Effect of tissue inhibitors of metalloproteinases and matrix metalloproteinases on capsular formation around smooth and textured silicone gel implants

The activation of FPR3/PKA/Rap1/ERK1/2 and FPR3/p-IκB/NF-κB axis in fibroblasts promote capsular contracture after rhinoplasty

BACKGROUND

Capsular contracture may occur after rhinoplasty due to rejection of silicone implants by the immune system. Our previous high-throughput sequencing of RNA in nasal capsular contracture tissue revealed that FPR3 was significantly increased in grade IV capsular contracture tissue, compared with grade II.

OBJECTIVE

This study aimed to elucidate the effect and specific mechanism of FPR3 on capsular formation and contracture following rhinoplasty.

METHODS

Using the GeneMANIA Database, the genes involved with FPR3 expression were searched, and the Gene Ontology analysis was performed to annotate the biological functions of the aforementioned genes. The mRNA and protein expressions of related genes in fibroblasts and capsular contracture tissues were analyzed using quantitative real-time PCR, western blot, and immunohistochemical staining. CCK-8 was used to determine the viability of cells. The migration capacity of fibroblasts was assessed using a wound healing assay. ELISA was used to detect levels of IL-1β, TNF-α, and IL-6.

RESULTS

After rhinoplasty, the expression of FPR3 in the capsular tissue increased in proportion to the degree of contracture. By activating the PKA/Rap1/ERK1/2 axis, overexpression of FPR3 can significantly increase the cell viability of fibroblasts and promote their transformation into myofibroblasts. Moreover, FPR3 phosphorylates IκB to decrease NF-κB inhibition, thereby promoting the synthesis and release of the inflammatory cytokines IL-1β, TNF-α, and IL-6.

CONCLUSION

FPR3 is a crucial molecule that causes capsular development and contracture following rhinoplasty. In the future, local suppression of FPR3 may be an effective treatment for relieving capsular contracture.

Silicone Breast Implant Surface Texture Impacts Gene Expression in Periprosthetic Fibrous Capsules

BACKGROUND

Silicone breast implants with smooth outer shells are associated with higher rates of capsular contracture, whereas textured implants have been linked to the development of breast implant-associated anaplastic large cell lymphoma. By assessing the gene expression profile of fibrous capsules formed in response to smooth and textured implants, insight into the development of breast implant-associated abnormalities can be gained.

METHODS

Miniature smooth or textured silicone implants were surgically inserted into female rats ( n = 10) and harvested for the surrounding capsules at postoperative week 6. RNA sequencing and quantitative polymerase chain reaction were performed to identify genes differentially expressed between smooth and textured capsules. For clinical correlation, the expression of candidate genes was assayed in implant capsules harvested from human patients with and without capsular contracture.

RESULTS

Of 18,555 differentially expressed transcripts identified, three candidate genes were selected: matrix metalloproteinase-3 ( MMP3 ), troponin-T3 ( TNNT3 ), and neuregulin-1 ( NRG1 ). In textured capsules, relative gene expression and immunostaining of MMP3 and TNNT3 was up-regulated, whereas NRG1 was down-regulated compared to smooth capsules [mean relative fold change, 8.79 ( P = 0.0059), 4.81 ( P = 0.0056), and 0.40 ( P < 0.0001), respectively]. Immunostaining of human specimens with capsular contracture revealed similar gene expression patterns to those of animal-derived smooth capsules.

CONCLUSIONS

An expression pattern of low MMP3 /low TNNT3 /high NRG1 is specifically associated with smooth implant capsules and human implant capsules with capsular contracture. The authors' clinically relevant breast implant rat model provides a strong foundation to further explore the molecular genetics of implant texture and its effect on breast implant-associated abnormalities.

CLINICAL RELEVANCE STATEMENT

The authors have demonstrated that there are distinct gene expression profiles in response to smooth versus textured breast implants. Since surface texture may be linked to implant-related pathology, further molecular analysis of periprosthetic capsules may yield strategies to mitigate implant-related complications.

Effect of Carboxymethyl Chitin on Capsule Formation around Silicone Implants: An In Vivo and In Vitro Study

BACKGROUND

Capsular contracture is a serious complication that occurs after augmentation mammaplasty. The authors previously identified that carboxymethyl chitin had an inhibitory effect on capsule formation. This study was performed to elucidate the possible molecular mechanisms through which carboxymethyl chitin inhibits the formation of a capsule around silicone implants.

METHODS

In this study, the authors cultured human dermal fibroblasts and treated them with carboxymethyl chitin in vitro. The difference in proliferation between treated and untreated cells was analyzed through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Protein levels of transforming growth factor beta-1 and alpha smooth muscle actin (α-SMA) were examined by Western blot analysis. Expression levels of type I and type III collagen were checked by enzyme-linked immunosorbent assay. In vivo, silicone implants were placed under the pectoralis muscle in 12 female rabbits. The thickness of the capsule was measured by histologic analysis, and the effect of carboxymethyl chitin on α-SMA, collagen type I and III expression levels was evaluated by real-time polymerase chain reaction analysis, enzyme-linked immunosorbent assay, Western blot, and immunofluorescence analysis.

