Unique Running Pattern and Mucosal Morphology Found in the Colon of Cotton Rats

Tsolmon Chuluunbaatar; Osamu Ichii; Teppei Nakamura; Takao Irie; Takashi Namba; Md Rashedul Islam; Yuki Otani; Md Abdul Masum; Yuko Okamatsu-Ogura; Yaser Hosny Ali Elewa; Yasuhiro Kon

doi:10.3389/fphys.2020.587214

Unique Running Pattern and Mucosal Morphology Found in the Colon of Cotton Rats

Front Physiol. 2020 Oct 26:11:587214. doi: 10.3389/fphys.2020.587214. eCollection 2020.

Authors

Tsolmon Chuluunbaatar^{1

2}, Osamu Ichii^{1

3}, Teppei Nakamura^{1

4}, Takao Irie^{5

6}, Takashi Namba¹, Md Rashedul Islam^{1

7}, Yuki Otani¹, Md Abdul Masum^{1

8}, Yuko Okamatsu-Ogura⁹, Yaser Hosny Ali Elewa^{1

10}, Yasuhiro Kon¹

Affiliations

¹ Laboratory of Anatomy, Department of Basic Veterinary Sciences, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
² Department of Basic Science of Veterinary Medicine, School of Veterinary Medicine, Mongolian University of Life Science, Ulaanbaatar, Mongolia.
³ Laboratory of Agrobiomedical Science, Faculty of Agriculture, Hokkaido University, Sapporo, Japan.
⁴ Department of Biological Safety Research, Chitose Laboratory, Japan Food Research Laboratories, Chitose, Japan.
⁵ Medical Zoology Group, Department of Infectious Diseases, Hokkaido Institute of Public Health, Sapporo, Japan.
⁶ Laboratory of Veterinary Parasitic Diseases, Department of Veterinary Sciences, Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan.
⁷ Department of Surgery and Theriogenology, Faculty of Animal Science and Veterinary Medicine, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh.
⁸ Department of Anatomy, Histology and Physiology, Faculty of Animal Science and Veterinary Medicine, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh.
⁹ Laboratory of Biochemistry, Department of Basic Veterinary Sciences, Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
¹⁰ Department of Histology, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.

Abstract

Cotton rats are one of the experimental rodents used for testing different infectious and non-infectious diseases, including gastrointestinal tract pathology. However, their intestinal morphological characteristics are still poorly understood. Here, we clarified the anatomical and histological characteristics of the cecum and ascending colon (AC) of young (1-3-month old), adult (4-6-month old), and old (10-12-month old) cotton rats. The large intestine (LI) in cotton rats is composed of the cecum, AC, transverse and descending colons, and rectum, and is similar to that of other mammals. The AC begins with a double or triple spiral loop-like flexure (SLLF) and ends with a coupled horseshoe-like flexure (HSLF). A single longitudinal mucosal fold (SLMF) was found at the beginning of the AC along the mesentery line and developed with age. Furthermore, the SLMF contained several lymphatic nodules (LNs), indicating their role in digestive and immunological functions. Small and large protuberant LNs were found in the cecum and SLLF, respectively, whereas thin and flat LNs were observed in the HSLF and transverse colon, respectively. Regarding sex-related differences, adult females had a significantly longer AC with a higher number of SLLFs compared to males. The SLMF length and LN number were also longer and higher, respectively, in adult females compared to adult males. These are crucial findings, indicating the presence of sex-related differences in the morphology of the LI in cotton rats, and ours is the first study to discover a sex difference in the mammalian LI lining. Our study clarified the unique morphology of the LI in cotton rats, which could serve as the principal model for elucidating species-specific digestive tract functions and gastrointestinal disorders.

Keywords: colon; cotton rat; large intestine; longitudinal fold; morphology; sex difference.