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PubMed2005

Expression and characterization of human-elastin-repeat-based temperature-responsive protein polymers for biotechnological purposes.

Rapid progress has been made in the design and synthesis of oligomers and polymers that emulate the properties of natural proteins. Molecular bioengineering offers the chance to design and produce artificial polymeric proteins with tailored polymeric properties. The elastin-like polypeptides are a well-defined family of polymers with noteworthy characteristic based on the VPGVG repeated motif of bovine elastin. In the human homologue, the most regular sequence is represented by the repetition of the VAPGVG hexapeptidic motif. On the basis of this sequence, a synthetic gene has been designed, cloned and expressed in Escherichia coli to obtain artificial protein polymers. The rapid one-step in-frame cloning of any biologically active sequence can be achieved directly in the expression vector, allowing further improvement of the potential of the resulting product.

Amino Acid Motifs↗
PubMed2002

The influence of body mass index on skin susceptibility to sodium lauryl sulphate.

BACKGROUND: The influence of nutrition on the physiological functions of man is well studied. Numerous diseases can be exacerbated by obesity. However, it has not yet been determined whether body weight and body mass index (BMI), as an indicator of a high body fat store, can influence skin sensitivity. OBJECTIVE: This study investigates the correlation between body mass index and the epidermal functions, evaluated by bioengineering methods, before and after an irritant patch test with sodium lauryl sulphate (SLS). METHODS: Epidermal functions were evaluated using an evaporimeter, chromameter and laser-Doppler-flowmeter. Patch testing was conducted for 48 h with two different concentrations of SLS (0.25% and 0.5%) on the forearms of healthy volunteers. Measurements were performed 24h after patch removal. RESULTS: Obese individuals showed significantly increased transepidermal water loss (TEWL), skin blood flow and skin colour (red) as compared to a control group. However, the degree of skin sensitivity to SLS was not correlated with BMI. CONCLUSION: Basal biophysical parameters of the skin are primarily correlated with the BMI. This may be caused by obesity-induced physiological changes, e.g. increased sweat gland activity, high blood pressure and physiological temperature-regulating system. The epidermal barrier function, as evaluated after SLS patch testing is, however, not correlated with a high BMI, indicating a normal skin barrier.

Adolescent↗
PubMed2002

Occlusion vs. skin barrier function.

BACKGROUND/AIMS: Skin occlusion may increase percutaneous absorption of applied chemicals, with some exceptions. It also obstructs the normal ventilation of the skin surface and increases stratum corneum hydration and hence compromises skin barrier function. METHODS/RESULTS: This review focuses the effects of occlusion on skin barrier function, in particularly, as defined with objective skin bioengineering technology. CONCLUSIONS: The effects of occlusion on skin barrier function have been defined with various techniques. Optimal hydrocolloid materials can absorb excess water and reduce the unfavourable effects of occlusion.

Administration, Cutaneous↗
PubMed2004

Damage and recovery of skin barrier function after glycolic acid chemical peeling and crystal microdermabrasion.

BACKGROUND: Superficial chemical peeling and microdermabrasion have become increasingly popular methods for producing facial rejuvenation. However, there are few studies reporting the skin barrier function changes after these procedures. OBJECTIVE: To evaluate objectively the degree of damage visually and the time needed for the skin barrier function to recover after glycolic acid peeling and aluminum oxide crystal microdermabrasion using noninvasive bioengineering methods. METHODS: Superficial chemical peeling using 30%, 50%, and 70% glycolic acid and aluminum oxide crystal microdermabrasion were used on the volar forearm of 13 healthy women. The skin response was measured by a visual observation and using an evaporimeter, corneometer, and colorimeter before and after peeling at set time intervals. RESULTS: Both glycolic acid peeling and aluminum oxide crystal microdermabrasion induced significant damage to the skin barrier function immediately after the procedure, and the degree of damage was less severe after the aluminum oxide crystal microdermabrasion compared with glycolic acid peeling. The damaged skin barrier function had recovered within 24 hours after both procedures. The degree of erythema induction was less severe after the aluminum oxide crystal microdermabrasion compared with the glycolic acid peeling procedure. The degree of erythema induced after the glycolic acid peeling procedure was not proportional to the peeling solution concentration used. The erythema subsided within 1 day after the aluminum oxide crystal microdermabrasion procedure and within 4 days after the glycolic acid peeling procedure. CONCLUSION: These results suggest that the skin barrier function is damaged after the glycolic acid peeling and aluminum oxide crystal microdermabrasion procedure but recovers within 1 to 4 days. Therefore, repeating the superficial peeling procedure at 2-week intervals will allow sufficient time for the damaged skin to recover its barrier function.

