[biofox]

I don't work in this area, but ECM scaffolds undergo significant change with age. Crosslinks and age-related remodelling degrade the mechanical properties of the scaffold and interfere with normal cell migration and differentiation.

You would want to start with a healthy organ before decellularising and reseeding.

[improbable22]

But perhaps not quite as critical as for current transplants? At least that's my uneducated guess... anyone know?