R Roy

Laval University, Quebec City, Quebec, Canada

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Publications (47)144.41 Total impact

  • 04/2013; 7(8):821. DOI:10.4267/10608/4460
  • European Journal of Paediatric Neurology 09/2007; 11:76-76. DOI:10.1016/S1090-3798(08)70536-1 · 1.93 Impact Factor
  • Transplantation 01/2004; 78. DOI:10.1097/00007890-200407271-01175 · 3.78 Impact Factor
  • Transplantation 01/2004; 78. DOI:10.1097/00007890-200407271-01174 · 3.78 Impact Factor
  • Human Immunology 10/2002; 63(10). DOI:10.1016/S0198-8859(02)00614-6 · 2.28 Impact Factor
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    ABSTRACT: This study investigated the basic biocompatibility aspects of two types of polypyrrole (PPy)-coated polyester fabrics for possible use as vascular prostheses. These PPy-coated fabrics, PPy-Phos and PPy-Plas, were sterilized with ethylene oxide (EO) and the following characterizations were performed: surface morphology by scanning electron microscope, EO residuals analysis by the headspace method, acute systemic toxicity in the mouse model, hemolysis, blood coagulation time, viability and proliferation of endothelial cells measured with the WST-1 method, and activation of polymorphonuclear (PMN) cells indicated by the specific expression of interleukin 8 mRNA measured by reverse transcription polymerase chain reaction. Virgin polyester fabrics, expanded poly(tetrafluoroethylene) (ePTFE), and medical-grade Bionate 80A poly(carbonate urethane) were used as references in the cell culture experiments. The PPy-coated fabrics revealed different surface morphologies by showing more PPy lamina and clusters on the PPy-Plas. Neither of the PPy-coated fabrics had an adverse effect on hemolysis and coagulation time, and they did not cause any acute systemic toxicity. The EO residual level was as low as 5 ppm or less, which is considered quite acceptable. Although exhibiting a relatively low initial cell adhesion at 24 h, the two PPy-coated samples showed no cytotoxicity at 72 and 168 h. Bionate 80A and ePTFE recorded cytotoxicity at 72 and 168 h, respectively. The virgin fabrics also demonstrated a decrease of viable cells at 72 h that was not significant. The activation of PMN cells induced by both PPy-coated fabrics, the ePTFE, and the negative control was significantly lower than that induced by their respective tumor necrosis factor-alpha controls. These results therefore highlighted the potential of PPy-coated fabrics for use as cardiovascular prostheses. It was suggested that cell adhesion moieties should be incorporated into the PPy/fabric composite to increase cell adhesion and subsequent cell proliferation.
    Journal of Biomedical Materials Research 11/2001; 57(1):63-71.
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    ABSTRACT: Prevention of acute rejection is the most prevalent measure used to reduce the long-term risk of chronic allograft rejection. Until now, biopsy was the only useful diagnostic tool for monitoring allograft acute rejection, but invasiveness of this procedure limits its use. The aim of this study was to investigate the implication of peripheral blood immune markers as a predictive diagnostic tool preceding biopsy in acute renal allograft rejection determination. Of the 61 patients studied, 13 had no rejection episodes, 8 had a proven acute rejection, and 40 were excluded for graft dysfunction causes. Mitogen-induced peripheral blood mononuclear cells were tested for interleukin- (IL) 2, IL-4, IL-5, IL-6, IL-10, IL-15, Interferon-gamma, Perforin, Granzyme B, and Fas L using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). An up-regulated mRNA expression value was calculated in which a patient's sample was deemed positive if its differential expression value was equal or higher than the mean differential expression value calculated from the nonrejecting patients. IL-4, IL-5, IL-6, Interferon-gamma, Perforin, and Granzyme B mRNA levels were associated with acute rejection. When at least two of these cytokine markers were up-regulated in a given patient, 75% of the rejecting recipients were identified against 15% of the nonrejecting patients. We have shown that acute rejection episodes in renal transplant recipients were associated with an increase in mRNA expression of cytokines in mitogen-induced peripheral blood mononuclear cells. The evaluation of pro-inflammatory cytokines and cytotoxic molecules prove useful in the clinical identification of acutely rejecting transplant recipients and in the justification of concomitant antirejection therapy before histological diagnosis confirmation.
