First-ever 3D human arrhythmic tissue created

Scientists, including one of Indian-origin, have engineered the first-ever living, three-dimensional human arrhythmic tissue.
The research was made possible after scientists successfully formulated the precise type and ratio of cell types that produce highly functional cardiac tissue.
Arrhythmia is a condition in which the feedback of electrical pulses of the heart is interrupted, leaving the heart unable to contract and pump blood effectively.
With the right cellular composition, the researchers were able to engineer the circular tissue model associated with arrhythmia.
The team then applied electrical pulses to the arrhythmic tissues, 'zapping' the irregularly beating tissue into a state of regular contractions.

The new study was conducted by researchers at the University of Toronto's Institute of Biomaterials & Biomedical Engineering (IBBME) and the McEwen Centre for Regenerative Medicine.

"Hearts are not just composed of one type of cell," said fourth-year IBBME PhD student Nimalan Thavandiran, who is the first author of the study.
Until now, scientists have not known how to mix different cell types in engineered heart tissue in such a way that the tissue achieves the composition and maturity level of the native human heart.
Thavandiran solved this mystery by methodically separating out different cell types derived from human pluripotent stem cells and precisely mixing them back together.

Using scoring metrics associated with functional hearts - contraction, electrical activity and cell alignment - Thavandiran was able to develop a formula for engineering highly functional heart tissue.
"The composition of the cells is vital. We discovered that a mixture of 25 per cent cardiac fibroblasts (skin-like cells) to 75 per cent cardiomyoctes (heart cells) worked best," said Thavandiran.
"The carefully composed cell ratios were then grown in three-dimensional "wires" that mimic the structure of human heart tissue," he said.
"An exciting result of our study is our ability to miniaturise the tissues into human heart micro-tissues that can be used to measure normal and diseased human heart responses to drugs," said Professor Peter Zandstra, corresponding author of the study.