The Effects And Related Mechanism Of IGF-1-treated Mesench-ymal Stem Cells In Pulmonary Fibrosis In Rats

Objective To research the new therapy of pulmonary fibrosis by observing the effects of IGF-1 treated mesenchymal stem cells in the rats with bleomycin-induced pulmonary fibrosis.Methods Bone marrow mesenchymal stem cells(BMSCs) were harvested from 6-week old male SD rats in vitro and spread for the experiment.48 SD rats(weight from 200-240g) were randomly divided into 4 groups:negative control group(N),positive control group/bleomycin group(B),mesenchymal stem cells grafting group(M) and IGF-1 treated mesenchymal stem cells grafting group(Ⅰ).Group B,GroupM and GroupⅠwere made as pulmonary fibrosis models by intratracheal injected with bleomycin (1 ml,5mg/kg).Group N were given saline by the same way.Group M/I were injected the suspension of the CM-Dil labled-mesenchymal stem cells(with no treatment/pre-incubated with IGF-1 for 48 hours)(0.5ml,2×106) via the tail vein 2 days after injected bleomycin and Group B were injected the saline(0.5ml) the same day by the same way.The rats were sacrificed at days 7,14,28 after modeling.The histological changes of lung tissue were studied by HE and Masson's trichrome staining.Hydroxyproline level in lung tissue was measured by digestion method.Frozen sections were made to observe the distribution of BMSCs in lung tissue and the mRNA expression of hepatpocyte growth factor(HGF) was assayed by RT-PCR.Results It was found that the red fluorescence of BMSCs existed in Group M and I under the microscope and the IOD of GroupⅠwas higher than Group M at any time point.But the fluorescence was attenuated both in Group M and Group I until day 28.In the earlier period,the alveolitis in Group B was more severe than the two cells-grafting groups in which Group I was more abviously milder.But there was on significant difference among Group I,M and Group N when it was day 28. Pulmonary fibrosis in Group B,M and I were significantly more severe than that in Group N on day 14,but it was milder in Group M and GroupⅠthan Group B on day 28.Otherwise, no difference existed between the two cells-grafting groups for all the time. The content of hydroxyproline in Group B was significantly higher than the other three groups all through the experiment while there was on significant difference between GroupⅠand Group N from the beginning to the end.The value of Group M was higer than GroupⅠand Group N in the earlier period but down to the level of negative control group on day 28. Content of HGF mRNA in Group N and GroupⅠwas maintained at a low level during the whole testing process. The expression of HGF in GroupⅠwas comparable to Group M on day 7 and exceeded on day 14,the difference of which was more conspicuous when it was day 28.Conclusion IGF-1 can enhance the migratory capacity of mesenchymal stem cells and contribute a more effective treatment of lung disease. The mechanism might be related to the increasing expression of HGF in MSC.