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Biomedical subjects

L Germain

Publications and source records attributed to L Germain.

100 records · Page 6Linked to original sources
PubMedDate not supplied

Permanent grafting of living skin substitutes: surgical parameters to control for successful results.

Autologous mesh grafting, widely used in the treatment of severe burns, remains the most conventional approach for permanent skin replacement. However, during the last decade several types of skin substitutes were reported as suitable alternatives for full-thickness burn wound coverage. The clinical use of such dressings requires new surgical skills to maintain the integrity of the grafts and favor their permanent implantation in vivo. This article reports observations made on nude mice grafted with cultured human skin equivalents. Some parameters such as the quality of adhesion between the implant and the graft bed, the size, the stability and the thickness of the graft, the humidity of the chamber, and the protocol of antibiotic administration were identified as crucial for the success of the surgery. The grafting procedures are described in this paper. These results should be taken into consideration in all transplantations of skin grafts in vivo.

Animals↗
PubMedDate not supplied

Cyclic traction machine for long-term culture of fibroblast-populated collagen gels.

Our research group has been investigating the effect of cyclic deformations on the evolution of fibroblast populated collagen gels (FPCG). Since existing traction machines are not designed for such an application, we had to design a cyclic traction machine adapted to tissue culture inside an incubator over an extended period of time. Biocompatible materials were used for fabrication to allow for easy sterilization and to prevent any adverse reaction from the tissue. The traction machine is based on a computer-controlled stepping motor system for easy adjustment of the deformation amplitude and frequency. The maximum stretching speed achieved is around 1 mm/s. The traction machine can measure FPCG mechanical properties and perform rupture tests to determine its ultimate strength. Several FPCGs have been successfully cultured with the machine for up to four weeks without any adverse reaction.

Biocompatible Materials↗
PubMedDate not supplied

Localization of Merkel cells at hairless and hairy human skin sites using keratin 18.

Merkel cells are neurosecretory cells of the skin with epithelial features such as desmosomes and expression of keratins 8, 18, 19, and 20. Merkel cells are scarcely distributed in adult human skin. Although they are present in hair follicles, their density is higher at hairless anatomic sites such as palms and soles. These cells are often innervated by sensory nerve fibers and are thought to be specialized mechanosensory skin receptor cells. However, their precise origin and function are not clearly established. The aim of this study was to localize Merkel cells in human hairless and hairy skin by immunohistochemistry with antibodies Ks18.174 and Ks19.1 directed against keratins 18 and 19, respectively. In glabrous skin of palm and sole, Merkel cells have been localized at the bottom of the rete ridges, in the epidermal basal layer. To study Merkel cell distribution at hairy anatomic sites, we have chosen breast skin, a tissue containing small hair follicles typical of those covering most of the body's surface. Merkel cells were present in the interfollicular epidermis. In hair follicles, they have been identified in the isthmus region.

Adult↗
PubMedDate not supplied

Reconstructed human cornea produced in vitro by tissue engineering.

The aim of the present study was to produce a reconstructed human cornea in vitro by tissue engineering and to characterize the expression of integrins and basement membrane proteins in this reconstructed cornea. Epithelial cells and fibroblasts were isolated from human corneas (limbus or centre) and cultured on plastic substrates in vitro. Reconstructed human corneas were obtained by culturing epithelial cells on collagen gels containing fibroblasts. Histological (Masson's trichrome staining) and immunohistological (laminin, type VII collagen, fibronectin as well as beta1, alpha3, alpha4, alpha5, and alpha6 integrin subunits) studies were performed. Human corneal epithelial cells from the limbus yielded colonies of small fast-growing cells when cultured on plastic substrates. They could be subcultured for several passages in contrast to central corneal cells. In reconstructed cornea, the epithelium had 4-5 cell layers by the third day of culture; basal cells were cuboidal. The basement membrane components were already detected after 3 days of culture. Integrin stainings, except for the alpha4 integrin, were also positive after 3 days. They were mostly detected at the epithelium-stroma junction. Such in vitro tissue-engineered human cornea, which shows appropriate histology and expression of basement membrane components and integrins, provides tools for further physiological, toxicological and pharmacological studies as well as being an attractive model for gene expression studies.

Cell Division↗
PubMedDate not supplied

Production of bioengineered cancer tissue constructs in vitro: epithelium-mesenchyme heterotypic interactions.

