Cardiac fibroblasts support cardiac inflammation in heart failure.

Cardiac remodeling and inflammation are hallmarks of cardiac failure and correlate with outcome in patients. However, the basis for the development of both remains unclear. We have previously reported that cardiac inflammation triggers transdifferentiation of fibroblasts to myofibroblasts and therefore increase accumulation of cardiac collagen, one key pathology in cardiac remodeling. Hence, identifying key pathways for inflammation would be beneficial for patients suffering from heart failure also. Besides their well-characterized function in matrix regulation, we here investigate the role of fibroblasts in the inflammatory process. We address for the first time the role of fibroblasts as inflammatory supporter cells in heart failure. Using endomyocardial biopsies from patients with heart failure and dilated cardiomyopathy, we created a primary human cardiac fibroblast cell culture system. We found that mechanical stretch mimicking cardiac dilation in heart failure induces activation of fibroblasts and not only stimulates production of extracellular matrix but more interestingly up-regulates chemokine production and triggers typical inflammatory pathways in vitro. Moreover, the cell culture supernatant of stretched fibroblasts activates inflammatory cells and induces further recruitment of monocytes by allowing transendothelial migration into the cardiac tissue. Our findings reveal that cardiac fibroblasts provide pro-inflammatory mediators and may act as sentinel cells activated by mechanical stress. Those cells are able to recruit inflammatory cells into the cardiac tissue, a process known to aggravate outcome of patients. This might be important in different forms of heart failure and therefore may be one general mechanism specific for fibroblasts.

Single-target RNA interference for the blockade of multiple interacting proinflammatory and profibrotic pathways in cardiac fibroblasts.

Therapeutic targets of broad relevance are likely located in pathogenic pathways common to disorders of various etiologies. Screening for targets of this type revealed CCN genes to be consistently upregulated in multiple cardiomyopathies. We developed RNA interference (RNAi) to silence CCN2 and found this single-target approach to block multiple proinflammatory and profibrotic pathways in activated primary cardiac fibroblasts (PCFBs). The RNAi-strategy was developed in murine PCFBs and then investigated in "individual" human PCFBs grown from human endomyocardial biopsies (EMBs). Screening of short hairpin RNA (shRNA) sequences for high silencing efficacy and specificity yielded RNAi adenovectors silencing CCN2 in murine or human PCFBs, respectively. Comparison of RNAi with CCN2-modulating microRNA (miR) vectors expressing miR-30c or miR-133b showed higher efficacy of RNAi. In murine PCFBs, CCN2 silencing resulted in strongly reduced expression of stretch-induced chemokines (Ccl2, Ccl7, Ccl8), matrix metalloproteinases (MMP2, MMP9), extracellular matrix (Col3a1), and a cell-to-cell contact protein (Cx43), suggesting multiple signal pathways to be linked to CCN2. Immune cell chemotaxis towards CCN2-depleted PCFBs was significantly reduced. We demonstrate here that this RNAi strategy is technically applicable to "individual" human PCFBs, too, but that these display individually strikingly different responses to CCN2 depletion. Either genomically encoded factors or stable epigenetic modification may explain different responses between individual PCFBs. The new RNAi approach addresses a key regulator protein induced in cardiomyopathies. Investigation of this and other molecular therapies in individual human PCBFs may help to dissect differential pathogenic processes between otherwise similar disease entities and individuals.

Cardiovascular RNA interference therapy: the broadening tool and target spectrum.

Understanding of the roles of noncoding RNAs (ncRNAs) within complex organisms has fundamentally changed. It is increasingly possible to use ncRNAs as diagnostic and therapeutic tools in medicine. Regarding disease pathogenesis, it has become evident that confinement to the analysis of protein-coding regions of the human genome is insufficient because ncRNA variants have been associated with important human diseases. Thus, inclusion of noncoding genomic elements in pathogenetic studies and their consideration as therapeutic targets is warranted. We consider aspects of the evolutionary and discovery history of ncRNAs, as far as they are relevant for the identification and selection of ncRNAs with likely therapeutic potential. Novel therapeutic strategies are based on ncRNAs, and we discuss here RNA interference as a highly versatile tool for gene silencing. RNA interference-mediating RNAs are small, but only parts of a far larger spectrum encompassing ncRNAs up to many kilobasepairs in size. We discuss therapeutic options in cardiovascular medicine offered by ncRNAs and key issues to be solved before clinical translation. Convergence of multiple technical advances is highlighted as a prerequisite for the translational progress achieved in recent years. Regarding safety, we review properties of RNA therapeutics, which may immunologically distinguish them from their endogenous counterparts, all of which underwent sophisticated evolutionary adaptation to specific biological contexts. Although our understanding of the noncoding human genome is only fragmentary to date, it is already feasible to develop RNA interference against a rapidly broadening spectrum of therapeutic targets and to translate this to the clinical setting under certain restrictions.

CCN1: a novel inflammation-regulated biphasic immune cell migration modulator.

In this study, we performed a comprehensive analysis of the effect of CCN1 on the migration of human immune cells. The molecule CCN1, produced by fibroblasts and endothelial cells, is considered as an important matrix protein promoting tissue repair and immune cell adhesion by binding various integrins. We recently reported that CCN1 therapy is able to suppress acute inflammation in vivo. Here, we show that CCN1 binds to various immune cells including T cells, B cells, NK cells, and monocytes. The addition of CCN1 in vitro enhances both actin polymerization and transwell migration. Prolonged incubation with CCN1, however, results in the inhibition of migration of immune cells by a mechanism that involves downregulation of PI3Kγ, p38, and Akt activation. Furthermore, we observed that immune cells themselves produce constitutively CCN1 and secretion is induced by pro-inflammatory stimuli. In line with this finding, patients suffering from acute inflammation had enhanced serum levels of CCN1. These findings extend the classical concept of CCN1 as a locally produced cell matrix adhesion molecule and suggest that CCN1 plays an important role in regulating immune cell trafficking by attracting and locally immobilizing immune cells.