    Transplantation 11/2000; 70(7):1074-80. DOI:10.1097/00007890-200010150-00014 · 3.78 Impact Factor
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    ABSTRACT: Membranes made from 4 commercial poly(carbonate urethanes): Carbothane (CB), Chronoflex (CF), Corethane 80A (CT80), and Corethane 55D (CT55), and from 2 poly(ether urethanes): Tecoflex (TF) and Tecothane (TT) were prepared by solution casting and sterilized by either ethylene oxide (EO) or gamma radiation. Their biocompatibility was evaluated in vitro in terms of proliferation, cell viability, and adhesion characteristics of human umbilical veins (HUVEC), monocytes (THP-1), and skin fibroblasts, and by measuring complement activation through the generation of the C3a complex. Their hemocompatibility was determined by measuring the level of radiolabeled platelet, neutrophil, and fibrin adhesion in an ex vivo arteriovenous circuit study in piglets as well as via an in vitro hemolysis test. The results of this study showed no endothelial cell proliferation on any of the materials. The cell viability study revealed that the CB, CF, and TF membranes sterilized by EO maintained the highest percentage of monocyte viability after 72 h of incubation (>70%) while none of the gamma-sterilized membranes displayed any cell viability. The fibroblast adhesion and C3a generation assays revealed that none of the materials supported any cell adhesion or activated complement, regardless of the sterilization method. The hemolysis test also confirmed that the 4 poly(carbonate urethanes) were hemolytic while none of the poly(ether urethanes) were. Finally, the ex vivo study revealed that significantly more platelets adhered to the CB and CT55 membranes while the levels of neutrophil and fibrin deposition were observed to be similar for all 6 materials. In conclusion, the study identified the CF and TF membranes as having superior biocompatibility and hemocompatibility compared to the other polyurethanes.
    Artificial Organs 11/2000; 24(11):879-88. · 1.87 Impact Factor
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    ABSTRACT: The electrically conductive properties of polypyrrole (PPy) as a coating on polyester material are very attractive for the manufacture of small diameter blood conduits. However, before these PPy-coated materials can be investigated for their capacity to generate endothelialized luminal surfaces, they must first be studied for their innocuousness in a living environment. The specific goal of the present study was to investigate the in vivo interactions of PPy-coated and noncoated woven polyester materials implanted subcutaneously in rats for prescheduled periods of 2, 5, 10, 20, and 30 days. The in vivo magnetic resonance (MR) relaxation times were computed for a small area of muscle tissue adjacent to the implants. A correlation was concurrently attempted with blood monocyte activation studies as well as histological observations of the tissue-material interface. The progressive pattern of the slower transversal relaxation time (T2s) values revealed a more persistent tissue reaction for the most conductive PPy-coated materials and a shorter acute tissue response as the surface resistivity increased. Similarly, the blood monocyte activation studies indicated that the thickness of the PPy coating, which correlated with the conductivity, was directly related to tissue response. Furthermore, both the MR and biological studies showed that the PPy-coated material with a high surface resistivity displayed the lowest tissue reaction over the entire period of implantation. The results obtained from the blood monocyte activation studies and histological observations correlate well with the noninvasive MR measurements of the body's healing process. The conductive materials with high surface resistivities must be further investigated. Finally, the noninvasive nature of MR relaxometry reveals its outstanding potential for future in vivo investigations of the body's tissue interactions with polymers and nonferromagnetic biomaterials.
