INJECTABLE CARTILAGE

Slowly polymerizing calcium alginate gels were investigated as a means of delivering large numbers of isolated chondrocytes by means of inje ction to determine if these gels would promote engraftment and could p rovide three-dimensional templates for new cartilage growth. Chondrocy tes isolated from the articular surface of calf forelimbs were added t o a 1% sodium alginate dissolved in a 0.1 M potassium phosphate buffer solution (pH 7.4) to generate a final cellular density of 10 X 10(6)/ ml (representing approximately 10 percent of the cellular density of h uman juvenile articular cartilage). The calcium alginate-chondrocyte m ixture was injected through a 22-gauge needle in 100-mu l aliquots und er the panniculus carnosus on the dorsum of nude mice and incubated fo r 6 (n = 4), 8 (n = 11), and 12 (n = 12) weeks in vivo. Time-zero spec imens (n = 10) consisting of 100-mu l aliquots of the calcium alginate -chondrocyte mixture it ere used to calculate initial weight. At harve st, all. calcium alginate-chondrocyte specimens exhibited a pearly opa lescence and were firm to palpation as early as 6 weeks after injectio n. By 12 weeks of in vivo incubation, the specimens weighed 0.15 +/- 0 .04 gm, significantly more than the initial weight of 0.11 +/- 0.01 gm (p < 0.05). Specimens stained with hematoxylin and eosin demonstrated lacunae within a basophilic ground-glass substance. Control specimens of calcium alginate without chondrocytes (n = 4) had a doughy consist ency 12 weeks after injection and had no histologic evidence of cartil age formation. This study demonstrates that an injectable calcium algi nate matrix can provide a three-dimensional scaffold for the successfu l transplantation and engraftment of chondrocytes. This technique hold s the promise of a minimally invasive means of delivering autogenous c artilage to correct or reconstruct facial contour deficiencies.