S Méthot

Université du Québec à Montréal, Montréal, Quebec, Canada

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Publications (7)30.11 Total impact

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    ABSTRACT: 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. 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. 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. This detailed assessment of collagen architecture could benefit the development of cartilage repair strategies intended to recreate functional collagen architecture.
    Osteoarthritis and Cartilage 12/2011; 19(12):1458-68. · 4.26 Impact Factor
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    ABSTRACT: Cartilage repair strategies aim to resurface a lesion with osteochondral tissue resembling native cartilage, but a variety of repair tissues are usually observed. Histology is an important structural outcome that could serve as an interim measure of efficacy in randomized controlled clinical studies. The purpose of this article is to propose guidelines for standardized histoprocessing and unbiased evaluation of animal tissues and human biopsies. Methods were compiled from a literature review, and illustrative data were added. In animal models, treatments are usually administered to acute defects created in healthy tissues, and the entire joint can be analyzed at multiple postoperative time points. In human clinical therapy, treatments are applied to developed lesions, and biopsies are obtained, usually from a subset of patients, at a specific time point. In striving to standardize evaluation of structural endpoints in cartilage repair studies, 5 variables should be controlled: 1) location of biopsy/sample section, 2) timing of biopsy/sample recovery, 3) histoprocessing, 4) staining, and 5) blinded evaluation with a proper control group. Histological scores, quantitative histomorphometry of repair tissue thickness, percentage of tissue staining for collagens and glycosaminoglycan, polarized light microscopy for collagen fibril organization, and subchondral bone integration/structure are all relevant outcome measures that can be collected and used to assess the efficacy of novel therapeutics. Standardized histology methods could improve statistical analyses, help interpret and validate noninvasive imaging outcomes, and permit cross-comparison between studies. Currently, there are no suitable substitutes for histology in evaluating repair tissue quality and cartilaginous character.
    Cartilage 01/2011; 2(2):153-172.
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    ABSTRACT: Collagen organization, a feature that is critical for cartilage load bearing and durability, is not adequately assessed in cartilage repair tissue by present histological scoring systems. Our objectives were to develop a new polarized light microscopy (PLM) score for collagen organization and to test its reliability. This PLM score uses an ordinal scale of 0-5 to rate the extent that collagen network organization resembles that of young adult hyaline articular cartilage (score of 5) vs a totally disorganized tissue (score of 0). Inter-reader reliability was assessed using Intraclass Correlation Coefficients (ICC) for Agreement, calculated from scores of three trained readers who independently evaluated blinded sections obtained from normal (n=4), degraded (n=2) and repair (n=22) human cartilage biopsies. The PLM score succeeded in distinguishing normal, degraded and repair cartilages, where the latter displayed greater complexity in collagen structure. Excellent inter-reader reproducibility was found with ICCs for Agreement of 0.90 [ICC(2,1)] (lower boundary of the 95% confidence interval is 0.83) and 0.96 [ICC(2,3)] (lower boundary of the 95% confidence interval is 0.94), indicating the reliability of a single reader's scores and the mean of all three readers' scores, respectively. This PLM method offers a novel means for systematically evaluating collagen organization in repair cartilage. We propose that it be used to supplement current gold standard histological scoring systems for a more complete assessment of repair tissue quality.
    Osteoarthritis and Cartilage 10/2010; 19(1):126-35. · 4.26 Impact Factor
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    ABSTRACT: Growth factor therapy is an emerging treatment modality that enhances tissue vascularization, promotes healing and regeneration and can treat a variety of inflammatory diseases. Both recombinant human growth factor proteins and their gene therapy are in human clinical trials to heal chronic wounds. As platelet-derived growth factor-bb (PDGF-BB) and fibroblast growth factor-2 (FGF-2) are known to induce chemotaxis, proliferation, differentiation, and matrix synthesis, we investigated a non-viral means for gene delivery of these factors using the cationic polysaccharide chitosan. Chitosan is a polymer of glucosamine and N-acetyl-glucosamine, in which the percentage of the residues that are glucosamine is called the degree of deacetylation (DDA). The purpose of this study was to express PDGF-BB and FGF-2 genes in mice using chitosan-plasmid DNA nanoparticles for the controlled delivery of genetic material in a specific, efficient, and safe manner. PDGF-BB and FGF-2 genes were amplified from human tissues by RT-PCR. To increase the secretion of FGF-2, a recombinant 4sFGF-2 was constructed bearing eight amino-acid residues of the signal peptide of FGF-4. PCR products were inserted into the expression vector pVax1 to produce recombinant plasmids pVax1-4sFGF2 and pVax1-PDGF-BB, which were then injected into BALB/C mice in the format of polyelectrolyte nanocomplexes with specific chitosans of controlled DDA and molecular weight, including 92-10, 80-10, and 80-80 (DDA-number average molecular weight or M(n) in kDa). ELISA assays on mice sera showed that recombinant FGF-2 and PDGF-BB proteins were efficiently expressed and specific antibodies to these proteins could be identified in sera of injected mice, but with levels that were clearly dependent on the specific chitosan used. We found high DDA low molecular weight chitosans to be efficient protein expressors with minimal or no generation of neutralizing antibodies, while lowering DDA resulted in greater antibody levels and correspondingly lower levels of detected recombinant protein. Histological analyses corroborated these results by revealing greater inflammatory infiltrates in lower DDA chitosans, which produced higher antibody titers. We found, in general, a more efficient delivery of the plasmids by subcutaneous than by intramuscular injection. Specific chitosan carriers were identified to be either efficient non-toxic therapeutic protein delivery systems or vectors for DNA vaccines.
    Gene therapy 06/2009; 16(9):1097-110. · 4.75 Impact Factor
  • Osteoarthritis and Cartilage 01/2007; 15. · 4.26 Impact Factor
  • Osteoarthritis and Cartilage 01/2007; 15. · 4.26 Impact Factor
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    ABSTRACT: Chitosan is a biodegradable natural polysaccharide that has shown potential for gene delivery, although the ideal molecular weight (MW) and degree of deacetylation (DDA) for this application have not been elucidated. To examine the influence of these parameters on gene transfer, we produced chitosans with different DDAs (98%, 92%, 80% and 72%) and depolymerized them with nitrous acid to obtain different MWs (150, 80, 40 and 10 kDa). We produced 64 formulations of chitosan/pDNA complexes (16 chitosans, 2 amine-to-phosphate (N:P) ratios of 5:1 and 10:1 and 2 transfection media pH of 6.5 and 7.1), characterized them for size and surface charge, and tested them for gene transfection in HEK 293 cells in vitro. Several formulations produced high levels of transgene expression while two conditions, 92-10-5 and 80-10-10 [DDA-MW-N:P ratio] at pH 6.5, showed equivalence to our best positive control. The results also revealed an important coupling between DDA and MW of chitosan in determining transgene expression. Maximum expression was obtained with a certain combination of DDA and MW that depended on N:P ratio and the pH, but similar expression levels could be achieved by simultaneously lowering MW and increasing DDA or lowering DDA and increasing MW, suggesting a predominant role of particle stability, through co-operative electrostatic binding, in determining transfection efficiency.
    Biomaterials 10/2006; 27(27):4815-24. · 8.31 Impact Factor

Publication Stats

177 Citations
30.11 Total Impact Points

Institutions

  • 2011
    • Université du Québec à Montréal
      Montréal, Quebec, Canada
    • Montreal Polytechnic
      • Institut de génie biomédical
      Montréal, Quebec, Canada