ATOMIC-FORCE MICROSCOPY OF RENAL-CELLS - LIMITS AND PROSPECTS

In this brief review, we present three-dimensional images of living Ma din-Darby canine kidney (MDCK) cells and CV-1 cells that illustrate th e possibilities and limits in the use of atomic force microscopy (AFM) for studying the topography of the cell surfaces and of isolated biol ogical membranes. We show that microvilli can be imaged at the surface of living epithelial cells. However, when these microvilli are abunda nt and close to each other, the geometry of the AFM tip only allows an access to the upper part of the structures and precludes nanometer ra nge imaging of the cell surface. Such a nanometer range imaging was ob tained with other cell types like CV-1 cells and with isolated biologi cal membranes. It reveals that protruding particles 5 to 60 nm xy size , likely corresponding to membranes proteins, occupy most of the membr ane surface. These images indicate that the AFM already gives an acces s to the cell surface structure at the mesoscopic scale, which constit utes a major step for the understanding of the structure-function rela tionships in membranes. Perspectives for a further step, the imaging a t molecular resolution of membranes, are discussed.