RESULTS

In the in vitro study, we confirmed that carboxymethyl chitin inhibited the proliferation of fibroblasts. The protein expression levels of collagen type I, transforming growth factor beta-1, and α-SMA were inhibited by carboxymethyl chitin treatment. In vivo, carboxymethyl chitin treatment reduced capsular thickness and the expression of α-SMA and collagen types I and III in capsules around silicone implants.

CONCLUSION

The authors' results showed that carboxymethyl chitin could influence capsule formation around silicone implants by inhibiting the fibroblast activity, interrupting fibroblast-to-myofibroblast differentiation, and decreasing collagen synthesis.

CLINICAL RELEVANCE STATEMENT

Carboxymethyl chitin influence capsule formation around silicone implants. Although more clinical studies are needed to verify the effect of carboxymethyl chitin on capsular contracture, the authors believe that it will play an effective role in the clinical application of reducing the occurrence of capsular contracture.

Progranulin Promotes the Formation and Development of Capsules Caused by Silicone in Sprague-Dawley Rats

Background

Silicone implants are currently the most widely used artificial materials in plastic surgery. Capsule formation following implant application is unavoidable. When the capsule is excessively thick and strongly contracted, it can lead to obvious symptoms, clinically known as capsular contracture. Biological factors have always been the focus of research on the capsule formation. As a growth factor, progranulin (PGRN) plays an important regulatory role in wound healing, tissue fibrosis, tumor proliferation and invasion, and inflammation regulation. At present, the research on the capsule mainly involves the regulation of tissue healing and fibrosis under the influence of inflammation. Because PGRN has a regulatory role in these processes, we believe that the study of both can provide a new theoretical basis and intervention sites for monitoring and inhibiting the development of the capsule.

Methods

In this experiment, the effects of different surgical operations on the content of PGRN in the surgical site and plasma of rats were detected. Sprague-Dawley (SD) rat dermal fibroblasts were co-cultured by recombinant PGRN. The effects of r-PGRN on fibroblasts were detected by 5-ethynyl-2’-deoxyuridine (EdU) assay, wound healing assay and Western blot assay. Finally, the effect of PGRN on capsule formation and contracture was studied by changing the content of PGRN in the prosthesis in rats after operation.

Results

Surgical trauma and silicone implant increased plasma and local PGRN levels in SD rats. PGRN can activate the TGF-β/SMAD signaling pathway in a dose-dependent manner, thereby promoting fibroblast proliferation, differentiation and migration and inhibiting apoptosis and enhancing cell function, thereby promoting capsule formation and contracture.

Conclusion

PGRN promotes the formation and contracture of the silicone implant capsule in SD rats by activating the TGF-β/SMAD signaling pathway. This discovery may provide new therapeutic targets and detection indicators.

Expression of NF-κB-p65 and α-SMA in the Study of Capsules formed by Surface Textured Implants Versus Foam Covered Silicone Implants in a Rat Model

BACKGROUND

We aimed to compare inflammatory and intercellular transcription responses induced by surface textured (ST) implants versus foam covered (FC) silicone implants placed on the dorsal aspect of rats.

METHODS

We utilized 80 female rats of the Wistar lineage. The rats were divided into four subgroups of 20 with one type of implant placed in the dorsum per rat. Analysis was carried out on peri-implant capsules at 90 d and at 180 d post-surgery with microscopic evaluation of inflammatory and immuno-histochemical response of NF-κB-p65 and α-SMA in fibroblasts. This study was carried out at the Evangelical Faculty of Parana and at the Ivo Pitanguy Institute, Brazil in 2015.

RESULTS

The FC exhibited higher levels of acute and chronic inflammation on evaluation in both time frames. The capsule surrounding the ST implants was significantly thicker with well-organized collagen fibres. NFκB-p65 expression in the capsule surrounding the FC implant was more pronounced. There was higher and more significant α-SMA expression in the capsules of the surface textured (ST) silicone implants compared to the foam-covered (FC) silicone implants.

CONCLUSION

Activation of NFκB-p65 plays a key role in the evolution of capsule formation and maintenance of inflammation by regulating the healing process. Similarly, higher and more prolonged levels of inflammation (increased NF-κB-p65 results in increased inflammation) and lower α-SMA (higher α-SMA is protective against capsular contracture) did not directly translate to a thicker capsule and ultimately, capsular contracture in foam covered silicone implants.

Angiotensin-Converting Enzyme Inhibitor Reduces Radiation-Induced Periprosthetic Capsular Fibrosis

BACKGROUND

The capsular contracture is one of the main complications after radiotherapy in patients with implant-based reconstruction. The aim of this study is to evaluate the efficacy of ramipril for the prevention of radiation-induced fibrosis around the silicone implant.

