Repairing of acute lung injury by transvenous injection of bone marrow-derived stem cells

Introduction

Bone marrow stromal cells (BMSC) are progenitors for bone, cartilage, hematopoietic stroma, adipocyte, brain and neural cells. Recently some reports suggested that BMSC had a potency of differentiating lung epithelial cells. In this study, we tried to implant BMSC transvenously to a bleomycin-induced lung injury model, and evaluate the differentiation of BMSC.

Materials and methods

The study was approved by the Institutional Review Boad. We used green fluorescent protein transgenic rats (green rat, TgN [act-EGFP] OsbCZ-004; Japan SLC Co.) as the BMSC donors, and SD rats as the bleomycin-induced lung injury model for BMSC recipients (Japan SLC Co.). Two days before BMSC implantation, bleomycin was injected transtracheally by transient tracheostomy in recipient SD rats. 5-FU (fluorouracil, antineoplastic agent) had been injected intra-peritoneally into the green rats to increase the yield of BMSC. On the experiment day, the green rats were anesthetized, and then femurs were removed immediately, and a part of the bone cut to obtain BMSC. At the same time, the surgery of recipient SD rats was performed to identify and obtain the femoral veins, which were cannulated and filled with heparinized saline. The collected BMSC in a syringe were injected to recipient SD rats via the cannulated femoral vein for implantation. For the control sham operation, saline was injected instead of BMSC. Ten days, and 4 weeks after implantation, recipient rats were sacrificed and the lungs were fixed and examined.

Results

We obtained well-proliferated BMSC. Then SMSC also had microspheres with good proliferation. We showed the presence of BMSC alive in the implanted lung tissue, and these BMSC spread widely. In a short survival, we did not find the alveolar cells expressing both SP-A and green fluorescent. In a long survival after implantation, we found that some small population of implanted BMSC expressed SP-A. The BMSC with histological SP-A-positive were present out of the vessels.

Discussion

We showed excellent viability of BMSC and presence alive after transvenous implantation. We thought that the implanted BMSC remain in the vessel or migrate to the alveolus, and then some BMSC remaining in the vessel will migrate later and differentiate to the alveolar cells, which will contribute to constructing the injured lungs. Further studies are in progress to clarify differentiation of BMSC to alveolar cells.