    Artificial Organs 11/1999; 23(10):910-9. · 1.87 Impact Factor
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    ABSTRACT: The CD8+CD38+ T-cell subset can predict progression to acquired immune deficiency syndrome among human immunodeficiency virus-positive subjects. This T-cell subset usually increases during other active viral infections (cytomegalovirus [CMV], Epstein Barr virus). We report on its usefulness in the early detection of CMV infection in kidney transplant recipients. Quantitation of CD8+CD38+ T cells was monitored by dual-color flow cytometry analysis on 77 patients during the posttransplantation period. Seventeen of the 52 patients at risk for CMV disease (33%) had primary infection or reactivation and three patients had herpes simplex virus infection only. In every patient with CMV disease, high values for the CD8+CD38+ subset were detected with a 90% positive predictive value for the primary infections. Elevated values were observed at the very first clinical signs of the viral disease or within the few preceeding days. Acute rejection episodes did not provoke false-positive results. This immunologic marker is sensitive and easily obtainable on a daily basis. It may help to direct therapy during rejection or serve as a tool for early detection of clinical viral diseases.
    Transplantation 02/1998; 65(2):279-82. DOI:10.1097/00007890-199801270-00026 · 3.78 Impact Factor
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    ABSTRACT: Myoblast transplantation is a potential treatment for Duchenne muscular dystrophy. One of the problems possibly responsible for the limited success of clinical trials is the rapid death of the myoblasts after transplantation. To investigate this problem, myoblasts expressing beta-galactosidase were injected in the tibialis anterior muscles of mice. Beta-galactosidase activity was reduced by 74.7% after 3 days. Myoblast death observed at 3 days was reduced to 57.2% when the hosts were irradiated. This result suggested that host cells were contributing to this phenomenon. Transplantation in SCID and FK506-treated mice did not reduce cell death, indicating that mortality was not due to an acute specific reaction. In contrast, administration of the anti-LFA-1 (TIB-213) mAb markedly reduced myoblast death at 3 days without altering leukocyte tissue infiltration. We postulated that neutrophils were mediating myoblast mortality by an LFA-1-dependent mechanism. To test this hypothesis, IL-1beta-activated myoblasts were loaded with 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate, di(acetoxymethylester) (DCFH), a marker for oxidative stress. Addition of neutrophils and zymosan-activated serum resulted in a time-dependent DCFH fluorescence; this neutrophil-induced oxidation was considerably inhibited by TIB-213. These results indicate that an effective control of the inflammatory reaction will be necessary for any new clinical trials of myoblast transplantation and suggest that neutrophil-mediated myoblast injury occurs by an LFA-1-dependent pathway.
    The Journal of Immunology 10/1997; 159(5):2522-31. · 5.36 Impact Factor
  • Transplantation Proceedings 07/1997; 29(4):1932-4. DOI:10.1016/S0041-1345(97)00166-8 · 0.95 Impact Factor
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    ABSTRACT: Myoblasts obtained from donors histoincompatible for several non-major histocompatibility complex antigens (i.e., including minor histocompatibility antigens) and from syngeneic donors were transplanted without any immunosuppression into the muscles of male dystrophic C57BL/10J mdx/mdx mice. Myoblasts from syngeneic mice resulted in the formation of a high percentage of dystrophin-positive fibers 16 weeks after the transplantation. There was no evidence of a cellular immune reaction against the donor myoblasts, i.e., no infiltration by CD4 or CD8 lymphocytes and no increased expression of granzyme B and interferon-gamma mRNAs. Transplantation of myoblasts obtained from donors histoincompatible only for non- major histocompatibility complex antigens produced a transient increase of dystrophin-positive fibers at 4 weeks after transplantation for some donor strains but not for others. For donor strains that did produce an increase at 4 weeks, the number of dystrophin-positive fibers was reduced 16 weeks after the transplantation. There was evidence of a cellular immune reaction-infiltration by CD4 and by CD8 lymphocytes and increased expression of granzyme B and interferon-gamma mRNAs. Transplantation of myoblasts obtained from male C57BL/10J +/+ mice into female C57BL/10J mdx/mdx mice also led to the presence of only a few dystrophin-positive fibers with the same signs of cellular immune reaction. In this later case, the cellular immune response was attributed to the H-Y minor antigens. Finally, antibodies against fetal calf serum were detected after both syngeneic and nonsyngeneic transplantations, indicating that the culture medium may also be a source of antigens. In mice, the presence of these antibodies against culture medium did not reduce the success of a first syngeneic transplantation.