Adult↗
PubMed2003

Review article: a medicine based on cell transplantation -- is there a future for treating liver diseases?

Cell-based therapies, comprising isolated hepatocyte transplantation, ex vivo gene therapy and bioartificial liver devices, may actually design a new scenario in the treatment of patients with liver failure. Recent advances in the liver repopulation field and the considerable excitement surrounding the use of haematopoietic stem cells for a 'regenerative medicine', allow us to see under a new light the alternative cell sources actually under investigation. In particular, the major drawbacks and the most important advantages of xenogenic primary cells, tumour-derived cell lines, immortalised hepatocytes and stem cells in the wide range of experimental and clinical applications are presented. Even if up to now none of them represent a 'gold standard' in the clinical practice, the intersecting advances in the development of mechanical components of artificial devices and in the liver biology and bioengineering will open tantalising possibilities to treat patients with liver failure, by tailoring the therapeutic choice on the basis of the aetiology and the stage of liver disease.

Artificial Organs↗
PubMed1997

Differential irritant skin responses to tandem application of topical retinoic acid and sodium lauryl sulphate: II. Effect of time between first and second exposure.

In clinical practice, the cutaneous exposure to chemical irritants such as surfactants and topical drugs is frequent. Topical all-trans retinoic acid (RA) is often associated with irritation and induces epidermal changes similar to those produced by sodium lauryl sulphate (SLS). Using bioengineering techniques, e.g. assessing transepidermal water loss (TEWL), capacitance and chromametry, we investigated the variations of the skin response to SLS and RA and to both chemicals applied sequentially, allowing different time periods (from 1 h to 2 weeks) between applications of SLS and RA. Both chemicals caused irritation as assessed by visual scoring, but the values from the objective variables differed at different time periods. TEWL increased dramatically shortly after applying SLS but the increase was delayed after RA. After applying SLS, the capacitance generally decreased then returned to basal values; treatment with RA produced an overall increase. Only the results from chromametry were similar. After tandem application, the drugs were synergistic for all variables except capacitance, showing an antagonistic interaction for skin hydration. These results suggest that non-specific skin irritation profoundly reflects different mechanisms of action at tissue level. With sequential application, SLS injury modified the response to RA for at least 1 week after applying SLS. These late effects of detergents should be considered when studying irritant chemical interactions and in developing strategies for the management of occupational and other irritant dermatitis.

Adult↗
PubMed1998

Topical melatonin in combination with vitamins E and C protects skin from ultraviolet-induced erythema: a human study in vivo.

In this randomized, double-blind human study, the short-term photoprotective effects of different antioxidants and their combinations were evaluated in vivo. Vitamin C (ascorbic acid), vitamin E (alpha-tocopherol) and melatonin (N-acetyl-5-methoxytryptamine) were topically applied, alone or in combination, 30 min before ultraviolet-irradiation of the skin. The erythemal reaction was evaluated visually and non-invasively using different bioengineering methods (skin colour and skin blood flow). The results showed a modest protective effect of the vitamins when applied alone and a dose-dependent photoprotective effect of melatonin. Topical application of combinations of both vitamins, or of melatonin with vitamins, enhanced the photoprotective response. Better protection was obtained by using the combination of melatonin with both vitamins. The role of reactive oxygen species and oxygen-derived free radicals, as well as potential sunscreening properties of the employed antioxidants, are discussed in view of possible mechanisms to explain this elevated photoprotective effect.

Administration, Cutaneous↗
PubMed2001

Testing for irritation with a multifactorial approach: comparison of eight non-invasive measuring techniques on five different irritation types.

