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Effect of DDR2 on Rheology of Collagen type I Fibers

Sivakumar, Lalitha
http://rave.ohiolink.edu/etdc/view?acc_num=osu1243537065

Abstract Details

2009, Master of Science, Ohio State University, Biomedical Engineering.
Collagen fibers in the vertebrate tissue are responsible for its tensile strength. A disruption in the morphological or rheological properties of collagen fibers is bound to impact tensile strength and contractility of tissues and affect physiological processes. Several collagen binding proteins have been shown to affect the morphology of collagen fibers. However little is understood about how these morphological changes affect the rheology of collagen fibers. It was recently established that binding of the discoidin domain receptor (DDR2) with collagen type I resulted in disruption of the native structure and morphology of collagen fibers. These results led us to investigate if DDR2 affects the rheological properties of collagen fibers. We used an analytical approach to determine the persistence length (PL) of collagen fibers using transmission electron microscope (TEM) images of immobilized collagen. The fluctuations in the curvature of collagen fibers formed in-vitro (with and without DDR2 or a control protein TrkB) were analyzed to ascertain their PL. For collagen fibers (15 μg/ml), we found a PL of 9.10 μm (± 0.33 μm) whereas collagen fibers formed in the presence of DDR2-Fc under similar conditions had a 40% reduction in PL to 5.20 μm (± 0.20 μm). These results show that DDR2 significantly reduced the PL of collagen fibers. We also found that PL for native collagen fibers increases monotonically as a function of collagen concentration with little dependence on fiber diameter. These results reveal that differences in PL are mainly due to the amount and/or density of collagen incorporated into the fibers. The PL values and fiber-diameter measurements were utilized to ascertain the Young’s Modulus (E) of collagen fibers formed in the presence and absence of DDR2. E for collagen fibers with and without DDR2 was 300 Pa (± 12 Pa) and 1300 Pa (± 47 Pa) respectively. Further collagen gel-contraction studies were carried out to evaluate how cells expressing the soluble or membrane anchored isoforms of DDR2 (and lacking the intracellular kinase domain of DDR2) affect contraction of collagen gels. Cells overexpressing DDR2 ECD and DDR2 /-KD inhibit contraction of collagen gels by ~30% and ~15% respectively in comparison to the untransfected cells. We elucidate that DDR2 reduces the PL and E of collagen fibers and decreases contractility of collagen fibers by osteoblast cells. Our results signify a physiological role of DDR2 in modulating matrix stiffness, which may be especially relevant in developing tissues and matrix remodeling.
GUNJAN AGARWAL (Advisor)
GREGORY LAFYATIS (Committee Member)
45 p.
Biomedical Research
collagen; fiber; discoidin domain receptor 2 (DDR2); persistence length; transmission electron microscopy; Young&8217; s modulus

Recommended Citations

Citations

  • Sivakumar, L. (2009). Effect of DDR2 on Rheology of Collagen type I Fibers [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243537065

    APA Style (7th edition)

  • Sivakumar, Lalitha. Effect of DDR2 on Rheology of Collagen type I Fibers. 2009. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1243537065.

    MLA Style (8th edition)

  • Sivakumar, Lalitha. "Effect of DDR2 on Rheology of Collagen type I Fibers." Master's thesis, Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243537065

    Chicago Manual of Style (17th edition)

osu1243537065
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© 2009, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.