Figure 5. Protein expression in articular chondrocytes from untreated and treated MPS VI rats.

(A) MPS VI rats were subjected to the ERT or combined ERT/anti-TNF-alpha treatment for 8 months, as described in the text (n = 8/group). The animals were euthanized 2 days after the last injection, and articular chondrocytes were isolated and processed for western blotting. As shown in this representative experiment, ERT alone increased expression of collagen X, and to a more modest degree collagen IIA1. Similar observations were seen in the combined treatment group, except that the levels of collagen IIA1 expression were even more pronounced. To confirm these observations, immunofluorescent microscopic analysis of collagen IIA1 was carried out on articular cartilage sections from untreated, ERT-treated, and combined treatment animals (B). As evident in this figure, higher collagen IIA1 expression (red) was present in the combined treatment group, similar to normal. The expression of the apoptosis marker, PARP, also was examined in the treated and control animals by western blotting, and was only reduced by combined treatment. This is consistent with our previous work showing that anti-TNF-alpha therapy reduced TUNEL staining in articular chondrocytes of the MPS VI rats [18]. In addition, the levels of the aggrecanase, ADAMTS5, which is elevated in MPS VI, was reduced by both treatment protocols.