Role of PDGFs/PDGFRs signaling pathway in myocardial fibrosis of DOCA/salt hypertensive rats

Abstract

This study aimed to investigate the role of PDGF/PDGFR signaling pathway in myocardial fibrosis of desoxycorticosterone (DOCA) induced salt-sensitive hypertensive rats and explore the influence of PDGF/PDGFR signaling pathway on fibroblasts and myofibroblasts in the heart. 60 male SD rats underwent right nephrectomy and bred with 1% sodium chloride and 0.1% potassium chloride for 4 weeks, and then randomly divided into 3 groups (CON group, DOCA group and DOCA+IMA group). Results showed that: 1) 14 and 28 days after intervention, the SBP in DOCA and DOCA+IMA group was significantly higher than that in CON group. At days 28, the severity of myocardial fibrosis and PVCA/VA ratio in DOCA group were significantly increased when compared with CON group. The severity of myocardial fibrosis and PVCA/VA ratio in DOCA+IMA group were markedly lower than those in DOCA group although they were higher than those in CON group. 2) At days 14, the mRNA expressions of PDGFRα and PDGFRβ in DOCA group were significantly higher than CON and DOCA+IMA group. At days 28, the mRNA expressions of PDGFRβ, FSP-1, α-SMA, procollagen I and procollagen III in DOCA group were significantly higher than those in CON group. In addition, in a specific group, the PDGFRβ mRNA expression was higher than the PDGFRα mRNA expression. In DOCA+IMA group, the mRNA expressions of PDGFRβ, FSP-1, α-SMA, procollagen I and procollagen III were markedly reduced when compared with DOCA group. 3) At 14 days, the protein expressions of PDGFRα and PDGFRβ in DOCA group were significantly higher than those in CON group. The PDGFRα protein expression in DOCA+IMA group was markedly lower than that in DOCA group. At days 28, the protein expressions of PDGFRα and PDGFRβ in DOCA group were significantly increased when compared with CON group. The protein expressions of PDGFRα and PDGFRβ in DOCA+IMA group were significantly lower than those in DOCA group. At day 28, the cardiac interstitium mainly contained vimentin positive fibroblasts, and α-SMA positive cells were less identified in CON group. In DOCA group, α-SMA positive fibroblasts (spindle-shaped) increased significantly, but the myofibroblasts reduced significantly in DOCA+IMA group when compared with DOCA group. 4) PDGFRα protein expression was observed in fibroblasts and myofibroblasts, but not in VSMCs. PDGFRβ protein expression was noted in not only fibroblasts and myofibroblasts but also VSMCs. Thus, During myocardial fibrosis of DOCA induced salt-sensitive hypertensive rats, PDGFRα acts at early stage, but PDGFRβ functions in the whole process. PDGFRα and PDGFRβ expressions increase in fibroblasts and myofibroblasts, suggesting that PDGF/PDGFR signaling pathway is involved in the myocardial fibrosis via stimulating fibroblasts to proliferate and transform into myofibroblasts.

Keywords: Platelet-derived growth factor; desoxycorticosterone; fibroblasts; imatinib; myocardial fibrosis; myofibroblasts; platelet-derived growth factor receptor.

Figure 1

Sirius red staining of myocardial interstitium in different groups on day 28 (× 200). A: CON; B: DOCA; C: DOCA+IMA. Myocardial fibrosis was the most severe in DOCA group, but attenuated in DOCA+IMA group.

Figure 2

Sirius red staining of perivascular interstitium in different groups on day 28 (× 200). A: CON; B: DOCA; C: DOCA+IMA. Perivascular fibrosis was the most severe in DOCA group, but attenuated in DOCA+IMA group.

Figure 3

mRNA expressions of PDGFRα and PDGFRβ in different groups. x̅±s, n=10. **P<0.01 vs CON. ##P<0.01 vs DOCA.

Figure 4

mRNA expressions of procollagen I, procollagen III, FSP-1 and α-SMA in different groups on day 28. x̅±s, n=10. **P<0.01 vs CON. ##P<0.01 vs DOCA.

Figure 5

Immunohistochemistry for PDGFRα in different groups on days 14 and 28 (× 200). A: Day 14 CON; B: Day 14 DOCA; C: Day 14 DOCA+IMA; D: Day 28 CON; E: Day 28 DOCA; F: Day 28 DOCA+IMA. G, x̅±s, n=10. **P<0.01 vs CON. ##P<0.01 vs DOCA.

Figure 6

Immunohistochemistry for PDGFRβ and p-PDGFRβ in different groups on days 14 and 28 (× 200). A-F: PDGFRβ, A: Day 14 CON; B: Day 14 DOCA; C: Day 14 DOCA+IMA; D: Day 28 CON; E: Day 28 DOCA; F: Day 28 DOCA+IMA. G-I: p-PDGFRβ, G: Day 28 CON; H: Day 28 DOCA; I: Day 28 DOCA+IMA.

Figure 7

Immunohistochemistry for α-SMA and vimentin and α-SMA positive spindle-shaped cells in different groups on day 28 (× 200). A: Vimentin CON; B: Vimentin DOCA; C: Vimentin DOCA+IMA; D: α-SMA CON; E: α-SMA DOCA; F: α-SMA DOCA+IMA.

Figure 8

Immunofluorescence staining of PDGFRα and PDGFRβ (× 200). PDGFRα was located in fibroblasts and myofibroblasts, but not in VSMCs. PDGFRβ was not only located in fibroblasts and myofibroblasts, but also in VSMCs. A: DAPI, B: Vimentin, C: PDGFRα, D: Merged; E: DAPI, F: α-SMA, G: PDGFRα, H: Merged; I: DAPI, J: α-SMA, K: PDGFRβ, L: Merged; M: DAPI, N: Vimentin, O: PDGFRβ, P: Merged.