title: Ultrasound speed and attenuation in progressive trypsin digested articular cartilage.
abstract: Subtle changes of articular cartilage (AC) can lead to tissue degeneration and even osteoarthritis (OA). The early degeneration of AC is closely related to a change in proteoglycans (PG) content. The observation of PG is therefore an appropriate way of studying OA and evaluating the degree of AC degeneration. In this study, 20 cartilage-bone samples were prepared from normal porcine femoral condyle cartilage and 10 samples were digested over 2 h using 0.25% trypsin solution. The dynamic process of PG-digestion was explored using a conventional A-mode ultrasound (US) experimental system with a 10 MHz center frequency. Quantitative acoustic parameters were calculated from ultrasonic radio-frequency echo signals and included US speed (USS), US amplitude attenuation coefficient (UAA) and broadband US attenuation coefficient (BUA). The experimental results showed that the conventional A-mode ultrasound is valuable for tracking the degree of PG-digestion. Histology also confirmed the validity of the ultrasound observations. For every AC sample, the degree of PG-digestion within a given time was different and was affected by individual differences. After two hours of degeneration, USS showed a mean decrease of 0.4% (P<0.05). UAA was significantly lower after a two-hour PG depletion period (from (2.45±0.23) to (2.28±0.41) dB mm⁻¹). BUA showed no significant differences during this process. In conclusion, conventional ultrasound can provide useful information about trypsin-induced progressive PG depletion in AC and can reflect variations of PG content via the quantitative acoustic parameters USS and UAA. The results of this study may be used to identify an indirect indicator of cartilage matrix integrity and OA disease progression.
authors.affiliation: State Key Laboratory of Software Development Environment, Key Laboratory of Ministry of Education for Biomechanics and Mechanobiology, School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China.
authors.forename: HaiJun
authors.initials: H
authors.lastname: Niu
authors.forename: LiFeng
authors.initials: L
authors.lastname: Li
authors.forename: Feng
authors.initials: F
authors.lastname: Sun
authors.forename: Yan
authors.initials: Y
authors.lastname: Yan
authors.forename: YueXiang
authors.initials: Y
authors.lastname: Wang
authors.forename: DeYu
authors.initials: D
authors.lastname: Li
authors.forename: YuBo
authors.initials: Y
authors.lastname: Fan
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000737:chemistry* / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D010003:Osteoarthritis / Q000000981:diagnostic imaging / Q000473:pathology; D011509:Proteoglycans / Q000032:analysis; D013552:Swine; D014357:Trypsin / Q000737:chemistry* / Q000378:metabolism*; D014465:Ultrasonics / Q000379:methods*; D014463:Ultrasonography
chemical_list: D011509:Proteoglycans; D014357:Trypsin