Question

What would be needed to regrow a human limb in the lab to later be transplanted on an amputee?

Answer 1

A blastema is a mass of multipotent progenitor cells that forms at a wound site in animals capable of regeneration. The missing part is regenerated from the blastema with mostly correct pattern and restored function. Instruct the Blastema cells with protein factors that helps them differentiate to particular tissue, like BMP9 here. Balstema have positional memory as well, so they copy the morphology from the amputated part.

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https://www.nature.com/articles/s41467-018-08278-4