    Transplantation 04/1997; 63(6):893-9. · 3.78 Impact Factor
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    ABSTRACT: Myoblasts were grown from monkey muscle biopsies and infected in vitro with a defective retroviral vector containing a cytoplasmic beta-galactosidase (beta-gal) gene. These myoblasts were then transplanted to 14 different monkeys, 6 of which were immunosuppressed with FK506. Without immunosuppression, only a few myoblasts and myotubes expressing beta-gal were observed 1 week after the transplantation, but no cells expressing beta-gal were observed after 4 weeks. This result was attributed to immune responses since infiltration by CD4+ or CD8+ lymphocytes was abundant 1 week after transplantation but not after 4 weeks. The expression of interleukin 6 (IL-6), interleukin 2 (IL-2), granulocyte/macrophage colony stimulating factor (GM-CSF), transforming growth factor-beta (TGF-beta) and granzyme B mRNAs was increased in the myoblast-injected muscle indicating that the infiltrating lymphocytes were activated. Moreover, antibodies against the donor myoblasts were detected in 3 out of 6 cases. When the monkeys were immunosuppressed with FK506, muscle fibers expressing beta-galactosidase (beta-gal) were present 1, 4 and 12 weeks after the transplantation. There was neither significant infiltration by CD4 or CD8 lymphocytes, nor antibodies detected. The mRNA expression of most cytokines was significantly reduced as compared to the nonimmunosuppressed monkeys. These results indicate that FK506 is effective in controlling short-term immune reactions following myoblast transplantation in monkeys and suggest that it may prove useful for myoblast transplantation in Duchenne Muscular Dystrophy patients.
    Journal of Neuropathology and Experimental Neurology 07/1996; 55(6):687-97. DOI:10.1097/00005072-199606000-00002 · 4.37 Impact Factor
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    ABSTRACT: We studied the effects of single and repeated sets of injections in the same muscle of mdx mice of myoblasts grown with or without a high concentration 100 ng ml-1 of basic fibroblast growth factor (bFGF). The injected myoblasts were obtained from non-dystrophic transgenic mice expressing the beta-galactosidase gene under the control of a muscle-specific promoter. In these experiments, the host muscle was not irradiated to prevent muscle regeneration by host myoblasts. The host muscle was not damaged before myoblast transplantation with notexin, marcaïne or cold to trigger a regeneration-degeneration cycle. Without such pretreatments, the first set of injections of myoblasts grown without bFGF produced only 8% beta-galactosidase-positive and dystrophin-positive muscle fibers 1 month after transplantation. The percentage of muscle fibers containing the donor reporter gene increased, however, to 26% following a second set of injections in the same muscle. The percentage of muscle fibers expressing the donor reporter gene was significantly higher when the myoblasts were grown with a high dose of bFGF. Indeed the first set of injections produced 34% beta-gal-positive fibers while a second set of injections raised this percentage to 54%. In all cases, the percentage of dystrophin-positive fibers was similar to that of beta-gal-positive fibers. Therefore a high percentage of muscle fibers of donor origin can be obtained without preliminary damaging treatments of the mdx muscle when myoblasts grown with bFGF are injected several times. The effects of bFGF is not produced by increasing the percentage of myoblasts in a primary muscle culture since improvement of myoblast transplantation was obtained with a pure myoblast clone even with a lower concentration (10 ng ml-1) of bFGF.
