Tissue-engineered bone regeneration

Bone lesions above a critical size become scarred rather than regenerated, leading to nonunion. We have attempted to obtain a greater degree of regene ration by using a resorbable scaffold with regeneration-competent cells to recreate an embryonic environment in injured adult tissues, and thus improv e clinical outcome, We have used a combination of a coral scaffold with in vitro-expanded marrow stromal cells (MSC) to increase osteogenesis more tha n that obtained with the scaffold alone or the scaffold plus fresh bone mar row, The efficiency of the various combinations was assessed in a large seg mental defect model in sheep, The tissue-engineered artificial bone underwe nt morphogenesis leading to complete recorticalization and the formation of a medullary canal with mature lamellar cortical bone in the most favorable cases. Clinical union never occurred when the defects were left empty or f illed with the scaffold alone, In contrast, clinical union was obtained in three out of seven operated limbs when the defects were filled with the tis sue-engineered bone.