Ovine or human fibroblasts, either as an underlying monolayer or integrated within human engineered heart tissue, significantly reduced force generation compared with fibroblast-free controls.
An engineered heart tissue model demonstrates that both paracrine and contact-dependent signals from cardiac fibroblasts significantly modulate cardiomyocyte contractile function and drive structural remodeling.
Abstract Background - Cardiovascular diseases are a leading cause of mortality, with aging as the primary risk factor. Cardiac remodelling leading to heart failure involves fibroblast (FB)-driven fibrosis and cardiomyocyte (CM) hypertrophy/dysfunction. Dysregulation in the bidirectional crosstalk involving direct and chemical signalling between these cell types has recently emerged as a key mediator of pathological cardiac remodelling. The nature and changes of this crosstalk are not however fully understood. Patient comorbidities and presence of multiple interacting cell types in native tissue raises challenges to Identifying mechanisms of cell crosstalk making the use of simpler models necessary. Purpose – To establish a 3D-engineered heart tissue (EHT) model to investigate FB-CM interactions using primary cardiac FB from human and sheep. Methods - Human-iPSC-cardiomyocytes (hiPSC-CM) were differentiated and matured for 12 days; non-CM were depleted with 4 mM L-Lactate. Single-cell hiPSC-CM were incorporated into a fibrin/Matrigel matrix to generate EHTs. To assess direct/indirect CM–FB interactions, EHTs were prepared under 3 conditions: (1) Control EHTs containing 1×106 hiPSC-CM only; (2) EHT/FB monolayer, identical to (1) but cultured above a confluent FB monolayer to test influence of FB secreted factors; and (3) Integrated EHTs, generated by combining hiPSC-CM with sheep (or human) FB at a 1:11 ratio, enabling testing of direct/ indirect interactions. EHTs were maintained for 21 days. Contractile function was quantified by video-analysis in a temperature-controlled chamber with electrical stimulation at 1, 2, and 3 Hz (40 V, 30 s). Results - EHTs in the presence of human or ovine FB showed robust spontaneous contractions and followed pacing at 1 and 2Hz. Both EHT/FB monolayer (2) and integrated EHT (3) generated significantly lower force than pure hiPS-CM EHT. Across groups, force declined with increasing stimulation frequency. Integrated EHT (3) developed progressively greater force over time in culture relative to control and monolayer conditions and showed marked tissue shortening. Spontaneous beat frequencies did not differ overall; however, control EHT(1) displayed a significant increase in beat frequencies by day 21 that was absent in FB integrated EHT (3). Summary – The presence of ovine FB underlying monolayer or integrated within the human EHT results in a significant modification in contraction kinetics and reduced force generation compared with FB-free controls. Integrated EHTs exhibited pronounced tissue shortening, consistent with FB-driven structural remodeling. Differences between monolayer and integrated conditions indicate that both paracrine and contact-dependent FB signals modulate CM function. Future studies will identify paracrine factors responsible for the force decline in EHTs. Collectively, these findings support EHTs as a suitable platform for mechanistic studies of FB-CM interactions across pathological aetiologies.
Pradhan et al. (Fri,) conducted a other in Cardiac remodelling. Fibroblast integration or monolayer vs. Fibroblast-free control EHTs was evaluated on Contractile function. Ovine or human fibroblasts, either as an underlying monolayer or integrated within human engineered heart tissue, significantly reduced force generation compared with fibroblast-free controls.