Biomedical subjects

Hiroko Takita

Publications and source records attributed to Hiroko Takita.

4 recordsLinked to original sources

PubMed2003

[Bone morphogenetic protein (s) (BMP): structure and new functions].

Classical function of BMP was to induce cartilage and bone when implanted into animal skin or muscle. In spite of this remarkable function, which attracted the attention of clinicians, it took 37 years to obtain a FDA approval for clinical use ever since the discovery of BMP. This situation was contrast to the discovery of insulin that went directly to clinic and to Nobel Prize within only 2 years. There were two reasons why BMP took so long time before clinical application. (1) BMP is a cytokine, which works multi-functionally and is relating with many other factors. (2) BMP requires suitable carriers for reasonable bone induction. Design of the recommendable carrier required systematic understanding of the nature of artificial ECM. In addition to the classical function of bone induction, new functions as a morphogen were comparatively described in a table. Examples of the new functions includes developmental patterning of dorso-ventral axis of vertebrate embryo, formation of morphogen gradient in Drosophila embryo and the mechanism of feather - branching morphogenesis were introduced.

English Abstract↗

PubMed2002

Inhibition of BMP-induced ectopic bone formation by an antiangiogenic agent (epigallocatechin 3-gallate).

Epigallocatechin 3-gallate (EGCG), which is one of the components of green tea, was recently shown to inhibit endothelial cell growth in vitro and angiogenesis in vivo [5]. We have previously shown that bone and cartilage formation by bone morphogenetic protein (BMP) is highly dependent on the geometry of the carrier (vasculature-inducing or -inhibiting geometry [2]. To verify the function of angiogenesis in the BMP induction system, we examine in this article whether inhibition of angiogenesis enhances chondrogenesis and suppresses osteogenesis. Fibrous glass membrane used as a BMP carrier was mixed with 1.2 micrograms rhBMP-2 and 1-10 micrograms of EGCG and was implanted into rats subcutaneously. As the dose of EGCG increased, alkaline phosphatase activity and calcium content were decreased, whereas the type II collagen content was increased. The results clearly indicated that inhibition of vascularization enhanced chondrogenesis and suppressed osteogenesis.

Alkaline Phosphatase↗

PubMed2002

Geometry of artificial ECM: sizes of pores controlling phenotype expression in BMP-induced osteogenesis and chondrogenesis.

This study aims to elucidate the feasible geometry of the scaffolds in bone and periodontal tissue engineering. Several biomaterials with different geometries are compared in terms of their patterns of ectopic BMP-induced chondrogenesis and osteogenesis. The materials include a honeycomb-shaped hydroxyapatite (HCHAP) with different tunnel sizes, a laser-perforated collagen membrane (LPM), and CPSA bioglass fibers. Implanted pellets were removed at 1-4 weeks and analyzed for bone and cartilage formation histologically and biochemically. Porous particles of hydroxyapatite (PPHAP), porous blocks of hydroxyapatite (PBHAP), and LPM did not induce detectable cartilage formation. In straight tunnel structures with various diameters in honeycomb-shaped hydroxyapatite (HCHAP), tunnels with smaller diameters (approximately 0.1 mm) induced cartilage followed by bone formation, while one with a larger diameter (0.35 mm) directly induced bone formation within the tunnels. It is concluded that the "vasculature-inducing geometry" of the carrier as an ECM is crucially important for osteogenesis.

Animals↗

PubMed2002

Pleiotrophin regulates bone morphogenetic protein (BMP)-induced ectopic osteogenesis.

We previously isolated pleiotrophin (PTN) from bovine bone as a protein and showed that it stimulated osteoblastic growth and differentiation. Further details of its function, however, have not been fully clarified. The aim of this paper was to elucidate the effects of PTN on bone morphogenetic protein (BMP)-induced ectopic osteogenesis. Recombinant human BMP (rhBMP)-2 (1.2 microg) was combined with a fibrous glass membrane, which had been established as an effective carrier. Various amounts of the purified bovine PTN (5, 10, 50, and 100 microg) or rhPTN (5 and 10 microg) were added to the rhBMP-2/carrier composites and implanted into rats subcutaneously as reported. It was found that the amount of bone induced in the system increased with the addition of 10 microg of either purified PTN or rhPTN. However, the amount of bone decreased with the addition of 50 or 100 microg of purified PTN dose-dependently, as judged by both alkaline phosphatase activity and calcium content in the retrieved implants. It was concluded that purified PTN or rhPTN, at ratios of concentration of 10-100 microg of PTN to 1.2 microg of rhBMP-2 in the carrier, regulated the ectopic bone-inducing activity of rhBMP-2.

Animals↗