Objective: To observe the effect of isolating the chondrocytes from articular cartilage with the method of three-step enzymatic digestion, and the biological characteristics of the isolated chondrocytes during cultivation in vitro in order to evaluate their biological activity.
Methods: The method of three-step enzymatic digestion was designed that the articular cartilage was digested one by one with the 1 g/L trypsin and 1 g/L EDTA, 1 g/L hyaluronidase and 2 g/L collagenase I in the culture medium to isolate chondrocytes. The harvesting and viability rate of the primary chondrocytes were detected. During the passage cultivation in vitro, the changes of the chondrocytes shape and growth were observed, the changes of the collagen type I and II and aggrecan in the extracellular matrix were investigated and detected.
Results: (1) The extracellular matrix of articular cartilage was completely dissolved by the three-step enzymatic digestion, and the chondrocytes were completely isolated from the solid matrix. The number of the harvested chondrocytes from every gram of wet cartilage was 50.3 x 10(6) on average, and their viability rate was 98.8% on average. (2) The primary and first passage chondrocytes had triangle or multi-angle shape, and became elliptic shape at the growing confluence with the positive immunohistochemical stain of collagen type II and the strong heterochromia to toluidine blue. The content of sulfate glycosaminoglycans (GAG) in the extracellular matrix of the primary passage cells was (92 +/- 10) microg/cm(2). The chondrocytes after the third passaging gradually became spindle shape with the negative stain of collagen type II and the weak heterochromia to toluidine blue. The content of sulfate GAG of the fourth passage cells was (48 +/- 12) microg/cm(2).
Conclusion: (1) The method of three-step enzymatic digestion can make the extracellular matrix of articular cartilage completely degraded, and has advantages in the high efficiency of harvesting primary chondrocytes, high cellular viability rate and simple manipulation. (2) The primary and first passage chondrocytes have fine biological activity, and the chondrocytes after the third passaging have lost their special biological activity.