Dendritic Bone Marrow Derived Cells in the Mouse Cornea

Abstract

Purpose: : To demonstrate the appearance of bone marrow derived cells in the cornea.

Methods: : Haematopoietic stem cells were obtained with standard methods from C57Bl/6 mice expressing enhanced GFP. Normal 8 week old mice of the same strain were lethally irradiated and then injected intravenously with the cells. The animals were examined after 3 months for the presence of GFP containing cells, which were also classified immunohistochemically. The markers used were CD45, CD11b, CD11c, and alpha smooth muscle actin.

Results: : The eyes were replaced by scar tissue in 2 of a total of 7 animals, and notably phthisic in 1. The eyes were macroscopically normal in 4. The phthisis and the scar tissue replacing the eyes in some of the animals might be a murine version of graft–versus–host disease. GFP fluorescent cells (i. e. derived from the transplanted bone marrow) appeared in all parts of the cornea and in all layers, but were most numerous at the limbus, where they often lined vessels. GFP containing cells were also more common in the superficial half of the cornea than in the inner. In both epithelium and stroma, the GFP containing cells often had a dendritic morphology, most commonly in the superficial layers. Most but not all GFP containing cells were immunoreactive for CD45. Many were also immuno–reactive for CD11b. Fewer were immunoreactive for CD11c. Many of the GFP–labelled cells also contained smooth muscle actin, suggesting similarities with mobile myofibroblasts.

Conclusions: : There is an active exchange of immunocompetent cells between cornea and bone marrow. Both dendritic bone–marrow derived cells appear as well as more macrophage–like ones. The observations call for a revision of the simple notion that the cornea is readily transplantable because it lacks immunocompetent cells. It is possible that graft–versus–host disease occurs also in mice eyes.

Keywords: cornea: basic science • cornea: stroma and keratocytes • cornea: epithelium