Biomedical Engineering Reference
In-Depth Information
11.3.3
Results and Discussion ........................................... 419
11.3.3.1
Free Diffusion .......................................... 419
11.3.3.2
Diffusion with Cyclic Deformation and IGF-I,
IGFBP Interaction .................................... 420
11.4
IGF Transport with Competitive Binding in a Deforming
Articular Cartilage ........................................................ 423
11.4.1
Introduction ...................................................... 423
11.4.1.1
Competitive Binding of IGFs to Their
IGFBPs in Cartilage .................................. 424
11.4.2
Model Development for a Competitor Growth Factor ........... 425
11.4.2.1
Law of Mass Action with Competitive Binding ....... 426
11.4.2.2
Steady-State Growth Factor Uptake .................. 427
11.4.2.3
Model Calibration ..................................... 427
11.4.2.4
Competitive Binding in a Deforming Cartilage ....... 429
11.4.2.5
Radial IGF-I and -II Transport in Cartilage
under Unconfined Dynamic Compression ............. 430
11.4.2.6
Free Diffusion with Competitor ....................... 431
11.4.2.7
Growth Factor Transport with Competitor
and Cyclic Deformation ............................... 431
11.5
An Integrated Model of IGF-I and Mechanical-Loading-Mediated
Biosynthesis in a Deformed Articular Cartilage........................... 434
11.5.1
Introduction ...................................................... 434
11.5.1.1
IGF-I and Mechanical-Loading-Mediated
Cartilage Biosynthesis ................................. 435
11.5.2
Biosynthesis Model Construction ................................ 435
11.5.2.1
IGF-I Transport and Interaction with IGFBPs and
Receptors .............................................. 436
11.5.2.2
Cartilage ECM Biosynthesis .......................... 437
11.5.2.3
IGF-I Mediated Aggrecan Biosynthesis ............... 437
11.5.2.4
Mechanical-Stimuli-Mediated Aggrecan Biosynthesis
438
11.5.2.5
Aggrecan Molecule Transport in Cartilage ............ 439
11.5.3
Biosynthesis Model Validation and Predictions .................. 440
11.6
Summary .................................................................. 444
11.7
References ................................................................. 445
11.1 Overview
Articular cartilage is the smooth glistening white tissue, slippery to feel, that
covers the surface of the diarthrodial joints. The functions of articular cartilage
in joints are to reduce load per unit area and to provide a smooth, low-friction,
and wear resistant bearing [1]. The composition and structural properties of
cartilage allow it to achieve and maintain proper biomechanical function over
the majority of a human lifespan [2]. Structurally, cartilage is a porous, fluid-
filled, deformable material that is composed of cells (called chondrocytes),
a fluid (predominantly water), and an ECM [3]. The ECM largely consists of
collagen, proteoglycan, and small amounts of other molecules [4].
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