title: Effect of hyaluronic acid on chondrocyte apoptosis.
abstract: OBJECTIVE
  To determine the percentage of apoptotic cells in a contusion model of osteoarthritis (OA) and to assess whether intra-articular injection of high doses of hyaluronic acid (HA) immediately after trauma reduces chondrocyte apoptosis.
  
  
  METHODS
  Forty knees from adult rabbits were impacted thrice with a 1 kg block released through a 1 meter tall cylinder (29.4 Joules). Subsequently, 2 mL of HA was injected in one knee and 2 mL saline in the contra-lateral knee. Medication were administered twice a week for 30 days, when animals were sacrificed. Specimens were prepared for optical microscopy exam and terminal deoxynucleotidyl transferase end labeling assay (TUNEL).
  
  
  RESULTS
  The apoptosis rate in the contusion model was 68.01% (± 19.73%), a higher rate than previously described. HA significantly reduced the rate of apoptosis to 53.52% (± 18.09) (p <0.001).
  
  
  CONCLUSIONS
  Intra-articular HA administration started immediately after trauma reduces impact-induced chondrocyte apoptosis rates in rabbits.
authors.affiliation: Universidade de São Paulo, Faculdade de Medicina, Department of Orthopedics and Traumatology, São Paulo, SP, Brazil, 1. Department of Orthopedics and Traumatology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Ronald Bispo
authors.initials: RB
authors.lastname: Barreto
authors.affiliation: Universidade de São Paulo, Faculdade de Medicina, Department of Orthopedics and Traumatology, São Paulo, SP, Brazil, 1. Department of Orthopedics and Traumatology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: David
authors.initials: D
authors.lastname: Sadigursky
authors.affiliation: Universidade de São Paulo, Faculdade de Medicina, Department of Orthopedics and Traumatology, São Paulo, SP, Brazil, 1. Department of Orthopedics and Traumatology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Marcia Uchoa
authors.initials: MU
authors.lastname: de Rezende
authors.affiliation: Universidade de São Paulo, Faculdade de Medicina, Department of Orthopedics and Traumatology, São Paulo, SP, Brazil, 1. Department of Orthopedics and Traumatology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Arnaldo José
authors.initials: AJ
authors.lastname: Hernandez
keywords: Apoptosis; Chondrocytes; Hyaluronic acid; Knee; Osteoarthritis; Rabbits