Growth-factor-induced healing of partial-thickness defects in adult articular cartilage.

We have previously shown (Hunziker and Rosenberg, J Bone Joint Surg 1996;78A:721-33) that synovial cells can be induced to migrate into partial-thickness articular cartilage defects, therein to proliferate and subsequently to deposit a scar-like tissue. We now wished to ascertain whether these synovial cells could be stimulated to transform into chondrocytes, and thus to lay down cartilage tissue, by the timely introduction of a differentiation factor. Partial-thickness defects were created in the knee-joint cartilage of adult miniature pigs. These were then filled with a fibrin matrix containing a free chemotactic/mitogenic factor and a liposome-encapsulated chondrogenic differentiation one. Tissue was analyzed (immuno)histochemically at 2, 6 and 12 months. Defects became filled with cartilage-like tissue which registered positive for all major cartilage-matrix components; it remained compositionally stable throughout the entire follow-up period. Although still requiring considerable refinement, our one-step, growth-factor-based treatment strategy has the basic potential to promote intrinsic healing of partial-thickness articular cartilage defects, thus obviating the need for transplanting cells or tissue.