Abstract
Purpose::
To investigate the rate of epithelial chimerism in conjunctiva of female patients with graft versus host diseae (GvHD) after sex mismatched haematopoietic stem cell transplantation (HSCT).
Methods::
Conjunctival biopsies of 7 female patients after sex-mismatched HSCT with GvHD were obtained in accordance to the Helsinki Declaration. The slides were stained by a combination of FISH for the Y-chromosome (Y), immunofluorescent stain for cytokeratin (CK), immunostain for CD45 followed by a secondary antibody labelled with Alexa Fluor 633 and a DAPI counterstain. Evaluation was done by laser-scanning confocal microscopy. Thereafter, slides were counterstained with H/E and evaluated by light microscopy. A median of 400 cells per slide were counted. Adjacent slides were stained for CD15 & CD68 by immuno-histology to exclude macrophages.
Results::
Donor derived epithelial cells were Y+/CK+/CD45-, contained the Y-signal within the DAPI-stained nucleus and revealed an epithelial morphology by light microscopy (Y+/CK+/CD45-/HEepith+). In 4 patients donor derived epithelial cells could be found (57%) with a mean incidence of 6.7% (range 2.42% - 7.91%). Down-regulation of CD45 expression by tissue macrophages could be excluded by CD68/CD15 staining.
Conclusions::
Our examination demonstrates that peripheral blood HSCT in humans results not only in replacement of the lymphohaematopoietic system, but also in generation of individual donor-derived epithelial cells in the conjunctiva. The rate of chimerism (3.84%) was greater than in oral mucosa (1.8%) and colon crypts (0.18%) found by other groups. This may be due to a higher incidence of GvHD (85%) in our samples. Cell-cell fusion may also play a role. Replacement of a local stem cell by a circulating bone marrow derived cell (BMDC) should result in multiple cells lying next to each other. We found that the Y+/CK+ cells were single cells lying within Y-/CK+ cells. Thus a transdifferentiation-process of single BMDC’s to epithelial cells may be presumed. Moreover, it has been shown that a small fraction of BMDC’s express cytokeratin while being negative for CD45.
Keywords: conjunctiva • differentiation • transplantation