title: Long-term normoglycemia in rats receiving transplants with encapsulated islets.
abstract: BACKGROUND
  To follow up on previously successful transplantation of encapsulated islets in mice, the present study was performed in rats to determine the effects of several factors, including alginate composition and concentration of cross-linking agent and capsule size on the effectiveness of encapsulated islets.
  
  
  METHODS
  Highly purified alginate of either high guluronic acid or high mannuronic acid (M) with low endotoxin content was used. Regular-size (0.8-1.1 mm) or small microcapsules (0.5-0.7 mm) were produced by cross-linking with BaCl2 without additional poly-L-lysine coating and were transplanted into abdominal cavity of normoglycemic (empty capsules) or streptozotocin induced diabetic Lewis rats (islet containing capsules).
  
  
  RESULTS
  Empty regular-size capsules made of different alginate compositions had similar biocompatibility and stability results. Compared with empty capsules, regular-size capsules made of high-M alginate containing syngeneic islets had inferior stability indicated with lower fractional volume retrieved. Islet-containing smaller-size microcapsules made of high-M alginate were more stable and had less cellular attachment compared with the regular-size capsules, although the normoglycemic period was comparable between two groups of rats receiving transplants with smaller-size microcapsules (48+/-8 days, n=8) or regular-size capsules (59+/-11 days, n=4) in allogeneic experiments. In syngeneic experiments, all of the rats (n=4) maintained normoglycemia up to 210 days after transplantation.
  
  
  CONCLUSIONS
  These results indicate that regular-size alginate capsules do less well in rats than in our previous experiments with mice. Smaller capsules made of alginate cross-linked with barium appear to provide better stability and may be a useful strategy for use in larger recipients.
authors.affiliation: Section on Islet Transplantation and Cell Biology, Joslin Diabetes Center, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Abdulkadir
authors.initials: A
authors.lastname: Omer
authors.forename: Valerie
authors.initials: V
authors.lastname: Duvivier-Kali
authors.forename: Justin
authors.initials: J
authors.lastname: Fernandes
authors.forename: Vaja
authors.initials: V
authors.lastname: Tchipashvili
authors.forename: Clark K
authors.initials: CK
authors.lastname: Colton
authors.forename: Gordon C
authors.initials: GC
authors.lastname: Weir
mesh_terms: D000818:Animals; D017609:Barium Compounds / Q000494:pharmacology; D001786:Blood Glucose / Q000032:analysis*; D002096:C-Peptide / Q000032:analysis; D002712:Chlorides / Q000494:pharmacology; D005951:Glucose Tolerance Test; D006085:Graft Survival; D016381:Islets of Langerhans Transplantation / Q000379:methods*; D008297:Male; D051381:Rats; D011917:Rats, Inbred Lew
chemical_list: D017609:Barium Compounds; D001786:Blood Glucose; D002096:C-Peptide; D002712:Chlorides; C024986:barium chloride