What is the problem with 3D printing blood vessels/blood cells?

3D-printed blood vessels incorporating living cells may help take vascular disease out of circulation for good.

Blood clots and fatty plaque residues on vessel walls can hinder or block blood flow and increase pressure in the vascular system. That deprives tissues and organs throughout the body of oxygen and nutrients their cells need to survive. Over time, a patient’s risk increases for cardiac emergencies like heart attack and stroke, as well as for chronic debilitating complications like leg pain, organ failure, tissue death, and gangrene.                                                                                              

Explanation:

primary succession occurs in essentially lifeless areas regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier. secondary succession occurs

not always but somethings can be reproduced in a laboratory.