Gene expression markers in horse articular chondrocytes: Chondrogenic differentiaton IN VITRO depends on the proliferative potential and ageing. Implication for tissue engineering of cartilage.

This research examines chondrocyte differentiation in horses, a process that could potentially impact therapies for cartilage repair. It focuses on gene expression markers in horse articular chondrocytes and presents evidence that the differentiation status of these cells changes as they are cultured.

Understanding Chondrocyte Dedifferentiation

• This research addresses a major stumbling block in current cartilage repair therapies: chondrocyte dedifferentiation, where cartilage cells lose their specialized characteristics.
• Using horse articular chondrocytes from joints (both metacarpophalangeal and metatarsophalangeal) of various aged horses, the researchers cultured the cells and observed changes in their phenotype (observable characteristics) and gene expression.
• The study found that the cells underwent significant morphological and phenotypic changes when they proliferated in vitro, specifically, they start to lose their specialized state early in culture (P0-P1).

Impact of Aging and Proliferation

• The findings indicate that as the cells were subcultured more (more time in culture), the dedifferentiation became more pronounced.
• The study observed that in older horses, chondrocytes showed signs of dedifferentiation soon after being isolated, this was associated with a reduced capacity to proliferate, implying aging may impact cells’ abilities to retain their specialized state.
• The researchers suggest that the proliferation phase after the third subculture (P3) could be critical for determining whether cells maintain or lose their ability to differentiate. This has significant implications on determining the best culture duration for optimal chondrocyte implantation.

Significance of Mature Cartilage Markers

• The gene expression of major cartilage markers (Col2, Aggrecan, SOX9) was observed to decrease very early (by the first passage) in proliferating chondrocytes, irrespective of age.
• In adult horses, some markers of mature cartilage (Col6, Fibromodulin, SOX6, TGβ1) showed a more stable expression up to the third subculture (P3).
• These markers could be useful in determining the level of dedifferentiation, aiding in identifying the optimal time for implantation of the cells.

Implications for Cartilage Repair and Tissue Engineering

• These findings potentially offer a way to determine the best stage to implant chondrocytes to ensure they retain their differentiated phenotype. The research could enhance the effectiveness of biomaterial scaffolds or chondroinductive signals to maintain or recover the chondrocyte phenotype.
• The identification of levels and time-related expression of these markers could be relevant for the chondroinduction (inducing the differentiation into cartilage) of mesenchymal stem cells, which are commonly used in tissue engineering procedures.