Contribution of bone marrow hematopoietic stem cells to adult mouse inner ear: mesenchymal cells and fibrocytes.
Bone marrow (BM)-derived stem cells have shown plasticity with a capacity to differentiate into a variety of specialized cells. To test the hypothesis that some cells in the inner ear are derived from BM, we transplanted either isolated whole BM cells or clonally expanded hematopoietic stem cells (HSCs) prepared from transgenic mice expressing enhanced green fluorescent protein (EGFP) into irradiated adult mice. Isolated GFP(+) BM cells were also transplanted into conditioned newborn mice derived from pregnant mice injected with busulfan (which ablates HSCs in the newborns). Quantification of GFP(+) cells was performed 3-20 months after transplant. GFP(+) cells were found in the inner ear with all transplant conditions. They were most abundant within the spiral ligament but were also found in other locations normally occupied by fibrocytes and mesenchymal cells. No GFP(+) neurons or hair cells were observed in inner ears of transplanted mice. Dual immunofluorescence assays demonstrated that most of the GFP(+) cells were negative for CD45, a macrophage and hematopoietic cell marker. A portion of the GFP(+) cells in the spiral ligament expressed immunoreactive Na, K-ATPase, or the Na-K-Cl transporter (NKCC), proteins used as markers for specialized ion transport fibrocytes. Phenotypic studies indicated that the GFP(+) cells did not arise from fusion of donor cells with endogenous cells. This study provides the first evidence for the origin of inner ear cells from BM and more specifically from HSCs. The results suggest that mesenchymal cells, including fibrocytes in the adult inner ear, may be derived continuously from HSCs.
Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, South Carolina 29425, USA. langh@musc.edu
Hainan
H
Lang
Yasuhiro
Y
Ebihara
Richard A
RA
Schmiedt
Hitoshi
H
Minamiguchi
Daohong
D
Zhou
Nancy
N
Smythe
Liya
L
Liu
Makio
M
Ogawa
Bradley A
BA
Schulte
D000818:Animals; D000831:Animals, Newborn; D002452:Cell Count / Q000379:methods; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D007758:Ear, Inner / Q000166:cytology* / Q000528:radiation effects / Q000637:transplantation*; D005347:Fibroblasts / Q000502:physiology; D005434:Flow Cytometry / Q000379:methods; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D007150:Immunohistochemistry / Q000379:methods; D017493:Leukocyte Common Antigens / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009474:Neurons / Q000378:metabolism*; D011419:Propidium; D011828:Radiation Chimera; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014916:Whole-Body Irradiation / Q000009:adverse effects
D028021:Sodium-Potassium-Chloride Symporters; D049452:Green Fluorescent Proteins; D011419:Propidium; D017493:Leukocyte Common Antigens; D000254:Sodium-Potassium-Exchanging ATPase