Caroline Hoemann | École Polytechnique de Montréal (original) (raw)

Papers by Caroline Hoemann

Operative Techniques in Orthopaedics, 2006

Journal of Orthopaedic Research, 2009

Meniscus injury is a frequently encountered clinical orthopedic issue and is epidemiologically co... more Meniscus injury is a frequently encountered clinical orthopedic issue and is epidemiologically correlated to osteoarthritis. The development of new treatments for meniscus injury is intimately related to the appropriateness of animal models for their investigation. The purpose of this study was to structurally compare human menisci to sheep and rabbit menisci to generate pertinent animal models for meniscus repair. Menisci were analyzed histologically, immunohistochemically, and by environmental scanning electron microscopy (ESEM). In all species, collagen I appeared throughout most menisci, but was absent from the inner portion of the tip in some samples. Collagen II was present throughout the inner main meniscal body, while collagen VI was found in pericellular and perivascular regions. The glycosaminoglycan-rich inner portion of menisci was greater in area for rabbit and sheep compared to human. Cells were rounded in central regions and more fusiform at the surface, with rabbit being more cellular than sheep and human. Vascular penetration in rabbit was confined to the very outermost region (1% of meniscus length), while vessels penetrated deeper into sheep and human menisci (11-15%). ESEM revealed a lamellar collagenous structure at the articulating surfaces of sheep and human menisci that was absent in rabbit. Taken together, these data suggest that the main structural features that will influence meniscus repair-cellularity, vascularity, collagen structure-are similar in sheep and human but significantly different in rabbit, motivating the development of ovine meniscus repair models. ß

Osteoarthritis and Cartilage Oars Osteoarthritis Research Society, Jul 31, 2009

Objective: Chitosaneglycerol phosphate (chitosan-GP) is a unique polymer solution that is mixed w... more Objective: Chitosaneglycerol phosphate (chitosan-GP) is a unique polymer solution that is mixed with whole blood and solidified over microfractured or drilled articular cartilage defects in order to elicit a more hyaline repair cartilage. For clinical ease-of-use, a faster in situ solidification is preferred. Therefore, we investigated the mechanisms underlying chitosaneGP/blood implant solidification.

Supervised by Ron D.G. McKay. Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Appl... more Supervised by Ron D.G. McKay. Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Applied Biological Sciences, 1988. Includes bibliographical references (leaves 97-105).

Genes & Development

The MMTVD/myc transgenic mice spontaneously develop oligoclonal CD4+CD8+ T-cell tumors. We used p... more The MMTVD/myc transgenic mice spontaneously develop oligoclonal CD4+CD8+ T-cell tumors. We used provirus insertional mutagenesis in these mice to identify putative collaborators of c-myc. We found that Notch1 was mutated in a high proportion (52%) of these tumors. Proviruses were inserted upstream of the exon coding for the transmembrane domain and in both transcriptional orientations. These mutations led to high expression of truncated Notch1 RNAs and proteins (86-110 kD). In addition, many Notch1-rearranged tumors showed elevated levels of full-length Notch1 transcripts, whereas nearly all showed increased levels of full-length (330-kD) or close to full-length (280-kD) Notch1 proteins. The 5' end of the truncated RNAs were determined for some tumors by use of RT-PCR and 5' RACE techniques. Depending on the orientation of the proviruses, viral LTR or cryptic promoters appeared to be utilized, and coding potential began in most cases in the transmembrane domain. Pulse-chase ...

