Stephan Schreml

Wound healing in the 21st century

Delayed wound healing is one of the major therapeutic and economic issues in medicine today. Cutaneous wound healing is an extremely well-regulated and complex process basically divided into 3 phases: inflammation, proliferation, and tissue remodeling. Unfortunately, we still do not understand this process precisely enough to give direction effectively to impaired healing processes. There have been many new developments in wound healing that provide fascinating insights and may improve our ability to manage clinical problems. Our goal is to acquaint the reader with selected major novel findings about cutaneous wound healing that have been published since the beginning of the new millennium. We discuss advances in areas such as genetics, proteases, cytokines, chemokines, and regulatory peptides, as well as therapeutic strategies, all set in the framework of the different phases of wound healing.

Cytokines, chemokines and growth factors in wound healing.

In wound healing, a variety of mediators have been identified throughout the years. The mediators discussed here comprise growth factors, cytokines and chemokines. These mediators act via multiple (specific) receptors to facilitate wound closure. As research in the last years has led to many new findings, there is a need to give an overview on what is known, and on what might possibly play a role as a molecular target for future wound therapy. This review aims to keep the reader up to date with selected important and novel findings regarding growth factors, cytokines and chemokines in wound healing.

Intense pulsed light (IPL): A review

Intense pulsed light (IPL) devices use flashlamps and bandpass filters to emit polychromatic incoherent high‐intensity pulsed light of determined wavelength spectrum, fluence, and pulse duration. Similar to lasers, the basic principle of IPL devices is a more or less selective thermal damage of the target. The combination of prescribed wavelengths, fluences, pulse durations, and pulse intervals facilitates the treatment of a wide spectrum of skin conditions.

Photodynamic therapy in dermatology: state‐of‐the‐art

Photodynamic therapy (PDT) has become an established treatment modality for dermatooncologic conditions like actinic keratosis, Bowens disease, in situ squamous cell carcinoma and superficial basal cell carcinoma. There is also great promise of PDT for many non‐neoplastic dermatological diseases like localized scleroderma, acne vulgaris, granuloma anulare and leishmaniasis. Aesthetic indications like photo‐aged skin or sebaceous gland hyperplasia complete the range of applications. Major advantages of PDT are the low level of invasiveness and the excellent cosmetic results. Here, we review the principal mechanism of action, the current developments in the field of photosensitizers and light sources, practical aspects of topical PDT and therapeutical applications in oncologic as well as non‐oncologic indications.

Clinical and morphological conditions in capsular contracture formed around silicone breast implants.

Background: A study was performed to investigate histological changes in capsules formed around silicone breast implants and their correlation with the clinical classification of capsular contracture defined by the Baker score. For histological classification, the authors used the classification introduced by Wilflingseder, which identifies four grades of contracture. Methods: The study included 24 female patients (average age, 40 ± 12 years) with capsular contracture after bilateral cosmetic breast augmentation with smooth silicone gel implants (Mentor, Santa Barbara, Calif.). The Baker score was determined preoperatively for each patient. Samples of capsular tissue were obtained from all patients for histologic and immunohistochemical analyses. Capsular thickness, age of the collagen fibers, presence of synovia-like metaplasia on the inner surface of the capsule, number of histiocytes, giant cells, and other inflammatory cells, amount of silicone, foreign body granulomas, and capsule calcification were evaluated. Results: There was a positive correlation between capsular thickness (p < 0.05) and Baker score. Silicone-containing deposits were found in all four histological capsule types. A trend toward greater capsular thickness was documented in patients with severe inflammatory reaction. These patients also had more clinical symptoms. Greater capsular thickness was associated with a higher number of silicone particles and silicone-loaded macrophages in the peri-implant capsule. Conclusions: The authors demonstrated a positive correlation (p < 0.05) between the clinical classification (Baker score I to IV) and the histological classification introduced by Wilflingseder (Wilflingseder score I to IV). An exact histological classification is needed to describe precisely the morphological changes in capsular contracture.

2D luminescence imaging of pH in vivo

Luminescence imaging of biological parameters is an emerging field in biomedical sciences. Tools to study 2D pH distribution are needed to gain new insights into complex disease processes, such as wound healing and tumor metabolism. In recent years, luminescence-based methods for pH measurement have been developed. However, for in vivo applications, especially for studies on humans, biocompatibility and reliability under varying conditions have to be ensured. Here, we present a referenced luminescent sensor for 2D high-resolution imaging of pH in vivo. The ratiometric sensing scheme is based on time-domain luminescence imaging of FITC and ruthenium(II)tris-(4,7-diphenyl-1,10-phenanthroline). To create a biocompatible 2D sensor, these dyes were bound to or incorporated into microparticles (aminocellulose and polyacrylonitrile), and particles were immobilized in polyurethane hydrogel on transparent foils. We show sensor precision and validity by conducting in vitro and in vivo experiments, and we show the versatility in imaging pH during physiological and chronic cutaneous wound healing in humans. Implementation of this technique may open vistas in wound healing, tumor biology, and other biomedical fields.

The impact of the pH value on skin integrity and cutaneous wound healing

The process of cutaneous wound healing comprises three overlapping major phases: inflammation, proliferation and tissue remodelling. However, while mechanisms are studied scientifically on the cellular and subcellular level, there is still a lack of knowledge concerning basic clinical parameters like wound pH or pO2. It could be proven that wound healing is affected by wound pH changes as they can lead to an inhibition of endogenous and therapeutically applied enzymes. Besides, the conformational structure of proteins and their functionality in wound healing is altered. Furthermore, the likelihood of bacterial colonization, which is a common problem in chronic wound pathogenesis, is affected by wound pH alterations. However, wound pH is rarely taken into account in current wound therapy strategies. A routinely performed monitoring of the wound pH and a subsequently adapted wound therapy would most possibly improve chronic wound therapy.

