The effects of rapid- or intermediate-acting insulin on the proliferation and differentiation of cultured chondrocytes.

In cartilage regenerative medicine, which is highly expected in the face of our aging society, insulin is the potent factor for culture media. To secure the safety of culture media, we attempted to use medical insulin formulations, and compared their effects on human articular or auricular chondrocytes between regular human insulin (R) and neutral protamine hagedorn insulin (N). In monolayer culture with the media containing either R or N, the cell growth reached approximately 15-fold-increase in 6 days, which showed no significant difference between them. These cells showed the equivalent ability to produce cartilage matrices, both in vitro and in vivo. Also, in the 3D culture of the dedifferentiated chondrocytes, either R or N increased gene expression of type II collagen at 3-4 folds in the combination with other growth factors, compared with basal medium, while insulin could similarly enhance both the redifferentiation and cartilage maturation. The in vitro half-life of each insulin in the presence of chondrocytes neither decreased within 3 days, suggesting little degradation in the culture media, unlike in the body. Although both R and N showed similar biological effects on cultured chondrocytes, we may choose the R for clinical practice because of its pure composition.