Our proprietary in vitro osteoblast assays have been designed for pharmacodynamic testing of new anabolic agents against osteoporosis before entering animal studies. They involve culturing mesenchymal progenitor cells that are first allowed to differentiate into mature osteoblasts, enabling to study direct effects of drug candidates on osteoblast differentiation. The culture period can then be extended to allow the formed osteoblasts to form bone nodules, enabling to study effects of drug candidates on bone forming activity of mature osteoblasts.

Intracellular alkaline phosphatase (ALP) is measured as an index of osteoblast differentiation at the end of the osteoblast differentiation period, and the amount of calcium deposited into the formed bone nodules is determined as an index of inorganic bone matrix formation after extending the culture period for an additional 5 days. Further accuracy can be achieved by measuring secreted N-terminal propeptide of type I procollagen (PINP) released into the culture medium as an index of organic bone matrix formation.

We use mouse mesenchymal progenitor cells (KS483) that are cultured on collagen coated wells in the presence of ascorbic acid and β-glycerophosphate. Our bone formation assays are excellent tools for fast and reliable efficacy testing of new anabolic therapies against osteoporosis. They are also the most sensitive commercially available estrogen responsive in vitro pharmacodynamic testing platform.