Donor stromal cells from human blood engraft in NOD/SCID mice

Little is known about the presence, frequency, and in vivo proliferative po tential of stromal cells within blood-derived hematopoietic transplants. In this study, nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice were injected with human CD34(+) peripheral blood cells (PBCs) or cord blood cells (CBCs, either enriched for CD34 or density-gradient separated mononuclear cells). Flow cytometric analysts 5 to 11 weeks after transplant ation revealed the presence of a human lymphomyeloid hematopoiesis within t he murine bone marrow. Immunohistochemical staining of bone marrow cell sus pensions using human-specific antibodies showed human cells staining positi ve far human fibroblast markers, human von Wille-brand factor (vWF) and hum an KDR (vascular endothelial growth factor receptor-2) in mice transplanted with CD34+ PBCs or CBCs, with mean frequencies between 0.6% and 2.4%, In s tromal layers of bone marrow cultures established from the mice, immunohist ochemical staining using human-specific antibodies revealed flattened retic ular cells or spindle-shaped cells staining positive with human-specific an tifibroblast antibodies (mean frequency, 2.2%). Cell populations of more ro unded cells stained positive with human-specific antibodies recognizing CD3 4 (1.5%), vWF (2.2%), and KDR (1.6%). Reverse transcriptase-polymerase chai n reaction (RT-PCR) analysis and subsequent complementary DNA sequencing de tected transcripts of human KDR (endothelial specific) and human proline hy droxylase-alpha (fibroblast specific) within the bone marrow and spleen of transplanted mice. Analysis of nontransplanted control mice yielded negativ e results in immunocytochemistry and RT-PCR. Cells expressing endothelial a nd fibroblast markers were also detected in the grafts before transplantati on, and their numbers increased up to 3 log in vivo after transplantation. These results indicate that stromal progenitor cells are present in human c ytokine-mobilized peripheral blood or cord blood that engraft in NOD/SCID m ice. (C) 2000 by The American Society of Hematology.