Anneke M Sijbers

Disruption of the Cathepsin K Gene Reduces Atherosclerosis Progression and Induces Plaque Fibrosis but Accelerates Macrophage Foam Cell Formation

Background— Cathepsin K (catK), a lysosomal cysteine protease, was identified in a gene-profiling experiment that compared human early plaques, advanced stable plaques, and advanced atherosclerotic plaques containing a thrombus, where it was highly upregulated in advanced stable plaques. Methods and Results— To assess the function of catK in atherosclerosis, catK−/−/apolipoprotein (apo) E−/− mice were generated. At 26 weeks of age, plaque area in the catK−/−/apoE−/− mice was reduced (41.8%) owing to a decrease in the number of advanced lesions as well as a decrease in individual advanced plaque area. This suggests an important role for catK in atherosclerosis progression. Advanced plaques of catK−/−/apoE−/− mice showed an increase in collagen content. Medial elastin fibers were less prone to rupture than those of apoE−/− mice. Although the relative macrophage content did not differ, individual macrophage size increased. In vitro studies of bone marrow derived–macrophages confirmed this observation. Scavenger receptor–mediated uptake (particularly by CD36) of modified LDL increased in the absence of catK, resulting in an increased macrophage size because of increased cellular storage of cholesterol esters, thereby enlarging the lysosomes. Conclusions— A deficiency of catK reduces plaque progression and induces plaque fibrosis but aggravates macrophage foam cell formation in atherosclerosis.

Least absolute regression network analysis of the murine osteoblast differentiation network

MOTIVATION We propose a reverse engineering scheme to discover genetic regulation from genome-wide transcription data that monitors the dynamic transcriptional response after a change in cellular environment. The interaction network is estimated by solving a linear model using simultaneous shrinking of the least absolute weights and the prediction error. RESULTS The proposed scheme has been applied to the murine C2C12 cell-line stimulated to undergo osteoblast differentiation. Results show that our method discovers genetic interactions that display significant enrichment of co-citation in literature. More detailed study showed that the inferred network exhibits properties and hypotheses that are consistent with current biological knowledge.

Gene Array Analysis of Bone Morphogenetic Protein Type I Receptor-Induced Osteoblast Differentiation†

The genomic response to BMP was investigated by ectopic expression of activated BMP type I receptors in C2C12 myoblast using cDNA microarrays. Novel BMP receptor target genes with possible roles in inhibition of myoblast differentiation and stimulation of osteoblast differentiation were identified.

Noninvasive diagnosis of ruptured peripheral atherosclerotic lesions and myocardial infarction by antibody profiling

Novel biomarkers, such as circulating (auto)antibody signatures, may improve early detection and treatment of ruptured atherosclerotic lesions and accompanying cardiovascular events, such as myocardial infarction. Using a phage-display library derived from cDNAs preferentially expressed in ruptured peripheral human atherosclerotic plaques, we performed serological antigen selection to isolate displayed cDNA products specifically interacting with antibodies in sera from patients with proven ruptured peripheral atherosclerotic lesions. Two cDNA products were subsequently evaluated on a validation series of patients with peripheral atherosclerotic lesions, healthy controls, and patients with coronary artery disease at different stages. Our biomarker set was able to discriminate between patients with peripheral ruptured lesions and patients with peripheral stable plaques with 100% specificity and 76% sensitivity. Furthermore, 93% of patients with an acute myocardial infarction (AMI) tested positive for our biomarkers, whereas all patients with stable angina pectoris tested negative. Moreover, 90% of AMI patients who initially tested negative for troponin T, for which a positive result is known to indicate myocardial infarction, tested positive for our biomarkers upon hospital admission. In conclusion, antibody profiling constitutes a promising approach for noninvasive diagnosis of atherosclerotic lesions, because a positive serum response against a set of 2 cDNA products showed a strong association with the presence of ruptured peripheral atherosclerotic lesions and myocardial infarction.

Unravelling the murine osteoblast differentiation pathway by network structure analysis using time-series microarray data

We propose a reverse engineering scheme to discover genetic regulation from genome-wide transcription data that monitors the dynamic transcriptional response after a change in cellular environment. The interaction network is estimated by solving a linear model using simultaneous shrinking of the least absolute weights and the prediction error. The proposed scheme has been applied to the murine C2C12 cell-line stimulated to undergo osteoblast differentiation. Results show that our method discovers genetic interactions that display significant enrichment of co-citation in literature. More detailed study showed that the inferred network exhibits properties and hypotheses that are consistent with current biological knowledge.