Cardiomyocyte progenitor cell mechanoresponse unrevealed: strain avoidance and mechanosome development

The mechanosensitivity of cardiomyocyte progenitor cells (CMPCs) is developed upon early cardiac differentiation, together with the development of the mechanosome.

Material-based engineering strategies for cardiac regeneration

Cardiac tissue is composed of muscle and non-muscle cells, surrounded by extracellular matrix (ECM) and spatially organized into a complex three-dimensional (3D) architecture to allow for coordinated contraction and electrical pulse propagation. Despite emerging evidence for cardiomyocyte turnover in mammalian hearts, the regenerative capacity of human cardiac tissue is insufficient to recover from damage, e.g. resulting from myocardial infarction (MI). Instead, the heart 'repairs' lost or injured tissue by ongoing synthesis and remodeling of scar tissue. Conventional therapies and timely (stem) cell delivery to the injured tissue markedly improve short-term function and remodeling, but do not attenuate later stage adverse remodeling, leading to functional deterioration and eventually failure of the heart. Material-based therapies have been successfully used to mechanically support and constrain the post-MI failing heart, preventing it from further remodeling and dilation. When designed to deliver the right microenvironment for endogenous or exogenous cells, as well as the mechanical and topological cues to guide neo-tissue formation, material-based therapies may even reverse remodeling and boost cardiac regeneration. This paper reviews the up-to-date status of material-based cardiac regeneration with special emphasis on 1) the use of bare biomaterials to deliver passive constraints that unload the heart, 2) the use of materials and cells to create engineered cardiac constructs for replacement, support, or regeneration of damaged myocardium, and 3) the development of bio-inspired and bioactive materials that aim to enhance the endogenous regenerative capacity of the heart. As the therapies should function in the infarcted heart, the damaged host environment and engineered in vitro test systems that mimic this environment, are reviewed as well.

Matrix production and remodeling capacity of cardiomyocyte progenitor cells during in vitro differentiation

Cell-based therapy has emerged as a treatment modality for myocardial repair. Especially cardiac resident stem cells are considered a potential cell source since they are able to differentiate into cardiomyocytes and have improved heart function after injury in a preclinical model for myocardial infarction. To avoid or repair myocardial damage it is important not only to replace the lost cardiomyocytes, but also to remodel and replace the scar tissue by "healthy" extracellular matrix (ECM). Interestingly, the role of cardiac stem cells in this facet of cardiac repair is largely unknown. Therefore, we investigated the expression and production of ECM proteins, matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) in human cardiomyocyte progenitor cells (CMPCs) undergoing differentiation towards the cardiomyogenic lineage. Our data suggest that CMPCs have the capacity to synthesize and modulate their own matrix environment, especially during differentiation towards the cardiomyogenic lineage. While undifferentiated CMPCs expressed collagen I, III, IV and fibronectin, but no elastin, during the process of differentiation the expression of collagen I, III, IV and fibronectin increased and interestingly also elastin expression was induced. Furthermore, undifferentiated CMPCs express MMP-1 -2 and -9 and upon differentiation the expression of MMP-1 decreased, while the expression of MMP-2 and MMP-9, although the latter only in the early stage of differentiation, increased. Additionally, the expression of TIMP-1, -2 and -4 was induced during differentiation. This study provides new insights into the matrix production and remodeling capacity of human CMPCs, with potential beneficial effects for the treatment of cardiac injury.