Osteoarthritis (OA) mainly affects the articular cartilage covering the bones. In this thesis we investigated the relation between levels of inflammatory mediators, genes involved in their... Show moreOsteoarthritis (OA) mainly affects the articular cartilage covering the bones. In this thesis we investigated the relation between levels of inflammatory mediators, genes involved in their regulation and the disease status of OA. We investigated the role of genetic variation at the interleukin(IL)-1 gene cluster in the innate bio-availability of IL-1beta. A haplotype that associated to low innate bio-availability also associated to higher hand OA scores. Although this is counterintuitive with respect to the generally accepted hypothesis that a pro-inflammatory status is detrimental to the cartilage it underlines a complex relationship between inflammation and OA. For the C-reactive protein we identified a haplotype associated to high CRP levels as well as to severe hand OA, which is more in line with expected directions of associations. Analysis of baseline cytokine and chemokine levels indicated that chemokine levels associated to hand OA scores, again with low levels associated to high OA scores. In a follow up functional genomic analysis of a previously identified OA susceptibility gene (DIO2) in our studies we show that the risk allele of this gene is transcribed at higher levels as compared to the non-risk allele. Furthermore, we showed increased DIO2 protein presence in OA affected cartilage. Show less
Osteoarthritis (OA) refers to a heterogeneous group of conditions. This thesis focuses on OA with a hereditary background; Familial OA at multiple joint sites and radiological hand OA at middle age... Show moreOsteoarthritis (OA) refers to a heterogeneous group of conditions. This thesis focuses on OA with a hereditary background; Familial OA at multiple joint sites and radiological hand OA at middle age. The main objective is to identify risk factors that play a role in the development of OA in order to gain further insight in the aetiology of OA. The secondary objective is to investigate factors that determine the outcome in OA. This thesis provides evidence that familial clustering of symptomatic OA is most prominent for hand and hip OA. In search for genetic risk factors, we present data suggesting that a proportion of the genetic susceptibility for OA at multiple sites is encoded by variation in innate cytokine activity. Further, we find HLA-DR antigens to be associated with radiological hand OA. In addition to genetic risk factors, this thesis demonstrates that other systemic risk factors such as hormonal status and local factors, to be important in the susceptibility of familial OA at multiple sites, underscoring the multicausal etioliology of this phenotype. Finally, this thesis addresses the resulting disability from OA. Using the International Classification of Functioning, Disability and Health as framework, we show illness perceptions and mental health to be important modifying factors in OA in the hands and lower extremities. Show less
