Kai Pinkernell

Effect of freshly isolated autologous tissue resident stromal cells on cardiac function and perfusion following acute myocardial infarction

BACKGROUND The aim of this study was to investigate the effect of intracoronary administration of freshly isolated, uncultured autologous tissue-derived stromal cells on cardiac function and perfusion after acute infarction in pigs. METHODS A transmural myocardial infarction in a porcine model was induced by occlusion of the mid LAD with an angioplasty balloon for 3 h. Upon reperfusion, freshly isolated, uncultured autologous stromal cells (1.5×10⁶ cells/kg) or control solution was injected into the infarct artery. Cardiac function and area at risk were determined by (99m)Tc-SPECT. RESULTS Eight weeks after infarction, cell treated pigs showed a 20% smaller myocardial perfusion defect compared to control animals (35±9% vs. 44±5% of LV, treated vs. control, respectively, p<0.05). The reduction of the perfusion defect was associated with a significantly higher myocardial salvage index in the cell group as well as a significant increase in ejection fraction compared to control (EF at 8 weeks 43±7% vs. 35±3%, treated vs. control, respectively, p<0.05). This functional improvement was reflected by an increased wall thickness of the infarct and border zone in the treated group (11.2±2.2 mm) compared to control (8.6±1.6 mm, p<0.05) as well as an increased capillary density in the border zone (treated vs. control; 41.6±17.9 vs. 32.9±12.6 capillaries per 0.1 mm², p<0.05). CONCLUSIONS This study demonstrates for the first time that recovery and intracoronary delivery of uncultured autologous tissue derived stromal cells at time of vessel reperfusion is feasible and improves ventricular function.

Protein Kinase C Mediates Basic Fibroblast Growth Factor–Induced Proliferation Through Mitogen-Activated Protein Kinase in Coronary Smooth Muscle Cells

Proliferation of coronary smooth muscle cells (cSMCs) contributes to the pathogenesis of arteriosclerosis and restenosis after angioplasty, and basic fibroblast growth factor (bFGF) is a powerful mitogen for cSMCs. In this study, we investigated the involvement of mitogen-activated protein kinase (MAPK), protein kinase C (PKC), and the transcription factor c-myc in bFGF-stimulated mitogenesis, as well as the functional relationship between these factors. cSMC stimulation with bFGF resulted in phosphorylation of p42 MAPK, as well as the phosphorylation and increased expression of c-myc. The MAPK kinase (MEK) inhibitor PD98059 blocked bFGF-stimulated MAPK phosphorylation and resulted in both a decrease of c-myc expression and inhibition of bFGF-stimulated DNA synthesis in cSMCs. bFGF also increased PKC activity in cSMCs in a time-dependent manner. The inhibition of PKC by chelerythrine or its downregulation by phorbol 12-myristate 13-acetate (PMA) inhibited bFGF-induced DNA synthesis and blocked the phosphorylation of MAPK and c-myc expression in response to bFGF. This indicates an involvement of phorbol ester-sensitive PKC isoforms in MAPK activation and mitogenic signaling by bFGF. Western blot analysis revealed the presence of the phorbol ester-sensitive isoforms PKC alpha, epsilon, and gamma as well as the PKC isoforms iota, lambda, micro, and zeta in cSMCs. In this study, we show that the MAPK cascade is required for bFGF-induced proliferation and that phorbol ester-sensitive PKC isoforms contribute to the bFGF-induced cSMC mitogenesis in cSMCs.

Stem cell induced cardiac regeneration: Fusion/mitochondrial exchange and/or transdifferentiation?

Potentially, adult stem cell-based therapy provides a new therapeutic option for myocardial regeneration. However, to date, with regard to the benefits seen, the mechanisms involved in stem cell-based therapy are not well understood. Suggested pathways proposed so far include fusion of stem cells with cardiomyocytes, transdifferentiation into cardiac and vascular cells and secretion of paracrine factors. In a recent study, our group examined the fate of human adipose tissue-derived stem cells (hASCs) fused with rat cardiomyocytes after treatment with fusion-inducing hemagglutinating virus of Japan (HVJ). In this study, we demonstrated that cells of fused hASC cardiomyocytes display a cardiomyocyte phenotype and spontaneous rhythmic contraction and generate an action potential in vitro. As part of the work underlying this paper, we co-cultured rat neonatal cardiomyocytes with hASCs or pig bone marrow-derived mesenchymal stem cells (MSCs), where ASCs or MSCs had previously been transduced with a lentivirus encoding eGFP. Our data evidence early cardiac contractile proteins, such as Titin and MF20, identified in eGFP-positive cells, suggesting a cardiomyogenic phenotype. Recent work by others has shown that the myogenic conversion increased when BMSCs were cultured with apoptotic cells. In this Extra View article, we review the current understanding of stem cell-derived factors, fusion/partial fusion and the manner in which the exchange of cellular contents between stem cells and cardiomyocytes might contribute to the reprogramming of fully differentiated cardiomyocytes based on recently published literature.

Technique and Imaging for Transthoracic Echocardiography of the Laboratory Pig

(ECHOCARDIOGRAPHY, Volume 21, July 2004)

Angiotensin AT1 receptor upregulates expression of basic fibroblast growth factor, basic fibroblast growth factor receptor and coreceptor in human coronary smooth muscle cells

Abstract.Autocrine stimulation and paracrine interaction between coronary smooth muscle cells (cSMC) and endothelial cells (EC) act as regulators of the vascular angiogenesis. Basic fibroblast growth factor (bFGF), its receptor FGF-R1, and coreceptor heparansulfate proteoglycan (HSPG) are important components involved in this angiogenic process. We investigated the influence of angiotensin (Ang) II on this trimolecular bFGF complex, the underlying signaling and the proliferative process in human cSMC. Ang II induces an AT1 receptor-dependent expression of bFGF and also upregulates the FGF-R1 and HSPG expression which is suppressed by losartan, the AT1 receptor blocker. AT1 receptor signaling which is characterized by phosphorylation of p42-mitogen-activated protein kinase (MAPK) is involved in Ang II-induced bFGF, FGF-R1 and HSPG upregulation and DNA synthesis in human cSMC. In contrast, inhibition of the AT2 receptor by PD123,319 has no influence on these Ang II-stimulated and via the MAPK cascade-mediated proangiogenic effects. Finally, our data show that the Ang II-induced DNA synthesis in cSMC is mediated via the bFGF expression. In conclusion, our results suggest that the Ang II-induced angiogenic effects in the vessel wall are supported by the AT1 receptor-stimulated and MAPK pathway-mediated upregulation of the autocrine/paracrine trimolecular bFGF complex in cSMC.