title: Microencapsulation to reduce mechanical loss of microspheres: implications in myocardial cell therapy.
abstract: OBJECTIVE
  Previous regenerative studies have demonstrated massive cell losses after intramyocardial cellular delivery. Therefore, efforts at reducing mechanical losses may prove more successful in optimising cellular therapy. In this study, we hypothesized that escalating mesenchymal stem cells (MSCs) dose will not produce corresponding improvement in cardiac function due to washout of the small cells in microcirculation. Using microspheres similar in size to MSCs, that are encapsulated in alginate-poly-l-lysine-alginate (APA), we tested the hypothesis that size is an important factor in early losses.
  
  
  METHODS
  In experiment I, five groups of rats (n=9 each) underwent coronary ligation; group I had no treatment; the other groups received escalating 0.5 × 10(6), 1.5 × 10(6), 3 × 10(6) and 5 × 10(6) of MSCs each. Echocardiogram was performed at baseline, 2 days and 7 weeks after surgery. In experiment II, cell-sized microspheres (10 μm) were encapsulated in APA microcapsules. In group I (n=16), rats received bare microspheres, group II (n=16) microspheres within 200 μm microcapsules and in group III (n=16), microspheres within 400 μm microcapsules. After 20 min, hearts were quantified for the amount retained.
  
  
  RESULTS
  Myocardial function did not improve further with escalating cell doses beyond an initial response at 1.5 × 10(6) cells. Encapsulated microspheres in 200 μm and 400 μm microcapsules demonstrated a fourfold increase in retention rate compared with 10 μm microspheres.
  
  
  CONCLUSIONS
  We concluded that suboptimal functional improvement in this animal model starts at 1.5 × 10(6) cells and does not respond to escalating cell doses. Improving mechanical retention is possible by increasing the size of the injectate. Microencapsulation could be used to encapsulate donor cells and facilitate functional improvement in cellular heart failure therapy.
authors.affiliation: Divisions of Cardiac Surgery and Surgical Research, McGill University Health Center, McGill University, Montreal, Quebec, Canada.
authors.forename: Adil H
authors.initials: AH
authors.lastname: Al Kindi
authors.forename: Juan Francisco
authors.initials: JF
authors.lastname: Asenjo
authors.forename: Yin
authors.initials: Y
authors.lastname: Ge
authors.forename: Guang Yong
authors.initials: GY
authors.lastname: Chen
authors.forename: Jasmine
authors.initials: J
authors.lastname: Bhathena
authors.forename: Ray C-J
authors.initials: RC
authors.lastname: Chiu
authors.forename: Satya
authors.initials: S
authors.lastname: Prakash
authors.forename: Dominique
authors.initials: D
authors.lastname: Shum-Tim
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D018421:Cardiomyoplasty / Q000379:methods*; D002470:Cell Survival; D002921:Cicatrix / Q000473:pathology; D004195:Disease Models, Animal; D004339:Drug Compounding; D005260:Female; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D008297:Male; D045164:Mesenchymal Stem Cell Transplantation / Q000379:methods*; D008863:Microspheres; D010316:Particle Size; D051381:Rats; D011917:Rats, Inbred Lew; D014463:Ultrasonography; D016277:Ventricular Function, Left / Q000502:physiology