increasing the accumulation of newly synthesized, soluble, collagen in the bone at a rate faster than the formation of crosslinkages between the collagen molecules. Pretreating bone in vitro with fluoride increased the weight of cultured bone primarily by increasing the mineral content. The effect was greatest in the presence of a low rate of collagen synthesis. When collagen synthesis was accelerated by ascorbic acid, fluoride pretreatment caused a lesser increase in bone mass and actually depressed collagen synthesis. It would appear, therefore, that the effect of fluoride pretreatment on bone growth is dependent in part on the rate of collagen synthesis by bone cells. Fluoride pretreatrnent decreased the solubility of the collagen matrix of bone indicating an affect on intermolecular crosslinking. The increased degree of crosslinking due to the fluoride pretreatment may account, in part, for the inhibition of bone resorption in tissue culture.     

The appearance of bone resorbing activity in ligature induced gingivitis in dogs

The in vitro bone resorbing activity of extracts from healthy and inflamed dog gingiva were compared and the appearance of the resorbing factor between 1 and 6 weeks of gingivitis was measured. Seven adult dogs were used. The gingiva were initially rendered healthy by scaling and polishing. Plaque retentive ligatures were placed around the necks of teeth so that at the end of the experiment samples of healthy gingiva and gingiva with 1 and 6 week old ligature induced gingivitis could be harvested from each dog. The bone resorbing activity of extracts from these gingival samples was studied by measuring the release of ⁴⁵Ca from prelabeled fetal rat long bones in organ culture. Six out of 7 extracts from healthy quadrants had no bone resorbing potential whereas 13 out of 14 extracts from ligatured quadrants stimulated significant amounts of bone resorption. The resorbing activity appeared during the first week after ligature placement and no significant increase in resorbing potential was noted between extracts obtained 1 and 6 weeks after ligature placement. It was concluded that the appearance of the bone resorbing factor(s) is related to the accumulation of plaque and/or the resultant inflammation and that it may be responsible for the alveolar bone loss seen in ligature induced periodontal disease in dogs.     

Human dental plaque: Stimulation of bone resorption in tissue culture

Soluble extracts of plaque from adults with periodontitis and children without evidence of destructive periodontal disease stimulated bone resorption in tissue culture. This effect was associated with the formation of osteoclasts. The extracts did not stimulate resorption of heat-devitalized bones. The bone resorptive factor in plaque behaved the same as purified endotoxin by two criteria: resistance to boiling and non-dialysability.     

骨组织工程种子细胞体外培养模式的发展概况

种子细胞是组织工程学的基本要素之一。种子细胞体外大规模扩增培养是组织工程学的一个重要方面,与传统的二维培养方式相比新型的生物反应器在培养及扩增间充质干细胞等种子细胞方面有着明显的优势,本文要论述随着近年来越来越多关于生物反应器的研究发展及其在培养干细胞具体存在的那些特点。     

The effect of ascorbic acid on the turnover of collagen in bone in tissue culture

Ascorbic acid is required for collagen synthesis but its role in other aspects of collagen metabolism is unclear. Neonatal mouse calvaria were incubated in tissue culture in the presence of 0·05 or 50·0 μg/ml ascorbic acid to determine the effect on bone collagen synthesis, crosslinking and degradation. H³-proline was added to the culture media to label the collagen newly synthesized in vitro with H³-hydroxyproline. Ascorbic acid increased the synthesis but descreased the degradation of the H³-hydroxyproline-labeled bone collagen. Ascorbate increased the specific activity (CPM H³-hyp/μg hyp) of the insoluble collagen, with no effect on the: acid-soluble collagen, indicating that the newly synthesized bone matrix was more highly crosslinked. On the other hand, the degradation of the preformed unlabeled collagen appeared to be increased. It was concluded that ascorbic acid increased bone collagen remodeling in vitro by favouring the the accumulation of newly synthesized bone collagen and the removal or degradation of the older preformed material.     

The effect of ascorbic acid on the turnover of collagen in bone in tissue culture

Ascorbic acid is required for collagen synthesis but its role in other aspects of collagen metabolism is unclear. Neonatal mouse calvaria were incubated in tissue culture in the presence of 0·05 or 50·0 μg/ml ascorbic acid to determine the effect on bone collagen synthesis, crosslinking and degradation. H³-proline was added to the culture media to label the collagen newly synthesized in vitro with H³-hydroxyproline. Ascorbic acid increased the synthesis but descreased the degradation of the H³-hydroxyproline-labeled bone collagen. Ascorbate increased the specific activity (CPM H³-hyp/μg hyp) of the insoluble collagen, with no effect on the acid-soluble collagen, indicating that the newly synthesized bone matrix was more highly crosslinked. On the other hand, the degradation of the preformed unlabeled collagen appeared to be increased. It was concluded that ascorbic acid increased bone collagen remodeling in vitro by favouring the the accumulation of newly synthesized bone collagen and the removal or degradation of the older preformed material.     

Characterization of bone resorbing activity in gingival crevicular fluid from patients with periodontitis

BACKGROUND: In attempts to elucidate factors stimulating bone resorption in patients with different inflammatory diseases in the vicinity of the skeleton, e.g., peridontal disease and rheumatoid arthritis, we are investigating the presence of bone-resorbing activity in a variety of inflammatory exudates. The aim of the present study was to characterize the bone-resorbing activity present in patients with periodontitis. METHODS: Bone-resorbing activity was assessed in gingival crevicular fluids (GCFs) collected from patients with periodontitis and from patients with no signs of gingivitis. Bone-resorbing activity was evaluated by analyzing the capacity of GCFs to stimulate the release of minerals and the breakdown of bone matrix proteins in cultured neonatal mouse calvariae. The concentrations of IL-1alpha, IL-1beta and PGE2 were determined with ELISA and RIA techniques, respectively. RESULTS: GCF eluates from 24 different healthy sites caused a 1.23+/-0.05 fold stimulation of 45Ca release, whereas GCF eluates from 45 different diseased (periodontitis) sites caused a 2.46+/-0.10 fold stimulation. The effect on 45Ca release was time- and concentration-dependent, inhibited by 3 different osteoclast inhibitors and associated with enhanced release of 3H from [3H]-proline-labelled bones. The activity in GCF causing enhanced 45Ca release was unaffected, or in some samples partially reduced, by ultrafiltration using a filter with a molecular weight cut-off of 3000 Daltons. The bone-resorbing activity was temperature sensitive (+90degrees C, 10 min). The concentrations of prostaglandin E2 (PGE2) in the diluted GCF eluates, used in the bone resorption bioassay, were too low to be responsible for the release of 45Ca. Antisera specifically neutralizing human IL-1a inhibited the stimulatory effect of GCF pooled from several diseased sites. The specific, recombinant human IL-1 receptor antagonist completely inhibited the effect of pooled GCFs. GCF eluates from diseased sites contained human IL-1alpha and IL-1beta at concentrations of 1838+/-294 pg/ml and 512+/-91 pg/ml, respectively. CONCLUSIONS: These data show that GCF contains activity(ies) stimulating osteoclastic bone resorption in vitro. The factor primarily responsible for this activity seems to be IL-1alpha, but IL-1alpha is not the sole activator of bone resorption in GCF.