So we have been handling the low-hanging fruit: bladders, skin, urethras and cartilage were being clinically trialled (ie. put into people) as of September 2018.

https://3dprint.com/224629/3d-bioprinted-bladder/

The complexity of the heart is weird -- there's a lot of physical structure that's important, but at the same time I believe there's relatively little differentiation: it's mostly muscle; it's not a kidney or a lung. It's probably directly the opposite challenges to skin -- skin probably has more internal differences, but the physical layout are likely to just be laminar sheets.

(I am not an expert on biology.)

My brother died at age 21 back in '93, due to organ failure brought on by his heart which had been deformed since birth. He waited in Denver's Children's Hospital on the heart transplant list for several months before dying.

A friend I knew had the top part of his heart replaced with a leatherized cadaver graft, after suffering from a massive infection under the pericardium. He died about 8 years after that.

Veins and valves and hair issues have some avenues for treatment and don't necessarily result in death.

3D printing any mildly complex tissue is a huge challenge. Let alone getting that printed tissue to function in vivo. Almost all press releases like this one will hype that things are just around the corner. The truth is that bioengineering any organ system is extraordinarily complex, but likely achievable some day in the future.

I haven't read the paper behind the press release, but I'm skeptical of claims about 3D printed tissue. The primary obstacle in the heart is having a perfusable network of vasculature that is simultaneously mechanically & electrically functional. This requires intact extracellular matrix as well as functioning cardiomyocytes & supporting cell types. Maybe that's just my bias though (I'm an author on: https://www.ahajournals.org/doi/full/10.1161/CIRCRESAHA.115....).

> Journalists were shown a 3D print of a heart about the size of a cherry, immersed in liquid, at Tel Aviv University on Monday as the researchers announced their findings, published in the peer-reviewed journal Advanced Science.

https://www.timesofisrael.com/israeli-scientists-unveil-worl...

It is not. This is another example of "looks like, but doesn't work like". You often see people print noses, ears, whatever that have cells in them. That doesn't make it functional tissue.

Source: I lead a tissue engineering project to print human organs for transplantation.

> 3d printing a heart is one of the most complex organs to replicate

That may make it a suitable target if you want to start out with a boom and getting some PR, while first "products" out the door would be less complex ones.

Yes, please print me some hair