Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2018 Dec 4;9(1):335.
doi: 10.1186/s13287-018-1083-y.

Targeted migration of bone marrow mesenchymal stem cells inhibits silica-induced pulmonary fibrosis in rats

Xiaoli Li  1   2 , Guoliang An  2 , Yan Wang  2 , Di Liang  2 , Zhonghui Zhu  2 , Lin Tian  3
Affiliations

Targeted migration of bone marrow mesenchymal stem cells inhibits silica-induced pulmonary fibrosis in rats

Xiaoli Li et al. Stem Cell Res Ther. .

Abstract

Background: Silicosis is a common occupational disease, characterized by silicotic nodules and diffuse pulmonary fibrosis. We demonstrated an anti-fibrotic effect of bone marrow mesenchymal stem cells (BMSCs) in silica-induced lung fibrosis. In the present study, we sought to clarify the homing ability of BMSCs and the specific mechanisms for their effects.

Methods and results: The biodistribution of BMSCs was identified by near-infrared fluorescence (NIRF) imaging in vivo and in vitro. The results showed that BMSCs labeled with NIR-DiR dyes targeted silica-injured lung tissue, wherein they reached a peak at 6 h post-injection and declined dramatically by day 3. Based on these findings, a second injection of BMSCs was administered 3 days after the first injection. The injected BMSCs migrated to the injured lungs, but did not undergo transformation into specific lung cell types. Interestingly, the injection of BMSC-conditioned medium (BMSCs-CM) significantly attenuated silica-induced pulmonary fibrosis. The collagen deposition and number of nodules were decreased in lung tissues of BMSCs-CM-treated rats. In parallel with these findings, the mRNA levels of collagen I, collagen III, and fibronectin, and the content of transforming growth factor (TGF)-β1 and hydroxyproline were decreased in the BMSCs-CM-treated group compared with the silica group. In addition, alveolar epithelial markers were upregulated by BMSCs-CM treatment.

Conclusions: BMSCs migrated to injured areas of the lung after silica instillation and attenuated pulmonary fibrosis. The anti-fibrotic effects of BMSCs were mainly exerted in paracrine manner, rather than through their ability to undergo differentiation.

Keywords: Bone marrow mesenchymal stem cells; Migration; Pulmonary fibrosis; Silicosis.

