Biomedical subjects

C J Doillon

Publications and source records attributed to C J Doillon.

At least 37 records · Page 2Linked to original sources

PubMed1993

Growth factors and biological supports for endothelial cell lining: in vitro study.

Endothelial cell covering over the vascular prosthesis luminal surface is a process that may require the presence of growth factors (GFs) and extracellular matrix supports. Endothelialization could be improved by combining both GFs and an extracellular matrix analog. In the present study, different biological substrates made of type I or IV collagens, gelatin, fibronectin, fibrin, laminin, chondroitin sulphate, heparan sulphate, heparin or hyaluronic acid were used to support endothelial cell culture. An endothelial cell growth supplement (ECGS) was incorporated in (group 1) or overlaid on (group 2) the substrates; or present in medium (group 3); or absent (group 4). GF binding assay using 125I bFGF showed that more GF remained combined to the substrates in group 2 than those in group 1. Growth and morphology of human umbilical vein endothelial cells were sequentially analyzed in vitro for 8 days using DNA (nuclei counts) and F-actin labelings. Growth was relatively stable for the first 48 hours, later in groups 1, 2 and 4, cell death was observed on all the substrates except for fibronectin. Growth failure could be related to the degradation or inefficient release of ECGS. In group 3, growth increased and confluency was reached within 5-8 days on all the substrates except for gelatin and type I collagen. Confluent cells containing actin filaments were organized on glycoproteins and disorganized on glycosaminoglycans and fibrin. Despite that glycoproteins can enhance cell adhesion and lining pattern, GFs continually delivered in a fresh soluble form seem to be the appropriate condition to obtain an endothelial cell lining.

Actins↗

PubMed1992

Wettability of cross-linked collagenous biomaterials: in vitro study.

Collagenous biomaterials can be treated by chemical and physical agents to decrease biodegradation rate. Treatments to collagen may modify surface properties and subsequently cell and platelet behaviour. Collagenous films were either uncross-linked and cross-linked by glutaraldehyde, formaldehyde or cyanamide and/or treated by a severe dehydration. Contact angles, platelet contacting assay and fibroblast morphology were investigated. After severe dehydration, wettability was diminished except for formaldehyde-cross-linked and severely dehydrated films. Glutaraldehyde-cross-linked collagen results in an increase in wettability. Platelets were similarly distributed, except on formaldehyde-cross-linked films that exhibited no platelet aggregation. Fibroblasts were in a spreading phase on most collagenous films. However, cytotoxicity was noticed on some aldehyde-cross-linked films. No direct relationship was found between contact angles and platelet-cell attachment.

Animals↗

PubMed1992

Skin replacement using collagen extracted from bovine hide.

This paper reviews the use of biological sponge-shape matrices as dermal replacements in order to orient newly formed wound tissue. Sponge-shape matrices consist of a scaffold made of cross-linked collagen extracted from bovine hide. Other molecules with specific activities on wound tissue ingrowth are bound to collagen. The lamination of sponge with a synthetic material allows this device to be implanted as a temporary skin substitute. For the epidermal cell layer replacement, a biological film-shape matrix can be used in order to cultivate autologous cells during the period that biological sponge-shape matrices are invaded by wound tissue.

Animals↗

PubMed1992

In vitro angiogenesis in fibrin matrices containing fibronectin or hyaluronic acid.

Angiogenesis involved numerous interactions between extracellular matrix and endothelial cells which may exhibit changes in actin filament distribution. Using an in vitro model, capillary endothelial cells were grown in fibrin matrix containing fibronectin or hyaluronic acid. Actin filament distribution, nucleus localization and cell morphology were observed. Preliminary study showed the formation of tube-, branche- and capillary-like structures within fibrin. In the presence of both fibrin and fibronectin, cells with actin filament stress fibers were more spreading than those in fibrin. In the presence of hyaluronic acid, tubes were limited in extension into the fibrin. In addition, the study of co-localization of nucleus and actin filaments showed different cell behaviours. Migratory cells seem to arrange in parallel to each other and a capillary-like structure may be formed at the proximal extremity of this cell pattern.

Actins↗

PubMed1992

In vitro contraction rate of collagen in sponge-shape matrices.

