Collagen expression, ultrastructural assembly, and mineralization in cultures of chicken embryo osteoblasts.

Abstract

Abstract. A newly defined chick calvariae osteoblast culture system that undergoes a temporal sequence of differentiation of the osteoblast phenotype with subsequent mineralization (Gerstenfeld, L. C., S. Chipman, J. Glowacki, and J. B. Lian. 1987. Dev. Biol. 122:49-60) has been examined for the regulation of collagen synthesis, ultrastructural organization of collagen fibrils, and extracellular matrix mineralization. Collagen gene expression, protein synthesis, processing, and accumulation were studied in this system over a 30-d period. Steady state mRNA levels forpro al(I) and pro ~t2 collagen and total collagen synthesis increased 1.2-and 1.8-fold, respectively, between days 3 and 12. Thereafter, total collagen synthesis decreased 10-fold while mRNA levels decreased 2.5-fold. In contrast to the decreasing protein synthesis after day 12, total accumulated collagen in the cell layers increased sixfold from day 12 to 30. Examination of the kinetics of procollagen processing demonstrated that there was a sixfold increase in the rate of procollagen conversion to ~t chains from days 3 to 30 and the newly synthesized collagen was more efficiently incorporated into the extracellular matrix at later culture times.The macrostructural assembly of collagen and its relationship to culture mineralization were also examined. High voltage electron microscopy demonstrated that culture cell layers were three to four cells thick. Each cell layer was associated with a layer of well developed collagen fibrils orthogonally arranged with respect to adjacent layers. Fibrils had distinct 64-70-nm periodicity typical of type I collagen. Electron opaque areas found principally associated with the deepest layers of the fibrils consisted of calcium and phosphorus determined by electron probe microanalysis and were identified by electron diffraction as a very poorly crystalline hydroxyapatite mineral phase.These data demonstrate for the first time that cultured osteoblasts are capable of assembling their collagen fibrils into a bone-specific macrostructure which mineralizes in a manner similar to that characterized in vivo. Further, this matrix maturation may influence the processing kinetics of the collagen molecule.T HE processes by which mineralization is initiated and regulated in bone and other vertebrate calcifying tissues are incompletely understood. It is known, however, that a prerequisite for mineralization is the synthesis and assembly of an extracellular matrix into which mineral may be deposited. Collagen type I has been shown to be the major extracellular matrix protein of bone. It comprises between 60-70% of its organic components and between 20-30% of its total dry mass (20). Physiologically, type I collagen provides the protein basis for the architecture of bone and the scaffold into which mineral is accumulated (5,20,41). The importance of collagen type I in maintaining structural integrity and proper mineralization of bone has been demonstrated for one form of inherited osteogenesis imperfecta. A specific frame shift m...

Effects of electrospun scaffolds of di-O-butyrylchitin and poly-(ε-caprolactone) on wound healing

“…This observation, suggests that these polymers may increase the deposition of insoluble collagen in wounds treated with DBC or PCL. 32,33 Histological studies show similar responses of the tissue to implantation of both PCL and DBC. The implantation of biomaterials ( Fig.…”

“…The solubility of collagen in neutral salt solutions reflects its degree of maturation, cross-linking or catabolism. 32 Collagen fibre maturation occurs when intermolecular covalent bond formation causes progressive loss of solubility of the molecule. In both the DBC and PCL groups, the soluble collagen level was lower in the second week of healing and persisted at the lower level for the duration of the experiment (Fig.…”

The effects of patient age on human osteoblasts' response to Ti–6Al–4V implants in vitro

“…The nodules stain for alkaline phosphatase [4,42], and are the regions where bone extracellular matrix proteins are deposited [36] and mineralization occurs. Previous studies have shown that the mineralized nodules resemble woven bone that is produced in vivo [4,8,13,20,42]. On implant disks, phalloidin labeling of the actin-based cytoskeleton showed a confluent layer of cells with multilayering creating nodules (Fig.…”

The Mineralization of Crystalline Inorganic Components in Japanese Serow Horn

“…Presumably, it seems that the ability of the keratin fibers have the capacity to form the seeds to produce feather like HA, Ca/P will tend to approach 1.67 with crystal growth (Elliott, 1969;Hauschka et al , 1975;Moreno et al , 1977). Gerstenfeld et al (1988) studied a relationship between certain protains and the functional development of matrix mineralization (Dimuzio et al, 1978;Kallenbach, 1986;Termine et al , 1981). In general, there are two different posibilities of the process of mineralization; one is the mineralization induced by matrix vesicle as an initiator (Bernard et al, 1981), the other directly relates with mineral deposition among the keratin fibres.…”