Immobilization of pamidronic acids on the nanotube surface of titanium discs and their interaction with bone cells.

Self-assembled layers of vertically aligned titanium nanotubes were fabricated on a Ti disc by anodization. Pamidronic acids (PDAs) were then immobilized on the nanotube surface to improve osseointegration. Wide-angle X-ray diffraction, X-ray photoelectron microscopy, and scanning electron microscopy were employed to characterize the structure and morphology of the PDA-immobilized TiO2 nanotubes. The in vitro behavior of osteoblast and osteoclast cells cultured on an unmodified and surface-modified Ti disc was examined in terms of cell adhesion, proliferation, and differentiation. Osteoblast adhesion, proliferation, and differentiation were improved substantially by the topography of the TiO2 nanotubes, producing an interlocked cell structure. PDA immobilized on the TiO2 nanotube surface suppressed the viability of the osteoclasts and reduced their bone resorption activity.

Enhanced osteoblast responses to poly(methyl methacrylate)/hydroxyapatite electrospun nanocomposites for bone tissue engineering.

Hydroxyapatite (HA)-containing polymers have been proposed for improving the biological properties of bone cements. Poly(methyl methacrylate) (PMMA) has long been used to secure orthopedic implants to skeletal bones. The aim of this study was to determine whether the incorporation of HA nanoparticles into the PMMA nanofibrous scaffolds enhances the biological functions of osteoblasts. The number of osteoblasts adhered and proliferated on the PMMA/HA nanofibrous scaffolds was significantly larger than that on the PMMA alone. The cytoskeletal organization and alkaline phosphatase (ALP) activity of the osteoblasts on the PMMA/HA nanofibrous scaffolds were clearly higher than that on the PMMA control. The amount of calcium ions released from 20 wt% HA-containing PMMA nanofibrous scaffolds (PMMA/HA20) was much higher than that released from 10 wt% HA-containing PMMA nanofibrous scaffolds (PMMA/HA10) (HA, 10 wt%). These findings suggested that osteoblast differentiation was accelerated by the incorporation of HA into the PMMA nanofibrous scaffolds. Therefore, the incorporation of HA into the PMMA nanofibrous scaffolds could be a useful method. This can be used for providing PMMA scaffolds with enhanced osteogenic properties.

Axonal synapses utilize multiple synaptic ribbons in the mammalian retina.

In the mammalian retina, bipolar cells and ganglion cells which stratify in sublamina a of the inner plexiform layer (IPL) show OFF responses to light stimuli while those that stratify in sublamina b show ON responses. This functional relationship between anatomy and physiology is a key principle of retinal organization. However, there are at least three types of retinal neurons, including intrinsically photosensitive retinal ganglion cells (ipRGCs) and dopaminergic amacrine cells, which violate this principle. These cell types have light-driven ON responses, but their dendrites mainly stratify in sublamina a of the IPL, the OFF sublayer. Recent anatomical studies suggested that certain ON cone bipolar cells make axonal or ectopic synapses as they descend through sublamina a, thus providing ON input to cells which stratify in the OFF sublayer. Using immunoelectron microscopy with 3-dimensional reconstruction, we have identified axonal synapses of ON cone bipolar cells in the rabbit retina. Ten calbindin ON cone bipolar axons made en passant ribbon synapses onto amacrine or ganglion dendrites in sublamina a of the IPL. Compared to the ribbon synapses made by bipolar terminals, these axonal ribbon synapses were characterized by a broad postsynaptic element that appeared as a monad and by the presence of multiple short synaptic ribbons. These findings confirm that certain ON cone bipolar cells can provide ON input to amacrine and ganglion cells whose dendrites stratify in the OFF sublayer via axonal synapses. The monadic synapse with multiple ribbons may be a diagnostic feature of the ON cone bipolar axonal synapse in sublamina a. The presence of multiple ribbons and a broad postsynaptic density suggest these structures may be very efficient synapses. We also identified axonal inputs to ipRGCs with the architecture described above.