The American Journal of Sports Medicine, 2015

Current cartilage repair histological scoring systems are unable to explain the relationship betw... more Current cartilage repair histological scoring systems are unable to explain the relationship between collagen type II deposition and overall repair quality. The purpose of this study was to develop a novel zonal collagen type (ZCT) 5-point scoring system to measure chondroinduction in human clinical biopsy specimens collected after marrow stimulation. The hypothesis was that the ZCT scores would correlate with the International Cartilage Repair Society-II (ICRS-II) overall histological repair assessment score and glycosaminoglycan (GAG) content. Descriptive laboratory study. After optimizing safranin O staining for GAG and immunostaining for human collagen type II and type I (Col2 and Col1, respectively), serial sections from clinical osteochondral repair biopsy specimens (13 months after microfracture or microfracture with BST-CarGel; n = 39 patients) were stained and 3 blinded readers performed histomorphometry for percentage of staining, ICRS-II histological scoring, polarized light microscopy (PLM) scoring, and 5-point ZCT scoring based on tidemark morphology, zonal distribution of Col2 and Col1, and Col1 percentage stain. Because 1 biopsy specimen was missing bone, 38 biopsy specimens were evaluated for ICRS-II, PLM, and ZCT scores. Chondroinduction was identified in 21 biopsy specimens as a Col2 matrix fused to bone that spanned the deep-middle-superficial zones ("full-thickness hyaline repair"), deep-middle zones, or deep zone ("stalled hyaline") that was covered with a variable-thickness Col1-positive matrix, and was scored, respectively, as ZCT = 1 (n = 4 biopsy specimens), ZCT = 2 (n = 6) and ZCT = 3 (n = 11). Other biopsy specimens (n = 17) were fibrocartilage (n = 9; ZCT = 4), fibrous tissue (n = 4, ZCT = 5), or non-marrow derived (n = 4; ZCT = 0). Non-marrow derived tissue had a mean mature tidemark score of 84 out of 100 versus a regenerating tidemark score of 24 for all other biopsy specimens (P = .005). Both "stalled hyaline" repair and fibrocartilage had the same mean Col2 percentage stain; however, fibrocartilage was distinguished by heavy Col1 deposits in the deep zone, a 2-fold higher mean Col1 percentage stain (P = .001), and lower surface integrity (P = .03). ZCT scores correlated with GAG content and the ICRS-II overall assessment score, especially when combined with the PLM score for collagen organization (R = 0.82). Histological scores of the deep zone strongly predicted the ICRS-II overall assessment score (R = 0.99). The ICRS-II overall repair assessment score and GAG content correlated with the extent of Col2 deposition free of fibrosis in the deep/middle zone rather than bulk accumulation of Col2. Biopsy tissue from the BST-CarGel randomized clinical trial (microfracture without and with BST-CarGel, as treatment groups were not unblinded) showed regenerated tissue consistent with a chondroinduction mechanism in at least half of the treated lesions.

Purpose: Mechanical testing of articular cartilage is recommended by the FDA for products intende... more Purpose: Mechanical testing of articular cartilage is recommended by the FDA for products intended for the repair or replacement of knee cartilage. One experimental configuration that has many practical advantages is indentation. However, one limitation is the need to perpendicularly position the articular surface to the indenter. The objective of this study was to investigate the ability of a novel technique to automatically characterize mechanical properties of an entire articular surface with rapidity, precision, and reproducibility in indentation. Materials &Methods: Mature ovine and murine tibial plateau and femoral condyles were biomechanically mapped in vitro. The mechanical tester used was the 3-axis Mach-1 v500css from Biomomentum Inc. This novel technique detects the normal vector at each position and moves a spherical indenter (R=0.5 mm) along that vector while measuring the resulting force. Results: High-resolution mappings were obtained for the tibial plateau (Fig. 1) a...

Plasma Processes and Polymers

Thromboelastography uses cups and pins made of Cyrolite® plastic to analyze the rate of fibrin cl... more Thromboelastography uses cups and pins made of Cyrolite® plastic to analyze the rate of fibrin clot formation in blood samples. In this study, TEG cups and pins were modified by 4 distinct coating types using plasma‐enhanced chemical vapor deposition (PECVD): carboxylated, amine‐rich, hydrophobic, SiO2, and analyzed for surface chemistry and wettability. We tested the hypothesis that the coagulation kinetics of recalcified citrated blood plasma is controlled by surface chemistry, in the absence of clot activator. Only carboxylated surfaces became negatively charged upon wetting, and accelerated clot formation in a highly reproducible manner, whereas Cyrolite® and the other coatings had delayed and unpredictable clotting times. These data are consistent with a model whereby carboxylated surfaces selectively adsorb and activate factor XII while repelling other more abundant anionic blood proteins, resulting in reproducible clot kinetics.

Journal of Histotechnology, 2004

Chitosan is a naturally abundant cationic polysaccharide with unique physicochemical properties r... more Chitosan is a naturally abundant cationic polysaccharide with unique physicochemical properties resulting in its utilization in a vast array of biomedical applications including wound repair, drug delivery and tissue engineering. However, despite numerous and diverse studies investigating its use, there have been no detailed reports describing specific staining methods for cell culture and histopathological studies using chitosan based materials. Here, we describe methods for staining chitosan in both cell culture and within paraffin sections. Procedural models employed included identifying chitosan within in vitro whole blood clots, and culture wells, and in vivo chitosan hydrogel implants in multiple anatomical sites. First, a staining process for identifying chitosan was optimized using 0.03% Cibacron Brilliant Red-3BA. A second sensitive, and more versatile method utilizing 0.01% Fast Green in conjunction with the known Safranin-O Method was demonstrated, and may prove to be a key advancement in the histological study of chitosanbased biotechnological products. The method described here is broadly applicable to histological in situ detection of chitosan scaffolds of multiple deacetylation level and of variable fabrication.

