Donor fibroblast chimerism in the pathogenic fibrotic lesion of human chronic graft-versus-host disease

PURPOSE. Tissue atrophy and excessive fibrosis are prominent histologic features of chronic graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation, but the underlying mechanism remains unknown. The current study was undertaken to investigate whether the increase in fibroblasts at the site of pathogenic fibrosis originated from transplanted donor cells in patients with chronic GVHD. METHODS. Lacrimal gland biopsy specimens were obtained from nine patients with chronic GVHD. The male-specific sequences detected by fluorescein in situ hybridization (FISH) and in situ hybridization (ISH) were used as markers for the donor cells in seven female patients who had received a transplant from male donors. Primary fibroblast cultures were generated from lacrimal gland biopsy specimens and examined for mismatched genetic markers between recipients and donors. RESULTS. In lacrimal gland specimens obtained from seven female patients who received a sex-mismatched transplant, 13.4% to 26.7% of CD34⁺ fibroblasts that accumulated in the fibrotic lesion were donor derived, as determined by FISH for the Y-chromosome. The male-specific mRNA was also detected in the lacrimal gland fibroblasts by ISH. Primary lacrimal gland fibroblast cultures were generated from four patients with chronic GVHD and further examined for mismatched genetic markers between recipients and donors. As a result, the presence of donor origin of the fibroblasts was demonstrated by detecting the Y-chromosome sequence and donor-specific microsatellite genetic markers. CONCLUSIONS. These findings together indicate the chimeric status of accumulated CD34⁺ fibroblasts in the lacrimal gland of patients with chronic GVHD. Fibroblasts originating from circulating donor-derived precursors may participate in the excessive fibrosis in these patients.