Biomedical subjects

Charles W Hewitt

Publications and source records attributed to Charles W Hewitt.

10 recordsLinked to original sources

PubMed2006

Vascularized lymph node transplantation induces graft-versus-host disease in chimeric hosts.

BACKGROUND: The role of lymph nodes (LNs) in adaptive immune responses has been the subject of extensive research. In previous studies, the surgical removal of lymph nodes from rat hind limbs prevented the development of lethal graft-versus-host disease (GVHD) after allogeneic hind limb transplantation to chimeric recipient rats. The purpose of this study was to establish the role of the cellular fraction versus the microenvironment of LNs in the development of GVHD in this model. METHODS: A rat model for vascularized LN transplantation was developed and graft-versus-host responses were compared after: 1) naive ACI LN cells were infused into Wistar-Furth (WF) rats as chimeric recipients (e.g. [ACI-->WF]); 2) vascularized WF lymph nodes were transplanted to syngeneic WF recipients; 3) nonvascularized ACI lymph nodes were transplanted to [ACI-->WF] chimeric recipients; 4) vascularized ACI lymph nodes were transplanted to [ACI-->WF] chimeric recipients. RESULTS: Transplantation of vascularized ACI lymph nodes to [ACI-->WF] chimeric recipient rats resulted in severe and sometimes lethal GVHD. In contrast, neither the infusion of purified ACI LN cells nor the transplantation of nonvascularized LNs led to GVHD in chimeric recipients. CONCLUSIONS: When introducing allogeneic cells into chimeric recipients, concomitant transplantation of the vascularized LN microenvironment makes a manifest difference between induction and absence of GVHD. This illustrates the important role of the LN microenvironment in adaptive immune responses.

Animals↗

PubMed2006

From experimental rat hindlimb to clinical face composite tissue allotransplantation: historical background and current status.

The purpose of this article is to review the historical background and clinical status of composite tissue allotransplantation and to discuss the scientific evolution of clinical face transplantation. Composite tissue allotransplantation (CTA) rapidly progressed in the 1980s with the discovery of cyclosporine. Although the most success has been achieved with hand transplantation, others have made progress with allografts of trachea, peripheral nerve, flexor tendon apparatus, vascularized knee, larynx, abdominal wall, and most recently, partial face. The world's first partial face allotransplantation occurred in November 2005 in France. In April of 2006, there was a second performed in China. As of today, there are now multiple institutions with plans to attempt the world's first full facial/scalp transplant. Complete facial/scalp allotransplantation offers a viable alternative for unfortunate individuals suffering severe facial disfigurement and is a product of many decades of experimental research, beginning with rat hindlimb allografts.

Animals↗

PubMed2004

Lymphadenectomy prior to rat hind limb allotransplantation prevents graft-versus-host disease in chimeric hosts.

In previous rat studies, the use of mixed allogeneic chimerism (MAC) to induce host tolerance to hind limb allografts has resulted in severe graft-versus-host disease (GVHD). The purpose of this study was to determine if immunocompetent cells in bone marrow (BM) and/or lymph nodes (LNs) of transplanted limbs were responsible for inducing GVHD in mixed chimeric hosts. [ACI-->Wistar Furth] chimeric rats received ACI hind limbs that were non-irradiated, irradiated (1050 cGy) or lymphadenectomized. Rejection, GVHD and donor chimerism was assessed. Chimeric hosts rejected none of their limbs. However, hosts of non-irradiated hind limbs succumbed to GVHD 22.4+/-0.8 days after transplantation. In contrast, chimeras that received irradiated or lymphadenectomized ACI hind limbs showed no clinical or histological signs of GVHD at 5 months. We conclude that mixed chimeric hosts are susceptible to GVHD due to the immunocompetent cell load provided by the LNs, not the BM, of hind limb allografts.

Animals↗

PubMed2004

Absence of graft-versus-host disease in the isolated vascularized bone marrow transplant.

