The Basic Research On The Biological Effects Of Bone Marrow Stem Cell Transplantation On Acute Lung Injuries

Objectives: To determine the role of stem cell transplantation in the repair of acute lung tissue injury and the possible mechanisms, and discuss the potentiality of cellular therapy for acute lung injury.Methods: Firstly, MSCs were isolated from adult rat bone marrow and cultured in vitro. Phenotypes of MSCs were examined by immunocytochemistry and flow cytometry. The plasticity of MSCs was evaluated by in vitro induction and MSCs were labelled by BrdU or DAPI. Secondly, rat acute lung injury model was established by LPS injection intravenously (5mg/kg). Briefly, 72 male Wistar rats were randomized into three groups: l)acute lung injury plus MSCs administration (L+M, n=24);2)acute lung injury plus normal saline (L, n=24);3) normal control (C, n=24). Animals were killed at 2h, 4h, 6h after LPS exposure respectively. Blood samples were collected to detect plasma TNF-a and IL-6 expression using ELISA. Lungs were removed and used for evaluation of wet/dry ratio and MPO activity. Part of the lung tissues were paraffin-embedded for immunohistochemistry to assess lung tissue damage quantitatively and to identify the phenotype of engrafted MSCs.Results: (1) The phenotype and the multi-diferentiation of MSCs: rat MSCs were positive for CD29 and CD44, while negative for CD34, a marker of hemapoietic stem cells. The reproductive activity of MSCs was attenuated after passages. The label rate of BrdU was about 74% and DAPI was above 90%. Cell cycle has no obvious difference between MSCs labeled with BrdU and MSCs not labeled. The in vitro inductive culture demonstrates adipocyte and osteoblast differentiations, showing a multipotent plasticity.(2) Role of MSCs transplantation in acute lung injury: MSCs homing was confirmed by immunohistochemistry. No detectablecell phenotype convertion was found except some morphological changes. TheL+M group showed a obvious amelioration in tissue injury when compared withgroup L. Compared with the normal saline group, the W/D , MPO and plasmaTNF-a/IL-6 level were significantly increased (PO.01). But in MSCs treatmentgroup these indexes were significantly lower than those in the group of LPS (P<0.01).Conclusions: (1) The MSCs isolation and purification were successful by meansof density gradient centrifugation and the stem cells obtained were multipotency.(2) MSCs transplantation in early phsae of ALI revealed lung homing and cellmorphological changes, and the W/D value, lung MPO activity and plasmaTNF-a/IL-6 level were degraded, suggesting benefits to tissue repair and inflammationresolution.