Fibroblasts are coupled to myocytes in heart muscle by nanotubes: a bigger and better syncytium?

This editorial refers to ‘Long-distance intercellular connectivity between cardiomyocytes and cardiofibroblasts mediated by membrane nanotubes’ by K. He et al. , pp. 39–47, this issue. In larger mammalian species including humans, cardiac fibroblasts represent the most numerous nonmyocytes in the myocardium. These cells function to synthesize and organize collagens, fibronectins, and other interstitial components and thus maintain the integrity of the cardiac extracellular matrix (matrix). The term ‘fibroblast’ itself designates a highly heterogenous group of cells that exhibit distinct differentiated phenotypes in different organs.1 In particular, the investigation of cardiac fibroblast and myofibroblast biology in specific organs is important but remains a largely understudied area. Their prevalence alone provides significant impetus for gaining a more complete understanding of their physiology. The common assumption that fibroblasts serve to support cardiomyocyte-mediated force transduction insofar as they synthesize and organize matrix proteins such as fibrillar collagens, elastin, and others to provide a complex interstitial weave and thus tether cardiomyocytes has been in place for many years. An extension of this traditional view is that the nature of the interstitial matrix may be to provide a hammock-like weave that, by its parallelogram structure, assists in protecting the muscle fibre from overstretching as well as contributes to active relengthening of the myocytes, and thus the matrix may lend a suction-pump function to the heart.2 Nonetheless, more recent advances in the field of intercellular communication, particularly in …