Journal of Biomedical Materials Research Part A, 2015

In the context of porous bone void filler for oral bone reconstruction, peptides that suppress mi... more In the context of porous bone void filler for oral bone reconstruction, peptides that suppress microbial growth and promote osteoblast function could be used to enhance the performance of a porous bone void filler. We tested the hypothesis that P15-CSP, a novel fusion peptide containing collagen-mimetic osteogenic peptide P15, and competence-stimulating peptide (CSP), a cationic antimicrobial peptide, has emerging properties not shared by P15 or CSP alone. Peptide-coated surfaces were tested for antimicrobial activity toward Streptoccocus mutans, and their ability to promote human mesenchymal stem cell (MSC) attachment, spreading, metabolism, and osteogenesis. In the osteogenesis assay, peptides were coated on tissue culture plastic and on thin films generated by plasma-enhanced chemical vapor deposition to have hydrophilic or hydrophobic character (water contact angles 63°, 42°, and 92°, respectively). S. mutans planktonic growth was specifically inhibited by CSP, whereas biofilm formation was inhibited by P15-CSP. MSC adhesion and actin stress fiber formation was strongly enhanced by CSP, P15-CSP, and fibronectin coatings and modestly enhanced by P15 versus uncoated surfaces. Metabolic assays revealed that CSP was slightly cytotoxic to MSCs. MSCs developed alkaline phosphatase activity on all surfaces, with or without peptide coatings, and consistently deposited the most biomineralized matrix on hydrophilic surfaces coated with P15-CSP. Hydrophobic thin films completely suppressed MSC biomineralization, consistent with previous findings of suppressed osteogenesis on hydrophobic bioplastics. Collective data in this study provide new evidence that P15-CSP has unique dual capacity to suppress biofilm formation, and to enhance osteogenic activity as a coating on hydrophilic surfaces. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2015.

Journal of biomedical materials research. Part A, Jan 11, 2014

Poly(epsilon-caprolactone) (PCL) is a hydrophobic bioplastic under development for bone tissue en... more Poly(epsilon-caprolactone) (PCL) is a hydrophobic bioplastic under development for bone tissue engineering applications. Limited information is available on the role of internal geometry and cell-surface attachment on osseous integration potential. We tested the hypothesis that human bone marrow mesenchymal stem cells (MSCs) deposit more mineral inside porous 3D PCL scaffolds with fully interconnected 84 or 141 µm pores, when the surfaces are coated with chitosan via Layer-by-Layer (LbL)-deposited polyelectrolytes. Freshly trypsinized MSCs were seeded on PCL 3D cylinders using a novel static cold seeding method in 2% serum to optimally populate all depths of the scaffold discs, followed by 10 days of culture in proliferation medium and 21 additional days in osteogenic medium. MSCs were observed by SEM and histology to spread faster and to proliferate more on chitosan-coated pore surfaces. Most pores, with or without chitosan, became filled by collagen networks sparsely populated wit...

Osteoarthritis and cartilage / OARS, Osteoarthritis Research Society, 2014

The hand-held Arthro-BST™ device is used to map electromechanical properties of articular cartila... more The hand-held Arthro-BST™ device is used to map electromechanical properties of articular cartilage. The purpose of the study was to evaluate correlation of electromechanical properties with histological, biochemical and biomechanical properties of cartilage. Electromechanical properties (quantitative parameter (QP)) of eight human distal femurs were mapped manually ex vivo using the Arthro-BST (1 measure/site, 5 s/measure, 3209 sites). Osteochondral cores were then harvested from different areas on the femurs and assessed with the Mankin histological score. Prior to histoprocessing, cores were tested in unconfined compression. A subset of the cores was analyzed with polarized light microscopy (PLM) to assess collagen structure. Biochemical assays were done on additional cores to obtain water content and glycosaminoglycan (GAG) content. The QP corresponding to each core was calculated by averaging all QPs collected within 6 mm of the core center. The electromechanical QP correlated ...