An isolated vascularized bone marrow transplant (iVBMT) model was developed to study the contribution of the bone marrow component in a composite tissue allograft. We hypothesized that the iVBMT would be functional and cause graft-versus-host disease (GVHD) in a fraction of the recipients. Lewis iVBMT grafts were transplanted to Lewis-Brown Norway recipients. Animals were sacrificed at various times from 1 to 14 weeks. Polymerase chain reaction for microchimerism was performed on the host's marrow. No animals exhibited signs of GVHD at death. Histologic examination of the grafts showed a normal mix of hematopoietic and fatty elements and appeared to be functional. Tissues usually affected-tongue, ear, liver, and gut-also showed no evidence of disease. Polymerase chain reaction demonstrated microchimerism in both groups. These findings suggest that the vascularized bone marrow within a composite tissue allograft is not the component that causes GVHD; rather, it may serve an immunomodulatory function for tolerance induction.

Animals↗

PubMed2004

Nicotine induces mononuclear leukocyte adhesion and expression of adhesion molecules, VCAM and ICAM, in endothelial cells in vitro.

The pathology of atherosclerotic cardiovascular disease (ASCVD) has been characterized as an inflammatory response to vessel injury. The initial steps of this response involve mononuclear leukocyte (MNL) attachment and infiltration into the vessel wall. Leukocyte adhesion is potentiated by expression of cellular adhesion molecules. Vascular cell adhesion molecule-1 (VCAM) and intracellular adhesion molecule-1 (ICAM) are markers of cellular activation and have the ability to attach leukocytes to the endothelium, which is an initial event in the inflammatory response in the vessel wall. Human umbilical vein endothelial cells (HUVEC) were plated in endothelial growth medium (EGM) on plastic coverslips and grown until cells were 75% confluent. Free base nicotine (FBN) was diluted in EGM to a concentration of 10(-8) M and added to experimental cells. At 3 hr, coverslips were removed and fixed. Immunohistochemical staining (IHCS) was performed using a monoclonal antibody to human ICAM and VCAM. Digital image analysis (DIA) was performed to quantify the expression of ICAM and VCAM. An intensity stain index (ISI) measuring area and intensity of stain/total cellular area was determined. Additional HUVEC grown in a similar manner were either exposed to 10(-8) M FBN in EGM or EGM control for 4 hr, then were exposed to MNL suspension for 10 min. Coverslips were removed, rinsed, and fixed. Hematoxylin and eosin staining was performed and cells examined under light microscopy. Leukocyte number per high power field (HPF) was counted and compared to controls. Data were analyzed using analysis of variants (ANOVA) and Student's t-test. Differences were considered significant if p < 0.05. ICAM and VCAM expression was absent in control cells. Nicotine exposure at 3 hr induced expression of VCAM (ISI = 30.85+/-0.77) and to a lesser extent ICAM (ISI = 16.6+/-1.39) (p < 0.001). MNL adhesion was markedly increased in cells exposed to nicotine (79.4+/-16.9/HPF) when compared to control cells (1.8+/-0.91/HPF) exposed to MNL (p < 0.01). These data show nicotine's ability to activate HUVEC as evidenced by induction of ICAM and VCAM expression in vitro. The biological effects of these adhesion molecules are demonstrated by a marked increase in MNL adhesion to HUVEC as demonstrated by leukocyte adhesion assay (LAA). MNL adhesion and subsequent migration into the intima, if occurring in vivo, may be a vital step in the pathogenesis of ASCVD associated with nicotine exposure.

Cell Adhesion↗

PubMed2003

An extraperitoneal isolated vascularized bone marrow transplant model in the rat.

An isolated vascularized bone marrow transplant (iVBMT) model was previously developed in the rat to specifically study the role of bone marrow and its environment in a composite tissue allotransplant. An extraperitoneal model was successfully created to avoid laparotomy and cross-clamping of the great vessels. The extraperitoneal iVBMT model consisted of a left donor femur that was harvested with its nutrient vessels, anastomosed to the right femoral vessels in a syngeneic host, and then placed subcutaneously in the abdominal wall. At explant, the graft vessels were grossly patent, and histology of the graft bones showed a viable marrow compartment. Polymerase chain reaction demonstrated peripheral chimerism in the recipients. This model is technically simple with minimal morbidity in the recipient animals. By using the iVBMT, future studies across semiallogeneic and allogeneic barriers will help define the role of the bone marrow compartment in composite tissue allotransplants to potentially induce immune tolerance.

Animals↗

PubMed2002

Real-time, high-definition, three-dimensional microscopy for evaluating problematic cervical Papanicolaou smears classified as atypical squamous cells of undetermined significance.

