Experimental study
Other graft
Therapeutic Effects of Bone Marrow-Derived Mesenchymal Stem Cells Engraftment on Bleomycin-Induced Lung Injury in Rats

https://doi.org/10.1016/j.transproceed.2008.01.080Get rights and content

Abstract

Previous studies have demonstrated that bone marrow-derived mesenchymal stem cell (MSC) engraftment attenuated lung injury in a model induced by bleomycin in mice. However, the mechanisms are not completely understood. The primary objective of the present study was to determine whether MSC engraftment can also protect lungs against bleomycin-induced injury in rats and to observe any beneficial effects of cytokines. Twelve hours after bleomycin (5 mg/kg) or phosphate-buffered saline was perfused into the trachea, 5×106 DAPI-labeled MSCs or DMEM-F12 were injected into the tail vein of rats. Two weeks later, MSCs labeled with DAPI were detected by pan-cytokeratin staining. The level of laminin and hyaluronan in bronchoalveolar lavage fluid was measured by radioimmunoassay. Collagen content in lung tissue was calculated by the hydroxyproline assay. TGF-β1, PDGF-A, B, and IGF-I were measured by real-time PCR. It was observed that some MSCs positive for pan-cytokeratin staining, an indicator of alveolar epithelial cells, were present in injured lung tissue. Bleomycin injection increased the content of hydroxyproline in lung tissue, as well as laminin and hyaluronan in bronchoalveolar lavage fluid, markers for lung injury and fibrosis. However, these effects were attenuated by MSC treatment. Furthermore, the increased mRNA levels of TGF-β1, PDGF-A, PDGF-B, and IGF-I following bleomycin injection were also significantly decreased by MSC treatment. These observations provided evidence that MSCs are still present in the lung 2 weeks after the initial MSC treatment in rats, as well as documented the beneficial effects of MSC engraftment against bleomycin-induced lung injury associated with changes in TGF-β1, PDGF-A, PDGF-B, and IGF-I. These results may provide an experimental base for clinical therapy of pulmonary fibrosis in the future.

Section snippets

Animals

Adult Sprague-Dawley rats (200–250 g body weight) were obtained from our laboratory animal center. Animals were kept in accordance with the National Institutes of Health Guidelines on the Use of Laboratory Animals. All animals used in this study were of the same genetic background. The experimental protocols were approved by the Fourth Military Medical University Committee on Animal Care.

Preparing for Bone Marrow-Derived MSCs

MSCs were isolated from rat bone marrow. In brief, whole marrow was flushed from the tibia and femur of

Histopathologic Analysis

Rat lung histologic sections from each experimental group are shown in Figs 1 A–H. There was no obvious lesion in the lung of normal control rats. In the lung injury group, HE staining showed the pulmonary alveolus cavity to obviously be decreased in size, the alveolar wall thickened, mesenchyme expanded with increased numbers of fibroblasts and macrophages. In Masson stains collagen, was increased in the lung interstitium as well as around blood vessels and bronchi when compared with normal

Discussion

Our studies showed that MSCs differentiated into alveolar epithelial cells in BLM-induced injury of rat lung. The decreased HYP, LN, and HA confirmed that MSC engraftment attenuated lung injury and fibrosis. We believe that the amelioration was associated with the decrease in TGF-β1, PDGF-A, PDGF-B, and IGF-I in injured rat lungs.

The technique of cell labeling in this study was important to identify differentiating cells derived from donor animals. The fluorescent dye DAPI selectively binds to

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