PubMed Disclaimer

Conflict of interest statement

Ethics approval and consent to participate

All procedures performed in the study involving animals were obeyed by the ethical standards of the institution detailed in “Materials and methods”.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Homing of BMSCs to the silica-injured lung. a A diagram of experimental protocol. Rats were monitored using an in vivo imaging system at 1 h, 6 h, 24 h, 3 days, 15 days, and 30 days after transplantation of DiR-BMSCs. b Cytotoxicity of DiR in vitro. Relative cell viabilities of BMSCs were measured after being incubated with various doses DiR for 24 h, 48 h, and 72 h. Up to 5 μg/ml, DiR did not change cell viability. **p < 0.01 compared with 0 μg/ml group. c Whole-body imaging was monitored with the in vivo imaging system. DiR fluorescence intensity reached a peak at 6 h, declined dramatically by day 3, reduced over a long period (at least 15 days), and disappeared by day 30. BMSCs were predominantly distributed to the liver region in the DiR-BMSCs + control group, while many cells were accumulated in the thoracic (lung) region in the DiR-BMSCs + silica group. Scale bar = 5 cm. d, e Quantification of the fluorescence intensity in the whole body and in the lung. Much more cells were accumulated in the thoracic (lung) region in the DiR-BMSCs + silica group compared with the DiR-BMSCs + control group. The data were presented as the means ± SD. **p < 0.01 versus the DiR-BMSCs + control group
Fig. 2
Fig. 2
Ex vivo NIRF imaging of BMSCs in the lung. a A diagram of experimental protocol. The serial fluorescence images were also obtained in ex vivo organs (lung, live, kidney, spleen, heart) at designated time points. b DiR-BMSCs were predominantly distributed to the lung region, declined dramatically by days 3. Scale bar = 2 cm. c Quantification of the fluorescence intensity in the lung at 1 h, 6 h, 24 h, 3 days, 15 days, and 30 days. Compared with the DiR-BMSCs + control group, the fluorescence intensity in the lung was apparently increased in the DiR-BMSCs + silica group. The data were presented as the means ± SD. **p < 0.01 versus the DiR-BMSCs + control group
Fig. 3
Fig. 3
Optimal dose and timing of BMSCs administration to attenuate silica-induced pulmonary fibrosis. H&E staining (a) and Masson’s trichrome staining (b) in the rat lungs at 15 days after silica instillation. Light micrograph magnification × 100 and × 200. Scale bar, 100 μm and 50 μm. Quantitatively analyzed image stained in H&E (c) or Masson’s trichrome (d). The pathology index of lung tissue and the fibrotic areas were significantly increased in the silica group compared with the control group, but decreased in the BMSCs-4 group. The ratio of lung/body weight (e), level of TGF-β1 (f), content of HYP (g), expression of collagen I (h), collagen III (i), and FN (j) were significantly increased in the silica group in comparison with the control group, but were decreased in the BMSCs-4 group. BMSCs (2 × 106 cells, days 1 and 4) attenuated silica-induced pulmonary fibrosis. Values are expressed as mean ± SD, n = 8. **p < 0.01 compared with the control group; #p < 0.05, ##p < 0.01 compared with the silica group
Fig. 4
Fig. 4
BMSCs barely adopt alveolar cell phenotypes. a, b Quantified engraftment levels of BMSCs in the lungs by real-time PCR analysis. Sry, representing male BMSCs DNA, was only shown up in the silica + BMSCs group on day 15 (a), but did not show up on day 30 (b). The male rat lung served as the positive control. The data were presented as the means ± SD. **p < 0.01 versus the control group. c, d Immunofluorescence (IF) of the lung sections was tested on day 15 (c) and on day 30 (d) by using a confocal microscopy. Nuclear staining (DAPI, blue), BMSCs (RBMY, green), and the ATI cells (AQP-5, red). The level of AQP-5 (red) protein expression was reduced in the silica group, but increased after treatment with BMSCs. Little RBMY protein (green) was detected in the lung tissue from the silica + BMSCs group on day15, but not on day 30. Colocalization, indicated by a yellow color, was not observed in the merged panel in the silica + BMSCs group. Male rat lung served as the positive control. Scale bar = 250 μm. e, f Quantification of fluorescence intensity was analyzed in each group on days 15 (e) and 30 (f). Values are expressed as mean ± SD, n = 8. **p < 0.01 compared with the control group; ##p < 0.01 compared with the silica group; &&p < 0.01 compared with the silica + BMSCs group
Fig. 5
Fig. 5
BMSCs-CM inhibited silica-induced pulmonary fibrosis in rats. a, c H&E staining, (a) 15 days after instillation; (c) 30 days after instillation. b, d Masson’s trichrome staining. The result revealed that the collagen deposition (blue areas) was significantly increased in the silica group but decrease in the silica + BMSCs-CM group on 15 (b) and 30 days (d). Light micrograph magnification × 100 and × 200. Scale bar, 100 μm and 50 μm. e, f The levels of TGF-β1(e) and content of HYP (f) were increased in the silica group compared with those in the control group, but they were decreased after the addition of BMSCs-CM (p < 0.01). The data were presented as the means ± SD. **p < 0.01 versus the control group; ##p < 0.01 versus the silica group; &p < 0.05 versus the silica + BMSCs group
Fig. 6
Fig. 6
BMSCs-CM decreased the levels of genes for fibrosis and attenuated the injured alveolar epithelial cells. BMSCs-CM attenuate silica-induced pulmonary fibrosis and increase the expression of alveolar epithelial. The fibrosis marker expression of collagen I (a, b), collagen III (c, d), and FN (e, f) in the silica group was significantly increased compared with that in the control group, but was decreased after addition of BMSCs-CM. For the alveolar epithelial markers, either the level of AQP-5 (g, h) or SP-C (i, j) was decreased in the silica group compared with that in the control group. But the expression was increased by BMSCs-CM for day 15 (a, c, e, g, i) and for day 30 (b, d, f, h, j). The data were presented as the means ± SD. **p < 0.01 versus the control group; ##p < 0.01 versus the silica group; &p < 0.05, &&p < 0.01 versus the silica + BMSCs group
Fig. 7
Fig. 7
Graphical abstract of our research. BMSCs could migrate to the injured lungs and inhibit silica-induced pulmonary fibrosis. The mechanism may be due to paracrine action rather than the potential of BMSCs to differentiate into alveolar epithelial cells
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Leung CC, Yu ITS, Chen W. Silicosis. Lancet. 2012;379:2008–2018. doi: 10.1016/S0140-6736(12)60235-9. - DOI - PubMed
    1. Monsel A, Zhu YG, Gennai S, et al. Cell-based therapy for acute organ injury: preclinical evidence and ongoing clinical trials using mesenchymal stem cells. Anesthesiology. 2014;121:1099–1121. doi: 10.1097/ALN.0000000000000446. - DOI - PMC - PubMed
    1. Gao F, Chiu SM, Motan DA, et al. Mesenchymal stem cells and immunomodulation: current status and future prospects. Cell Death Dis. 2016;7:e2062. doi: 10.1038/cddis.2015.327. - DOI - PMC - PubMed
    1. Ansboro S, Roelofs AJ, De Bari C. Mesenchymal stem cells for the management of rheumatoid arthritis: immune modulation, repair or both? Curr Opin Rheumatol. 2017;29:201–207. doi: 10.1097/BOR.0000000000000370. - DOI - PubMed
    1. Kidder D. Mesenchymal stem cells attenuate ischemic acute kidney injury by inducing regulatory T cells through splenocyte interactions. Kidney Int. 2014;85:981–982. doi: 10.1038/ki.2013.562. - DOI - PubMed

Publication types

MeSH terms