Characteristics of interstitial fibrosis and inflammatory cell infiltration in right ventricles of systemic sclerosis-associated pulmonary arterial hypertension

Abstract

Objective. Systemic sclerosis-associated pulmonary arterial hypertension (SScPAH) has a disturbed function of the right ventricle (RV) when compared to idiopathic PAH (IPAH). Systemic sclerosis may also affect the heart. We hypothesize that RV differences may occur at the level of interstitial inflammation and-fibrosis and compared inflammatory cell infiltrate and fibrosis between the RV of SScPAH, IPAH, and healthy controls. Methods. Paraffin-embedded tissue samples of RV and left ventricle (LV) from SScPAH (n = 5) and IPAH (n = 9) patients and controls (n = 4) were picrosirius red stained for detection of interstitial fibrosis, which was quantified semiautomatically. Neutrophilic granulocytes (MPO), macrophages (CD68), and lymphocytes (CD45) were immunohistochemically stained and only interstitial leukocytes were counted. Presence of epi- or endocardial inflammation, and of perivascular or intimal fibrosis of coronary arteries was assessed semiquantitatively (0-3: absent to extensive). Results. RV's of SScPAH showed significantly more inflammatory cells than of IPAH (cells/mm(2), mean ± sd MPO 11 ± 3 versus 6 ± 1; CD68 11 ± 3 versus 6 ± 1; CD45 11 ± 1 versus 5 ± 1 , P < .05) and than of controls. RV interstitial fibrosis was similar in SScPAH and IPAH (4 ± 1 versus 5 ± 1%, P = .9), and did not differ from controls (5 ± 1%, P = .8). In 4 SScPAH and 5 IPAH RV's foci of replacement fibrosis were found. No differences were found on epi- or endocardial inflammation or on perivascular or intimal fibrosis of coronary arteries. Conclusion. SScPAH RVs display denser inflammatory infiltrates than IPAH, while they do not differ with respect to interstitial fibrosis. Whether increased inflammatory status is a contributor to altered RV function in SScPAH warrants further research.

Figure 1

Sections of myocardial tissue stained with antibodies against (a) neutrophilic granulocytes (MPO positive), (b) macrophages (CD68 positive), or (c) lymphocytes (CD45 positive). Arrows indicate positive cells.

Figure 2

The number of (a) myeloperoxidase positive cells, (b) CD68 positive cells, and (c) CD45 positive cells was determined in the RV and the LV of systemic sclerosis-associated pulmonary arterial hypertension (SScPAH), idiopathic pulmonary arterial hypertension (IPAH) patients and in control subjects. Median and range are shown.

Figure 3

Representative samples of picrosirius red-stained myocardial sections of the RV of SScPAH and IPAH patients, used for quantification of interstitial fibrosis. Arrows indicate the red-coloured strains of fibrosis.

Figure 4

Quantification of picrosirius red staining in the RV of SScPAH, IPAH, and control subjects in (a) the RV and (b) the LV. Median and range are shown.

Figure 5

Representative samples of Elastica von Gieson stained myocardial sections of the RV of SScPAH patients, used for studying fibrosis in detail. (a) Some RV's of SScPAH patients revealed a pattern patchy replacement fibrosis, mostly localized subendocardially. This was also seen in some hearts of IPAH patients, but not observed in control. (b) In few cases, a pattern of strands of collagenous fibrous tissue surrounding microvasculature was observed, radiating from the epicardial coronary arteries to the subendocardial myocardium. (c) In some cases small infarcts in both SSc and IPAH hearts were observed. (d) An increase in perivascular fibrosis in some SScPAH hearts and in 1 IPAH heart was observed. All these observations were not made in control hearts.