SPONTANEOUS REPAIR OF SUPERFICIAL DEFECTS IN ARTICULAR-CARTILAGE IN AFETAL LAMB MODEL

A fetal lamb model was developed to investigate the capacity of fetal articular cartilage for repair after the creation of a superficial def ect. Superficial defects, 100 micrometers deep,were made in the articu lar cartilage of the trochlear groove in the distal aspect of the femu r in eighteen fetal lambs that were halfway through the 145-day gestat ional period; the contralateral limb was used as a sham control. The w ounds were allowed to heal in utero for three, seven, fourteen, twenty -one, or twenty-eight days, Seven days after the injury, the defects w ere filled with a hypocellular matrix, which stained lightly with safr anin O. At twenty-eight days, the staining of the matrix was similar t o that of the sham controls and the chondrocyte density and the archit ectural arrangement of the cell layers had been restored. An inflammat ory response was not elicited, and no fibrous scar tissue was observed . CLINICAL RELEVANCE: An orderly sequence of repair of articular carti lage was observed after the creation of partial-thickness defects in t he distal aspect of the femur of mid-gestational fetal lambs, The feta l lamb model may be useful for the investigation of interactions betwe en the chondrocyte and extracellular matrices after mechanical stimula tion, Fundamental knowledge of the metabolism of fetal articular carti lage may provide insight into latent reparative processes of mature ca rtilage.