Are the Matrix Metalloproteinases 2 and 9 beeing expressed in the mucosa of the rat small intestine during its intrauterine and postnatal life development ?

Abstract

MMP-2 and MMP-9 are proteins with well stablished roles on the remodeling of tissue during morphogenesis. This study aimed to evaluate the activity and expression of the MMP-2 and MMP-9 in the rat small intestine mucosa layer on 15 th and 18 th days of intratuterine life (i.u.) and at 3rd, 10 th , 17 th, 25 th , and 32 th days after birth (a.b.). Samples were submitted to zimography, immunohistochemistry methods and Masson trichrome staining. Results showed that MMP-2 and MMP-9 were not expressed in the small intestine epithelium during intrauterine life.MMP-9 was immunolocalized in the villi goblet cells and in the lamina propria in cells identified as being the mast cells (a.b.). We concluded that in the i.u. and a.b. life the MMP-2 and MMP-9 were not expressed in the small intestine epithelium. However, after birth, because MMP-9 was expressed in the mast cels present in the lamina propria it may be involved in the remodeling process of the innate immunity that occurs during the small intestine development.key words: rat small intestine, MMP-2, MMP-9, development, mast cells During the suckling and weaning phases, the intestinal epithelium becomes completely developed, and two compartments can be identified; the villi (functional compartment) and the crypts, which are considered the proliferative compartment where cells are produced and differentiated, before their migration to the villi to execute their digestive functions.The suckling phase represents the period from birth until the 16th day of life, where milk is the main food. Around the 17th day, during the third week of life, diet with milk is changed to diet with solid food (weaning phase). Therefore, during the first three weeks after birth, the mucosa layer , specially the epithelium, goes through several morphological and physiological remodeling related to digestive and absorptive processes. These functional changes are produced by a shift in the expression of different enzymes present in the cell membrane like lactase, maltase, sucrase and intestinal alkaline phosphatase (Goldstein et al, 1971; Uezato and Fujita, 1983;Tojyo, 1984; Gomes et al., 2016).However, in this decade it has been demonstrated that another kind of enzymes denominated matrix metalloproteinases seem to have important roles during the development, growth and morphological maturation of different parts of the body like bones (Holmbeck et al, 1999; Yang et al., 2008), vascular system, skeletal muscle (Oh et al., 2004s), kidney and dental structures (Gomes et al., 2010, 2011, Omar et al., 2011, 2017.Metalloproteinases found in the extracellular matrix are denominated matrix metalloproteinases (MMPs) such as MMP-2 and MMP-9 (also denominated gelatinases) or may be anchored in the cell membrane which is denominated membrane matrix metalloproteinase (MT-MMPs). Despite this, there are still few descriptions about the involvement of MMPs in this process concerning to the development of the small intestine (Kurakata et al., 2008; Camargo et al., 2016) and none report regarding ex...