Direct Confirmation of Migration of Bone Marrow Cells into Normal and Inflamed Corneas

Abstract

Abstract: : Purpose: The purpose of this study was to determine whether bone marrow (BM) cells capable of migrate into normal corneas, and to evaluate distribution of BM cells in normal corneas and inflamed corneal allografts. Methods: Adult male C57BL/6 mice received 11 Gy of irradiation with a lead eye protector, and were injected with 1 X 10⁷ BM cells prepared from male enhanced green fluorescence protein (EGFP) transgenic mice (C57BL/6 background) through tail vein. Six weeks after GFP⁺ syngeneic BM cells transplantation, some of these C57BL/6 recipients received orthotopic corneal allografts using normal corneas of BALB/c donors. Corneas and BM were harvested at 2 weeks after corneal allografting (at 8 weeks after syngeneic BM transplantation). BM and normal corneas were harvested from the mice received GFP⁺ syngeneic BM cells transplantation alone without following corneal transplantation. BM reconstruction with GFP⁺ BM cells was confirmed by flow cytometry. Whole mounted corneas were observed by confocal microscopy to evaluate the distribution of GFP⁺ BM cells. Results: Approximately 50% of BM cells expressed GFP at 8 weeks after GFP⁺ BM cells transplantation. Confocal study revealed that a small number of GFP⁺ cells were present only in stroma, and these cells were rarely present in epithelium or endothelium of normal corneas. Accepted corneal allografts showed increase in the number of GFP⁺ cells distribute only in stroma. Whereas, GFP⁺ cells were found in all three layers of epithelium, stroma and endothelium of rejected allografts in increased numbers. Vast majority GFP⁺ cells are present in stroma, and accumulate in the graft junction rather than in the recipient bed or in the donor central area. Conclusions:The present study directly demonstrates migration of BM cells in normal corneas. BM cells keep migrating primarily in stroma in normal corneas. It is suggested that BM cells accumulate mainly in the stromal graft junction and participate in immune and inflammatory responses in corneal allografts.

Keywords: antigen presentation/processing • inflammation • transplantation