Effects of bacterial cellulose gel on the anorectal resting pressures in rats submitted to anal sphincter injury

Abstract

The aim of this study is to evaluate if a gel of bacterial cellulose gel can revert the loss of anal resting pressure after anorectum sphincter injury in rat model, elected as a model to simulate fecal incontinence. Thirty-nine animals were equally divided into three groups: Control (CG), Sphincter injury plus Saline injection (SG) and Sphincter injury plus Bacterial Cellulose Gel injection (BCG). Anal pressure at rest was assessed for all animal in the three groups using anorectum manometry. Saline and Gel groups were subject to anorectum sphincter injury to reduce the anal pressure at rest. Fifteen days later Saline or Gel was injected into the anorectum, according to their groups. Sixty days later first manometry, the anorectum of all animals were removed and processed histologically. The CG group showed maintenance of their mean anorectal resting pressure levels; SG presented a fall in their mean anorectal resting pressure. The BCG presented a significant elevation of the mean anorectal resting pressure levels, surpassing the pressure of CG. The gel of bacterial cellulose remained at the injection site and was neovascularized, colonized by fibroblasts and dense conjunctive tissue. Those data suggest that BC can be used as a future filling agent treatment for fecal incontinence in clinical trial protocols.

Keywords: Medicine; Surgery.

Fig. 1

Design of perfusion system used for the assessment of anal pressure. A: water; B: mercury; C: air; ΔH: difference between the heights; N10F and N6F: Nelaton probes number 10 and 06, respectively; T: three-way stopcock; Ba: latex balloon and S: 1ml syringe.

Fig. 2

Animal sphincter resection and BCG injection. A: Rat internal and external sphincter anal canal pulled by Kelly clamp curve. B: Anatomy of the anal sphincter after resection of the left semicircle of sphincter complex. It is possible look at the rectum and ischiorectal fat. C: Appearance of the anal canal on the fifteenth post-operative day (D15). And D: BCG injection under direct view and use of speculum.

Fig. 3

Curve of anorectal resting pressures for each 0.1mL added in the balloon and for time points D0, D15 and D45 for the three studied groups. D0: day of the beginning of the study, when sphincter injury was done for SG and BCG. D15 and D45: fifteen and forty-five days after the beginning. CG: Control group; SG: Sphincter injury group; BCG: Bacterial Cellulose gel group. D0 pressures were measured after sphincter injury (except for CG); D15 pressures were measured after injection (except for CG). Control Group has 12 animals. Saline Group has 11 animals. BCG group has 11 animals.

Fig. 4

Difference curve of anorectal resting pressures for the three groups studied between time points D15-D0 and D45-D0. x-axis: Volume of water (mL). BCG: Bacterial cellulose gel injection group.

Fig. 5

Photomicrographies of rectus transverse sections of adult Wistar rats that underwent anorectal injury followed of Bacterial Cellulose (BC) Gel implants. A: hematoxylin and eosin staining under polarized light. B: hematoxylin and eosin staining under plain light. C and D: Details of BC implants in a subtle process of absorption and integration under light microscopy and polarized light, respectively. E and F: BC aspects and cells infiltrate with Trichrome Masson's staining. Legends represent epidermis (x); adipose tissue present in hypodermis (H); Bacterial Cellulose (BC); Rectal external muscular layer (*); Submucosal layer (°); Mucosa layer (m); Intestinal light (lu); Multinucleated giant cells (+); Inflammatory cells (-); Fibroblasts (>). New blood vessels, from the periphery to the center of the implants (→). A and B: Scale bars = 2000μm; C and D: bars = 500μm and E and F: bars = 50μm.