Human primary articular chondrocytes, chondroblasts-like cells, and dedifferentiated chondrocytes: differences in gene, microRNA, and protein expression and phenotype.

In this study we have isolated human primary uncultured articular chondrocytes. When these cells are allowed to proliferate within their own extracellular matrix (ECM), they begin to produce hyaline ECM molecules similar to embryological chondroblasts. These cells are called chondroblast-like cells. Upon continued culture these cells spread onto the plastic surface and dedifferentiate. We have characterized these three stages of chondral cells by gene expression and expression of microRNAs (miRNAs) and proteins. Gene expression was quantified by real-time reverse transcriptase (RT) polymerase chain reaction, miRNA expression by miRNA arrays, and protein synthesis by extra- and intracellular flow cytometry. Many of the genes, miRNAs, and proteins were differentially expressed in the different stages of chondral cells. In the context of cellular therapy, expression of some genes is a cause for concern. The best source of cells for treatment of lesions of hyaline cartilage has not yet been identified. Adult chondroblast-like cells may be strong candidates. Profound understanding of how expression of genes and synthesis of proteins are regulated in these cells, for instance, by miRNAs, may reveal new strategies for improving their synthesis of hyaline ECM. This insight is important to be able to use these cells in the clinic.