title: The Placenta: Applications in Orthopaedic Sports Medicine.
abstract: BACKGROUND
  Placenta has a long history of use for treating burns and wounds. It is a rich source of collagen and other extracellular matrix proteins, tissue reparative growth factors, and stem cells, including mesenchymal stem cells (MSCs). Recent data show its therapeutic potential for orthopaedic sports medicine indications.
  
  
  OBJECTIVE
  To provide orthopaedic surgeons with an anatomic description of the placenta, to characterize its cellular composition, and to review the literature reporting the use of placenta-derived cells and placental tissue allografts for orthopaedic sports medicine indications in animal models and in humans.
  
  
  METHODS
  Systematic review.
  
  
  METHODS
  Using a total of 63 keyword combinations, the PubMed and MEDLINE databases were searched for published articles describing the use of placental cells and/or tissue for orthopaedic sports medicine indications. Information was collected on placental tissue type, indications, animal model, study design, treatment regimen, safety, and efficacy outcomes. Results were categorized by indication and subcategorized by animal model.
  
  
  RESULTS
  Outcomes for 29 animal studies and 6 human studies reporting the use of placenta-derived therapeutics were generally positive; however, the placental tissue source, clinical indication, and administration route were highly variable across these studies. Fourteen animal studies described the use of placental tissue for tendon injuries, 13 studies for osteoarthritis or articular cartilage injuries, 3 for ligament injuries, and 1 for synovitis. Both placenta-derived culture-expanded cells (epithelial cells or MSCs) and placental tissue allografts were used in animal studies. In all human studies, commercial placental allografts were used. Five of 6 human studies examined the treatment of foot and ankle pathological conditions, and 1 studied the treatment of knee osteoarthritis.
  
  
  CONCLUSIONS
  A review of the small number of reported studies revealed a high degree of variability in placental cell types, placental tissue preparation, routes of administration, and treatment regimens, which prohibits making any definitive conclusions. Currently, the clinical use of placenta is limited to only commercial placental tissue allografts, as there are no placenta-derived biological drugs approved for the treatment of orthopaedic sports medicine conditions in the United States. However, this review shows that the application of placental cells or tissue allografts appears to be safe and has potential to improve outcomes for orthopaedic sports medicine indications.
authors.affiliation: School of Medicine & Health Sciences, George Washington University, Washington, District of Columbia, USA.
authors.forename: James Alexander
authors.initials: JA
authors.lastname: McIntyre
authors.affiliation: Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Jones
authors.affiliation: Osiris Therapeutics Inc, Columbia, Maryland, USA.
authors.forename: Alla
authors.initials: A
authors.lastname: Danilkovich
authors.affiliation: Osiris Therapeutics Inc, Columbia, Maryland, USA.
authors.forename: C Thomas
authors.initials: CT
authors.lastname: Vangsness
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000293:injuries; D005260:Female; D006801:Humans; D008022:Ligaments / Q000293:injuries; D059630:Mesenchymal Stem Cells / Q000166:cytology; D009985:Orthopedics; D010003:Osteoarthritis / Q000628:therapy; D010920:Placenta / Q000166:cytology* / Q000637:transplantation*; D011247:Pregnancy; D013178:Sports Medicine; D013585:Synovitis / Q000628:therapy; D013708:Tendon Injuries / Q000628:therapy
keywords: amniotic membrane; placenta; regenerative medicine; stem cells; umbilical cord