BACKGROUND: Non-invasive bioengineering methods are widely used in the assessment of irritant skin reactions. OBJECTIVES: To assess the ability of eight non-invasive measurement techniques to distinguish changes in skin conditions over time, these changes being induced by five different irritants. METHODS: The following techniques were compared in a multivariate analysis: laser-Doppler perfusion imaging (LDI), laser-Doppler flowmetry (LDF), transepidermal water loss (TEWL), visual scoring (VS), colorimetric measurements (Chromameter CR 200 a* and L* scales), Mexameter Hb scale (Mexa Hb) and capacitance (Corneometer CM 820). Irritants tested were sodium lauryl sulphate 2% (SLS), tape stripping (TS), tretinoin 0.05% (TRET), ultraviolet (UV) exposure to 30 W m(-2) UVB/95 W m(-2) UVA, and dithranol 0.5% (DIT). Measurements were performed at baseline and after 24, 48 and 72 h. The study was conducted on the upper back of 11 healthy volunteers of both sexes aged 27-51 years. RESULTS: For DIT it was possible to discriminate over time with CR 200 a* and L*, VS, LDI, LDF and Mexa Hb. In SLS discrimination over time was seen with TEWL and LDF. Discrimination in TS was demonstrated for TEWL, VS, CR 200 a*, CM 820, LDF, LDI and Mexa Hb. In TRET discrimination ability was seen for LDI, LDF, Mexa Hb and VS. For UV it was possible to discriminate using VS, TEWL, LDF, LDI and Mexa Hb. CONCLUSIONS: Different irritation patterns need different measurement modalities in order to give optimal discrimination over time.

Adult↗
PubMed2000

Biomechanical measurement of skin distensibility in scleredema of Buschke associated with multiple myeloma.

We report a case of scleredema of Buschke associated with IgG kappa monoclonal hypergammaglobulinaemia. After myeloma polychemotherapy an improvement in skin involvement was observed and confirmed by means of noninvasive skin elasticity measurements. This suggests a relationship between the two diseases. The bioengineering method used can be useful for early detection and monitoring the skin involvement in patients with this disease association.

Biomechanical Phenomena↗
PubMed2000

Inhibition of Epstein-Barr virus (EBV)-specific CD8+ cytotoxic T lymphocyte (CTL) activity by soluble HLA class I in vitro.

In the present study, the effects of soluble HLA (sHLA) class I molecules against EBV-specific CTL were examined. Two different sources of sHLA class I, either bioengineered spliced form of HLA-B7 (sB7) or natural production from EBV-transformed B cells (natural sHLA), were added during the induction of CTL or incubated with MHC-restricted CD8+ CTL, which were selected by immunobeads just before testing for their cytotoxic activity. Both sB7 and natural sHLA class I blocked the generation of CD8+ CTL and also inhibited the cytotoxic activity of established CTL in a dose-dependent manner. In both ways, natural sHLA class I was effective in 10-fold lower concentrations compared with sB7. The inhibitory effect did not require a sharing of the HLA allotypes between sHLA and the CTL. CTL, after being treated with sHLA, underwent apoptosis, which was considered here as the main mechanism.

Apoptosis↗
PubMed2003

Functional differentiation of hepatocyte-like spheroid structures from putative liver progenitor cells in three-dimensional peptide scaffolds.

We investigated the ability of a new type of biological material, the self-assembling peptide scaffold, to foster tissue-like function by a putative adult rat hepatocyte progenitor cell line, Lig-8. In conventional adherent petri-dish cultures, Lig-8 cells divide exponentially, express markers for definitive endoderm HNF3 beta and hepatocyte lineage, including CK8 and alpha-fetoprotein, but lack expression of mature hepatocyte markers. However, in the three-dimensional peptide scaffold cultures, Lig-8 exhibits non-exponential cell kinetics, acquires a spheroidal morphology, and produces progeny cells with mature hepatocyte properties. The differentiated progeny cells display expression of transcription factor C/EBP alpha and several other indicators that suggest hepatocyte maturation, including binucleation, up-regulation of albumin, and expression of cytochrome P450s CYP1A1, CYP1A2, and CYP2E1. Moreover, all three cytochrome p450 enzyme activities are induced using 3-methylcholanthrene in these spheroids. These results suggest that a designed biological material may provide a conducive microenvironment in which putative adult progenitor cells differentiate into functional hepatocyte-like spheroid clusters. This bioengineered scaffold system provides a better physiological approach to "progenitor cell differentiation" for future biomedical and pharmaceutics applications.

Animals↗
PubMed2004

[Prevention and regeneration of barrier disturbances in occupational dermatology].

