Real-time atomic force fluorescence microscopy on living cells

ABSTRACT The reaction of bone cells after mechanical stimulation is a key issue in understanding the origins of osteoporosis. Weinvestigate mechanical stimulation of osteoblasts and their reaction with a new combination of an atomic force apparatuswith a fluorescence microscope. First measurements on the mechanically induced calcium response of osteoblasts arepresented. The average threshold force for stimulation is 300nN and the dynamics of the calcium response is in the severaltens of seconds range.Keywords: Atomic force microscope (AFM), calcium dynamics, osteoblasts, mechanotransduction 1. INTRODUCTION As for many other tissues and organisms, bone adapts its shape and structure according to the prevailing mechanicalenvironment. The mechanically stimulated remodeling of bone is generally accepted, as for other organisms, to be regulatedon the cellular level. Presently the mechanisms with which a bone cell transduces mechanical forces into a biochemicalsecond messenger are not completely understood and it is not known in how far the transduction mechanism is similar to themechanical transducing systems of sensory systems which are relatively well described. A number of different techniqueshave been introduced into the field for mechanical stimulation of cells, most of them are not well defined, and/or do notreproduce physiological amplitudes or frequencies. Different cell stretching systems, fluid shear flow and magnetic beadsystems have all been used in different modes and amplitudes