Osteoarthritis and Cartilage, 2010

Cartilage and Osteoarthritis, 2004

The procedure described below is useful for extracting proteins, nucleic acids, and glycosaminogl... more The procedure described below is useful for extracting proteins, nucleic acids, and glycosaminoglycans from 5-40 mg of cartilage or tissue-engineered cartilage samples. This extraction method will generate samples compatible with Western blot, RNase protection, dimethyl methylene blue (DMB) assay for glycosaminoglycan, Hoechst DNA assay, and hydroxyproline assay. Most soluble matrix molecules can be extracted from pulverized samples using 4 M guanidine HCl, during a 30-min period of vortex agitation at 4°C. Shorter agitation times can give inadequate solubilization. The guanidine HCl-insoluble pellet must be re-extracted with guanidine thiocyanate buffer, to solubilize RNA additionally. The final insoluble pellet can be rinsed with ethanol and digested with papain, to quantify collagen content as well as other insoluble or crosslinked material. Samples between 1 and 5 mg may be directly digested with a small volume of papain buffer for DMB, hydroxyproline, and Hoechst DNA assays.

Cartilage, 2010

Cartilage-bone integration is an important functional end point of cartilage repair therapy, but ... more Cartilage-bone integration is an important functional end point of cartilage repair therapy, but little is known about how to promote integration. We tested the hypothesis that chitosan-stabilized blood clot implant elicits osteoclasts to drilled cartilage defects and promotes repair and cartilage-bone integration. Bilateral trochlear defects in 15 skeletally mature rabbit knees were microdrilled and then treated with chitosan-glycerol phosphate (GP)/blood implant with fluorescent chitosan tracer and thrombin to accelerate in situ solidification or with thrombin alone. Chitosan clearance, osteoclast density, and osteochondral repair were evaluated at 1, 2, and 8 weeks at the outside, edge, and through the proximal microdrill holes. Chitosan was retained at the top of the drill holes at 1 week as extracellular particles became internalized by granulation tissue cells at 2 weeks and was completely cleared by 8 weeks. Osteoclasts burst-accumulated at microdrill hole edges at 1 week, in new woven bone at the base of the drill holes at 2 weeks, and below endochondral cartilage repair at 8 weeks. Implants elicited 2-fold more osteoclasts relative to controls (P < 0.001), a more complete drill hole bone repair, and improved cartilage-bone integration and histological tissue quality. Treated and control 8-week cartilage repair tissues contained 85% collagen type II. After 8 weeks of repair, subchondral osteoclast density correlated positively with bone-cartilage repair tissue integration (P < 0.0005). Chitosan-GP/blood implant amplified the acute influx of subchondral osteoclasts through indirect mechanisms, leading to significantly improved repair and cartilage-bone integration without inducing net bone resorption. Osteoclasts are cellular mediators of marrow-derived cartilage repair integration.

Cell growth & differentiation : the molecular biology journal of the American Association for Cancer Research, 1990

Two proteins expressed in Rat-1 cells which are targets for v-fos transformation-specific alterat... more Two proteins expressed in Rat-1 cells which are targets for v-fos transformation-specific alterations in gene expression were identified as alpha 1(I) and alpha 2(I) procollagen. While procollagen (I) proteins were synthesized in Rat-1 fibroblasts, their synthesis was dramatically reduced in Rat-1 cells transformed with the FBJ-v-fos oncogene. Revertant cell lines, which were previously shown to express a functional fos oncoprotein, resumed the synthesis of procollagen (I) at levels comparable to those seen in Rat-1 cells. Further results indicated that these procollagen proteins were also synthesized in Rat-1 cell lines that constitutively express high levels of a transfected c-fos protooncogene. Together, these observations suggested that constitutive fos protein expression was not sufficient to inhibit synthesis of these proteins. We have further demonstrated that Rat-1 cells transformed by most other oncogenes express abundant levels of procollagen (I), indicating that inhibitio...

Journal of Histotechnology, 2005

... Anik Chevrierl, Evgeny ~ ossomacha ~ , Michael D. ~ uschmann ' ~ ~ , and... more ... Anik Chevrierl, Evgeny ~ ossomacha ~ , Michael D. ~ uschmann ' ~ ~ , and Caroline D. ~oemann*'~' ' Chemical Engineering, Ecole Polytechnique, Montreal, Quebec, Canada ~ iomedical Engineering, Ecole Polytechnique, Montreal, Quebec, Canada BioSyntech Canada Inc ...

