Macrophages are vital in spontaneous intraocular tumor eradication.

PURPOSE: Injection of tumor cells transformed by the early region 1 of human adenovirus type 5 (Ad5E1) in the anterior chamber (AC) of C57BL/6 mice leads to intraocular tumor formation. This tumor disappears spontaneously 3 to 4 weeks after tumor inoculation without damaging the neighboring ocular tissues. Previous studies have shown that CD4+ T cells, IFNgamma, and TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) play a role in the spontaneous eradication of this particular intraocular tumor. This study was conducted to determine whether macrophages are involved in the natural elimination of this intraocular tumor. METHODS: Ad5E1-expressing tumor cells were inoculated into the AC of syngeneic C57BL/6 mice. Macrophage depletion was obtained by subconjunctival (scj), subcutaneous (sc), or intravenous (iv) injection of clodronate liposomes 2, 8, and 14 days after tumor inoculation. Control C57BL/6 mice received PBS liposomes at similar time points after tumor injection or were left untreated. The presence of macrophages in the AC tumor was determined with the macrophage marker F4/80. RESULTS: Progressive tumor growth was observed in mice that were subconjunctivally depleted of macrophages, whereas spontaneous tumor eradication occurred in all other groups. F4/80 staining was negative in the AC tumors of mice treated scj with clodronate liposomes in contrast to the positive F4/80 staining in the tumors of the other groups. Ad5E1 tumor antigen still reached the tumor-draining lymph nodes (DLNs) of mice locally depleted for macrophages. CONCLUSIONS: Local macrophages in the eye are involved in the process of spontaneous AC tumor eradication in mice. However, it is not conclusive from these data exactly how tumor-specific CD4+ T cells and macrophages interact with each other to eliminate the Ad5E1-AC tumor without any collateral eye damage.

A new three-dimensional model of the organization of proteoglycans and collagen fibrils in the human corneal stroma.

The purpose of the present study was to re-evaluate the three-dimensional organization of collagen fibrils and proteoglycans (PGs) in the human corneal stroma using an improved ultrastructural approach. After a short aldehyde prefixation, one half of seven fresh corneal buttons was stained for PGs with Quinolinic Phtalocyanin (QP) or Cupromeronic Blue (CB). Strips of 1 mm width were cut, subsequently treated with aqueous phosphotungstic acid (PTA) and further processed for light and electron microscopy. The other half of the corneas served as control and was routinely processed with OsO4. Embedding was as such that ultrathin sections could be cut precisely parallel (frontal sections) or perpendicular (cross sections) to the corneal surface. The mutual connections between collagen fibrils and PGs were studied and the length of PGs and their mutual distance were measured manually at a calibrated final magnification of 70,000 x. Prefixed fresh corneal tissue treated with QP and CB shows no signs of swelling and exhibits well contrasted PGs. In cross sections PGs form a repeating network of ring-like structures (approximately 45 nm) around the collagen fibrils. In frontal sections PGs are aligned orthogonal to the collagen fibrils, are equidistant (approximately 42 nm) attached to the collagen fibrils along their full length and have a thickness of approximately 11 nm and a length of approximately 54 nm. The observed maximal length of the PGs and the occurrence of ring-like structures enwrapping the collagen fibrils urged us to revisit the prevailing model of maurice (1962) on the organization of the corneal stroma. In the new model hexagonal arranged collagen fibrils are interconnected at regular distances with their next-nearest neighbours by groups of six PGs, attached orthogonal to the circumference of the fibrils. In this way a regular meshwork of ring-like structures enwrapping the collagen fibrils is formed. It is discussed that this new model more convincingly explains corneal resistance to compression and stretching and further rationalizes corneal transparency because of the low refractive index difference between the regularly arranged collagen fibrils and their inter-space filled with PGs.