Spontaneous repair of superficial defects in articular cartilage in a fetal lamb model

A fetal lamb model was developed to investigate the capacity of fetal articular cartilage for repair after the creation of a superficial defect. Superficial defects, 100 micrometers deep,were made in the articular cartilage of the trochlear groove in the distal aspect of the femur in eighteen fetal lambs that were halfway through the 145-day gestational period; the contralateral limb was used as a sham control. The wounds were allowed to heal in utero for three, seven, fourteen, twenty-one, or twenty-eight days, Seven days after the injury, the defects were filled with a hypocellular matrix, which stained lightly with safranin O. At twenty-eight days, the staining of the matrix was similar to that of the sham controls and the chondrocyte density and the architectural arrangement of the cell layers had been restored. An inflammatory response was not elicited, and no fibrous scar tissue was observed. CLINICAL RELEVANCE: An orderly sequence of repair of articular cartilage was observed after the creation of partial-thickness defects in the distal aspect of the femur of mid-gestational fetal lambs, The fetal lamb model may be useful for the investigation of interactions between the chondrocyte and extracellular matrices after mechanical stimulation, Fundamental knowledge of the metabolism of fetal articular cartilage may provide insight into latent reparative processes of mature cartilage.