Operative Techniques in Orthopaedics, 2006

Journal of Orthopaedic Research, 2009

Meniscus injury is a frequently encountered clinical orthopedic issue and is epidemiologically co... more Meniscus injury is a frequently encountered clinical orthopedic issue and is epidemiologically correlated to osteoarthritis. The development of new treatments for meniscus injury is intimately related to the appropriateness of animal models for their investigation. The purpose of this study was to structurally compare human menisci to sheep and rabbit menisci to generate pertinent animal models for meniscus repair. Menisci were analyzed histologically, immunohistochemically, and by environmental scanning electron microscopy (ESEM). In all species, collagen I appeared throughout most menisci, but was absent from the inner portion of the tip in some samples. Collagen II was present throughout the inner main meniscal body, while collagen VI was found in pericellular and perivascular regions. The glycosaminoglycan-rich inner portion of menisci was greater in area for rabbit and sheep compared to human. Cells were rounded in central regions and more fusiform at the surface, with rabbit being more cellular than sheep and human. Vascular penetration in rabbit was confined to the very outermost region (1% of meniscus length), while vessels penetrated deeper into sheep and human menisci (11-15%). ESEM revealed a lamellar collagenous structure at the articulating surfaces of sheep and human menisci that was absent in rabbit. Taken together, these data suggest that the main structural features that will influence meniscus repair-cellularity, vascularity, collagen structure-are similar in sheep and human but significantly different in rabbit, motivating the development of ovine meniscus repair models. ß

Osteoarthritis and Cartilage Oars Osteoarthritis Research Society, Jul 31, 2009

Objective: Chitosaneglycerol phosphate (chitosan-GP) is a unique polymer solution that is mixed w... more Objective: Chitosaneglycerol phosphate (chitosan-GP) is a unique polymer solution that is mixed with whole blood and solidified over microfractured or drilled articular cartilage defects in order to elicit a more hyaline repair cartilage. For clinical ease-of-use, a faster in situ solidification is preferred. Therefore, we investigated the mechanisms underlying chitosaneGP/blood implant solidification.

Supervised by Ron D.G. McKay. Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Appl... more Supervised by Ron D.G. McKay. Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Applied Biological Sciences, 1988. Includes bibliographical references (leaves 97-105).

Genes & Development

The MMTVD/myc transgenic mice spontaneously develop oligoclonal CD4+CD8+ T-cell tumors. We used p... more The MMTVD/myc transgenic mice spontaneously develop oligoclonal CD4+CD8+ T-cell tumors. We used provirus insertional mutagenesis in these mice to identify putative collaborators of c-myc. We found that Notch1 was mutated in a high proportion (52%) of these tumors. Proviruses were inserted upstream of the exon coding for the transmembrane domain and in both transcriptional orientations. These mutations led to high expression of truncated Notch1 RNAs and proteins (86-110 kD). In addition, many Notch1-rearranged tumors showed elevated levels of full-length Notch1 transcripts, whereas nearly all showed increased levels of full-length (330-kD) or close to full-length (280-kD) Notch1 proteins. The 5' end of the truncated RNAs were determined for some tumors by use of RT-PCR and 5' RACE techniques. Depending on the orientation of the proviruses, viral LTR or cryptic promoters appeared to be utilized, and coding potential began in most cases in the transmembrane domain. Pulse-chase ...