Over the past 10 years primary, secondary and tertiary prevention of occupational skin disorders has been shown to be successful, documented with appropriate statistical methods. Interventional strategies are the main features of secondary and tertiary prevention, now well-established in occupational dermatology. Primary prevention is best accomplished by health education measures, both in the form on individual counseling and seminars. This overview reviews the scientific background of hand eczema with respect to barrier damage and repair and then considers the options for individualized and focused prevention. Special anatomical features of the interdigital space and palms, as well as functional disorders, such as palmar hyperhidrosis, are discussed. The importance of barrier regeneration is considered in light of the role of an acid pH, the epidermal calcium gradient and aspects of percutaneous absorption. The effects of anti-oxidants are considered, and new bioengineering methods which rely on physiologic measuring techniques are reviewed.

Dermatology↗
PubMed2003

Bioartificial liver support devices: historical perspectives.

Fulminant hepatic failure (FHF) is an important cause of death worldwide. Despite significant improvements in critical care therapy there has been little impact on survival with mortality rates approaching 80%. In many patients the cause of the liver failure is reversible and if short-term hepatic support is provided, the liver may regenerate. Survivors recover full liver function and a normal life expectancy. For many years the only curative treatment for this condition has been liver transplantation, subjecting many patients to replacement of a potentially self-regenerating organ, with the lifetime danger of immunosuppression and its attendant complications, such as malignancy. Because of the shortage of livers available for transplantation, many patients die before a transplant can be performed, or are too ill for operation by the time a liver becomes available. Many patients with hepatic failure do not qualify for liver transplantation because of concomitant infection, metastatic cancer, active alcoholism or concurrent medical problems. The survival of patients excluded from liver transplantation or those with potentially reversible acute hepatitis might be improved with temporary artificial liver support. With a view to this, bioartificial liver support devices have been developed which replace the synthetic, metabolic and detoxification functions of the liver. Some such devices have been evaluated in clinical trials. During the last decade, improvements in bioengineering techniques have been used to refine the membranes and hepatocyte attachment systems used in these devices, in the hope of improving function. The present article reviews the history of liver support systems, the attendant problems encountered, and summarizes the main systems that are currently under evaluation.

Cells, Cultured↗
PubMed2003

Tissue engineering the kidney.

The means by which kidney function can be replaced in humans include dialysis and renal allotransplantation. Dialytic therapies are lifesaving, but often poorly tolerated. Transplantation of human kidneys is limited by the availability of donor organs. During the past decades, a number of different approaches have been applied toward tissue engineering the kidney as a means to replace renal function. The goals of one or another of them included the recapitulation of renal filtration, reabsorptive and secretory functions, and replacement of endocrine/metabolic activities. This review will delineate the progress to date recorded for five approaches: (1) integration of new nephrons into the kidney; (2) growing new kidneys in situ; (3) use of stem cells; (4) generation of histocompatible tissues using nuclear transplantation; and (5) bioengineering of an artificial kidney. All five approaches utilize cellular therapy. The first four employ transplantation as well, and the fifth uses dialysis.

Animals↗
PubMed2001

Current approaches to venous ulcers and compression.

BACKGROUND: Venous ulcers affect as many as 2.5 million people in the United States and can cause substantial pain and loss of function. OBJECTIVE: To review current approaches to venous ulcers and compression. METHOD: Treatment options that have been proposed in the literature are discussed utilizing the Cochrane library database, Medline, and the author's clinical experience. RESULTS: Diagnostic findings and management strategies for venous ulcers are reviewed. CONCLUSION: Good wound care and compression therapy will heal the majority of small venous ulcers of short duration. For ulcers that are slow to heal, other approaches such as venous surgery and grafting with conventional or bioengineered skin substitutes should be considered.

Bandages↗
PubMed2001

Healing of venous ulcers of long duration with a bilayered living skin substitute: results from a general surgery and dermatology department.

BACKGROUND: A laboratory-grown bilayered living skin substitute (LSS) has been shown to accelerate the healing of venous ulcers. However, issues related to optimal wound bed preparation prior to the application of LSS have not been addressed. OBJECTIVE: When combined with standard compression therapy and near elimination of wound exudate, bioengineered skin can achieve complete closure of venous ulcers which have been present for more than a year and which are difficult to heal. METHODS: In the general surgery (center A) and dermatology (center B) departments at two separate medical centers, LSS was used to treat venous ulcers of more than 1 year's duration and which had been unresponsive to conventional therapy. Wound bed preparation at both centers had as common goals the removal of necrotic tissue, optimal formation of granulation tissue, and elimination of wound exudate. RESULTS: There was great comparability between the two centers in the patients being treated, wound size and duration, and number of LSS applications. Both centers achieved a frequency of complete wound closure of greater than 70% within 6 months. CONCLUSION: At two separate clinical and specialty sites having a common goal of optimal wound preparation, treatment with LSS was associated with a high rate of complete closure of hard to heal venous ulcers.

