Clouding the issue still further..
According to some magazne articles and other stuff relased around the time of the TOS films (mid 80s), there was at least one member of the Federation that used extensivive cloneing and even cloned soldiers for the Federation. I'd have to check, but I think someone picked up on it for one of the fan produced PDF Trek suppmenets. Interestingly enough, this idea came out long before the idea that the Stormtroopers in Star Wars were clones was a given.
I don't believe that there is any on screen evidence of this, nor any evidence that the UFP clones replacement organs and limbs. It appears more like UFP medicine is capable of swtiching on an off DNA syquences allowing someone to regenerate/regrow organs combined with very advanced synthetic replacements.