Distraction-induced intestinal enterogenesis: preservation of intestinal function and lengthening after reimplantation into normal jejunum

Abstract

Background: Significant bowel lengthening can occur in an isolated intestinal segment with the use of linearly directed distractive forces, resulting in increased surface area and epithelial cell proliferation. We hypothesized that reimplantation of this lengthened intestine into normal jejunum would preserve this gain in intestinal length and function similar to normal jejunum.

Methods: An intestinal lengthening device was inserted into isolated jejunal segments in pigs, and fully expanded over 8 days. Lengthened segments were then reimplanted into normal intestinal continuity. Pigs were studied after another 28 days. Function was assessed by motility, mucosal enzyme activity, barrier function, and intestinal ion transport.

Results: Lengthened segments were significantly longer than control segments and had nearly 2-fold greater surface area. Bowel lengthening was maintained 4 weeks after reimplantation. Motility after reimplantation was similar to nonoperated pigs. Barrier function, mucosal disaccharidase levels, and electrophysiologic measures declined immediately after lengthening but returned to nearly normal levels 28 days after reimplantation.

Conclusion: Bowel lengthening results in a transient decline in mucosal absorptive function and smooth muscle contractility. However, function approaches that of normal bowel after reimplantation into enteric flow. These data may support the use of this technique as a potential new option for the treatment of patients with short bowel syndrome.

Figure 1

Schematic diagram of the operative technique and post-operative radiographic image.

1. Appearance of bowel at the beginning of the lengthening procedure. Note the single catheter shown is actually two, one drain and one infusion catheter.

2. Appearance of bowel at time of harvesting the lengthening segment during the re-implantation surgery.

3. Appearance of bowel after re-implantation. Note sutures on both ends are tagged with non-absorbable sutures for ease of identificatiton.

4. Radiographic image of a small bowel follow through. Note arrows represent the start of the small bowel, and was used to time the transit through small bowel.

Figure 2

Representative manometric tracing from a pig. Note 3 phases are shown: baseline prior to infusion of any substances; bethanechol; and carbachol, with one balloon within the mid-section of the lengthened bowel segment 4 weeks after re-implantation and one balloon in a non-operated area of jejunum. Note the degree of contractility and duration of this elevated contractile phase are similar between re-implanted and control segments of bowel. Time is shown in seconds, and at least 10 mins of level pressure readings was given prior to moving to the next phase. Pressure is given in cm of water.

Figure 3

Summary of isolated smooth muscle cell contraction studies comparing non-surgically manipulated cells from jejunum, immediately after lengthening and at the time of harvesting post-re-implantation. Results are given as the mean percent (±SD) contraction after stimulation by acetylcholine.

Figure 4

Epithelial cell proliferation

1. Epithelial cell proliferation is expressed as the mean percent of BrdU positive cells per crypt (±SD). BrdU was given 4 hours prior to harvesting of intestinal segments. Results are mean of at least 16 crypts per pig.

2. Representative histologic images of jejuna mucosa with BrdU staining. Magnification 40X.

Figure 4

Epithelial cell proliferation

1. Epithelial cell proliferation is expressed as the mean percent of BrdU positive cells per crypt (±SD). BrdU was given 4 hours prior to harvesting of intestinal segments. Results are mean of at least 16 crypts per pig.

2. Representative histologic images of jejuna mucosa with BrdU staining. Magnification 40X.

Figure 5

Assessment of epithelial barrier function

1. Passage of ³H-mannitol is shown as the percent of permeation of a tracer molecule from the mucosal to serosal surfaces. Results are cumulative and collected over a 90 min period. Note preserved barrier function between groups, no significant differences were detected.

2. Transepithelial resistance (TER) is shown as the Ω/cm² for all 3 study groups over a 90 minute incubation period in Ussing chambers. Note a significant loss of TER in the Lengthened group. Whereas, the re-implanted group regained TER levels similar to native jejunum.

Figure 5

Assessment of epithelial barrier function

1. Passage of ³H-mannitol is shown as the percent of permeation of a tracer molecule from the mucosal to serosal surfaces. Results are cumulative and collected over a 90 min period. Note preserved barrier function between groups, no significant differences were detected.

2. Transepithelial resistance (TER) is shown as the Ω/cm² for all 3 study groups over a 90 minute incubation period in Ussing chambers. Note a significant loss of TER in the Lengthened group. Whereas, the re-implanted group regained TER levels similar to native jejunum.

Figure 6

Changes in the isoelectric current (ISC) are shown (based on change from steady state baseline and given as µA/cm²) for the 3 study groups in response to glucose (A) and carbachol (B). Note a loss of responsiveness to glucose and carbachol in the Lengthened group, and a return to native jejunum levels in the Re-implanted group for glucose, but not carbachol. Values are mean ±SD, and not significantly different between the groups.

Figure 7

Tight junction molecules, ZO-1, claudin-1 and occludin, abundance in each group shown as mean ±SD, and representative immunoblots for each group. Note a significant loss of ZO-1 and claudin-1 in the Lengthened group, and a partial recovery in the re-implanted group. Note no significant changes for occludin.

Figure 8

Representative figures of tight junction staining (occludin and ZO-1) for each study group. Original magnification was 20X, staining was performed on freshly frozen tissue and imaging intensity was matched between samples. Note the loss of intensity and actual absence between some cells in the Lengthened group compared to the other two groups.