Microchimerism in salivary glands after blood- and marrow-derived stem cell transplantation

Abstract

Blood- and marrow-derived stem cells (BMDSCs) provide disease-ameliorating effects for cardiovascular and autoimmune diseases. Microchimerism from donor BMDSCs has been reported in several recipient tissues. We hypothesized that this finding suggests a potential use of BMDSCs in the treatment of salivary dysfunctions. We investigated the presence of Y chromosome-positive cells in salivary gland biopsies of 5 females who had received a marrow or blood stem cell transplant from male donors. One to 16 years after transplantation, all recipients exhibited scattered Y chromosome-positive cells in the acini, ducts, and stroma of their salivary glands (mean of 1.01%). Potentially, these cells can be markers of transplantation tolerance, contribute to neoplastic epithelial tissues, or engraft at sites of injury. In addition, transplantation of BMDSCs could be used for treatment of Sjögren's syndrome and salivary glands damaged by therapeutic irradiation for cancers of the head and neck.

Figure 1

Labial salivary gland biopsies from female recipients of male BMDSCs. (A) Salivary cells are stained with the epithelial marker cytokeratin 13 (green). Y chromosome-positive cells (nuclei with red fluorescent dots, shown by the arrows) reside in an intercalated duct (left) and a striated duct (right). (B, C) Cytokeratins 8, 18, 19 are shown in red. Y-positive cells (green) reside in epithelial cells (arrows) and stromal cells (arrowheads). Panel C shows 3 planes restored from a Z-stack of sections taken at 0.5-µm intervals. The y and z dimensions are shown on the two sides of the x plane image and demonstrate the presence of the Y chromosome (green) in the same plane with the cytokeratins (red) and the nuclei (DAPI, blue). Further characterization of the phenotypes of Y chromosome-positive cells using additional cell markers (shown in green) such as: (D) claudin-1 (a tight junction protein in salivary ducts), (E) Na⁺-K⁺-2Cl⁻ cotransporter (NKCC1; a marker for acini), and (F) von Willebrand factor IV (a marker for endothelial cells) indicate several epithelial and endothelial cells that are Y chromosome-positive (arrows); other Y-positive cells (arrowheads) in or near the wall of this blood vessel may be smooth muscle cells, fibroblasts, etc. (G) CD45 (a marker of the white blood cell lineage) in green (FITC); NKCC1 in yellow (CY5) and the Y chromosome in red (Alexa-594). All nuclei are blue (DAPI). The two arrows point to 2 CD45-positive cells in proximity to salivary cells. The intersection of the 2 red lines in this panel indicates a salivary epithelial cell (NKCC1, yellow) of male donor origin (Y chromosome, red dot). Panels D-G show 3 planes restored from a Z-stack of sections taken at 0.5-µm intervals. Scale bars equal 10 µm (A–C) and 16 µm in D–G.