Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.3 (collagenase)
 18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mice carrying a targeted mutation (r) in Col1a1, encoding a collagenase-resistant form of type I collagen, have altered skeletal remodeling. In hematoxylin and eosin-stained paraffin sections, we detect empty lacunae in osteocytes in calvariae from Col1a1(r/r) mice at age 2 weeks, increasing through age 10-12 months. Empty lacunae appear to result from osteocyte apoptosis, since staining of osteocytes/periosteal osteoblasts with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling is increased in Col1a1(r/r) relative to wild-type bones. Osteocyte perilacunar matrices stained with Ab that recognizes collagenase collagen alpha1(I) chain cleavage ends in wild-type but not Col1a1(r/r) calvariae. Increased calvarial periosteal and tibial/femoral endosteal bone deposition was found in Col1a1(r/r) mice from ages 3-12 months. Calcein labeling of calvarial surfaces was increased in Col1a1(r/r) relative to wild-type mice. Daily injections of synthetic parathyroid hormone for 30 days increased calcein-surface labeling in wild-type but caused no further increase in the already high calcein staining of Col1a1(r/r) bones. Thus, failure of collagenase cleavage of type I collagen in Col1a1(r/r) mice is associated with osteocyte/osteoblast death but increases bone deposition in a manner that mimics the parathyroid hormone-induced bone surface activation seen in wild-type mice.
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PMID:Osteocyte and osteoblast apoptosis and excessive bone deposition accompany failure of collagenase cleavage of collagen. 1103 54

Previous work has suggested that "calcospherulites" actively participate in the mineralization of developing and healing bone. This study sought to directly test this hypothesis by developing a method to isolate calcospherulites and analyzing their capacity to seed mineralization of fibrillar collagen. The periosteal surface of juvenile rat tibial diaphysis was enriched in spherulites of approximately 0.5-mum diameter exhibiting a Ca/P ratio of 1.3. Their identity as calcospherulites was confirmed by their uptake of calcein at the tibial mineralization front 24 h following in vivo injection. Periosteum was dissected and unmineralized osteoid removed by collagenase in order to expose calcospherulites. Calcein-labeled calcospherulites were then released from the mineralization front by dispase digestion and isolated via fluorescence flow sorting. X-ray diffraction analysis revealed they contained apatite crystals (c-axis length of 17.5+/-0.2 nm), though their Ca/P ratio of 1.3 is lower than that of hydroxyapatite. Much of their non-mineral phosphorous content was removed by ice-cold ethanol, elevating their Ca/P ratio to 1.6, suggesting the presence of phospholipids. Western blot analyses showed the presence of bone matrix proteins and type I collagen in these preparations. Incubating isolated calcospherulites in collagen hydrogels demonstrated that they could seed a mineralization reaction on type I collagen fibers in vitro. Ultrastructural analyses revealed crystals on the collagen fibers that were distributed rather uniformly along the fiber lengths. Furthermore, crystals were observed at distances well away from the observed calcospherulites. Our results directly support an active role for calcospherulites in inducing the mineralization of type I collagen fibers at the mineralization front of bone.
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PMID:Calcospherulites isolated from the mineralization front of bone induce the mineralization of type I collagen. 1793 99

Calcium-containing spherical bodies (calcospherulites) exist along the mineralization front of bone and are thought to play a role in bone formation. Existing methods to isolate calcospherulites involve harsh treatments that remove much of their organic matter. This study sought to isolate them using a less destructive approach to better preserve their organic components. Juvenile rats were injected with a low dose of calcein to label the newly formed mineral at the mineralization front of bone in vivo. Periosteum was completely dissected from the tibial diaphysis and unmineralized osteoid matrix was removed by collagenase in order to expose calcospherulites. Calcein-labeled calcospherulites of approximately 0.5 mum average diameter were observed all along the mineralization front and they exhibited a Ca/P ratio of 1.3 in situ. Calcospherulites were released from the mineralization front by a short dispase digestion and isolated via fluorescence flow sorting. X-ray diffraction revealed they contained apatite crystals (c-axis length of 17.5 +/- 0.2 nm) and their Ca/P ratio was preserved during isolation. Calcospherulites treated with ice-cold ethanol exhibited a Ca/P ratio of 1.6, suggesting the presence of some extractable phospholipids. Proteins extracted from isolated calcospherulites were resolved by SDS-PAGE into more than 20 distinct bands. Western blot analyses showed the presence of matrix proteins in these preparations. These results indicate that calcospherulites can be isolated from the mineralization front of bone in a form that can be used to study their proteome and lipid composition.
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PMID:Isolation of calcospherulites from the mineralization front of bone. 1876 29