title: Injectable hydrogel therapies and their delivery strategies for treating myocardial infarction.
abstract: BACKGROUND
  Heart failure following myocardial infarction (MI) impacts millions of people each year in the US. The field of tissue engineering has developed several potential therapies for treating MI including injectable acellular hydrogels. These injectable biomaterials can either be synthetic or naturally derived, and have the potential to be delivered minimally invasively.
  
  
  METHODS
  This review covers the different methods of delivery and presents the initial work on the use of injectable biomaterial scaffolds alone to improve cardiac function post-MI. Several naturally derived materials including alginate, collagen, chitosan, decellularized tissues, fibrin, hyaluronic acid, keratin, and Matrigel, as well as a few synthetic materials have shown promise on their own without the addition of therapeutics such as cells or growth factors. These biomaterials can be potentially delivered via endocardial, epicardial, or intracoronary injections and some can even utilize current catheter technology, indicating a potential for avoiding invasive surgical procedures. Once injected into the wall of the heart, these hydrogels create a scaffold that provides biochemical and structural cues, and the ability for cellular infiltration and remodeling of the local environment.
  
  
  CONCLUSIONS
  Injectable biomaterials have several crucial challenges that should be over come to design optimal therapies for MI and heart failure, including optimizing material properties, methods of injection and understanding the mechanisms of action. But, studies in both small and large animals have shown significant improvement in important parameters including wall thickness, vascularization of the ischemic region, left ventricular volumes, and cardiac function. Thus, the application of injectable biomaterials shows promise for developing into new therapies to treat MI, potentially improving millions of lives.
authors.affiliation: University of California San Diego, Sanford Consortium of Regenerative Medicine, Department of Bioengineering, 2880 Torrey Pines Scenic Drive, La Jolla, CA 92037, USA.
authors.forename: Todd D
authors.initials: TD
authors.lastname: Johnson
authors.forename: Karen L
authors.initials: KL
authors.lastname: Christman
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000008:administration & dosage* / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D016503:Drug Delivery Systems; D006321:Heart / Q000187:drug effects*; D006801:Humans; D020100:Hydrogels / Q000008:administration & dosage* / Q000737:chemistry; D007267:Injections; D009203:Myocardial Infarction / Q000188:drug therapy*; D004364:Pharmaceutical Preparations / Q000008:administration & dosage* / Q000737:chemistry; D023822:Tissue Engineering / Q000379:methods
chemical_list: D001672:Biocompatible Materials; D020100:Hydrogels; D004364:Pharmaceutical Preparations