The American Journal of Sports Medicine, 2015

Current cartilage repair histological scoring systems are unable to explain the relationship betw... more Current cartilage repair histological scoring systems are unable to explain the relationship between collagen type II deposition and overall repair quality. The purpose of this study was to develop a novel zonal collagen type (ZCT) 5-point scoring system to measure chondroinduction in human clinical biopsy specimens collected after marrow stimulation. The hypothesis was that the ZCT scores would correlate with the International Cartilage Repair Society-II (ICRS-II) overall histological repair assessment score and glycosaminoglycan (GAG) content. Descriptive laboratory study. After optimizing safranin O staining for GAG and immunostaining for human collagen type II and type I (Col2 and Col1, respectively), serial sections from clinical osteochondral repair biopsy specimens (13 months after microfracture or microfracture with BST-CarGel; n = 39 patients) were stained and 3 blinded readers performed histomorphometry for percentage of staining, ICRS-II histological scoring, polarized light microscopy (PLM) scoring, and 5-point ZCT scoring based on tidemark morphology, zonal distribution of Col2 and Col1, and Col1 percentage stain. Because 1 biopsy specimen was missing bone, 38 biopsy specimens were evaluated for ICRS-II, PLM, and ZCT scores. Chondroinduction was identified in 21 biopsy specimens as a Col2 matrix fused to bone that spanned the deep-middle-superficial zones ("full-thickness hyaline repair"), deep-middle zones, or deep zone ("stalled hyaline") that was covered with a variable-thickness Col1-positive matrix, and was scored, respectively, as ZCT = 1 (n = 4 biopsy specimens), ZCT = 2 (n = 6) and ZCT = 3 (n = 11). Other biopsy specimens (n = 17) were fibrocartilage (n = 9; ZCT = 4), fibrous tissue (n = 4, ZCT = 5), or non-marrow derived (n = 4; ZCT = 0). Non-marrow derived tissue had a mean mature tidemark score of 84 out of 100 versus a regenerating tidemark score of 24 for all other biopsy specimens (P = .005). Both "stalled hyaline" repair and fibrocartilage had the same mean Col2 percentage stain; however, fibrocartilage was distinguished by heavy Col1 deposits in the deep zone, a 2-fold higher mean Col1 percentage stain (P = .001), and lower surface integrity (P = .03). ZCT scores correlated with GAG content and the ICRS-II overall assessment score, especially when combined with the PLM score for collagen organization (R = 0.82). Histological scores of the deep zone strongly predicted the ICRS-II overall assessment score (R = 0.99). The ICRS-II overall repair assessment score and GAG content correlated with the extent of Col2 deposition free of fibrosis in the deep/middle zone rather than bulk accumulation of Col2. Biopsy tissue from the BST-CarGel randomized clinical trial (microfracture without and with BST-CarGel, as treatment groups were not unblinded) showed regenerated tissue consistent with a chondroinduction mechanism in at least half of the treated lesions.

Purpose: Mechanical testing of articular cartilage is recommended by the FDA for products intende... more Purpose: Mechanical testing of articular cartilage is recommended by the FDA for products intended for the repair or replacement of knee cartilage. One experimental configuration that has many practical advantages is indentation. However, one limitation is the need to perpendicularly position the articular surface to the indenter. The objective of this study was to investigate the ability of a novel technique to automatically characterize mechanical properties of an entire articular surface with rapidity, precision, and reproducibility in indentation. Materials &Methods: Mature ovine and murine tibial plateau and femoral condyles were biomechanically mapped in vitro. The mechanical tester used was the 3-axis Mach-1 v500css from Biomomentum Inc. This novel technique detects the normal vector at each position and moves a spherical indenter (R=0.5 mm) along that vector while measuring the resulting force. Results: High-resolution mappings were obtained for the tibial plateau (Fig. 1) a...

Plasma Processes and Polymers

Thromboelastography uses cups and pins made of Cyrolite® plastic to analyze the rate of fibrin cl... more Thromboelastography uses cups and pins made of Cyrolite® plastic to analyze the rate of fibrin clot formation in blood samples. In this study, TEG cups and pins were modified by 4 distinct coating types using plasma‐enhanced chemical vapor deposition (PECVD): carboxylated, amine‐rich, hydrophobic, SiO2, and analyzed for surface chemistry and wettability. We tested the hypothesis that the coagulation kinetics of recalcified citrated blood plasma is controlled by surface chemistry, in the absence of clot activator. Only carboxylated surfaces became negatively charged upon wetting, and accelerated clot formation in a highly reproducible manner, whereas Cyrolite® and the other coatings had delayed and unpredictable clotting times. These data are consistent with a model whereby carboxylated surfaces selectively adsorb and activate factor XII while repelling other more abundant anionic blood proteins, resulting in reproducible clot kinetics.

Journal of Histotechnology, 2004

Chitosan is a naturally abundant cationic polysaccharide with unique physicochemical properties r... more Chitosan is a naturally abundant cationic polysaccharide with unique physicochemical properties resulting in its utilization in a vast array of biomedical applications including wound repair, drug delivery and tissue engineering. However, despite numerous and diverse studies investigating its use, there have been no detailed reports describing specific staining methods for cell culture and histopathological studies using chitosan based materials. Here, we describe methods for staining chitosan in both cell culture and within paraffin sections. Procedural models employed included identifying chitosan within in vitro whole blood clots, and culture wells, and in vivo chitosan hydrogel implants in multiple anatomical sites. First, a staining process for identifying chitosan was optimized using 0.03% Cibacron Brilliant Red-3BA. A second sensitive, and more versatile method utilizing 0.01% Fast Green in conjunction with the known Safranin-O Method was demonstrated, and may prove to be a key advancement in the histological study of chitosanbased biotechnological products. The method described here is broadly applicable to histological in situ detection of chitosan scaffolds of multiple deacetylation level and of variable fabrication.

