Global Heterogeneity of Glomerular Volume-distribution Evaluated by Three-dimensional Analysis using Synchrotron Radiation X-ray MicroCT

100 %

1 / 1

100 %

1 / 1

A n e s t i m a t e d g l o m e r u l a r v o l u m e w i t h i n t h e r e s t r i c t e d h i s t o l o g i c a l s e c t i o n s h a s b e e n a c o n v e n t i o n a l i n d e x f o r r e n a l d y s f u n c t i o n . S u b t l e a s p e c t s o f g l o m e r u l a r r e m o d e l i n g a r e , h o w e v e r , d i f f i c u l t i e s w i t h t h e c o n v e n t i o n a l a p p r o a c h t h a t compresses three dimensions into two. Therefore, w e a i m e d a t v i s u a l i z i n g t h e e d i m e n s i o n a l ( 3 - D ) g l o m e r u l a r m i c r o - s t r u c t u r e s u s i n g a n X - r a y microCT ( CT ) at beamline BL20B2 , to accurately me as ur e gl om er ul ar vo lu me s th ro ug ho ut a co rt ex and quantitatively evaluate global heterogeneity of t h e v o l u m e - d i s t r i b u t i o n i n a r a t w i t h s p o n t a n e o u s Global Heterogeneity of Glomerular Volume-distribution Evaluated by Three-dimensional Analysis using Synchrotron Radiation X-ray MicroCT diabetes mellitus ( DM ). Using the Otsuka Long Evans Tokushima Fatty ( OLETF ) rats as rats of early stage DM (28 weeks) a n d c o n t r o l r a t s ( L o n g E v a n s T o k u s h i m a F a t t y ; L E T O , o f t h e s a m e a g e , t h e v e s s e l s o f t h e l e f t kidney was filled up with contrast media ( BaSO 4 + I n d i a i n k + 8 % g e l a t i n ) . A s a m p l e d r e n a l c o l u m n ( φ 3 - 4 mm ) was observed using two CT systems; BL20B2 CT for the highest image quality (3 - 6 m in reso luti on) and comm erci ally avai labl e CT (10 m i n r e s o l u t i o n ) ( F i g . 1 ) f o r d a t a a c c u m u l a t i o n . The glomerular volumes more than 400 per sample w e r e c o m p u t e d a n d n o r m a l i z e d t o b o d y w e i g h t . H e t e r o g e n e i t y i n g l o m e r u l a r v o l u m e - d i s t r i b u t i o n was evaluated by coefficient variation ( CV ). By stereomicroscopic observation, we confirmed c o m p l e t e - f i l l i n g o f t h e v e s s e l s w i t h t h e c o n t r a s t media. The glomeruli in OLETF were characterized b y i r r e g u l a r s t e r e o s t r u c t u r e s , w h e r e a s t h o s e i n L E T O w e r e c h a r a c t e r i z e d b y r e g u l a r g l o m e r u l a r (a) CT-imaging of renal cortex (b) 3D-volume rendering image of the glomerulus 20 m Fig. 1. Visualization of renal cortex by high resolution (3 m ) microCT. m 100 μ μ μ μ μ μ μ μ μ 27 s t r u c t u r e . T h e C V o f g l o m e r u l a r v o l u m e w a s s i g n i f i c a n t l y l a r g e r i n O L E T F t h a n L E T O ( 2 . 0 v s . 0 . 1 5 , p < 0 . 0 1 ) . I n a d d i t i o n , a b s o l u t e g l o m e r u l a r volume was larger in OLETF than LETO (2.3 ± 0.2 × 10 6 vs. 1.6 ± 0.2 × 10 6 m 3 , p < 0.01). The normalized g l o m e r u l a r v o l u m e w a s , h o w e v e r , c o m p a r a b l e ( N S ) , i n d i c a t i n g g l o m e r u l a r e n l a r g e m e n t i n e a r l y D M m a y a s s o c i a t e w i t h i n c r e a s e i n b o d y m a s s . Both CT provided similar results. H i g h l y h e t e r o g e n e o u s g l o m e r u l a r v o l u m e - d i s t r i b u t i o n i n D M r a t w a s q u a n t i t a t i v e l y d e m o n s t r a t e d us in g ou r de ve lo pe d 3- D gl om er ul ar mi cr o- st ru ct ur al visualizing method. This technique provides a new aspect for the evaluation of global heterogeneity in g l o m e r u l a r r e m o d e l i n g u n d e r t h e c h r o n i c r e n a l d y s f u n c t i o n , w h i c h m a y p r o v i d e m o r e s e n s i t i v e i n s i g h t i n t o e a r l y c o m p l i c a t i o n s o f d i a b e t i c nephropathy. O n t h e g l o m e r u l a r v o l u m e e v a l u a t i o n , t h e S P r i n g - 8 C T a n d t h e c o n v e n t i o n a l C T s h o w e d t h e s i m i l a r r e s u l t s . H o w e v e r , t h e S P r i n g - 8 C T s y s t e m w i t h t h e h i g h r e s o l u t i o n i s r e q u i r e d f o r evaluation of the more detailed microvasculature. Yasuo Ogasawara Kawasaki Medical School E-mail: ogasawara @ me.kawasaki-m.ac.jp References [1] Yasuo Ogasawara, Eiji Toyota, Tatsuya Kajita, F u m i y u k i S h i g e t o , T a k e s h i M a t s u m o t o , T a k a h i s a Asano and Fumihiko Kajiya, Jpn. J. Med. Electro. & Biol. Eng. 39 ( suppl. ) (2001) 490. [ 2 ] Y a s u o O g a s a w a r a , E i j i T o y o t a , F u m i y u k i S h i g e t o , T a t s u y a K a j i t a , T a k e s h i M a t s u m o t o , H i r o y u k i T a c h i b a n a , H i r o s h i N a k a m o t o , T o k u n o r i Ya m a m o t o a n d K a t s u k u n i F u j i m o t o, J p n . Ci rc ul at io n Journal (2002) - in press. μ μ μ μ μ 28