Aged↗
PubMedDate not supplied

Transplantation of virally transduced cells into the dermis of immunocompetent and immunodeficient (SCID) mice to determine gene expression profile and differential donor cell survival.

Cell therapy and bioengineering hold great promise as therapeutic approaches using cells and cell-derived factors to treat various pathologic or trauma-induced states. One possible application is the transplantation of cells into wounded tissue to help regulate tissue repair. Cells engineered for optimal wound healing may help to minimize scarring following surgery or to enhance the rate of healing of chronic wounds. The purpose of the current study was to determine the effect of a viral insert, the LacZ-bearing, first generation adenovirus AdRGD, on the survival of dermally transplanted murine skin allogenic fibroblasts. The LacZ insert facilitated quantitation of both cell survival and gene expression and was used here to measure viable cell number. In addition to bearing the LacZ marker, the AdRGD vector is capable of carrying therapeutic gene inserts, so this study tested the feasibility of gene therapy for wound healing. Murine skeletal muscle PP6 (i.e., Pre-Plate 6) myogenic stem cells served as an alternate donor cell type. Cells were labeled with the LacZ-bearing AdRGD adenovirus vector and injected (50,000 cells/site) into the dorsal skin of adult normal, immunocompetent mice as well as in immunodeficient SCID mice. Skin biopsies were taken on days 0, 1, 2, 3, and 7 post-transplant, and assayed for LacZ expression. Soon after transplant (day 1), cell numbers underwent a transient decrease, but by day 2 post-transplant they were present in appreciable numbers. Between days 2-7 post-transplant, both allogenic fibroblasts and PP6 myogenic stem cells maintained survivability in similar numbers. Further, survival of transplanted cell types was similar in both normal, immunocompetent as well as SCID mice during this time period. There were no signs of acute inflammation or rejection in any of the samples. This study shows that AdRGD-transduced cells are not immunogenic in the mouse skin model and the cells show similar survival for the first 7 days post-transplantation independent of the cell type or immunocompetence of the host.

Animals↗
PubMedDate not supplied

Debridement performance index and its correlation with complete closure of diabetic foot ulcers.

In recent years there has been wider acceptance of aggressive surgical debridement as a means to accelerate closure of diabetic foot ulcers. In a clinical trial by Steed et al.1 involving the use of a topically applied growth factor, thorough surgical debridement of surrounding callus, necrotic ulcer bed, and undermined ulcers' edges was associated with greater incidence of healing and effectiveness of the therapeutic agent. However, at present there is no established way to judge the appropriate extent of debridement and its performance. Here we describe a scoring system to assess whether debridement has been performed adequately. Our scoring system consists of the following three categories: debridement of a) callus; b) ulcer's edge undermining; and c) wound bed necrotic tissue. We assigned a score of 0-2 to each of these categories using the following criteria: 0 = debridement needed but not done, 1 = debridement needed and done, and 2 = debridement not needed. These three scores are then added to give a total ranging from 0 to 6, with the highest number being the optimal score. This instrument, the Debridement Performance Index, evaluates both the adequacy of debridement and whether the ulcer has been or is being properly debrided. To initiate the validation of this scoring system and determine its predictive value for wound closure by week 12, we applied it to 143 patients with diabetic foot ulcers who had been treated in a clinical trial involving either standard therapy (n = 65) or the application of a bioengineered skin construct (n = 78). We blindly evaluated sequential digital photographs of each diabetic foot ulcer and applied the Debridement Performance Index score at day 0, before initiation of either treatment. We found that the lower the baseline Debridement Performance Index the lower the incidence of ultimate wound closure by week 12 ( p = 0.0276). Patients with a Debridement Performance Index between 3 and 6 were 2.4 times more likely to heal than those with a score of 0-2. After controlling for treatment, the Debridement Performance Index was found to be an independent predictor of wound closure (odds ratio = 2.4 95% confidence interval = 1.0-5.6). In conclusion, this novel scoring system for debridement performance appears to be very promising as a predictive tool for determining outcome in clinical trials and, most likely, in clinical practice.

Adolescent↗