Development and validation of human psoriatic skin equivalents.

Psoriasis is an inflammatory skin disease driven by aberrant interactions between the epithelium and the immune system. Anti-psoriatic drugs can therefore target either the keratinocytes or the immunocytes. Here we sought to develop an in vitro reconstructed skin model that would display the molecular characteristics of psoriatic epidermis in a controlled manner, allowing the screening of anti-psoriatic drugs and providing a model in which to study the biology of this disease.

A novel translation re-initiation mechanism for the p63 gene revealed by amino-terminal truncating mutations in Rapp-Hodgkin/Hay-Wells-like syndromes.

Missense mutations in the 3' end of the p63 gene are associated with either RHS (Rapp-Hodgkin syndrome) or AEC (Ankyloblepharon Ectodermal defects Cleft lip/palate) syndrome. These mutations give rise to mutant p63alpha protein isoforms with dominant effects towards their wild-type counterparts. Here we report four RHS/AEC-like patients with mutations (p.

Long-term evaluation of porous PEGT/PBT implants for soft tissue augmentation.

Porous PEGT/PBT implants with different physico-chemical characteristics were evaluated to identify its potential as biodegradable and biofunctional soft tissue filler. Implants (50 x 10 x 5 mm3) were implanted subcutaneously in mini-pigs and tissue response, tissue volume generated and its consistency were assessed quantitatively with a 52 weeks follow-up. The absence of wound edema, skin irritation, and chronic inflammation demonstrated biocompatibility of all implants evaluated.

Identification of avarol derivatives as potential antipsoriatic drugs using an in vitro model for keratinocyte growth and differentiation.

Avarol, a marine sesquiterpenoid hydroquinone, and 14 avarol derivatives have shown interesting anti-inflammatory properties in previous studies. In this study, avarol and derivatives were evaluated in high-throughput keratinocyte culture models using cytokeratin 10 and SKALP/Elafin expression as markers for respectively normal and psoriatic differentiation. Avarol and five of its derivatives (5, 10, 13, 14 and 15) were selected for further study.

Synthetic scaffold morphology controls human dermal connective tissue formation.

Engineering tissues in bioreactors is often hampered by disproportionate tissue formation at the surface of scaffolds. This hinders nutrient flow and retards cell proliferation and tissue formation inside the scaffold. The objective of this study was to optimize scaffold morphology to prevent this from happening and to determine the optimal scaffold geometric values for connective tissue engineering.

Improved enzymatic isolation of fibroblasts for the creation of autologous skin substitutes.

The number of medical applications using autologous fibroblasts is increasing rapidly. We investigated thoroughly the procedure to isolate cells from skin using the enzymatic tissue dissociation procedure. Tissue digestion efficiency, cell viability, and yield were investigated in relation to size of tissue fragments, digestion volume to tissue ratio, digestion time, and importance of other protease activities present in Clostridium histolyticum collagenase (CHC) (neutral protease, clostripain, and trypsin).

Inhibition of early steps in the lentiviral replication cycle by cathelicidin host defense peptides.

Background: The antibacterial activity of host defense peptides (HDP) is largely mediated by permeabilization of bacterial membranes. The lipid membrane of enveloped viruses might also be a target of antimicrobial peptides. Therefore, we screened a panel of naturally occurring HDPs representing different classes for inhibition of early, Env-independent steps in the HIV replication cycle.

Transplantation of reconstructed human skin on nude mice: a model system to study expression of human tenascin-X and elastic fiber components.

Tenascin-X is a large extracellular matrix protein that is widely expressed in connective tissues during development and in the adult. Genetically determined deficiency of tenascin-X causes the connective tissue disease Ehlers-Danlos syndrome. These patients show reduced collagen density and fragmentation of elastic fibers in their skin.

Modulation of scar tissue formation using different dermal regeneration templates in the treatment of experimental full-thickness wounds.

The recovery of skin function is the goal of each burn surgeon. Split-skin graft treatment of full-thickness skin defects leads to scar formation, which is often vulnerable and instable. Therefore, the aim of this study was to analyze wound healing and scar tissue formation in acute full-thickness wounds treated with clinically available biopolymer dermal regeneration templates.

Stimulation of skin repair is dependent on fibroblast source and presence of extracellular matrix.

