Cardiospheres Recapitulate a Niche-Like Microenvironment Rich in Stemness and Cell-Matrix Interactions, Rationalizing Their Enhanced Functional Potency for Myocardial Repair

Abstract

Cardiac stem cells are promising candidates for use in myocardial regenerative therapy. We test the hypothesis that growing cardiac-derived cells as three-dimensional cardiospheres may recapitulate a stem cell niche-like microenvironment, favoring cell survival and enhancing functional benefit after transplantation into the injured heart. Cardiac stem cells and supporting cells from human endomyocardial biopsies were grown as cardiospheres and compared to cells cultured under traditional monolayer condition or dissociated from cardiospheres. Cardiospheres self-assembled into stem cell niche-like structures in vitro in suspension culture, while exhibiting greater proportions of c-kit+ cells and up-regulated expression of SOX2 and Nanog. Pathway-focused PCR array, quantitative RT-PCR, and immunostaining revealed enhanced expression of stem cell-relevant factors and adhesion/extracellular-matrix molecules (ECM) in cardiospheres, including IGF-1, HDAC2, Tert, integrin-α2, laminin-β1 and MMPs. Implantation of cardiospheres in SCID mouse hearts with acute infarction disproportionately improved cell engraftment and myocardial function, relative to monolayer-cultured cells. Dissociation of cardiospheres into single cells decreased the expression of ECM and adhesion molecules and undermined resistance to oxidative stress, negating the improved cell engraftment and functional benefit in vivo. Growth of cardiac-derived cells as cardiospheres mimics stem cell niche properties, with enhanced “stemness” and expression of ECM and adhesion molecules. These changes underlie an increase in cell survival and more potent augmentation of global function following implantation into the infarcted heart.

Spheroid three-dimensional culture enhances Notch signaling in cardiac progenitor cells

“…[8,21] The 3D environment and enhanced cell-cell and cell-ECM contacts offered by CSps can stimulate several molecular signaling and cellular functions. Notch is a highly conserved pathway that plays a key role in determining cell fate decisions in the heart.…”

“…[6,7] CSps can serve as an interesting in vitro model of the cardiac stem cell niche. [8] Compared with traditional two-dimensional (2D) culture, multicellular spheroids provide a microenvironment that more closely mimics the in vivo physiology. These model systems recapitulate key features of the endogenous cell niche, such as improved cellcell and cell-extracellular matrix (ECM) contacts, as well as gradients of oxygen and nutrients between periphery and core of the spheroid.…”

“…These model systems recapitulate key features of the endogenous cell niche, such as improved cellcell and cell-extracellular matrix (ECM) contacts, as well as gradients of oxygen and nutrients between periphery and core of the spheroid. [8][9][10][11] Improved knowledge on the mechanisms that regulate CPC behavior and functions, such as survival, proliferation, and differentiation, is needed. In particular, the interaction of CPCs with the niche in which they reside is of pivotal importance to ultimately direct their behavior toward cardiac regeneration.…”

Cellular and Molecular Characterization of Human Cardiac Stem Cells Reveals Key Features Essential for Their Function and Safety

“…Color images available online at www.liebertpub.com/ scd and sphere. Since the generation of spheres imitates the heart's three-dimensional niche condition [33], we have attempted to evaluate the effect of sphere generation on myogenic differentiation. We hypothesized that cell-cell communication might be an advantage for myogenic differentiation, so we cultured isolated cells in suspension media and allowed the cells to grow under sphere conditions.…”

Concise Review: Mending a Broken Heart: The Evolution of Biological Therapeutics

“…Another potential source for cardiac-derived stem cell therapy is cardiosphere derived cells (CDCs), a heterogeneous mixture of many different cell types derived by ex vivo culture of right ventricular endomyocardial biopsies [43]. The enhanced potency of cardiospheres for myocardial repair has been attributed to their growth properties that mimic stem cell niche properties with enhanced "stemness" and expression of ECM and adhesion molecules [44]. The CADUCEUS trial was a proof-of-concept study that evaluated the safety and efficacy of autologous CDCs in patients with a recent MI.…”