Lukas Prantl

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.

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.

Role of mesenchymal stem cells in tissue engineering of meniscus

Tissue engineering is a promising approach for the treatment of tissue defects. Mesenchymal stem cells are of potential use as a source of repair cells or of important growth factors for tissue engineering. The purpose of this study was to examine the role of mesenchymal stem cells in meniscal tissue repair. This was tested using several cell and biomaterial-based treatment options for repair of defects in the avascular zone of rabbit menisci. Circular meniscal punch defects (2 mm) were created in the avascular zone of rabbit menisci and left empty or filled with hyaluronan-collagen composite matrices without cells, loaded with platelet-rich plasma, autologous bone marrow, or autologous mesenchymal stem cells. In some experiments, matrices with stem cells were precultured in chondrogenic medium for 14 days before implantation. Rabbits were then allowed free cage movement after surgery for up to 12 weeks. Untreated defects and defects treated with cell-free implants had muted fibrous healing responses. Neither bone marrow nor platelet-rich plasma loaded in matrices produced improvement in healing compared with cell-free implants. The implantation of 14 days precultured chondrogenic stem cell-matrix constructs resulted in fibrocartilage-like repair tissue, which was only partially integrated with the native meniscus. Non-precultured mesenchymal stem cells in hyaluronan-collagen composite matrices stimulated the development of completely integrated meniscus-like repair tissue. The study shows the necessity of mesenchymal stem cells for the repair of meniscal defects in the avascular zone. Mesenchymal stem cells seem to fulfill additional repair qualities besides the delivery of growth factors.

Hypertrophy in Mesenchymal Stem Cell Chondrogenesis: Effect of TGF-β Isoforms and Chondrogenic Conditioning

Induction of chondrogenesis in mesenchymal stem cells (MSCs) with TGF-β leads to a hypertrophic phenotype. The hypertrophic maturation of the chondrocytes is dependent on the timed removal of TGF-β and sensitive to hypertrophy-promoting agents in vitro. In this study, we have investigated whether TGF-β3, which has been shown to be more prochondrogenic compared to TGF-β1, similarly enhances terminal differentiation in an in vitro hypertrophy model of chondrogenically differentiating MSCs. In addition, we tested the impact of the time of chondrogenic conditioning on the enhancement of hypertrophy. MSCs were chondrogenically differentiated in pellet culture in medium containing TGF-β1 or TGF-β3. After 2 or 4 weeks, chondrogenic medium was switched to hypertrophy-inducing medium for 2 weeks. Aggregates were analyzed histologically and biochemically on days 14, 28 and 42. The switch to hypertrophy medium after 14 days induced hypertrophic cell morphology and significant increase in alkaline phosphatase activity compared to the chondrogenesis only control using both TGF-β1 and TGF-β3. After 28 days predifferentiation, differences between hypertrophic and control groups diminished compared to 14 days predifferentiation. In conclusion, chondrogenic conditioning with both TGF-β isoforms similarly induced hypertrophy in our experiment and allowed the enhancement of the hypertrophic chondrocyte phenotype by hypertrophic medium. Enhancement of hypertrophy was seen more clearly after the shorter chondrogenic conditioning. Therefore, to utilize this experimental model as a tool to study hypertrophy in MSC chondrogenesis, a predifferentiation period of 14 days is recommended.

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.

Bacterial colonization is of major relevance for high-grade capsular contracture after augmentation mammaplasty.

Many studies indicate that subclinical bacterial colonization plays a pivotal role in capsular contracture. Nevertheless, it has not been clarified whether bacterial stimuli are only associated with high-grade (Baker III/IV) or low-grade (Baker I/II) capsular contractures. The study included 45 female patients suffering from unilateral capsular fibrosis following augmentation mammaplasty with silicone implants (smooth: n = 28; textured: n = 17). In total, there were 16 (35.6%) bacterially contaminated swabs. No significant difference could be detected between colonization rates of smooth (52.9%) and textured (25.0%) implants (z = 1.575, P = 0.115). Interestingly, no colonization was detected for Baker I/II contractures, but the colonization rate for Baker III/IV contractures amounted to 66.7%, showing a highly significant difference between the 2 groups (z = 4.351, P < 0.001). Our study shows significant differences in bacterial contamination rates between high-grade and low-grade capsular contractures. One might speculate that bacterial stimuli accelerate the process of inflammation and fibrosis in patients who tend to develop capsular fibrosis.