Connective tissue substitute can be made of collagen sponge-shaped matrice which is reconstituted by freeze-drying a collagen dispersion. This procedure is then followed by a crosslinking treatment to decrease the in vivo biodegradation rate. In the present study, collagen dispersions made of collagen fibrils with a D-staggered pattern were submitted to the following treatments: (1) cyanamide or glutaraldehyde was introduced during the dispersion step followed by the manufacture of sponges; (2) uncrosslinked sponges were exposed to formaldehyde vapor; or (3) uncrosslinked and crosslinked sponges were severely dehydrated. To characterize the in vitro contraction rate, the surface areas of sponges were sequentially recorded in relation to soaking time. Contraction did not significantly occur when sponges were chemically treated. However, collagen in sponges treated by either severe dehydration or by both cyanamide treatment and severe dehydration contracted. On the other hand, the different treatments of the collagen modified the distribution of the D-staggered pattern within fibrils. After glutaraldehyde treatment, the periodicity of collagen fibrils disappeared and large fibres were observed. These experiments show that the different treatments of the collagen can be useful for designing a contractile as well as a non-contractile biomaterial.

Absorption↗

PubMed1990

Method of growing vaginal mucosal cells on a collagen sponge matrix. Results of preliminary studies.

A method of obtaining and growing vaginal mucosal epithelial cells in culture on plastic and on a collagen sponge was developed. The results indicate that simultaneous culture of skin and vaginal epithelial cells from the same donor showed morphologically similar growth potential in culture on plastic and on a collagen sponge. Vaginal cells grown on a collagen sponge formed elongated clumps of cells similar to those observed for skin epithelial cells. The results suggest that vaginal cells grown in culture on a collagen matrix may be a suitable biomaterial for use in reconstructive surgery on women with the Rokitansky syndrome or in those who have had a malignancy.

Cells, Cultured↗

PubMed1990

New approaches for biocompatibility testing using cell culture.

We are proposing two modified assays for biocompatibility testing which analyze the effects of cytotoxic substances leached from a biomaterial in cell culture. The biocompatibility of two vascular prostheses made of polytetrafluoroethylene was analyzed using the modified assays. One test, the "fluid medium assay" was modified by using small pieces of graft glued to a screening lid, thereby reducing the possibility of mechanical injury to cultured cells by free fragments of the tested biomaterial. Another test, the "cell inhibition assay" was modified in that the biomaterial to be tested was ground into small pieces while at very low temperature. The measure of cell toxicity used was the effect on DNA replication. Our results suggest that these modified assay methods can be used to evaluate the biocompatibility of biomaterials.

Biocompatible Materials↗

PubMed1989

In vivo evaluation of hydrophobic and fibrillar microporous polyetherurethane urea graft.

Mitrathane hydrophobic and fibrillar microporous prosthesis was implanted as infrarenal arterial substitute in dogs; it was evaluated in terms of patency rates, healing characteristics and biostability. Segments of grafts were implanted in duplicate for a period of implantation of 24 h, 1 wk, 1 month and 6 month. Two control grafts from the Ontario Research Foundation were implanted: one for 1 month, the other for six month. All except the two Mitrathane grafts implanted for 6 month were patent at death. The Mitrathane grafts showed kinking at one and 6 month post-implantation. The ORF graft implanted for 1 month was found crinkled in its mid-section and the external capsule was ruptured in the graft implanted for 6 month, without crinkling. Histological studies showed fibrin deposits on the flow surface and infiltration of blood elements into the wall of the Mitrathane grafts implanted for 24 h and 1 wk. A thin internal capsule was present on the graft flow surface of both types of graft tested 1 month post-implantation; scanning electron microscopy revealed the presence of endothelial-like cells on the luminal surface, particularly in the vicinity of the anastomoses. At 6 month, the Mitrathane grafts were occluded by a thick thrombus originating from the anastomoses, while the ORF graft showed infiltration of collagen through the polyurethane fibrillar structure of the wall with an endothelial-like lining covering the flow surface in the vicinity of both anastomoses.

Animals↗

PubMed1988

Wound healing using a collagen matrix: effect of DC electrical stimulation.

