Abstract
BackgroundAcute respiratory distress syndrome (ARDS) is a life-threatening condition in critically ill patients. Recently, we have found that mesenchymal stem cells (MSC) improved the permeability of human lung microvascular endothelial cells by secreting hepatocyte growth factor (HGF) in vitro. However, the properties and functions of MSC may change under complex circumstances in vivo. Here, we sought to determine the role of the HGF-expressing character of MSC in the therapeutic effects of MSC on ARDS in vivo.MethodsMSC with HGF gene knockdown (MSC-ShHGF) were constructed using lentiviral transduction. The HGF mRNA and protein levels in MSC-ShHGF were detected using quantitative real-time polymerase chain reaction and Western blotting analysis, respectively. HGF levels in the MSC culture medium were measured by enzyme-linked immunosorbent assay (ELISA). Rats with ARDS induced by lipopolysaccharide received MSC infusion via the tail vein. After 1, 6, and 24 h, rats were sacrificed. MSC retention in the lung was assessed by immunohistochemical assay. The lung wet weight to body weight ratio (LWW/BW) and Evans blue dye extravasation were obtained to reflect lung permeability. The VE-cadherin was detected with inmmunofluorescence, and the lung endothelial cell apoptosis was assessed by TUNEL assay. The severity of lung injury was evaluated using histopathology. The cytokines and HGF levels in the lung were measured by ELISA.ResultsMSC-ShHGF with markedly lower HGF expression were successfully constructed. Treatment with MSC or MSC carrying green fluorescent protein (MSC-GFP) maintained HGF expression at relatively high levels in the lung at 24 h. MSC or MSC-GFP decreased the LWW/BW and the Evans Blue Dye extravasation, protected adherens junction VE-cadherin, and reduced the lung endothelial cell apoptosis. Furthermore, MSC or MSC-GFP reduced the inflammation and alleviated lung injury based on histopathology. However, HGF gene knockdown significantly decreased the HGF levels without any changes in the MSC retention in the lung, and diminished the protective effects of MSC on the injured lung, indicating the therapeutic effects of MSC on ARDS were partly associated with the HGF-expressing character of MSC.ConclusionsMSC restores lung permeability and lung injury in part by maintaining HGF levels in the lung and the HGF-expressing character is required for MSC to protect the injured lung.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-016-0320-5) contains supplementary material, which is available to authorized users.
Highlights
Acute respiratory distress syndrome (ARDS) is a life-threatening condition in critically ill patients
The result showed that hepatocyte growth factor (HGF) mRNA expression was significantly lower in the mesenchymal stem cells (MSC)-ShHGF group than in the MSC (p < 0.05) and MSC-green fluorescent protein (GFP) group (p < 0.05)
There was no significant difference between the MSC and MSC carrying green fluorescent protein (MSC-GFP) group (p > 0.05) (Fig. 1a) in the HGF mRNA expression
Summary
Ethics statement Male wild-type Sprague-Dawley (SD) rats (Laboratory Animal Center, Shanghai, China) were maintained under specific pathogen-free conditions. The culture medium was collected and HGF protein levels in the culture medium were quantified using an enzyme-linked immunosorbent assay (ELISA) kit (ExCellBio, Shanghai, China) according to the manufacturer’s instructions. The sections were blocked in 1 % bovine serum albumin (BSA) for 1 h at 37 °C and incubated with anti-GFP primary antibody (Abcam Ltd., Cambridge, UK) overnight at 4 °C, followed by HRP conjugated goat anti-rabbit IgG (Santa Cruz Biotechnology, Inc., Santa Cruz, CA, USA). TUNEL assay To assess the apoptosis of endothelial cells in the lung, the right lobe was collected and fixed in 4 % paraformaldehyde at 4 °C for 24 hours, and the lung sections were stained with a TUNEL Apoptosis Assay kit For comparisons between multiple groups, one-way analysis of variance (ANOVA) followed by Bonferroni’s post-hoc test was used. p values
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