Journal of Biomedical Materials Research Part A, 2015

In the context of porous bone void filler for oral bone reconstruction, peptides that suppress mi... more In the context of porous bone void filler for oral bone reconstruction, peptides that suppress microbial growth and promote osteoblast function could be used to enhance the performance of a porous bone void filler. We tested the hypothesis that P15-CSP, a novel fusion peptide containing collagen-mimetic osteogenic peptide P15, and competence-stimulating peptide (CSP), a cationic antimicrobial peptide, has emerging properties not shared by P15 or CSP alone. Peptide-coated surfaces were tested for antimicrobial activity toward Streptoccocus mutans, and their ability to promote human mesenchymal stem cell (MSC) attachment, spreading, metabolism, and osteogenesis. In the osteogenesis assay, peptides were coated on tissue culture plastic and on thin films generated by plasma-enhanced chemical vapor deposition to have hydrophilic or hydrophobic character (water contact angles 63°, 42°, and 92°, respectively). S. mutans planktonic growth was specifically inhibited by CSP, whereas biofilm formation was inhibited by P15-CSP. MSC adhesion and actin stress fiber formation was strongly enhanced by CSP, P15-CSP, and fibronectin coatings and modestly enhanced by P15 versus uncoated surfaces. Metabolic assays revealed that CSP was slightly cytotoxic to MSCs. MSCs developed alkaline phosphatase activity on all surfaces, with or without peptide coatings, and consistently deposited the most biomineralized matrix on hydrophilic surfaces coated with P15-CSP. Hydrophobic thin films completely suppressed MSC biomineralization, consistent with previous findings of suppressed osteogenesis on hydrophobic bioplastics. Collective data in this study provide new evidence that P15-CSP has unique dual capacity to suppress biofilm formation, and to enhance osteogenic activity as a coating on hydrophilic surfaces. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2015.

Journal of biomedical materials research. Part A, Jan 11, 2014

Poly(epsilon-caprolactone) (PCL) is a hydrophobic bioplastic under development for bone tissue en... more Poly(epsilon-caprolactone) (PCL) is a hydrophobic bioplastic under development for bone tissue engineering applications. Limited information is available on the role of internal geometry and cell-surface attachment on osseous integration potential. We tested the hypothesis that human bone marrow mesenchymal stem cells (MSCs) deposit more mineral inside porous 3D PCL scaffolds with fully interconnected 84 or 141 µm pores, when the surfaces are coated with chitosan via Layer-by-Layer (LbL)-deposited polyelectrolytes. Freshly trypsinized MSCs were seeded on PCL 3D cylinders using a novel static cold seeding method in 2% serum to optimally populate all depths of the scaffold discs, followed by 10 days of culture in proliferation medium and 21 additional days in osteogenic medium. MSCs were observed by SEM and histology to spread faster and to proliferate more on chitosan-coated pore surfaces. Most pores, with or without chitosan, became filled by collagen networks sparsely populated wit...

Osteoarthritis and cartilage / OARS, Osteoarthritis Research Society, 2014

The hand-held Arthro-BST™ device is used to map electromechanical properties of articular cartila... more The hand-held Arthro-BST™ device is used to map electromechanical properties of articular cartilage. The purpose of the study was to evaluate correlation of electromechanical properties with histological, biochemical and biomechanical properties of cartilage. Electromechanical properties (quantitative parameter (QP)) of eight human distal femurs were mapped manually ex vivo using the Arthro-BST (1 measure/site, 5 s/measure, 3209 sites). Osteochondral cores were then harvested from different areas on the femurs and assessed with the Mankin histological score. Prior to histoprocessing, cores were tested in unconfined compression. A subset of the cores was analyzed with polarized light microscopy (PLM) to assess collagen structure. Biochemical assays were done on additional cores to obtain water content and glycosaminoglycan (GAG) content. The QP corresponding to each core was calculated by averaging all QPs collected within 6 mm of the core center. The electromechanical QP correlated ...