Rapid fibroblast ingrowth and collagen deposition occurs in a reconstituted type I collagen matrix that is implanted on full-thickness excised animal dermal wounds. The purpose of this study is to evaluate the effects of direct current stimulation on dermal fibroblast ingrowth using carbon fiber electrodes incorporated into a collagen sponge matrix. Preliminary results suggest that fibroblast ingrowth and collagen fiber alignment are increased in collagen sponges stimulated with direct currents between 20 and 100 microA. Maximum fibroblast ingrowth into the collagen sponge is observed near the cathode at a current of 100 microA. These results suggest that electrical stimulation combined with a collagen matrix may be a method to enhance the healing of chronic dermal wounds.

Animals↗

PubMed1988

Behaviour of fibroblasts and epidermal cells cultivated on analogues of extracellular matrix.

A porous collagen sponge can be used for supporting epidermal cells and fibroblasts in order to manufacture an artificial skin. Fibroblasts were grown on analogues of extracellular matrix containing collagen and glycosaminoglycans and/or glycoproteins. Cell replication, and also infiltration of fibroblasts, were enhanced by the presence of hyaluronic acid and/or fibronectin. Epidermal cells grown on a collagen sponge have been characterized by microscopic observations. Epidermal cells on the surface of the sponge showed an incomplete differentiation in comparison to normal skin; clumps of epidermal cells were found in the interior of the sponge. Epidermal cell replication was enhanced in the presence of collagen sponge seeded with fibroblasts.

Animals↗

PubMed1988

Relationship between mechanical properties and collagen structure of closed and open wounds.

Mechanical properties and collagen structure of excisional wounds left open are compared with wounds closed by clips. In both wound models, collagen fiber diameter increases with time post-wounding and is related to tensile strength. Clipped wounds show a higher ultimate tensile strength and tangent modulus compared with open wounds. In clipped wounds, newly deposited collagen appears as a biaxially oriented network as observed in normal skin. In open wounds a delay in the organization of the collagen network is observed and parallel wavy-shaped ribbons of collagen fibers are deposited. At long term, the high extensibility observed in open wounds may be due to the sliding of ribbons of collagen fibers past each other.

Animals↗

PubMed1988

Porous collagen sponge wound dressings: in vivo and in vitro studies.

Collagen-based materials can be formed into a three-dimensional sponge for use as a wound dressing and as a support for cell cultured skin components. Factors such as biocompatibility, morphological structure and addition of non-collagenous molecules to collagen are analyzed and discussed. Large pores or channels, interchannel communications and combinations of macromolecules of the connective tissue enhance wound tissue infiltration in vivo as well as cell growth in vitro into collagen sponges. The presence of such factors can be useful in patients with excised burn wounds and pressure skin ulcers.

Animals↗

PubMed1988

Clinical applications of electron microscopy in the analysis of collagenous biomaterials.

Scanning and transmission electron microscopy are of clinical value in assessing the interaction between biomaterials and ingrowing tissues. Ultrastructural information allows the clinician and biomaterials specialist to determine events occurring during wound healing and the biocompatibility of prosthetic devices. This paper reviews some of the experimental and clinical studies done in our laboratory on the use of natural and reconstituted collagen as replacements for connective tissues. Consideration is given to collagen flakes used for the treatment of dermal ulcers, a collagen fiber prosthesis used for tendon and ligament replacement, the effects of chemical preservatives on cartilage used for replacement of tissues during plastic surgery and the growth and orientation of nerve cells on reconstituted collagen fibers. Our results show that reconstituted collagen can be prepared into prosthetic devices which encourage cell attachment and orientation thereby facilitating healing of injured tissues. Furthermore chemical preservation of cartilagenous tissues kills chondrocytes resulting in eventual resorption by inflammatory cells.

Biocompatible Materials↗

PubMed1988

Fibroblast and epidermal cell-type I collagen interactions: cell culture and human studies.

