Journal of Applied Physiology AJP: Cell Physiology
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J Appl Physiol (November 5, 2009). doi:10.1152/japplphysiol.00944.2009
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Submitted on August 21, 2009
Revised on October 23, 2009
Accepted on November 2, 2009

Lower strength of the human posterior patellar tendon seems unrelated to mature collagen cross-linking and fibril morphology

Philip Hansen1*, Bjarki Thor Haraldsson2, Per Aagaard3, Vuokko Kovanen4, Nick Avery5, Klaus Qvortrup6, Jytte Overgaard Larsen7, Michael Krogsgaard2, Michael Kjaer8, and S. Peter Magnusson9

1 Bispebjerg Hospital & Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen
2 Bispebjerg Hospital
3 University of Southern Denmark
4 University of Jyväskylä
5 University of Bristol
6 University of Copenhangen
7 University of Copenhagen
8 Bispebjerg Hospital and Faculty of Health Sciences, University of Copenhagen
9 Bispebjerg Hospital and Faculty of Health Sciences,

* To whom correspondence should be addressed. E-mail: hansen_philip{at}hotmail.com.

The human patellar tendon is frequently affected by tendinopathy but the etiology of the condition is not established, although differential loading of the anterior and posterior tendon may be associated with the condition. We hypothesized that changes in fibril morphology and collagen cross-linking would parallel differences in material strength between the anterior and posterior tendon. Tendon fascicles were obtained from elective ACL surgery patients and tested micromechanically. Transmission electron microscopy was used to assess fibril morphology, and collagen cross-linking was determined by HPLC. Anterior fascicles were markedly stronger (peak stress: 54.321.2 vs. 39.7 ± 21.3 MPa, p<0.05) and stiffer (624 ± 232 vs. 362 ± 170 MPa, p<0.01) than posterior fascicles. Notably, mature pyridinium type cross-links were less abundant in anterior fascicles (hydroxylysylpyridinoline: 0.859±0.197 vs. 1.416±0.250 mol/mol p=0.001; lysylpyridinoline: 0.023 ± 0.006 vs. 0.035 ± 0.006 mol/mol, p<0.01) while pentosidine and pyrrole concentrations showed no regional differences. Fibril diameters tended to be larger in anterior fascicles (7819 ± 2168 nm2 vs. 4897 ±1434; p=0.10). Material properties did not appear closely related to cross-linking or fibril morphology. These findings suggest region specific differences in mechanical, structural and biochemical properties of the human patellar tendon.







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