title: Optical tissue window: a novel model for optimizing engraftment of intestinal stem cell organoids.
abstract: BACKGROUND
  Intestinal malabsorption disorders and short bowel syndrome lead to significant morbidity. We recently demonstrated that grafting of intestinal organoids can grow a bioengineered intestinal neomucosa and cure bile acid malabsorption in rats. Now we have developed a novel system that permits direct observation of intestinal organoids in vivo to optimize conditions for engraftment.
  
  
  METHODS
  Optical Windows were created in C57BL/6J mice by externalizing an omental pedicle into a dorsal skin flap chamber. Following creation of windows, 5000 intestinal organoids from green-fluorescent protein transgene (GFP)+ donor mice were seeded directly either on omentum or on polyglycolic acid (PGA) disks that had been placed on omentum at 1 or 5 days. Engraftment of green fluorescent cells was evaluated on postseeding days 1, 3, 5, 7, 10, 12, and 21 using fluorescence microscopy.
  
  
  RESULTS
  An initial group had seeding onto omentum (n = 5) or biopolymer disks (n = 5) on postoperative day 1. After 7 days, there was mucosal cell engraftment onto omental tissue and biopolymers. GFP+ organoids engrafted significantly better when seeded onto biopolymers compared to omentum (P < 0.05). In a second study with increased sample size (n = 24) up to day 12, all four groups demonstrated adherence and growth. However, GFP+ organoids seeded onto delayed PGA biopolymer demonstrated significantly better engraftment (P < 0.05).
  
  
  CONCLUSIONS
  This novel system allows continuous in vivo observation of engrafted cells that are seeded on externalized omentum. The use of PGA mesh biopolymer may improve engraftment of intestinal organoids.
authors.affiliation: Department of Surgery, VA Greater Los Angeles Health Care System, University of California at Los Angeles, Los Angeles, California 90024, USA. dcchen@mednet.ucla.edu
authors.forename: David C
authors.initials: DC
authors.lastname: Chen
authors.forename: Vatche G
authors.initials: VG
authors.lastname: Agopian
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Avansino
authors.forename: Jane K
authors.initials: JK
authors.lastname: Lee
authors.forename: Steven M
authors.initials: SM
authors.lastname: Farley
authors.forename: Matthias
authors.initials: M
authors.lastname: Stelzner
mesh_terms: D000818:Animals; D007422:Intestines / Q000166:cytology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009852:Omentum; D009940:Organoids / Q000637:transplantation*; D011100:Polyglycolic Acid; D033581:Stem Cell Transplantation / Q000379:methods*; D023822:Tissue Engineering
chemical_list: D011100:Polyglycolic Acid