Satoshi Sezaki

Thrombospondin-1 is Induced in Rat Myocardial Infarction and its Induction is Accelerated by Ischemia/Reperfusion

Thrombospondin-1 (TSP-1) is a multifunctional, rapid-turnover matricellular protein. Recent studies demonstrated that TSP-1 has a role in regulating inflammatory reactions. Myocardial infarction (Ml) is associated with an inflammatory response, ultimately leading to healing and scar formation. In particular, an enhanced inflammatory reaction and a massive accumulation of monocytes/macrophages is seen with reperfusion after MI. To examine the role of TSP-1 in Ml, we isolated rat TSP-1 complementary DNA (cDNA) and analyzed the level and distribution of the mRNA expression. In infarcted rat hearts, TSP-1 mRNA increased markedly at 6 and 12 hrs after coronary artery ligation (27.97 ± 3.40-fold and 22.77 ± 1.83-fold, respectively, compared with sham-operated hearts). Western blot analysis revealed that TSP-1 protein was transiently induced in the infarcted heart. Using in situ hybridization analysis, TSP-1 mRNA signals were observed in the infiltrating cells at the border area of infarction. We then examined the effect of ischemia/reperfusion (I/R) on TSP-1 mRNA induction in the rats with infarcted hearts. Quantitative reverse transcriptase polymerase chain reaction (RT-PCR) demonstrated that I/R enhanced the TSP-1 mRNA expression approximately 4-fold, as compared with the level in the permanently ligated heart. Finally, we examined the effect of TSP-1 on proinflammatory cytokine release in mononuclear cells. The releases of interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) from human mononuclear cells were enhanced by TSP-1 in a dose-dependent manner. Thus, the immediate and marked increase of TSP-1 expression suggests that TSP-1 has an inflammatory-associated role in MI.

Increased expression of dermatopontin mRNA in the infarct zone of experimentally induced myocardial infarction in rats: comparison with decorin and type I collagen mRNAs

Abstract.Objectives: Dermatopontin, a 22 kDa extracellular matrix (ECM) protein, has been shown to interact with other ECM components, especially decorin, and to regulate ECM formation. We examined dermatopontin mRNA expression in the myocardial infarct zone. Methods: The cDNA encoding the rat dermatopontin was cloned by RT-PCR based on screening results from the Expressed Sequence Tag™ database. The dermatopontin mRNA expression was examined in the infarct zone after experimentally induced myocardial infarction in rats by the methods of Northern blotting and in situ hybridization. The expression of dermatopontin mRNA was compared to that of decorin and type I collagen mRNAs. Results: The isolated clone contained a 609 bp cDNA insert containing a complete open reading frame encoding 202 amino acids. The rat dermatopontin cDNA showed high homology to human and mouse counterparts (>96 %). Northern blotting demonstrated that dermatopontin mRNA expression did not markedly increase on day 2, but was increased on days 7, 14 and 28 by 2.4-, 4.1- and 4.2-fold, respectively, compared to that in preligation hearts. Dermatopontin mRNA expression was regulated almost in parallel with decorin mRNA expression. In situ hybridization demonstrated mRNA signals for dermatopontin in macrophages and spindle-shaped mesenchymal cells (fibroblasts and myofibroblasts) located in the infarct interior zone around infarcted necrotic tissue on day 7. Coexpression of dermatopontin mRNA with decorin and type I collagen mRNAs was observed in spindle-shaped mesenchymal cells. Conclusions: The present results demonstrated the time-dependent increase in the expression of dermatopontin mRNA in parallel with that of decorin mRNA in the infarct zone. Coexpression of dermatopontin mRNA with decorin and type I collagen mRNAs suggests that dermatopontin plays a role in ECM (fibrillar collagen matrix) reformation in the infarct along with decorin and type I collagen.

Concomitant expression of heparin-binding epidermal growth factor-like growth factor mRNA and basic fibroblast growth factor mRNA in myocardial infarction in rats

Abstract Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is mitogenic and chemotactic for many cell types. HB-EGF is induced in pathological states which require cell mitogenesis and proliferation, including angiogenesis, and has been reported to interact functionally with basic fibroblast growth factor (bFGF). To test our hypothesis that HB-EGF mRNA expression is increased in myocardial infarction, we used Northern hybridization in rats to investigate the expression of HB-EGF and EGF receptor mRNAs expression in the infarct zone compared to the expression of bFGF and FGF receptor mRNAs. We also performed in situ hybridization to identify the cells responsible for HB-EGF mRNA production. HB-EGF mRNA rapidly increased after ligation (mean ± SE, 5.6 ± 0.23-fold increase at 6 hours compared to the preligation heart levels) and reached a maximum level (9.1 ± 0.42-fold increase) around 12 hours. HB-EGF mRNA then gradually decreased on day 1 (5.8 ± 1.0-fold increase), day 2 (3.2 ± 0.94-fold increase) and day 3 (1.9 ± 0.33-fold increase) after ligation. Parallel changes in bFGF mRNA expression were observed (6, 12 hours, days 1, 2 and 3; 3.6 ± 0.42-, 5.3 ± 0.12-, 2.3 ± 0.12-, 1.7 ± 0.03- and 0.95 ± 0.03-fold increase, respectively). EGF receptor (ErbB-1) mRNA was gradually increased on day 2 (2.4 ± 0.53-fold increase), day 7(4.0 ± 0.61-fold increase) and day 14 (7.0 ± 0.61-fold increase). Similarly, FGF receptor (FGF receptor-1) mRNA was gradually increased (days 2, 7 and 14; 1.3 ± 0.13-, 1.5 ± 0.17- and 2.3 ± 0.15-fold increase, respectively). Reperfusion after a 2-hour ligation (too late to salvage myocytes) enhanced HB-EGF (12 hours, 16.8 ± 1.8-fold increase) and bFGF (12 hours, 10.4 ± 1.1-fold increase) mRNA expression. The cells responsible for the increased production of HB-EGF mRNA were shown by in situ hybridization to be surviving myocytes located in the infarct peripheral zone around infarct necrotizing tissue. In conclusion, our results demonstrated a rapid increase in HB-EGF mRNA expression concomitant with an increase in bFGF mRNA expression, suggesting that HB-EGF and bFGF might play some role in the course of pathological changes in the infarct in the early inflammatory phase. Reperfusion at times too late to salvage myocytes accelerated sequential changes in the expression of both HB-EGF and bFGF mRNAs.