Korean Circ J.  2018 Sep;48(9):839-853. 10.4070/kcj.2017.0394.

Hemodynamic and Histopathologic Benefits of Early Treatment with Macitentan in a Rat Model of Pulmonary Arterial Hypertension

• Kim KH
• Kim HK
• Chan SY
• Kim YJ
• Sohn DW

• KMID: 2418810
• DOI: http://doi.org/10.4070/kcj.2017.0394

Abstract

BACKGROUND AND OBJECTIVES
Macitentan (MAC) reduces morbidity and mortality among advanced-stage pulmonary arterial hypertension (PAH) patients. However, data regarding the histopathologic and hemodynamic benefits of MAC treatment at an early stage of PAH is lacking.
METHODS
One week after monocrotaline (MCT) injection, rats were randomly assigned to MAC (n=16), MAC combined with sildenafil (SIL) (MAC+SIL, n=16), or normal saline (MCT, n=16). Twelve sham rats (Sham) were included for comparison. Right ventricular (RV) systolic function was assessed via echocardiography as the RV fractional area change (RV-FAC). An invasive pressure-volume analysis using a Millar conductance catheter was performed 7 weeks after MCT injection. Rats were subsequently euthanized for histopathologic analysis.
RESULTS
RV-right atrial pressure gradient on echocardiography was significantly increased 3 weeks after MCT injection, but was maintained in the Sham. RV-FAC was less deteriorated in the MAC, compared to that in the MCT (44±3% vs. 25±7%, p < 0.05), and the co-administration of SIL showed no additional benefit (45±8%, p > 0.05 vs. the MAC). On invasive hemodynamic analyses, RV end-systolic (196±78 µL) and end-diastolic volumes (310±86 µL), pulmonary artery systolic pressure (89±7.2 mmHg), and end-systolic pressure-volume relationship (−254±25.1) were significantly worse in the MCT vs. in the MAC (101±45 µL, 235±55 µL, 40±10.5 mmHg, and −145±42.1, respectively) and MAC+SIL (109±47 µL, 242±46 µL, 38±9.2 mmHg, and −151±39.2, respectively) (all p < 0.05). However, the MAC and MAC+SIL did not differ (all p > 0.05). On histopathology, both RV and lung fibrosis were significantly reduced in the MAC and MAC+SIL vs. in the MCT (all p < 0.05); the 2 treatment groups did not differ.
CONCLUSIONS
MAC treatment at an earlier stage significantly attenuated experimental PAH progression hemodynamically and histopathologically.

Keyword

Macitentan; Pulmonary hypertension; Hemodynamics; Pathology

MeSH Terms

Animals
Atrial Pressure
Blood Pressure
Catheters
Echocardiography
Fibrosis
Hemodynamics*
Humans
Hypertension*
Hypertension, Pulmonary
Lung
Models, Animal*
Monocrotaline
Mortality
Pathology
Pulmonary Artery
Rats*
Sildenafil Citrate
Monocrotaline
Sildenafil Citrate

Figure

• 

  Figure 1 A schematic illustration of the preliminary experimental protocol is shown. Blue arrows indicate the time points at which body weight, echocardiography, and exercise capacity were assessed. The asterisk indicates the time point of the invasive pressure-volume hemodynamics assessment. MCT = monocrotaline; MAC = macitentan; N/S = normal saline; PAH = pulmonary arterial hypertension; SIL = sildenafil.

• 

  Figure 2 (A) Kaplan-Meier survival curves show a clear difference in survival between the MCT group and the MAC-based treatment groups (MAC and MAC+SIL groups) (p=0.04). (B) Serial changes in body weight over 7 weeks of MCT injection are shown. (C) Changes in systolic and diastolic blood pressure are compared among groups. MAC = macitentan; MCT = monocrotaline; SIL = sildenafil. *p<0.05 vs. the sham group; †p<0.05 vs. the MCT group; ‡p=0.07 vs. the sham group.

• 

  Figure 3 (A) Comparisons in exercise capacity. Exercise capacity began to deteriorate one week after MCT injection in the MCT group, but not in the sham group. In contrast, exercise duration was relatively preserved in the MAC group (p<0.05). Exercise capacity in the MAC+SIL group was comparable to that in the MAC group (p>0.05). (B) Serial assessments of RV-FAC. Serial echocardiography showed that rats with MCT-induced PAH rats had reduced RV-FAC beginning at 5 weeks. Treatment with MAC alone or combination with MAC and SIL attenuated the progression of RV systolic dysfunction. (C) Serial assessments of the RV-EDD on echocardiography. (D) Serial assessments of the RV wall thickness. (E) PAAT was measured from the time of the onset of systolic flow to the time of the peak pulmonary outflow velocity. Note the significant differences in the PAAT among the 4 groups beginning at 3rd weeks. (F) Serial assessments of the TAPSE. (G) Serial assessment of RV-RA PG. TR jet could be reliably quantified via continuous-wave Doppler around 3 weeks after MCT injection in the MAC and MAC+SIL groups. TR tracing was difficult to follow in the sham group, and thus, the RV-RA PG could not be reliably obtained in the sham group. (H) Serial assessment of LV-EDD. LV-EDD was smaller in the MCT group, where D-shaped LV at the parasternal short axis image was clearly visualized, indicating development of severe pulmonary hypertension. In contrast, both the MAC and the MAC+SIL groups showed no significant decrement in LV dimension with preservation of the LV geometry. LV = left ventricular; LV-EDD = left ventricular end-diastolic dimensions; MCT = monocrotaline; MAC = macitentan; PAH = pulmonary arterial hypertension; PAAT = pulmonary artery acceleration time; RA = right atrial; RV-FAC = right ventricular fractional area change; RV = right ventricular; RV-EDD = right ventricular end-diastolic dimension; RV-RA PG = right ventricular-right atrial pressure gradient; SIL = sildenafil; TAPSE = tricuspid annular plane systolic excursion; TR = tricuspid regurgitation. *p<0.05 vs. the sham group; †p<0.05 vs. the MCT group.

• 

  Figure 4 Representative echocardiographic images are shown for each group. LV = left ventricular; MCT = monocrotaline; MAC = macitentan; PAAT = pulmonary artery acceleration time; RV-RA PG = right ventricular-right atrial pressure gradient; SIL = sildenafil; TAPSE = tricuspid annular plane systolic excursion.

• 

  Figure 5 Representative pressure-volume images obtained via an invasive Millar conductance catheter system are shown for each group.

• 

  Figure 6 Histopathologic comparisons. The extent of perivascular and interstitial fibrosis is significantly greater in the MCT group compared to that in the MAC or the MAC+SIL groups (p<0.05). MAC = macitentan; MCT = monocrotaline; SIL = sildenafil.

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