POSTNATAL VASCULAR DEVELOPMENT IN THE LATERAL WALL OF THE COCHLEAR DUCT OF GERBILS - QUANTITATIVE-ANALYSIS BY ELECTRON-MICROSCOPY AND CONFOCAL LASER MICROSCOPY

The development of the capillary network in the stria vascularis and i n the underlying spiral ligament of gerbils was systematically and qua ntitatively investigated by conventional electron microscopy and confo cal laser microscopy in association with vascular labeling with fluore scent gelatin. The developmental changes of capillaries in the lateral wall were observed as the following series of events. (i) At 0 days a fter birth (DAB) capillaries already existed in the spiral ligament as a network. (ii) At 3-9 DAB the capillary network developed into two l ayers starting from the scala vestibuli side to the scala tympani side ; one layer was located in the stria and the other in the spiral ligam ent. (iii) At 9 DAB capillaries in the stria became separated from the spiral ligament, and the capillary network consisting of a two-layere d structure was complete. (iv) Total capillary length and capillary de nsity in the lateral wall increased until 9 DAB and leveled off therea fter, but changes in the relative position of capillaries in the stria toward the luminal surface of marginal cells continued until 31 DAB. On the basis of the above observations, we propose two possible mechan isms underlying the vascular development in the lateral wall: (i) the formation of new vasculature (angiogenesis), and (ii) changes in the p osition of cellular components relative to capillaries in association with the differentiation and maturation of marginal cells and intermed iate cells. (C) 1998 Elsevier Science B.V. All rights reserved.