    Neuromuscular Disorders 06/1996; 6(3):187-93. DOI:10.1016/0960-8966(96)00004-1 · 3.13 Impact Factor
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    ABSTRACT: The albumin-coated vascular graft (ACG) and its uncoated polyester substrate, the Vascular II (V-II), were evaluated in terms of biocompatibility and biofunctionality using two in vivo animal studies. Biocompatibility and immunoreactivity were assessed by implanting intraperitoneally in the rat small segments of the ACG and the V-II graft and harvesting them with their surrounding tissue 3d, 1, 2 and 4 weeks later. Cytofluorometric determination of total T cells (CD3), the ratio of CD4/CD8 subsets and the percentage of IL-2 receptor-positive T cells in the peripheral blood has revealed that no significant difference in any of the T cell populations was found between the ACG and the V-II graft. The cellular reactivity of the ACG in terms of acid phosphatase activity at the implant side was significantly greater at 3 d but not at longer periods. Biofunctionality was evaluated by implanting both grafts as a thoracoabdominal vascular bypass in dogs for 11 different periods ranging from 4 h to 6 months. The rate of albumin resorption was such that traces were still present at 1 month, but no longer observable at 2 months. Tissue incorporation into the graft wall was earlier for the V-II (2 weeks) than for the ACG (4 weeks), which showed complete encapsulation, tissue incorporation and endothelialization after 2 months in vivo. Only small differences were observed between both grafts in terms of platelet and fibrin uptake on the luminal surface. The prostacyclin/thromboxane A2 ratio increased to a level higher that 1.0 aorta within 1 month for the V-II and 4 months for the ACG. In conclusion, the Bard ACG has demonstrated excellent biocompatibility in terms of blood T cell behaviour and acid phosphatase activity at the implant site. Finally, its healing response is equivalent to that of the uncoated Dacron prosthesis once the albumin coating has been resorbed.
    Biomaterials 02/1996; 17(1):3-14. DOI:10.1016/0142-9612(96)80749-6 · 8.31 Impact Factor
  • ASAIO Journal 01/1996; 42(2). DOI:10.1097/00002480-199603000-00083 · 1.39 Impact Factor
  • ASAIO Journal 01/1996; 42(2). DOI:10.1097/00002480-199604000-00081 · 1.39 Impact Factor
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    ABSTRACT: Cyclophosphamide immunosuppression does not permit successful myoblast allotransplantation in mouse. Myoblast transplantation is a potential treatment for Duchenne muscular dystrophy. In one clinical trial, Duchenne patients were immunosuppressed with cyclophosphamide. We report here that myoblasts from transgenic mice expressing the beta-galactosidase reporter gene transplanted in mdx mice failed to form new muscle fibres when cyclophosphamide (2 or 10 mg kg-1 per day) was used for immunosuppression. At the lowest dose of cyclophosphamide (2 mg kg-1 per day), some mdx recipient mice formed antibodies against donor myoblasts; however, no humoral immune reaction was observed at the highest dose (10 mg kg-1 per day). The failure of transplantation under cyclophosphamide treatment was attributed to the low immunosuppressive activity at a low dose and to the toxic action of a high dose of this drug. These results could explain the lack of success of myoblast transplantation in a previous clinical trial.
    Neuromuscular Disorders 12/1995; 5(6):511-7. DOI:10.1016/0960-8966(95)00011-B · 3.13 Impact Factor

Publication Stats

2k Citations
144.41 Total Impact Points

Institutions

  • 1990–2007
    • Laval University
      • Département de Chirurgie
      Quebec City, Quebec, Canada
  • 2000
    • Centre Hospitalier Universitaire de Québec (CHUQ)
      Quebec City, Quebec, Canada
  • 1995–1996
    • Université du Québec
      Québec, Quebec, Canada
  • 1984–1995
    • Centre hospitalier de l'Université de Montréal (CHUM)
      Montréal, Quebec, Canada