So like. If we want to replace or create novel body parts, we'll need to grow cultures of tissues in coherent structures, right? Most of what I'm reading in the bioprinting realm seems kind of limited, though - like the most advanced bioprinted heart attempts seem very primitive if they're not working with a pre-existing ECM, which isn't very useful if you want to create a new heart - are there advances in the field that I'm somehow overlooking? Coherent muscle and tissue structure without a pre-existing ECM seems like a major challenge, even though probably to some extent you can rely on the existing pattern formation strategies - though the differentiation niche isn't going to quite fit - the most successful bioprint approaches seem only capable of creating small patches of tissue that can regenerate small portions of a heart, rather than the organ wholesale

https://pmc.ncbi.nlm.nih.gov/articles/PMC11795835/

I know there's various proteins, glycans, hybrid molecules, and other epitopes important for the cells to do their job right, though I'm not sure of the details