title: Age-related morphological regression of myelinated fibers and capillary architecture of distal peripheral nerves in rats.
abstract: Regression of myelinated peripheral nerve fibers in the lower extremities contributes to sarcopenia and balance dysfunction in normal aging. This subclinical regression of myelinated fibers (MFs) is heavily influenced by alterations in microvasculature, though the mechanism underlying these age-related degenerative phenomena remains unclear. The aim of the present study was to examine age-related regressions in myelinated distal peripheral nerve fibers as well as capillary architecture in rats using both morphological and histochemical methods.
  
  
  
  MFs were categorized into tertiles of 'large', 'medium', and 'small' sizes based on the distribution of MF diameters. A two-way ANOVA was used to assess effects of fiber size (large/medium/small) and group (young/elderly) on myelin thickness, axon diameter, myelin perimeter, axon perimeter, and G-ratio (axon diameter/fiber diameter). Significant main effects were observed for both MF size and group with respect to all dimensions except for G-ratio. Values for fiber diameter (P < 0.01), myelin thickness (P < 0.01), axon diameter (P < 0.01), myelin perimeter (P < 0.01), and axon perimeter (P < 0.01) were significantly lower than those in the young group. Additionally, mean capillary diameter and number of microvascular branch points were significantly lower in the elderly group than in the young group.
  
  
  
  The present study demonstrated that spontaneous age-related regression predominantly occurs for all fiber sizes in the distal peripheral nerves and the capillary architecture. The results of the present study further suggest that both the distal MFs and capillaries in the peripheral nerve may simultaneously regress with aging.
authors.affiliation: Department of Physical Therapy, Faculty of Health Sciences, Kyoto Tachibana University, 34 Oyakeyamada, Yamashina Ward, Kyoto City, Kyoto, 607-8175, Japan. sakita@tachibana-u.ac.jp.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sakita
authors.affiliation: Department of Physical Therapy, Faculty of Health Care Sciences, Himeji-Dokkyo University, 7-2-1 Kamiono, Himeji City, Hyogo, 670-0896, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Murakami
authors.affiliation: Department of Rehabilitation Science, Kobe University Graduate School of Health Sciences, 7-10-2 Tomogaoka, Suma Ward, Kobe City, Hyogo, 654-0412, Japan.
authors.forename: Hidemi
authors.initials: H
authors.lastname: Fujino
mesh_terms: D000375:Aging / Q000473:pathology*; D000704:Analysis of Variance; D000818:Animals; D001369:Axons / Q000473:pathology; D002196:Capillaries / Q000473:pathology*; D048429:Cell Size; D021621:Imaging, Three-Dimensional; D008297:Male; D018613:Microscopy, Confocal; D009186:Myelin Sheath / Q000473:pathology*; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D010525:Peripheral Nerves / Q000098:blood supply / Q000473:pathology*; D011897:Random Allocation; D017208:Rats, Wistar
keywords: Capillary; Myelinated fiber; Three-dimensional image; Tibial nerve