Dissecting Microscopes

purpose. In experimental autoimmune uveitis (EAU), recent work has demonstrated that retinal damage involves oxidative stress early in uveitis, before macrophage cellular infiltration. The purpose of this study was to determine whether oxidative mitochondrial DNA damage occurs early in EAU, before leukocyte infiltration.

methods. Lewis rats were immunized with S-antigen mixed with complete Freund adjuvant (CFA) to induce EAU. Nonimmunized animals and animals injected with CFA served as controls. Animals were killed on days 3, 4, 7, and 12 after immunization. Damage to mitochondrial DNA and nuclear DNA was assessed using a novel long quantitative polymerase chain reaction technique. TUNEL staining to detect apoptosis and immunohistochemical detection of leukocyte infiltration in EAU retinas were also performed at these times.

results. Mitochondrial DNA damage occurred early in EAU, from day 4 to day 12. In the early phase of EAU (days 4–7), there was no inflammatory cell infiltration. On day 12 inflammatory cells infiltrated the retina and uvea. Nuclear DNA damage occurred later in EAU at day 12. Neither mitochondrial nor nuclear DNA damage was detected in the controls. TUNEL-positive staining for apoptosis was detected only at day 12 in EAU retina.

conclusions. Oxidative mitochondrial DNA damage begins at day 4 in EAU, supporting the view that oxidative stress selectively occurs in the mitochondria in the early phase of EAU, before leukocyte infiltration. Such oxidative damage in the mitochondria may be the initial event leading to retinal degeneration in EAU.

Previously, a strong and bioactive ceramic scaffold consisting of a porous zirconia body coated with apatite double layers (fluorapatite (FA) as an inner layer and hydroxyapatite (HA) as an outer layer) was successfully fabricated. In this contribution, the authors investigate the in vivo performance of the engineered bioceramic scaffolds using a rabbit calvarial defect model. In particular, the porosity and pore size of the scaffolds are varied in order to observe the geometrical effects of the scaffolds on their bone formation behaviors. The scaffolds supported on a zirconia framework can be produced with an extremely high porosity (~84—87%), while retaining excellent compressive strength (~7—8 MPa), which has been unachievable in the case of pure apatite scaffolds (~74% porosity with ~2MPa strength).

The experimental groups used in this study include three types of zirconia scaffolds coated with apatite; high porosity (~87%) with large pore size (~500— 700 µm): AZ-HL, high porosity (~84%) with small pore size (~150—200 µm): AZ-HS, and low porosity (~75%) with large pore size (~500—700 µm): AZ-LL, as well as one type of HA porous scaffold: low porosity (~74%) with a large pore size (~500—700 µm) for the purpose of comparison. The scaffolds prepared with dimensions of ~ 10 mm (diameter) x 1.2 mm (thickness) are grafted in rabbit calvaria defects. The histological sections are made at 4 and 12 weeks after surgery and immunohistochemical analyses are performed on the samples.

All of the specimens show a good healing response without adverse tissue reactions. Good healing is shown at 4 weeks post-surgery with the ingrowth of new bone into the macropore-channels of the scaffolds. The newly formed bone amounts to ~19.9—24.2% of the initial defect area, depending on the scaffold type, but there is no statistical significance between the scaffold groups. However, the defects without the scaffolds (control group) show a significantly lower bone formation ratio (~4.3%). At twelve weeks after surgery, the extent of new bone formation is more pronounced in all of the scaffold groups. All of the scaffold groups show significantly higher bone formation ratios (26.7—46.9%) with respect to the control without the graft. In the comparison between the scaffold groups, those with high porosities (AZ-HL and AZ-HS) exhibit significantly higher bone formation as compared to the scaffold with low porosity (AZ-LL).

Based on the present in vivo test performed within a rabbit calvaria defect model, it is concluded that the apatite-coated zirconia scaffolds show good bone forming ability and are considered to be a promising scaffolding material for bone regeneration since they possess a high level of both mechanical and biological properties.