Described in certain aspects are composite extracellular matrix materialproducts including expanded collagenousmaterials in combination with non- expanded collagenous materials Methods fortheir preparation and use are also disclosed.Cer-tain expanded collagenous materials can be prepared by treating a firstcollagenous material with an alkaline substance undercon-ditions effective to expand the first collagenous material, and recoveringthe expanded material Expanded materials can exhibitbeneficial persistence and tissue generation characteristics when implanted,and can be used in the formation of highly porousmedical implant bodies which can be compressed to fractions of their originalvolume and will thereafter substantially recovertheir original volume