In this study in vitro and in vivo functions were compared between cultured dermal equivalents produced with human fibroblasts isolated either from papillary dermis or adipose tissue of the same donors. Papillary dermal fibroblasts had a normal spindle cell shape; in contrast, adipose tissue fibroblasts had a stellate cell shape, actin stress fibers containing alpha-smooth muscle actin, multiple narrow extensions at their edges, and longer focal adhesion plaques. After dynamic culture for 14 days in PEGT/PBT carrier scaffolds, cell numbers between the two cell sources were comparable, but tissue morphology was different between the cultured groups.

Upside-down transfer of porcine keratinocytes from a porous, synthetic dressing to experimental full-thickness wounds.

Currently, the use of cultured epithelial autografts as an alternative to split-thickness skin autografts for coverage of full-thickness wounds is limited due to fragility of the sheet and variability in the outcome of healing. This could be circumvented by the transfer of proliferating keratinocytes, instead of differentiated sheets, to the wound bed and the "in vivo" regeneration of epidermis. The aim of this study was to achieve re-epithelialization on experimental full-thickness wounds in the pig using a porous, synthetic carrier seeded with proliferating keratinocytes.

The use of PEGT/PBT as a dermal scaffold for skin tissue engineering.

Human skin equivalents (HSEs) were engineered using biodegradable-segmented copolymer PEGT/PBT as a dermal scaffold. As control groups, fibroblast-populated de-epidermized dermis, collagen, fibrin and hybrid PEGT/PBT-collagen matrices were used. Two different approaches were used to generate full-thickness HSE.

Neovascularization of poly(ether ester) block-copolymer scaffolds in vivo: long-term investigations using intravital fluorescent microscopy.

Poly(ether ester) block-copolymer scaffolds of different pore size were implanted into the dorsal skinfold chamber of balb/c mice. Using intravital fluorescent microscopy, the temporal course of neovascularization into these scaffolds was quantitatively analyzed. Three scaffold groups (diameter, 5 mm; 220-260 thickness, microm; n = 30) were implanted.

Engineering of a dermal equivalent: seeding and culturing fibroblasts in PEGT/PBT copolymer scaffolds.

The engineering of dermal skin substitutes, using autologous fibroblasts, requires high seeding efficiencies, a homogeneous cell distribution in the scaffolds, and optimal culture conditions. Dynamic seeding in spinner flasks was used to seed and subsequently culture fibroblasts in three-dimensional scaffolds. Several seeding and culture variables were investigated.

Crucial role of fibroblasts in regulating epidermal morphogenesis.

Epidermis reconstructed on de-epidermized dermis (DED) was used to investigate whether fibroblasts can substitute growth factors needed for generation of a fully differentiated epidermis. For this purpose, a centrifugal seeding method was developed to reproducibly incorporate different fibroblast numbers into DED. Using (immuno)histochemical techniques, we could demonstrate that in the absence of fibroblasts the formed epidermis consisted only of two to three viable cell layers with a very thin stratum corneum layer.

Morphometry of dermal collagen orientation by Fourier analysis is superior to multi-observer assessment.

In human dermis, collagen bundle architecture appears randomly organized, whereas in pathological conditions, such as scar tissue and connective tissue disorders, collagen bundle architecture is arranged in a more parallel fashion. Histological examination by one or two observers using polarized light is the most common method to determine collagen orientation. The hypothesis on which this study is based is that an objective image analysis technique, Fourier analysis, would improve the reliability (are the measurements reproducible?) and the accuracy (does the method measure what it is supposed to measure?) of collagen orientation assessment, compared with observer ratings.

Allogeneic fibroblasts in dermal substitutes induce inflammation and scar formation.

In the present study, we compared the use of autologous versus allogeneic fibroblasts in dermal skin substitutes in a porcine wound model. The allogeneic fibroblast populations were isolated from female and a male pig (allo-1, - 2 and - 3) and the controls, autologous fibroblasts, from female graft-recipient pigs (control). The histocompatibility of the three donor pigs with the recipient pigs was determined with a mixed lymphocyte reaction.

Long-term results of a clinical trial on dermal substitution. A light microscopy and Fourier analysis based evaluation.

Although dermal substitution is a main topic of current wound healing research, there is a paucity of clinical trials with a long-term clinical and histopathological evaluation. A clinical trial was conducted to perform an intra-individual comparison of conventional treatment (split-thickness autograft) to a collagen/elastin dermal substitute in combination with an autograft. Promising results with this substitute were obtained with respect to dermal organisation and scar elasticity in animal studies and clinical trials with a short-term follow-up.