Structural characteristics of the collagen network in human normal, degraded and repair articular cartilages observed in polarized light and scanning electron microscopies.
OBJECTIVE
This study characterizes collagen organization (CO) in human normal (n = 6), degraded (n = 6) and repair (n = 22) cartilages, using polarized light (PLM) and scanning electron (SEM) microscopies.


METHODS
CO was assessed using a recently developed PLM-CO score (Changoor et al. Osteoarthritis Cartilage 2011;19:126-35), and zonal proportions measured. SEM images were captured from locations matched to PLM. Fibre orientations were assessed in SEM and compared to those observed in PLM. CO was also assessed in individual SEM images and combined to generate a SEM-CO score for overall CO analogous to PLM-CO. Fibre diameters were measured in SEM.


RESULTS
PLM-CO and SEM-CO scores were correlated, r = 0.786 (P < 0.00001, n = 32), after excluding two outliers. Orientation observed in PLM was validated by SEM since PLM/SEM correspondence occurred in 91.6% of samples. Proportions of the deep (DZ), transitional (TZ) and superficial (SZ) zones averaged 74.0 ± 9.1%, 18.6 ± 7.0%, and 7.3 ± 1.2% in normal, and 45.6 ± 10.7%, 47.2 ± 10.1% and 9.5 ± 3.4% in degraded cartilage, respectively. Fibre diameters in normal cartilage increased with depth from the articular surface [55.8 ± 9.4 nm (SZ), 87.5 ± 1.8 nm (TZ) and 108.2 ± 1.8 nm (DZ)]. Fibre diameters were smaller in repair biopsies [60.4 ± 0.7 nm (SZ), 63.2 ± 0.6 nm (TZ) and 67.2 ± 0.8 nm (DZ)]. Degraded cartilage had wider fibre diameter ranges and bimodal distributions, possibly reflecting new collagen synthesis and remodelling or collagen fibre unravelling. Repair tissues revealed the potential of microfracture-based repair procedures to produce zonal CO resembling native articular cartilage structure. Values are reported as mean ± 95% confidence interval.


CONCLUSIONS
This detailed assessment of collagen architecture could benefit the development of cartilage repair strategies intended to recreate functional collagen architecture.
Institute of Biomedical Engineering, Department of Chemical Engineering, Ecole Polytechnique de Montreal, P.O. Box 6079, Station Centre-Ville, Montreal, Quebec, Canada H3C 3A7. adele.changoor@polymtl.ca
A
A
Changoor
M
M
Nelea
S
S
Méthot
N
N
Tran-Khanh
A
A
Chevrier
A
A
Restrepo
M S
MS
Shive
C D
CD
Hoemann
M D
MD
Buschmann
D001706:Biopsy; D002358:Cartilage, Articular / Q000737:chemistry / Q000293:injuries / Q000502:physiology / Q000648:ultrastructure*; D003094:Collagen / Q000648:ultrastructure*; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D008859:Microscopy, Polarization; D015207:Osteoarthritis, Hip / Q000378:metabolism / Q000473:pathology; D012038:Regeneration / Q000502:physiology; D055815:Young Adult
D003094:Collagen