Annals of Anatomy 196 (2014) 441–448 Contents lists available at ScienceDirect Annals of Anatomy journal homepage: www.elsevier.de/aanat Research article Changes in the connective tissue sheath of Wistar rat nerve with aging Marcelo Augusto Marretto Esquisatto a,∗ , Andrea Aparecida de Aro b , Haline Ballestero Fêo b , Laurecir Gomes b a Biomedical Sciences Graduate Program, Hermínio Ometto University Center – UNIARARAS, Av. Dr. Maximiliano Baruto 500, PC 13607-339 Araras, SP, Brazil b Department of Functional and Structural Biology, IB, State University of Campinas – UNICAMP, Av. Bertrand Russel, s/no Cx Postal 6109, PC 13083-865 Campinas, SP, Brazil article info Article history: Received 23 March 2014 Received in revised form 2 August 2014 Accepted 13 August 2014 Keywords: Nerve Connective sheath Aging Extracellular matrix Metalloproteinases abstract The alterations due to aging in the peripheral nerves can affect the physiology of these structures. Thus, the purpose of the present study was to describe the activity of the MMP-2 and MMP-9, as well as the structure and composition of the extracellular matrix of the rat sciatic nerve during maturation and aging. Our results have shown that the extracellular matrix of the sciatic nerve of 30-, 180- and 730- day-old Wistar rats present ultrastructural, morphometrical and biochemical changes during aging. The perineurium was the structure most affected by age, as evidenced by a decrease in thickness and in collagen fibril content. Cytochemical analysis detected proteoglycans in the basal membrane of Schwann cells and around perineural cells, as well as on the collagen fibrils of the perineurium and endoneurium at all ages. Biochemical analyses showed that the quantity of non-collagenous proteins was higher in 730- day-old animals compared to other ages, while the uronic acid content was higher in 30-day-old animals. Morphometrical analysis detected greater numbers of myelinated fibers and increased myelin thickness in 180-day-old animals. Zymography analysis detected greater amounts and activity of MMP-2 and MMP- 9 in 180- and 730-day-old animals compared to younger rats. In conclusion, our results showed changes in the structural organization and composition of extracellular matrix of the sciatic nerve during aging, such as increase in the non-collagenous protein content and higher MMP-2 and MMP-9 activity, decrease in uronic acid concentration and in collagen fibril content in the perineurium, as well as degeneration of nerve fibers. © 2014 Elsevier GmbH. All rights reserved. 1. Introduction The peripheral nerve has three connective tissue sheaths called the epineurium, perineurium and endoneurium, which create a microenvironment providing support to the nerve fibers and main- taining their physiology (Cavallotti et al., 2003). The endoneurial connective tissue and the Schwann cell-axon units of periph- eral nerves are surrounded by the perineurium (Sladjana et al., 2008). The endoneurium contains capillaries, mast cells and col- lagen fibrils produced by fibroblasts and Schwann cells, which release neurotrophic factors during the development and regener- ation of the nerve (Micheal et al., 2003). The perineurium isolates ∗ Corresponding author at: Biomedical Sciences Graduate Program, Hermínio Ometto University Center – UNIARARAS, Av. Dr. Maximiliano Baruto, 500 Jd. Uni- versitário, Araras, SP 13607-339, Brazil. Tel.: +55 19 3543 1440. E-mail addresses: marcelosquisatto@uniararas.br, mame98@linkway.com.br (M.A.M. Esquisatto). the individual nerve fascicles from the epineurial connective tis- sue, and it is composed of basement membranes that surround the perineurial cell layers on both sides (Cavallotti et al., 2003; Micheal et al., 2003). Basement membranes are specialized extra- cellular matrix (ECM) structures composed of type IV collagen associated with proteoglycans (PGs), which are constituted of long-chain glycosaminoglycans (heteropolymers of uronic acid and n-acetyl-glucosamines) (Barros et al., 2011); and non-collagenous proteins (NCPs), such as laminin and fibronectin which provide tis- sue architectonics and influence cell behavior (Podratz et al., 2001; El-Sayyad et al., 2014). The concentric layers of the perineurium are divided by collagen fibril bundles that maintain intrafascic- ular pressure, preserving endoneurial osmotic homeostasis. The perineurium also contains blood vessels, numerous pinocytotic vesicles and phosphorylated enzymes, indicating their role as an active metabolic diffusion barrier. The outer connective tissue sheath is the epineurium, which is composed of dense irregular connective tissue with abundant collagen fibrils and elastic fibrils, fibroblasts, mast cells and adipose cells (Barros et al., 2011). http://dx.doi.org/10.1016/j.aanat.2014.08.005 0940-9602/© 2014 Elsevier GmbH. All rights reserved.