tissue optical clearing and its application in vision science

Structural and functional analysis of cells and subcellular organelles at high resolution is one of the foundations of life science research. however, deep microscopic examination of intact tissues is limited because of biologic samples light scattering and light absorption properties. traditionally, adjacent tissue sections are studied, and a three-dimensional image of the whole sample is reconstructed to overcome such limitations. yet, mechanical tissue sectioning disrupts the continuity of neuronal and vascular elements, and three-dimensional reconstruction of the successive sections is labor-intensive, time-consuming, and subject to errors and artifacts. tissue optical clearing provides a solution to this obstacle by equalizing tissue s refractive index to the surrounding medium to minimize light scattering and absorption and enabling microscopic studying of intact, uncut tissue. however, because of the heavily pigmented layers surrounding the retina and the retina s delicate structure that is susceptible to damage by current, chemically harsh methods, most tissue optical clearing approaches have limited applications in vision science. this presentation will review the optical and physiological principles of tissue optical clearing, commonly-used methods, and methods applicable to central nervous system tissues. then, i will introduce a novel tissue clearing method using 2,2′-thiodiethanol (tde) combined with advanced labeling and 3d microscopy techniques as applied to intact whole retina and retina flat-mount samples. finally, the advantages and limitations of the tde method will be discussed.