Fibroblast and epidermal cell-type I collagen sponge interactions were studied in cell culture as well as in humans. In cell culture, fibroblasts were observed to migrate and proliferate throughout a type I collagen sponge containing either hyaluronic acid (HA) or fibronectin (FN). Fibroblasts accumulated in the center of the pores in sponges containing HA and appeared to surround themselves with newly synthesized extracellular matrix. In sponges containing FN, fibroblasts attached to and elongated along the collagen fibers of the sponge. In the absence of FN or HA protein synthesis of fibroblasts appeared to be inhibited by the presence of the type I collagen sponge. Epidermal cells grown on plastic or on type I collagen, formed sheets. Epidermal cells grown on a collagen sponge morphologically appeared different than cells grown on plastic. The type I collagen matrix studied in cell culture was applied to dermal wounds of patients with pressure ulcers in order to evaluate its effect on dermal wound healing. The areas of ulcers treated for 6 weeks with a type I collagen sponge decreased by about 40% compared with no change in the areas of untreated controls. Preliminary results suggest that a type I collagen sponge is a biocompatible substrate with fibroblasts and epidermal cells and may be effective in enhancing healing of chronic skin ulcers.

Animals↗

PubMed1987

Fibroblast growth on a porous collagen sponge containing hyaluronic acid and fibronectin.

We have previously shown that the presence of fibronectin (FN) and/or hyaluronic acid (HA) in a 3-dimensional type I collagen sponge enhances wound healing in vivo. In the present study the same material was used as a support for growth of fibroblasts in vitro. Using radiochemical techniques, scanning electron and light microscopy, the properties of fibroblasts cultured on the collagen sponge or on the sponge containing HA or FN have been compared with cultures grown on plastic dishes. Fibroblast replication and collagen synthesis were higher on plastic than on the collagen sponge. In the presence of HA or FN the entire thickness of the sponge was infiltrated by fibroblasts which rapidly replicated. The presence of HA or FN increased synthesis of collagen which was largely deposited around cells.

Animals↗

PubMed1987

Actin filaments in normal dermis and during wound healing.

During wound healing, it has been suggested, modified fibroblasts rich in actin filaments are responsible for wound contraction. With the use of specific fluorescent probe (NBD-phallacidin), the distribution of actin filaments are compared in normal dermis and in several wound contraction models, including open and burn wounds and full and thin-thickness skin autografts. Fibroblasts of normal dermis are slightly stained with NBD-phallacidin. Fibroblasts with actin filaments are increased in autografts, particularly at Days 15 and 21 after grafting, and are prominent in open and burn wounds. The wound contraction rate is not directly related to the presence of actin-staining fibroblasts. After stabilization of the contraction of open or burn wounds, fibroblasts rich in actin filaments remain. The superficial layer of full-thickness skin graft contains a similar actin distribution without concomitant contraction. It is concluded that the distribution of actin-rich fibroblasts corresponds morphologically to previous areas of necrosis or injury.

Actin Cytoskeleton↗

PubMed1986

Collagen-based wound dressings: control of the pore structure and morphology.

Collagen-based sponges have been used as both temporary and permanent coverings for dermal defects in animals and humans. Cellular ingrowth within such a sponge has been shown to depend on the porosity and the presence of fibrous structure. Collagen sponges were made by freezing and freeze-drying dispersions under acidic conditions. These studies involved the effects of dispersion pH and viscosity as well as freezing temperature on the surface and bulk morphology of collagen-based sponges. Using scanning electron and light microscopy, the results of these studies indicated that large surface pores that form connections (channels) with the interior of the sponge were formed using low-viscosity collagen dispersions. At high dispersion pH (3.2) and at a moderate freezing temperature (-30 degrees C), fibrous structure and a large number of channels were present. When a lower dispersion pH (2.0) and freezing temperature (-80 degrees C) were used, pores sizes were smaller with channels and fibrous structure, whereas a higher freezing temperature (-20 degrees C) resulted in a sheet-like structure and increased pore sizes. Differences in pore size and surface morphology were explained on the basis of ice crystal growth. In the case of abundant free water (high pH) and high freezing temperature, the pore size was greatest because of enhanced ice crystal growth.

Bandages↗

PubMed1986

Collagen-based wound dressing: effects of hyaluronic acid and fibronectin on wound healing.

Our previous studies have shown that a collagen-based wound dressing induces the spatial deposition of wound tissue. This study was conducted to determine the effects of hyaluronic acid and fibronectin on wound healing. These macromolecules play an important role in wound healing, embryonic development and cellular migration in vitro. The effects of the addition of varying levels of fibronectin and hyaluronate to a collagen sponge were studied. Low levels of both hyaluronate and fibronectin modified the structure of the implant, and resulted in increased chemoattraction, replication and collagen deposition in an in vivo wound healing model.

Animals↗