So they grew this thing in a scaffold. My questions are:

Is this just a kidney shaped blob of base kidney cells or are there sub-organs and differentiated tissues?

What's the scaffold made out of? Are different parts of it doped with different growth factors to spur tissue specialization?

What role does gravity play? Were these things spun around in one of those spinning bio-reactors to eliminate gravity? Or was a gravitational vector established to encourage certain cells to migrate to the certain parts of the organ?

I guess the thing I am getting at here is that even gall bladders (Which, I read in the news a few months ago, they've grown around little balloon scaffolds in dogs.) are complex. To grow these organs outside the body is very tricky.

In the end the bio-reactor these things are grown in may wind up being as complex as the body itself in order to provide all the influencing factors needed to ensure all that specilization of tissues. Complexity often needs a context.