Restoration of tubular epithelial cells during repair of the postischemic kidney occurs independently of bone marrow-derived stem cells
Jeremy S. Duffield, … , Takaharu Ichimura, Joseph V. Bonventre
Jeremy S. Duffield, … , Takaharu Ichimura, Joseph V. Bonventre
Published July 1, 2005
Citation Information: J Clin Invest. 2005;115(7):1743-1755. https://doi.org/10.1172/JCI22593.
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Research Article

Restoration of tubular epithelial cells during repair of the postischemic kidney occurs independently of bone marrow-derived stem cells

Abstract

Ischemia causes kidney tubular cell damage and abnormal renal function. The kidney is capable of morphological restoration of tubules and recovery of function. Recently, it has been suggested that cells repopulating the ischemically injured tubule derive from bone marrow stem cells. We studied kidney repair in chimeric mice expressing GFP or bacterial β-gal or harboring the male Y chromosome exclusively in bone marrow-derived cells. In GFP chimeras, some interstitial cells but not tubular cells expressed GFP after ischemic injury. More than 99% of those GFP interstitial cells were leukocytes. In female mice with male bone marrow, occasional tubular cells (0.06%) appeared to be positive for the Y chromosome, but deconvolution microscopy revealed these to be artifactual. In β-gal chimeras, some tubular cells also appeared to express β-gal as assessed by X-gal staining, but following suppression of endogenous (mammalian) β-gal, no tubular cells could be found that stained with X-gal after ischemic injury. Whereas there was an absence of bone marrow–derived tubular cells, many tubular cells expressed proliferating cell nuclear antigen, which is reflective of a high proliferative rate of endogenous surviving tubular cells. Upon i.v. injection of bone marrow mesenchymal stromal cells, postischemic functional renal impairment was reduced, but there was no evidence of differentiation of these cells into tubular cells of the kidney. Thus, our data indicate that bone marrow–derived cells do not make a significant contribution to the restoration of epithelial integrity after an ischemic insult. It is likely that intrinsic tubular cell proliferation accounts for functionally significant replenishment of the tubular epithelium after ischemia.

Authors

Jeremy S. Duffield, Kwon Moo Park, Li-Li Hsiao, Vicki R. Kelley, David T. Scadden, Takaharu Ichimura, Joseph V. Bonventre

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Figure 7

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X-gal stains tubular cells in the kidney of wild-type mice, reflecting e...
X-gal stains tubular cells in the kidney of wild-type mice, reflecting endogenous β-gal activity, but can be distinguished from bacterial β-gal when high-pH X-gal staining or anti–β-gal antibodies are used. (A) Occasional tubular cells stained blue, indicating β-gal, 7 days following I/R injury in chimeric mice (arrowheads). X-gal–stained cells colabeled with the proximal tubular cell marker gp330, seen as green fluorescence (inset). (B) The number of X-gal–positive cortical and outer medullary tubular cells per 40 HPF in contralateral kidneys (0 days) and in kidneys of both chimeric and wild-type C57BL/6J mice following I/R injury. Note that I/R resulted in an increase in the number of β-gal–stained cells in both nonchimeric and chimeric mice. (C) Sections at day 7 after I/R labeled with anti–β-gal antibodies. Note the bright staining in spleen cells (left) but no staining in regenerated tubules (right) (D) Sections (magnification, ×100) of I/R kidneys and spleen from wild-type (n = 3 per time point) and chimeric mice (n = 5 per time point) stained with X-gal solution at pH 6.5 or 7.5. Note faint blue tubules in kidneys of wild-type and chimeric animals (compare top and middle panels). Blue staining in kidney tubules but not spleen is suppressed using X-gal in solution at pH 7.5 in chimeric mice (compare bottom and middle panels). (E) Sagittal sections (0.2 mm) of normal C57BL/6J kidney stained with X-gal solution at pH 6.5 (left) and pH 7.5 (right). Note widespread cortical and outer medullary staining at low pH and milder restricted staining in the outer medulla at higher pH. (F) Kidney section (magnification, ×400) from LacZ donor mouse stained with X-gal, pH 7.5. Note intense blue staining of tubules indicative of bacterial β-gal. Scale bars: 50 μm.