A few models have been established to study cancer cells in vitro. However, the cellular interactions have rarely been studied specifically using bioengineered cancer constructs combining human carcinoma cells and tumor-associated fibroblasts. We developed an in vitro model of tridimensional bioengineered cancer tissue constructs (bCTC) by seeding mammary epithelial cancer cells or normal keratinocytes over a mesenchymal layer containing tumor-derived fibroblastic cells or normal skin fibroblasts. After the introduction of epithelial cells, each construct was cultured for another 10 d. Histologic analyses showed that carcinoma cell lines could invade the subjacent mesenchymal layer and that the capacity to migrate was related to the invasive potential of cancer cells and the type of fibroblasts used, while noninvasive populations did not. Of the tested epithelial cells, MDA-MB-231 and, to a lesser degree, HDQ-P1 cell lines were invasive, and the invasion was deeper into the mesenchymal component containing tumor-derived fibroblasts. However, with normal skin fibroblasts, the mesenchymal layer was degraded twice faster than with tumor-derived fibroblastic cells. MDA-MB-231 cells and normal keratinocytes induced the highest level of gelatinase B, and the level was lowest with the MCF-7 cell line. The activated form of gelatinase B was, however, induced to the highest levels in the keratinocyte-seeded bCTC containing tumor-derived but not normal fibroblasts. MDA-MB-231 was the only epithelial cancer cell line whose activity of gelatinase A was reduced when cocultured with tumor-derived fibroblasts but not under normal fibroblast stimulation. Finally, a 50/48-kDa gelatinase band has been observed in bCTCs with noninvasive epithelial cells only. Our study demonstrates the selective secretion of gelatinases according to the phenotype of the cells seeded in the various bCTCs.

Breast↗
PubMedDate not supplied

Production of tissue-engineered three-dimensional human bronchial models.

We have reported morphological and functional features of cells isolated from human bronchial biopsies. Both epithelial and fibroblastic cells were isolated from the same biopsies using collagenase. A few models have been established to study normal bronchial response to various agents and to understand the mechanisms responsible for some disorders, such as asthma. We produced three-dimensional bronchial equivalents in culture, using human epithelial and fibroblastic cells. We previously showed that peripheral anchorage can prevent the dramatic collagen contraction in gels seeded with fibroblasts when properly adapted to the size and type of cultured tissues. Our bilayered bronchial constructs were anchored and cultured under submerged conditions and at the air-liquid interface. Three culture media were compared. Serum-free medium supplemented with retinoic acid (5 x 10(-8) M) was found to be the best for maintenance of bronchial cell properties in the reconstructed bronchial tissue. Immunohistological and ultrastructural analyses showed that these equivalents present good structural organization, allowing ciliogenesis to occur in culture. Moreover, human bronchial goblet cells could differentiate and secrete mucus with culture time. Laminin, a major constituent of the basement membrane and basal cells, was also detected at the mesenchymoepithelial interface. Such models will be useful for studying human bronchial properties in vitro.

Bronchi↗
PubMedDate not supplied

[Juvenile myoclonic epilepsy. Life difficulties and response to treatment].

Juvenile myoclonic epilepsy (JME) may have different forms of clinical expression and produces different kinds of life difficulties. Both eventualities have not been sufficiently described in the literature. Treatment with valproic acid is useful but requires strict compliance of medical instructions. Thirty two patients with this disease, are presented in order to describe their presenting forms, associated life handicaps and the results of their treatment. The disease may first present as tonic-clonic, complex absence or complex partial seizures, followed months or years later, by typical myoclonic crisis or as JME to which other kinds of epileptic crisis may or not be added after some time. Twenty four (75%) patients had 38 life difficulties, these being, mainly, objects dropped from hand, burns and parental aggression. Eighteen (56.25%) patients had relapses during treatment. In 14 cases (77.77%) relapses were due to noncompliance, 8 (57.19%) patients couldn't afford the cost of valproic acid. Knowledge of the presenting forms of the disease may favor opportune diagnosis and treatment, which would prevent life difficulties. Relapses are mainly due to noncompliance and economic reasons.

Adolescent↗
PubMedDate not supplied

[Juvenile myoclonic epilepsy: Janz' syndrome].

Thirty two patients with juvenile myoclonic epilepsy are described. The most relevant aspects of the disease are the following: it starts at nearly 12 years of age or before; it is frequently associated with generalized tonic-clonic seizures; myoclonic and tonic-clonic seizures occur at time of awaking or shortly after; no pathological findings occur at the central nervous system; a large number of relatives show generalized seizures and the interictal electroencephalogram is usually disturbed by generalized epileptic activity. Valproic acid, preferably alone, is probably the treatment of choice for these patients.

Adolescent↗