Marrow cell infusion attenuates vascular remodeling in a murine model of monocrotaline-induced pulmonary hypertension

Abstract

There have been reports of marrow cells converting into pulmonary epithelial cells after marrow transplantation in irradiated mice. We evaluated the impact of whole bone marrow (WBM) infusion in mice, with or without total body irradiation (TBI), treated with saline or monocrotaline (MCT), which induces pulmonary hypertension (PH). C57BL/6 mice were injected with MCT or saline weekly for 4 weeks. Cohorts were then infused with saline vehicle (vehicle) or WBM from C57BL/-Tg(UBC-GFP)30Scha/J mice, with or without previous TBI (WBM or WBM/TBI). Four weeks later, right ventricular peak pressures (RVPP), right ventricular free wall-to-body weight ratios (RV/BW), and pulmonary vessel wall thickness-to-blood vessel diameter ratios (PVWT/D) were determined. WBM infusion and WBM following TBI induced increases in RVPP and RV/BW in saline-treated mice, while only TBI-exposed mice showed additional increases in PVWT/D. MCT increased RVPP, RV/BW, and PVWT/D in mice given vehicle or WBM alone, but not in mice given WBM/TBI. RVPP and RV/BW were not significantly lower in MCT mice given WBM/TBI than in MCT mice treated with vehicle, but MCT-treated mice given WBM or TBI/WBM had significantly lower PVWT/D compared to MCT-treated mice given saline vehicle. No donor WBM-derived pulmonary vascular cells were detected, suggesting that the observed effects of WBM infusion may be due to paracrine effects separate from cell conversions. The observation of PH after marrow infusion suggests an additional mechanism for lung toxicity seen in marrow transplantation. In conclusion, WBM alone appears to increase RVPP and RV/BW in normal mice but the combination of WBM and TBI attenuates MCT-induced PH.

FIG. 1.

Experimental design. Saline- and MCT-treated mice receiving either no further treatment (saline/vehicle, MCT/vehicle mice), marrow cell infusion (saline/WBM, MCT/WBM mice), or total body irradiation followed by marrow cell transplantation (saline/TBI/WBM, MCT/TBI/WBM mice).

FIG. 2.

Right ventricular peak pressure (RVPP) (A) and right ventricular free wall-to-body weight (RV/WB) ratios (B) of saline- and MCT-treated mice, with or without marrow cell infusion or total body irradiation.

FIG. 3.

Pulmonary vessel wall thickness-to-blood vessel diameter (PVWT/D) ratios and lung histology. PVWT/D ratios of saline- and MCT-treated mice, with or without marrow cell infusion or total body irradiation (A). Pulmonary blood vessel from saline/vehicle (B), saline/WBM (C), saline/TBI/WBM (D), MCT/vehicle (E), MCT/WBM (F), and MCT/TBI/WBM (G) groups. Red bar = 20 μm.

FIG. 4.

Marrow cell-derived vimentin+ cells. A pulmonary blood vessel from a MCT-injured mouse treated with marrow cell infusion and total body irradiation. Area (red box) and cells (red arrows) of interest (A) from an H&E stained lung section. Same area of interest (white box), fluorescent image (B and C, all filters), showing the same cells (white arrows), which are GFP+ (green), CD45+ (blue), and vimentin+ (red). Texas Red (D), FITC (E), and DAPI (F) filters. Red bar = 20 μm.

FIG. 5.

Marrow cell-derived lung cells are not pulmonary vascular endothelial cells. Pulmonary blood vessel from a MCT-injured mouse treated with marrow cell infusion and total body irradiation. Area (red box) and cells (red arrows) of interest (A) from an H&E stained lung section. Same area of interest (white box), fluorescent image (B and C, all filters), showing the same cells (white dashed arrows), which are GFP+ (green), CD45+ (blue), and von Willebrand factor− (red), representing donor marrow cell-derived hematopoietic cells. Texas Red (D), FITC (E), and DAPI (F) filters. The other cells (solid white arrows) are only GFP+, representing a marrow-derived nonhematopoietic cells. Red bar = 20 μm.