Osteoarthritis and Cartilage, 2010

Cartilage and Osteoarthritis, 2004

The procedure described below is useful for extracting proteins, nucleic acids, and glycosaminogl... more The procedure described below is useful for extracting proteins, nucleic acids, and glycosaminoglycans from 5-40 mg of cartilage or tissue-engineered cartilage samples. This extraction method will generate samples compatible with Western blot, RNase protection, dimethyl methylene blue (DMB) assay for glycosaminoglycan, Hoechst DNA assay, and hydroxyproline assay. Most soluble matrix molecules can be extracted from pulverized samples using 4 M guanidine HCl, during a 30-min period of vortex agitation at 4°C. Shorter agitation times can give inadequate solubilization. The guanidine HCl-insoluble pellet must be re-extracted with guanidine thiocyanate buffer, to solubilize RNA additionally. The final insoluble pellet can be rinsed with ethanol and digested with papain, to quantify collagen content as well as other insoluble or crosslinked material. Samples between 1 and 5 mg may be directly digested with a small volume of papain buffer for DMB, hydroxyproline, and Hoechst DNA assays.

Cartilage, 2010

Cartilage-bone integration is an important functional end point of cartilage repair therapy, but ... more Cartilage-bone integration is an important functional end point of cartilage repair therapy, but little is known about how to promote integration. We tested the hypothesis that chitosan-stabilized blood clot implant elicits osteoclasts to drilled cartilage defects and promotes repair and cartilage-bone integration. Bilateral trochlear defects in 15 skeletally mature rabbit knees were microdrilled and then treated with chitosan-glycerol phosphate (GP)/blood implant with fluorescent chitosan tracer and thrombin to accelerate in situ solidification or with thrombin alone. Chitosan clearance, osteoclast density, and osteochondral repair were evaluated at 1, 2, and 8 weeks at the outside, edge, and through the proximal microdrill holes. Chitosan was retained at the top of the drill holes at 1 week as extracellular particles became internalized by granulation tissue cells at 2 weeks and was completely cleared by 8 weeks. Osteoclasts burst-accumulated at microdrill hole edges at 1 week, in new woven bone at the base of the drill holes at 2 weeks, and below endochondral cartilage repair at 8 weeks. Implants elicited 2-fold more osteoclasts relative to controls (P < 0.001), a more complete drill hole bone repair, and improved cartilage-bone integration and histological tissue quality. Treated and control 8-week cartilage repair tissues contained 85% collagen type II. After 8 weeks of repair, subchondral osteoclast density correlated positively with bone-cartilage repair tissue integration (P < 0.0005). Chitosan-GP/blood implant amplified the acute influx of subchondral osteoclasts through indirect mechanisms, leading to significantly improved repair and cartilage-bone integration without inducing net bone resorption. Osteoclasts are cellular mediators of marrow-derived cartilage repair integration.

Cell growth & differentiation : the molecular biology journal of the American Association for Cancer Research, 1990

Two proteins expressed in Rat-1 cells which are targets for v-fos transformation-specific alterat... more Two proteins expressed in Rat-1 cells which are targets for v-fos transformation-specific alterations in gene expression were identified as alpha 1(I) and alpha 2(I) procollagen. While procollagen (I) proteins were synthesized in Rat-1 fibroblasts, their synthesis was dramatically reduced in Rat-1 cells transformed with the FBJ-v-fos oncogene. Revertant cell lines, which were previously shown to express a functional fos oncoprotein, resumed the synthesis of procollagen (I) at levels comparable to those seen in Rat-1 cells. Further results indicated that these procollagen proteins were also synthesized in Rat-1 cell lines that constitutively express high levels of a transfected c-fos protooncogene. Together, these observations suggested that constitutive fos protein expression was not sufficient to inhibit synthesis of these proteins. We have further demonstrated that Rat-1 cells transformed by most other oncogenes express abundant levels of procollagen (I), indicating that inhibitio...

Journal of Histotechnology, 2005

... Anik Chevrierl, Evgeny ~ ossomacha ~ , Michael D. ~ uschmann ' ~ ~ , and... more ... Anik Chevrierl, Evgeny ~ ossomacha ~ , Michael D. ~ uschmann ' ~ ~ , and Caroline D. ~oemann*'~' ' Chemical Engineering, Ecole Polytechnique, Montreal, Quebec, Canada ~ iomedical Engineering, Ecole Polytechnique, Montreal, Quebec, Canada BioSyntech Canada Inc ...