Production and characterization of monoclonal antibodies to human sclerostin

Scale-up production and characterization of anti-human cardiac troponin I monoclonal antibody in ascitic fluid of balb/c mice

The Human Cardiac Troponin I (hcTnI) is a 210 amino acid protein, 23 kDa in molecular weight. This biomarker is commonly used to diagnose myocardial infarction, micro injury, and acute coronary syndrome (ACS) in patients referring to emergency departments. The American Heart Association (AHA) and European Society of Cardiology (ESC) proposed troponin I as the gold biomarker for early detection of heart attack, especially in myocardial infarction (MI). Therefore, developing monoclonal antibodies against this biomarker could help in for early detection of heart attack. Hybridoma technology is a well-known technique introduced to produce monoclonal antibodies in specialized cells. The aim of this study was to produce large scale of monoclonal antibody against human cardiac troponin I using Hybridoma technology in order to design a diagnostic kit. The monoclonal antibody was produced using conventional Hybridoma technology in ascitic fluid of mouse and characterized for its ability to detect Human Cardiac Troponin I in a rapid test system. The results indicate the successful detection of Troponin I using the obtained monoclonal antibody. According to the achieved results it seems that ascites production of monoclonal antibody is very versatile, inexpensive, and economically useful for monoclonal antibody production.

The sclerostin-bone protein interactome

The secreted glycoprotein, sclerostin alters bone formation. To gain insights into the mechanism of action of sclerostin, we examined the interactions of sclerostin with bone proteins using a sclerostin affinity capture technique. Proteins from decalcified rat bone were captured on a sclerostin-maltose binding protein (MBP) amylose column, or on a MBP amylose column. The columns were extensively washed with low ionic strength buffer, and bound proteins were eluted with buffer containing 1M sodium chloride. Eluted proteins were separated by denaturing sodium-dodecyl sulfate gel electrophoresis and were identified by mass spectrometry. Several previously unidentified full-length sclerostin-interacting proteins such as alkaline phosphatase, carbonic anhydrase, gremlin-1, fetuin A, midkine, annexin A1 and A2, and collagen α1, which have established roles in bone formation or resorption processes, were bound to the sclerostin-MBP amylose resin but not to the MBP amylose resin. Other full-length sclerostin-interacting proteins such as casein kinase II and secreted frizzled related protein 4 that modulate Wnt signaling were identified. Several peptides derived from proteins such as Phex, asporin and follistatin that regulate bone metabolism also bound sclerostin. Sclerostin interacts with multiple proteins that alter bone formation and resorption and is likely to function by altering several biologically relevant pathways in bone.

Identification of a DNA aptamer that inhibits sclerostin's antagonistic effect on Wnt signalling

Sclerostin is an extracellular negative regulator of bone formation that is a recognized therapeutic target for osteoporosis therapy. In the present study, we performed DNA aptamer selection against sclerostin, then characterized aptamer-sclerostin binding and the ability to inhibit sclerostin function in cell culture. We show that a selected DNA aptamer was highly selective for binding to sclerostin with affinities in the nanomolar range as determined by solid-phase assays and by isothermal titration calorimetry. Binding between sclerostin and the aptamer was exothermic and enthalpically driven. CD confirmed that the aptamer had temperature-dependent parallel G-quadruplex characteristics. The aptamer was stabilized with 3' inverted thymidine to investigate efficacy at inhibiting sclerostin function in cell culture. The stabilized DNA aptamer showed potent and specific dose-dependent inhibition of sclerostin's antagonistic effect on Wnt activity using a reporter assay. Taken together, the present findings suggest an alternative approach to inhibiting sclerostin function with therapeutic potential.

Sclerostin binds and regulates the activity of cysteine-rich protein 61

Sclerostin, a secreted glycoprotein, regulates osteoblast function. Using yeast two-hybrid and direct protein interaction analyses, we demonstrate that sclerostin binds the Wnt-modulating and Wnt-modulated, extracellular matrix protein, cysteine-rich protein 61 (Cyr61, CCN1), which regulates mesenchymal stem cell proliferation and differentiation, osteoblast and osteoclast function, and angiogenesis. Sclerostin was shown to inhibit Cyr61-mediated fibroblast attachment, and Cyr61 together with sclerostin increases vascular endothelial cell migration and increases osteoblast cell division. The data show that sclerostin binds to and influences the activity of Cyr61.