Harvesting human adipose tissue-derived adult stem cells: resection versus liposuction

BACKGROUND Adipose tissue is an abundant source of mesenchymal stem cells (MSC), which can be used for tissue-engineering purposes. The aim of our study was to determine the more suitable procedure, surgical resection or liposuction, for harvesting human adipose tissue-derived stem cells (hASC) with regard to viability, cell count and differentiation potential. METHODS After harvesting hASC, trypan blue staining and cell counting were carried out. Subsequently, hASC were cultured, analyzed by fluorescence-activated cell sorting (FACS) and differentiated under adipogenic, osteogenic and chondrogenic conditions. Histologic and functional analyzes were performed at the end of the differentiation period. RESULTS No significant difference was found with regard to the cell counts of hASC from liposuction and surgically resected material (P=0.086). The percentage of viable cells was significantly higher for liposuction aspirates than for resection material (P=0.002). No significant difference was found in the adipogenic differentiation potential (P=0.179). A significantly lower number of cultures obtained from liposuction material than from resection material could be differentiated into osteocytes (P=0.049) and chondrocytes (P=0.012). DISCUSSION Even though some lineages from lipoaspirated hASC can not be differentiated as frequently as those from surgically resected material, liposuction may be superior for some tissue-engineering purposes, particularly because of the less invasive harvesting procedure, the higher percentage of viable cells and the fact that there is no significant difference between lipoaspirated and resected hASC with regard to adipogenic differentiation potential.

Does the Surface Structure of Implants Have an Impact on the Formation of a Capsular Contracture

BackgroundThe formation of a fibrous capsule around a silicone breast implant is part of a physiologic foreign body reaction after breast augmentation. In contrast, the formation of a capsular contracture is a local complication of unknown cause. This study aimed to discover whether the surface structure of the implant (textured vs smooth) has any impact on the formation of a capsular contracture.MethodsThis prospective study included 48 female patients with unilateral capsular fibrosis grades 1 to 4 in Baker’s clinical scaling system. Of these patients, 14 received implants with a textured surface (Mentor), and 34 received implants with a smooth surface (Mentor). The implants all were placed in a submuscular position by the same experienced plastic surgeon. The clinical data were assessed using standardized patient questionnaires. For histologic diagnosis, operatively excised capsular tissue was examined. Preoperatively, venous blood samples for determining serum hyaluronan concentrations were taken from the patients. The control group consisted of 20 patients without capsular fibrosis.ResultsThe separate analysis of clinical data for the patients with textured and those with smooth-surfaced breast implants showed a slightly reduced degree of symptoms for the patients with textured silicone breast implants, as compared with those who had smooth-surfaced implants. The histologic assessment of the fibrosis showed a symmetric distribution for Wilflingseder scores 1 to 3 (29% each), whereas 13% of the capsular tissues could be assigned to Wilflingseder score 4. In contrast, the histologic assessment of the patients with smooth-surfaced implants predominantly showed a Wilflingseder score of 3 (65%). The serologic investigations via enzyme-linked immunoassay (ELISA) showed serum hyaluronan concentrations of 10 to 57 ng/ml (25.0 ± 11.7 ng/ml). Therefore, no statistically significant differences in terms of serum hyaluronan levels could be determined between the two groups of patients. In comparison with the control group, the patients with implants showed elevated serum hyaluronan levels (p < 0.05).ConclusionsThe histologic examination and serum hyaluronan concentration analysis showed no statistically significant difference between smooth-surfaced and textured implants (Mentor) with respect to the development of capsular contracture. On the other hand, the severity of capsular contracture showed a positive linear correlation with the degree of local inflammatory reactions, which were independent of the implant surface.

Filaggrin Deficiency Leads to Impaired Lipid Profile and Altered Acidification Pathways in a 3D Skin Construct

Mutations in the filaggrin (FLG) gene are strongly associated with common dermatological disorders such as atopic dermatitis. However, the exact underlying pathomechanism is still ambiguous. Here, we investigated the impact of FLG on skin lipid composition, organization, and skin acidification using a FLG knockdown (FLG-) skin construct. Initially, sodium/hydrogen antiporter (NHE-1) activity was sufficient to maintain the acidic pH (5.5) of the reconstructed skin. At day 7, the FLG degradation products urocanic (UCA) and pyrrolidone-5-carboxylic acid (PCA) were significantly decreased in FLG- constructs, but the skin surface pH was still physiological owing to an upregulation of NHE-1. At day 14, secretory phospholipase A2 (sPLA2) IIA, which converts phospholipids to fatty acids, was significantly more activated in FLG- than in FLG+. Although NHE-1 and sPLA2 were able to compensate the FLG deficiency, maintain the skin surface pH, and ensured ceramide processing (no differences detected), an accumulation of free fatty acids (2-fold increase) led to less ordered intercellular lipid lamellae and higher permeability of the FLG- constructs. The interplay of the UCA/PCA and the sPLA2/NHE-1 acidification pathways of the skin and the impact of FLG insufficiency on skin lipid composition and organization in reconstructed skin are described.