title: An ultrasound study of altered hydration behaviour of proteoglycan-degraded articular cartilage.
abstract: BACKGROUND
  Articular cartilage is a solid-fluid biphasic material covering the bony ends of articulating joints. Hydration of articular cartilage is important to joint lubrication and weight-wearing. The aims of this study are to measure the altered hydration behaviour of the proteoglycan-degraded articular cartilage using high-frequency ultrasound and then to investigate the effect of proteoglycan (PG) degradation on cartilage hydration.
  
  
  METHODS
  Twelve porcine patellae with smooth cartilage surface were prepared and evenly divided into two groups: normal group without any enzyme treatment and trypsin group treated with 0.25% trypsin solution for 4 h to digest PG in the tissue. After 40-minute exposure to air at room temperature, the specimens were immerged into the physiological saline solution. The dehydration induced hydration behaviour of the specimen was monitored by the high-frequency (25 MHz) ultrasound pulser/receiver (P/R) system. Dynamic strain and equilibrium strain were extracted to quantitatively evaluate the hydration behaviour of the dehydrated cartilage tissues.
  
  
  RESULTS
  The hydration progress of the dehydrated cartilage tissue was observed in M-mode ultrasound image indicating that the hydration behaviour of the PG-degraded specimens decreased. The percentage value of the equilibrium strain (1.84 ± 0.21%) of the PG-degraded cartilage significantly (p < 0.01) decreased in comparison with healthy cartilage (3.46 ± 0.49%). The histological sections demonstrated that almost PG content in the entire cartilage layer was digested by trypsin.
  
  
  CONCLUSIONS
  Using high-frequency ultrasound, this study found a reduction in the hydration behaviour of the PG-degraded cartilage. The results indicated that the degradation of PG decreased the hydration capability of the dehydrated tissue. This study may provide useful information for further study on changes in the biomechanical property of articular cartilage in osteoarthritis.
authors.affiliation: Institute of Medical Information, School of Biomedical Engineering, Southern Medical University, Guangzhou 510515, China. qingwang8740@gmail.com.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.forename: Yi-Yi
authors.initials: YY
authors.lastname: Yang
authors.forename: Hai-Jun
authors.initials: HJ
authors.lastname: Niu
authors.forename: Wen-Jing
authors.initials: WJ
authors.lastname: Zhang
authors.forename: Qian-Jin
authors.initials: QJ
authors.lastname: Feng
authors.forename: Wu-Fan
authors.initials: WF
authors.lastname: Chen
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001834:Body Water / Q000378:metabolism*; D002358:Cartilage, Articular / Q000000981:diagnostic imaging* / Q000378:metabolism; D009995:Osmosis; D011509:Proteoglycans / Q000378:metabolism*; D012965:Sodium Chloride / Q000378:metabolism; D013314:Stress, Mechanical; D013552:Swine; D013997:Time Factors; D014357:Trypsin / Q000378:metabolism; D014463:Ultrasonography
chemical_list: D011509:Proteoglycans; D012965:Sodium Chloride; D014357:Trypsin