Well, then, can you mechanically create those stresses? Regularly send electrical signals to exercise the muscles, increase and reduce pressure and temperature

Well, then, can you mechanically create those stresses? Regularly send electrical signals to exercise the muscles, increase and reduce pressure and temperature (even have robot-controlled plates do a full massage), stretch and vibrate the whole setup, cycle through levels of certain hormones...? It may take some experimentation, but once you figure out a process that works, you can grow millions of organs with it. (The story "Mazer in Prison" mentioned, offhand, someone getting his muscles electrically stimulated while he slept as a substitute for exercise.)