Development of a novel approach to safely couple the intestine to a distraction-induced device for intestinal growth: use of reconstructive tissue matrix

Biologically inspired approaches to enhance human organoid complexity

Organoids are complex three-dimensional in vitro organ-like model systems. Human organoids, which are derived from human pluripotent stem cells or primary human donor tissue, have been used to address fundamental questions about human development, stem cell biology and organ regeneration. Focus has now shifted towards implementation of organoids for biological discovery and advancing existing systems to more faithfully recapitulate the native organ. This work has highlighted significant unknowns in human biology and has invigorated new exploration into the cellular makeup of human organs during development and in the adult - work that is crucial for providing appropriate benchmarks for organoid systems. In this Review, we discuss efforts to characterize human organ cellular complexity and attempts to make organoid models more realistic through co-culture, transplantation and bioengineering approaches.

Development of an endoluminal intestinal attachment for a clinically applicable distraction enterogenesis device

PURPOSE

Previous methods of distraction enterogenesis have relied upon blind-ending intestinal segments or transmural device fixation, requiring multiple operations and potential bowel injury. We hypothesized that using a novel attachment would allow reversible device coupling to the luminal bowel surface, achieving effective endoluminal distraction.

METHODS

A telescopic hydraulic device was designed with latex balloon attachments covered with high-friction mesh and a dilating fenestrated elastic mask (DFM attachment), allowing mesh-to-mucosa contact only with inflation. Yorkshire pigs underwent jejunal Roux-en-Y limb creation and device placement via jejunostomy. Devices underwent 3 cycles of balloon inflation and hydraulic extension/retraction per day for 7 days and then explanted and studied for efficacy.

RESULTS

DFM attachment allowed reversible, high-strength endoluminal coupling without tissue injury or reduction in bowel perfusion. After 7 day implant, distracted bowel achieved a 44 ± 2% increase in length vs. fed, nondistracted bowel, corresponding to a gain of 7.1 ± 0.3 cm. Distracted bowel demonstrated increased epithelial cell proliferation vs. control bowel. Attachment sites demonstrated villus flattening, increased crypt depth, thicker muscularis mucosa, and unchanged muscularis propria thickness vs.

CONCLUSION

Novel high-strength, reversible attachments enabled fully endoluminal distraction enterogenesis, achieving length gains comparable to open surgical techniques. This approach may allow development of clinically applicable technology for SBS treatment.

Repeated mechanical lengthening of intestinal segments in a novel model

PURPOSE

Currently, animal models used for mechanical intestinal lengthening utilize a single lengthening procedure prior to analysis or restoration back into continuity. Here we developed a novel surgical model to examine the feasibility of repeated lengthening of intestinal segments.

METHODS

A Roux-en-Y jejunojejunostomy with a blind Roux limb was created in rats. An encapsulated polycaprolactone spring was placed into a 1cm segment of the Roux limb. After 4 weeks, a second encapsulated PCL spring was inserted into a 1cm portion of the lengthened segment. After another 4 weeks, the repeatedly lengthened segments were retrieved for histological analyses.

RESULTS

Jejunal segments of the Roux limb were successfully lengthened from 1.0 cm to 2.6 ± 0.7 cm. Four weeks after the second PCL spring placement, 1.0 cm of the previously lengthened segment increased to 2.7 ± 0.8 cm. Stronger mechanical force was required to achieve subsequent re-lengthening. Lengthened and re-lengthened segments had increased smooth muscle thickness and crypt depth when compared to normal jejunal mucosa.

CONCLUSION

Using the Roux-en-Y model, previously lengthened segments of intestine can be successfully re-lengthened. Intestinal segments may be subjected to multiple lengthening procedures to achieve clinically significant length for the treatment of short bowel syndrome.

Development of an endoluminal intestinal lengthening device using a geometric intestinal attachment approach

BACKGROUND

Distraction enterogenesis may provide a novel therapy for short bowel syndrome. Previously described methods have relied on isolated intestinal segments or transmural fixation because of ineffective endoluminal attachment. We hypothesized that a novel approach of geometric coupling between a tapering device and the mesenteric curvature would allow trans-stomal distraction enterogenesis.

