Utility of NucleoCounter for the chondrocyte count in the collagenase digest of human native cartilage

Optimal conditions of collagenase treatment for isolation of articular chondrocytes from aged human tissues

Introduction

There are various types of cartilage, including the auricular and articular cartilages. These cartilages have different functions, and their matrix volume and density of chondrocytes may differ. Thus, different protocols may be required to digest different types of cartilage.

Methods

In this study, we examined protocols for the digestion of articular and auricular cartilages and determined the optimal conditions for articular cartilage digestion.

Results

Our histological findings showed that the articular cartilage has a larger matrix area and fewer cells than the auricular cartilage. In 1-mm² areas of articular and auricular cartilages, the average numbers of cells were 44 and 380, respectively, and the average matrix areas were 0.94 and 0.77 mm², respectively. The maximum numbers of viable cells (approximately 1 × 10⁵ cells/0.1 g of tissue) were obtained after digestion in 0.15, 0.3, or 0.6% collagenase for 24 h, in 1.2% collagenase for 6 h, or in 2.4% collagenase for 4 h. In tissues incubated in 0.15 or 0.3% collagenase, the cell numbers were lower than 1 × 10⁵, even at 24 h, possibly reflecting incomplete digestion of cartilage. No significant differences were observed in the results of apoptosis assays for all collagenase exposure times and concentrations. However, cell damage appeared to be greater when collagenase concentrations were high. When cells obtained after digestion with different concentrations of collagenase were seeded at a density of 3000 cells/cm², they yielded the maximum cell numbers after 1 week.

Conclusions

We recommend a 24-h incubation in 0.6% collagenase as the optimal condition for chondrocyte isolation from articular cartilage. Moreover, we found that the optimum cell-seeding density is approximately 3000 cells/cm². Conditions determined in this study would maximize the yield of isolated articular chondrocytes and enable the generation of a large quantity of cultured cells.

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Optimal conditions for articular cartilage digestion were determined.

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Articular cartilage had a larger matrix and fewer cells than auricular cartilage.

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A 24-h incubation in 0.6% collagenase was optimal for chondrocyte isolation.

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The optimum cell-seeding density was approximately 3000 cells/cm².

Optimal conditions of collagenase treatment for isolation of articular chondrocytes from aged human tissues

Introduction

There are various types of cartilage, including the auricular and articular cartilages. These cartilages have different functions, and their matrix volume and density of chondrocytes may differ. Thus, different protocols may be required to digest different types of cartilage.

Methods

In this study, we examined protocols for the digestion of articular and auricular cartilages and determined the optimal conditions for articular cartilage digestion.

Results

Our histological findings showed that the articular cartilage has a larger matrix area and fewer cells than the auricular cartilage. In 1-mm² areas of articular and auricular cartilages, the average numbers of cells were 44 and 380, respectively, and the average matrix areas were 0.94 and 0.77 mm², respectively. The maximum numbers of viable cells (approximately 1 × 10⁵ cells/0.1 g of tissue) were obtained after digestion in 0.15, 0.3, or 0.6% collagenase for 24 h, in 1.2% collagenase for 6 h, or in 2.4% collagenase for 4 h. In tissues incubated in 0.15 or 0.3% collagenase, the cell numbers were lower than 1 × 10⁵, even at 24 h, possibly reflecting incomplete digestion of cartilage. No significant differences were observed in the results of apoptosis assays for all collagenase exposure times and concentrations. However, cell damage appeared to be greater when collagenase concentrations were high. When cells obtained after digestion with different concentrations of collagenase were seeded at a density of 3000 cells/cm², they yielded the maximum cell numbers after 1 week.

Conclusions

We recommend a 24-h incubation in 0.6% collagenase as the optimal condition for chondrocyte isolation from articular cartilage. Moreover, we found that the optimum cell-seeding density is approximately 3000 cells/cm². Conditions determined in this study would maximize the yield of isolated articular chondrocytes and enable the generation of a large quantity of cultured cells.