sRANKL (free) Human ELISA (Osteoprotegerin Ligand)

Research topic

Bone and cartilage metabolism

Features

• The free assay time is about 4 hours.
• The kit measures free sRANKL

Storage/Shipping

Store the kit at 2–8°C. Under these conditions, the kit is stable until the expiration date (see label on the box).

Summary

sRANKL, receptor activator of nuclear factor (NF)-κB ligand (also: osteoprotegerin ligand, OPGL), is a part of the TNF superfamily with high similarity to other members of that protein species. (SwissProt Nr. O14788).

Three isoforms are produced by alternate splicing, two type II membrane proteins (ISOFORM 1, 317 AA, and ISOFORM 3, 270 AA), and a secreted molecule (ISOFORM 2, 244 AA). ISOFORM 1 is identical to previously reported RANKL and possesses intracellular, transmembrane, and extracellular domains; ISOFORM 2 does not have the intracellular and transmembrane domains, and ISOFORM 3 does not have the intracellular domain. A soluble form arises by proteolytic processing from membrane isoforms.

Although all forms are bioactive, the membrane-bound proteins seem to be the homeostatic forms, while the production of soluble RANKL signals pathological conditions.

RANKL, RANK, and osteoprotegerin (OPG) have been identified as the key molecular regulation system for bone remodelling. RANKL is the main stimulatory factor for the formation of mature osteoclasts and is essential for their survival. Therefore, an increase in RANKL expression leads to bone resorption and bone loss. RANKL is produced by osteoblastic lineage cells and activated T lymphocytes. It activates its specific receptor RANK, which is located on osteoclasts and dendritic cells. The effects of RANKL are counteracted by OPG, which is secreted by various tissues and acts as an endogenous soluble receptor antagonist.

Imbalances of the RANKL/OPG system have been related to the pathogenesis of Paget’s disease, benign and malignant bone tumors, postmenopausal osteoporosis, rheumatoid arthritis, bone metastases and hypercalcemia. Several studies using animal models have shown that restoring the RANKL/OPG balance (e.g. by administering OPG) reduces the severity of these disorders.

Indication

• Postmenopausal and senile osteoporosis
• Diseases with locally increased bone resorption activity
• Paget´s disease
• Periodontal disease
• Cardiovascular disease, arterial calcification
• Inflammatory diseases
• Immunological disorders
• Arthritis
• Oncology

Assay format

Sandwich ELISA, Biotin-labelled antibody

Sample requirements

5 µl/well

Applications

Plasma-EDTA, Serum

Calibration Curve

Calibration range

0.4 to 20 pmol/l

Limit of detection

Analytical Limit of Detection (LOD) is calculated from the real sRANKL values in wells and is 0.2pmol/l

Limit of quantification

Assay Sensitivity (LOQ) takes the dilution of samples into consideration and is calculated according to the formula:

Assay Sensitivity = Analytical Limit of Detection x sample dilution = 0.2pmol/l x 25 = 5 pmol/l

Intra-assay (Within-Run, n=8)

CV = 7.1 %

Inter-assay (Run-to-Run, n=4)

CV = 7.9 %

Spiking Recovery

5 pmol/l

Cross-Reactivity

104 %