METHODS

A catheter device was designed with tapering stiffness, consisting of a stiff catheter with a taper to a flexible latex tip to prevent perforation. Yorkshire pigs underwent creation of a jejunal Roux limb with device placed via jejunostomy. Intestinal attachment was achieved without a substantial decrease in bowel perfusion as measured by laser Doppler. An external clamp was secured at the stoma to provide external fixation of the device. The catheter was advanced 1 cm/day for either 7 or 14 days before explant.

RESULTS

After 7 days, the distracted segment achieved a mean ± SD increase in length of 37 ± 6% versus fed, nondistracted bowel, corresponding to an absolute gain of 10.6 ± 1.7 cm (1.5 cm/day). After 14 days, the Roux limb achieved an 80 ± 2% increase in length versus fed control bowel, corresponding to an absolute gain of 16.8 ± 3.0 cm (1.2 cm/day). No perforation or stoma-related complication occurred.

CONCLUSION

We describe a novel catheter device with tapering stiffness allowing for endoluminal distraction enterogenesis via geometric coupling. This approach may allow development of clinically applicable technology for the treatment of patients with short bowel syndrome.

A novel double-balloon catheter device for fully endoluminal intestinal lengthening

OBJECTIVE

Distraction enterogenesis may provide a novel therapy for short bowel syndrome (SBS). Previously described methods have relied upon isolated intestinal segments or transmural fixation. Our objective was to develop a novel, fully endoluminal device, permitting placement and removal through an enteral stoma or orifice.

METHODS

A flexible device was designed consisting of two latex balloons mounted on coaxial catheters. The inner catheter allowed longitudinal force transmission from an external spring. Yorkshire pigs underwent jejunal Roux limb creation with device placement via jejunostomy. Balloons were inflated to 52 mmHg without significant reduction in bowel perfusion as measured by laser Doppler. The device was explanted after 7 days.

RESULTS

Distracted bowel achieved an increase in length of 26.1 ± 6.1 % vs nondistracted fed bowel. As the device resided in unfed bowel, a 66.7 ± 14.5% increase vs unfed bowel was noted. These corresponded to a gain of 6.3 ± 2.3 cm (0.9 ± 0.3 cm/day) and 12.9 ± 7.6 cm (1.8 ± 1.1 cm/day), respectively. Attachment sites demonstrated occasional epithelial sloughing with no balloon-associated perforation.

CONCLUSION

A novel double-balloon catheter device allows for fully endoluminal distraction enterogenesis. This approach may allow development of clinically applicable technology for the treatment of patients with SBS.

Distraction-induced intestinal growth: the role of mechanotransduction mechanisms in a mouse model of short bowel syndrome

Novel strategies are needed to address the problem of patients with short bowel syndrome. We previously demonstrated a three-fold lengthening of pig bowel after 2 weeks of applied distractive forces, but we have not elucidated the mechanisms facilitating this growth. We used a mouse model of distraction-induced enterogenesis. High molecular weight polyethylene glycol (PEG) osmotically stretched an isolated small bowel segment (PEG-stretch). Significant increases in villus height and crypt depth and in intestinal epithelial cell length and numbers suggested epithelial remodeling in addition to proliferation during enterogenesis. LC-MS/MS analysis showed a two-fold upregulation of α-actinin-1 and -4. We also demonstrated that p-focal adhesion kinase (FAK), FAK, α-actinin, and Rac1 were significantly upregulated and that F-actin was relocalized in PEG-stretch versus controls. Blockade of the phosphotidyl inositol 3' kinase pathway failed to influence the increase in proliferation or decline in apoptosis after stretch, suggesting alternative signaling pathways are used, including MEK and P38MAPK, which were both upregulated during enterogenesis. Our data suggests that several known mechanotransduction pathways drive distraction-induced enterogenesis.