Static-strain-induced adaptation of the fibrous periosteum
Citation for published version (APA):Foolen, J., Donkelaar, van, C. C., Huiskes, H. W. J., & Ito, K. (2008). Static-strain-induced adaptation of the fibrous periosteum. Poster session presented at Mate Poster Award 2008 : 13th Annual Poster Contest.
Document status and date: Published: 01/01/2008
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Static-strain-induced adaptation
of the fibrous periosteum
Jasper Foolen, René van Donkelaar, Rik Huiskes, Keita Ito
Bone & Orthopaedic Biomechanics
Variabele tekst of logo’s
/ Department of Biomedical Engineering
Introduction
The mechanism by which fibrous tissues adapt in response to alterations in mechanical environment, e.g. during growth and wound healing, remains unresolved. We questioned how fibrous tissue adapts mechanically and biochemically in response to static strain. Periosteum of embryonic chicks was used as a model system.
Method
Periosteum of e15 chick tibiotarsi was cultured for 3 days in a tensile tester at stretch levels ranging from 0.85 to 1.05 (for a detailed description, see caption fig 1).
Fig 1. Dissected tibiotarsi were loaded in an ElectroForce LM1 TestBench. Suture wires a) were guided via a single longitudinal incision in between bone and periosteum b). At this in vivo length, proximal c) and distal d) metaphyseal cartilage was cut by pulling the wires through the needle so that mineralized bone could be removed. Bottom row: periosteum at 5 different stretch levels. Scale bar represents 10 mm.
After culturing, a standardized force-stretch curve was obtained from 0.75 stretch to failure at 0.1%/sec (fig 2). Native e15 periosteum was used as control. Mechanical parameters (transition and stiffness) and biochemical properties (DNA, GAG, collagen and HP cross-links) were used for comparison.
Results
The transition stretch always approximated the applied stretch after 3 days of culturing (fig 2). However, at lower applied stretches an offset is apparent.
Fig 2. a) Representative force strain curves (with an illustration of the definition ‘transition’ stretch) of e15 control (n=12) and experimentally stretched periosteum (n=4 for all stretch levels). b) Applied versus measured transition stretch of experimental samples, dashed line represents a 1 to 1 ratio.
Stiffness proportionally increased with applied stretch (fig 2 & 3). Stiffness of samples stretched to 1.05 was significantly higher compared to control (fig 3).
Significant decreases in collagen and HP cross-links were observed with applied stretch (fig 4). All stretch groups had significantly higher HP content relative to e15 control.
Discussion
Surprisingly, proportional increase in transition stretch and stiffness with applied stretch were inversely related to collagen and HP cross-link content. We therefore propose that the tissue adaptation mechanism is based on structural reorganization of the collagen network with highly aligned collagen at 1.05 stretch and less aligned collagen at 0.85 stretch. Subsequent cross-linking fixes the reorganized network, which can explain changes in mechanical properties. The incomplete transition shift in 0.85 stretched samples is attributed to fixation by cross-links that precedes network reorganization.
Fig 4. Applied stretch was significantly related to collagen and HP cross-link content (linear regression analysis; p<0.05; R2 = 0.31 and 0.29 respectively). Asterisks indicate significant differences relative to e15 control (1-way ANOVA, bonferroni post-hoc test; p<0.05).
Conclusion
Applied static stretch is proportionally related to stiffness and transition stretch, however inversely related to collagen and HP cross-link content.
This insight improves our general understanding of growth and adaptation, useful for tissue engineering applications.
Acknowledgements
We gratefully acknowledge Jessica Snabel and Ruud Bank (TNO Leiden), Sarita Soekhradj–Soechit and Kang Yuen Rosaria–Chak. This project is funded by KNAW.
a b c d
~0.85 ~0.90 ~0.95 ~1.00 ~1.05
Fig 3. Stiffness is proportionally related to applied stretch (linear regression analysis; p<0.05; R2 = 0.77). Asterisk represents a significant difference relative to e15 control (1-way ANOVA; bonferroni post-hoc test; p<0.05).
