In vivo transfer of intracellular labels from locally implanted bone marrow stromal cells to resident tissue macrophages

• Published in: PloS one 2009-08, Vol.4 (8), p.e6712
• Main Authors: Pawelczyk, Edyta, Jordan, Elaine K, Balakumaran, Arun, Chaudhry, Aneeka, Gormley, Nicole, Smith, Melissa, Lewis, Bobbi K, Childs, Richard, Robey, Pamela G, Frank, Joseph A
• Format: Article
• Language: English
• Subjects: Angiogenesis; Animals; Bone marrow; Bone Marrow Cells - cytology; Brain research; Bromodeoxyuridine; Bromodeoxyuridine - metabolism; Cell Biology; Cell cycle; Cell death; Cell Lineage; Cytometry; Dextran; Dextrans; Drawing and ironing; Ferric oxide; Flow Cytometry; Fluorescence; Fluorescence microscopy; Green fluorescent protein; Green Fluorescent Proteins - genetics; Heart; Hematology/Bone Marrow and Stem Cell Transplantation; Histology; Humans; Immunology/Immune Response; Implantation; In vivo methods and tests; Intracellular; Iron; Iron compounds; Iron oxides; Labels; Macrophages; Macrophages - cytology; Magnetic resonance; Magnetic Resonance Imaging; Mice; Microscopy; Microscopy, Fluorescence; Nanoparticles; NMR; Nuclear magnetic resonance; Perfusion; Plaques; Rodents; Stem cells; Stromal cells; Stromal Cells - cytology; Studies; Surgical implants; Viability
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0006712

Intracellular labels such as dextran coated superparamagnetic iron oxide nanoparticles (SPION), bromodeoxyuridine (BrdU) or green fluorescent protein (GFP) are frequently used to study the fate of transplanted cells by in vivo magnetic resonance imaging or fluorescent microscopy. Bystander uptake of labeled cells by resident tissue macrophages (TM) can confound the interpretation of the presence of intracellular labels especially during direct implantation of cells, which can result in more than 70% cell death. In this study we determined the percentages of TM that took up SPION, BrdU or GFP from labeled bone marrow stromal cells (BMSCs) that were placed into areas of angiogenesis and inflammation in a mouse model known as Matrigel plaque perfusion assay. Cells recovered from digested plaques at various time points were analyzed by fluorescence microscopy and flow cytometry. The analysis of harvested plaques revealed 5% of BrdU(+), 5-10% of GFP(+) and 5-15% of dextran(+) macrophages. The transfer of the label was not dependent on cell dose or viability. Collectively, this study suggests that care should be taken to validate donor origin of cells using an independent marker by histology and to assess transplanted cells for TM markers prior to drawing conclusions about the in vivo behavior of transplanted cells.