title: A high-throughput model of post-traumatic osteoarthritis using engineered cartilage tissue analogs.
abstract: OBJECTIVE
  A number of in vitro models of post-traumatic osteoarthritis (PTOA) have been developed to study the effect of mechanical overload on the processes that regulate cartilage degeneration. While such frameworks are critical for the identification therapeutic targets, existing technologies are limited in their throughput capacity. Here, we validate a test platform for high-throughput mechanical injury incorporating engineered cartilage.
  
  
  METHODS
  We utilized a high-throughput mechanical testing platform to apply injurious compression to engineered cartilage and determined their strain and strain rate dependent responses to injury. Next, we validated this response by applying the same injury conditions to cartilage explants. Finally, we conducted a pilot screen of putative PTOA therapeutic compounds.
  
  
  RESULTS
  Engineered cartilage response to injury was strain dependent, with a 2-fold increase in glycosaminoglycan (GAG) loss at 75% compared to 50% strain. Extensive cell death was observed adjacent to fissures, with membrane rupture corroborated by marked increases in lactate dehydrogenase (LDH) release. Testing of established PTOA therapeutics showed that pan-caspase inhibitor [Z-VAD-FMK (ZVF)] was effective at reducing cell death, while the amphiphilic polymer [Poloxamer 188 (P188)] and the free-radical scavenger [N-Acetyl-L-cysteine (NAC)] reduced GAG loss as compared to injury alone.
  
  
  CONCLUSIONS
  The injury response in this engineered cartilage model replicated key features of the response of cartilage explants, validating this system for application of physiologically relevant injurious compression. This study establishes a novel tool for the discovery of mechanisms governing cartilage injury, as well as a screening platform for the identification of new molecules for the treatment of PTOA.
authors.affiliation: McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address: mbhavana@mail.med.upenn.edu.
authors.forename: B
authors.initials: B
authors.lastname: Mohanraj
authors.affiliation: McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address: gmeloni@mail.med.upenn.edu.
authors.forename: G R
authors.initials: GR
authors.lastname: Meloni
authors.affiliation: McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA; Collaborative Research Partner Acute Cartilage Injury Program of AO Foundation, Davos, Switzerland; Translational Musculoskeletal Research Center, Philadelphia Veterans Administration Medical Center, Philadelphia, PA 19104, USA. Electronic address: lemauck@mail.med.upenn.edu.
authors.forename: R L
authors.initials: RL
authors.lastname: Mauck
authors.affiliation: McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Collaborative Research Partner Acute Cartilage Injury Program of AO Foundation, Davos, Switzerland; Translational Musculoskeletal Research Center, Philadelphia Veterans Administration Medical Center, Philadelphia, PA 19104, USA. Electronic address: gdodge@mail.med.upenn.edu.
authors.forename: G R
authors.initials: GR
authors.lastname: Dodge
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D002358:Cartilage, Articular / Q000187:drug effects / Q000293:injuries* / Q000473:pathology / Q000503:physiopathology; D061945:Caspase Inhibitors / Q000494:pharmacology; D002417:Cattle; D016923:Cell Death / Q000187:drug effects; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical / Q000379:methods; D006025:Glycosaminoglycans / Q000378:metabolism; D057166:High-Throughput Screening Assays / Q000379:methods; D008422:Materials Testing / Q000379:methods; D010003:Osteoarthritis / Q000209:etiology*; D010865:Pilot Projects; D020442:Poloxamer / Q000494:pharmacology; D013314:Stress, Mechanical; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D006025:Glycosaminoglycans; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D020442:Poloxamer; D000111:Acetylcysteine
keywords: Cartilage tissue analog (CTA); High-throughput screening; Impact loading; Injurious compression; Tissue engineering