The effects of low-molecular-weight heparin on lung and pulmonary artery injuries in acute pulmonary embolism rat model via platelet-derived growth factor-β

Abstract

Objective: To evaluate the effects of anticoagulant agent (low-molecular-weight heparin, LMWH) on the pulmonary artery intima hyperplasia of rats with acute pulmonary embolism (APE) by assaying platelet-derived growth factor-β (PDGF-β).

Methods: A total of 90 Sprague-Dawley rats were randomly assigned into the sham, APE, and LMWH groups with 30 rats in each group. The APE rat models were established by injecting autologous blood clots via external jugular veins. In each group, six mice were sacrificed at the 1st day (D1), 4th day (D4), 7th day (D7), 14th day (D14), and 28th (D28) subsequent to the induction of APE to collect the lungs. Right ventricle pressure (RVP) and mean pulmonary arterial pressure (mPAP) were measured. Western blot and RT-PCR analyses were used to assess PDGF-β expression at various time points. In addition, changes in lung pathology were evaluated using hematoxylin and eosin (H&E) staining and electron microscope.

Results: The overall success rate of establishing APE rat models was 85.7% (60/70). There was no difference in mPAP between the sham group and the APE group at the D1, D4, D7, and D14. However, at the D28, mPAP in the APE group was significantly higher than that in the sham group. There was no difference among the three groups regarding RVP. PDGF-β expression were decreased in the LMWH group at all time points compared with the sham and APE groups (P < 0.01). Furthermore, pulmonary embolism, alveolar wall necrosis and hemorrhage, and inflammation were significantly attenuated in the LMWH group compared with the sham and APE groups subsequent to the induction of APE.

Conclusion: LMWH attenuates lung and pulmonary artery injuries and improves prognosis. Decreased PDGF-β in the lungs may be the important factor in the effects observed.

Keywords: Acute pulmonary embolism (APE); Low Molecular Weight Heparin (LMWH); Platelet-derived growth factor-β (PDGF-β).

Fig. 1

The changes of mPAP and RVP after pulmonary embolism operation. There was no difference among three groups at the all time points.

Fig. 2

The cross sections of lungs (HE × 100). (A) Four days after APE, thrombi was partially dissolved. There were a lot of white blood cells infiltration. (B) 14 days after APE, there were pulmonary artery intima hyperplasia and vascular stenosis.

Fig. 3

The changes of wall area/tube area ratios and wall thickness/tube diameter ratios after pulmonary embolism operation. (A) The changes of wall area/tube area ratios. ^* compared with the sham and LMWH groups, the PTE group was significant higher, P < 0.05; (B) the changes of wall thickness/tube diameter ratios. ^* compared with the sham and LMWH groups, the PTE group was significant higher, P < 0.05.

Fig. 4

The images from electron microscope. (A) 14 days after APE, the nucleoli of pulmonary artery smooth muscle cells enlarged, cytoplasm was abundant. Rough endoplasmic reticulum and mitochondria increased. Part of the vacuolar degenerated. ×6000; (B) 14 days after APE, pulmonary artery SMCs morphology was normal in the LMWH group ×5000.

Fig. 5

Expression of PDGF-B. (A) 4 days after APE, there were a lot of PDGF-B expression in pulmonary artery wall. ×400; (B) expression in the sham and APE groups at the different time points. Expression in the LMWH and PTE groups at the different time points. M, S, P, L represent DNA marker, Sham, APE, and LMWH respectively 1, 4, 7, 14, 28 represent the days post pulmonary embolism ^*p < 0.05 PTE vs sham; ^#p < 0.05 LMWH vs PTE; Δp < 0.05 LMWH vs sham; (C) expression of PDGF-B protein in the LMWH and PTE groups, ^*p < 0.05 PTE vs sham; ^#p < 0.05 LMWH vs PTE; Δp < 0.05 LMWH vs sham; (D) expression of PDGF-B mRNA among the three groups, ^*p < 0.05 PTE vs sham, ^**p < 0.01 PTE vs sham; ^#p < 0.05 LMWH vs PTE; Δp < 0.05 LMWH vs sham.