BACKGROUND: The perceived inadequacies of the cervical Papanicolaou (Pap) smear have been attributed to sampling, screening, or interpretive errors. Within this type of cytologic preparation, there are thick cell clusters in which the cells are obscured. It may not possible to evaluate these areas by conventional microscopy. The authors clinically tested the hypothesis that high-definition, three-dimensional (3-D) microscopy based on multiple oblique illumination (MOI), with its ability to penetrate into thick areas, would be useful in evaluating problematic cervical Pap smears, particularly those diagnosed as atypical squamous cells of undetermined significance (ASCUS). METHODS: ASCUS Pap smears and corresponding surgical biopsy specimens were evaluated prospectively using standard, axially illuminated microscopes and a new high-definition, 3-D microscope employing MOI. The Pap smears were reviewed in a blinded fashion with both types of microscopy. The rendered diagnoses were then compared with the subsequent tissue biopsies, which also were blinded, as the definitive end point. RESULTS: It was immediately apparent that the high-definition, 3-D MOI microscope had better resolution compared with the standard microscopes. Pap smears and biopsy diagnoses were correlated significantly for MOI (P < 0.001), and there were significant improvements (P = 0.0108) in accuracy when 3-D, high-definition microscopy was compared with conventional microscopy. The authors found no statistically significant correlation between ASCUS diagnoses that were rendered by using standard microscopes compared with the subsequent biopsy. CONCLUSIONS: Due to enhanced visualization through thick cell clusters, an increased depth of field, light penetration, and resolution, high-definition, 3-D microscopy based on MOI produced superior accuracy compared with conventional light microscopy in evaluating cervical Pap smears.

Adolescent↗

PubMed2002

Engineering a composite neotrachea with surgical adhesives.

BACKGROUND/PURPOSE: Reconstructive surgery often is limited by the availability of normal tissue. Tissue engineering provides promise in the development of "artificial tissues." The purpose of this study was to test the efficacy and viability of the use of a biologic surgical adhesive TISSEEL in combining engineered bronchial epithelium with engineered cartilage. METHODS: Using isolated human cells, bronchial epithelium and mature cartilage were engineered. Using a contact adhesive technique, TISSEEL was used to biologically fuse the bronchial epithelium and the cartilage. The fused composite then was supported for 5 days in tissue culture. The mechanical properties of the adhesion were tested, and the construct was studied morphologically to assess viability of the cartilage and the bronchial epithelium. The bronchial epithelium showed a normal cell size (337.2 microm2) and epithelial thickness (46.47 microm). RESULTS: TISSEEL was effective in fusing the epithelium to the cartilage. The construct remained viable for 5 days in culture. There was no difference in the dimensions of the bronchial epithelium or the epithelial cells. Mechanical adhesion was achieved. CONCLUSIONS: Biologically compatible fibrin glue is an effective surgical adhesive that allows the tissue types to be fused while remaining viable and morphologically accurate. Surgical adhesives may show promise in the development of composite tissue development in the field of bioengineering.

Biodegradation, Environmental↗

PubMed2002

Mechanisms of alloimmune tolerance associated with mixed chimerism induced by vascularized bone marrow transplants.

Rat limb allograft recipients represent surgically induced, immediately vascularized bone marrow transplant (VBMT) chimeras. The majority of these chimeras undergo tolerance while a minority develop graft versus host disease (GVHD). T-cell chimerism and associated mechanisms of cellular immune nonresponsiveness were investigated in tolerant VBMT chimeras. A strong correlation (p < 0.01) was observed between the clinical onset of GVHD and levels of donor T-cell chimerism approximating or greater than 50%. However, stable mixed chimerism was associated with tolerance. In conclusion, three major sequential mechanisms of immune nonresponsiveness were elucidated in tolerant VBMT chimeras over time and included development of nonspecific suppressor cells (which potentially represent natural suppressor cells), maturation of antigen-specific suppressor cell circuits, and eventually putative clonal inactivation.

Animals↗

PubMedDate not supplied

Composite tissue allotransplantation.

Composite tissue allotransplantation (CTA) recently took its first steps in the clinical arena in 1998 with the successful hand transplant performed in Lyons, France. That single operation represented a culmination of many years of laboratory research in multiple fields involving integumentary/musculoskeletal transplantation. Here we review the prerequisite developments in the field of immunology, microsurgery, and pharmacotherapy that helped bring CTA to clinical reality. This new field still has many unanswered questions which are addressed below. Additionally, new evolving research in CTA is also discussed.

Animals↗