Suprathel, a New Skin Substitute, in the Management of Partial-thickness Burn Wounds: Results of a Clinical Study

Objective:A prospective, randomized, bicentric, nonblinded, clinical study was conducted to evaluate the impact on wound healing of Suprathel in partial-thickness burn injuries. Suprathel represents an absorbable, synthetic wound dressing with properties of natural epithelium. Methods:Thirty patients suffering from second-degree burn injuries were included in the study, with a mean of age 40.4 years old. Burn injuries were randomly selected, partly treated with Omiderm and partly treated with Suprathel. The first gauze change was applied the fifth day postoperatively, followed by regular wound inspection until complete reepithelization. The study focused on patient pain score, healing time, analysis of wound bed, ease of care, and treatment costs. Results:There was no significant difference between the 2 materials tested regarding healing time and reepithelization. There was a significant lower pain score for patients treated with Suprathel (P = 0.0072). Suprathel becomes transparent when applied, thus allowing close monitoring of wound healing. In contrast to Omiderm, Suprathel shows better attachment and adherence to wounds. During the course of healing, it detaches smoothly, without damaging the reepithelized wound surface. Moreover, it reduces the frequency of dressing changes required. Ease of care of Suprathel has been rated outstanding by patients and healthcare professionals. When interviewed, patients reported Suprathel as their treatment preference. As dressing material, Omiderm is more cost-effective than Suprathel. Conclusion:Suprathel represents a reliable epidermal skin substitute, with a good impact on wound healing and pain reduction in partial-thickness burn injuries. Although it is less cost-effective than Omiderm, the significant increase of patient comfort makes this material represent a reliable and solid treatment alternative when dealing with partial-thickness burn injuries. Further studies with this synthetic dressing on other types of wounds are warranted.

Modern tattoos cause high concentrations of hazardous pigments in skin

Background:  Modern tattoo colourants frequently consist of azo pigments that not only contain multiple impurities but also are originally produced for car paint and the dyeing of consumer goods.

Luminescent Dual Sensors Reveal Extracellular pH-Gradients and Hypoxia on Chronic Wounds That Disrupt Epidermal Repair

Wound repair is a quiescent mechanism to restore barriers in multicellular organisms upon injury. In chronic wounds, however, this program prematurely stalls. It is known that patterns of extracellular signals within the wound fluid are crucial to healing. Extracellular pH (pHe) is precisely regulated and potentially important in signaling within wounds due to its diverse cellular effects. Additionally, sufficient oxygenation is a prerequisite for cell proliferation and protein synthesis during tissue repair. It was, however, impossible to study these parameters in vivo due to the lack of imaging tools. Here, we present luminescent biocompatible sensor foils for dual imaging of pHe and oxygenation in vivo. To visualize pHe and oxygen, we used time-domain dual lifetime referencing (tdDLR) and luminescence lifetime imaging (LLI), respectively. With these dual sensors, we discovered centripetally increasing pHe-gradients on human chronic wound surfaces. In a therapeutic approach, we identify pHe-gradients as pivotal governors of cell proliferation and migration, and show that these pHe-gradients disrupt epidermal barrier repair, thus wound closure. Parallel oxygen imaging also revealed marked hypoxia, albeit with no correlating oxygen partial pressure (pO2)-gradient. This highlights the distinct role of pHe-gradients in perturbed healing. We also found that pHe-gradients on chronic wounds of humans are predominantly generated via centrifugally increasing pHe-regulatory Na+/H+-exchanger-1 (NHE1)-expression. We show that the modification of pHe on chronic wound surfaces poses a promising strategy to improve healing. The study has broad implications for cell science where spatial pHe-variations play key roles, e.g. in tumor growth. Furthermore, the novel dual sensors presented herein can be used to visualize pHe and oxygenation in various biomedical fields.