MATERIALS AND METHODS

Thirty Wistar rats in 5 groups were used. Group 1: implant; group 2: implant + radiation; group 3: ramipril + implant; group 4: ramipril + implant + radiation; group 5: sham. Ramipril treatment was started 5 d before surgery and continued for 12 wk after surgery. A mini silicone implant was placed in the back of the rats. A single fraction of 21.5 Gy radiation was applied. Tissues were examined histologically and immunohistochemically (TGF-β1, MMP-2, and TIMP-2 expression). The alteration of plasma TGF-β1 levels was examined before and after the experiment.

RESULTS

After applying implant or implant + radiation, capsular thickness, percentage of fibrotic area, tissue and plasma TGF-β1 levels significantly increased, and MMP-2/TIMP-2 ratio significantly decreased compared with the sham group. In ramipril-treated groups, the decrease in capsular thickness, fibrosis, TGF-β1 positivity, and an increase in MMP-2/TIMP-2 ratio were found significant. In the ramipril + implant + radiation group, the alteration values of TGF-β1 dramatically decreased.

CONCLUSIONS

Our results show that ramipril reduces radiation-induced fibrosis and contracture. The results of our study may be important for the design of the clinical trials required to investigate the effective and safe doses of ramipril, which is an inexpensive and easily tolerated drug, on humans.

Identification of transcriptomic characteristics during nasal capsular contracture progression using RNA deep sequencing

Nasal capsular contracture is a prevalent complication commonly observed after rhinoplasty. However, the mechanism underlying the pathogenesis of nasal capsular contracture is largely unclear compared to that of breast capsular contracture. This study aimed to identify the key genes implicated in nasal capsular contracture progression using RNA deep sequencing (RNA-seq). Biopsy samples were taken from Grade II to Grade IV nasal fibrous capsular tissues. The former is regarded as the relatively normal tissues and thus was set as control group, while the latter was treated as pathological group. Results from RNA-seq underwent GO enrichment and KEGG pathway analysis and subsequent verification by quantitative reverse transcriptase polymerase chain reaction and western blot assays. RNA-seq analysis showed that 3149 genes were up-regulated and 3131 genes in pathological groups compared with controls. The top 30 up-regulated genes included many chemokines (e.g., CCL18, CCL13, CCL17 and CCL8), matrix metallopeptidases (e.g., MMP9 and MMP12) and integrin proteins (e.g., ITGAM and ITGB2). GO enrichment analysis demonstrated that the up-regulated genes affected various immune functions, including immune system process, cell activation, leukocyte activation, defence response and positive regulation of immune. The down-regulated gene primary influenced muscle development and functions as well as metabolic processes. In summary, this study reveal that abnormal changes of immune functions, muscle develop and metabolic processes are probably implicated in the pathogenesis of nasal capsular contracture.

Surface Texturization of Breast Implants Impacts Extracellular Matrix and Inflammatory Gene Expression in Asymptomatic Capsules

BACKGROUND

Texturing processes have been designed to improve biocompatibility and mechanical anchoring of breast implants. However, a high degree of texturing has been associated with severe abnormalities. In this study, the authors aimed to determine whether implant surface topography could also affect physiology of asymptomatic capsules.

METHODS

The authors collected topographic measurements from 17 different breast implant devices by interferometry and radiographic microtomography. Morphologic structures were analyzed statistically to obtain a robust breast implant surface classification. The authors obtained three topographic categories of textured implants (i.e., "peak and valleys," "open cavities," and "semiopened cavities") based on the cross-sectional aspects. The authors simultaneously collected 31 Baker grade I capsules, sorted them according to the new classification, established their molecular profile, and examined the tissue organization.

RESULTS

Each of the categories showed distinct expression patterns of genes associated with the extracellular matrix (Timp and Mmp members) and inflammatory response (Saa1, Tnsf11, and Il8), despite originating from healthy capsules. In addition, slight variations were observed in the organization of capsular tissues at the histologic level.

CONCLUSIONS

The authors combined a novel surface implant classification system and gene profiling analysis to show that implant surface topography is a bioactive cue that can trigger gene expression changes in surrounding tissue, even in Baker grade I capsules. The authors' new classification system avoids confusion regarding the word "texture," and could be transposed to implant ranges of every manufacturer. This new classification could prove useful in studies on potential links between specific texturizations and the incidence of certain breast-implant associated complications.

Size matters-in vitro behaviour of human fibroblasts on textured silicone surfaces with different pore sizes

Capsular contracture remains a challenge in plastic surgery and represents one of the most common postoperative complications following alloplastic breast reconstruction. The impact of the surface structure of silicone implants on the foreign body reaction and the behaviour of connective tissue-producing cells has already been discussed. The aim of this study was to investigate different pore sizes of silicone surfaces and their influence on human fibroblasts in an in vitro model. Four different textures (no, fine, medium and coarse texture) produced with the salt-loss technique, have been assessed in an in vitro model. Human fibroblasts were seeded onto silicone sheets and evaluated after 1, 4 and 7 days microscopically, with viability assay and gene expression analysis. Comparing the growth behaviour and adhesion of the fibroblasts on the four different textures, a dense cell layer, good adhesion and bridge-building ability of the cells could be observed for the fine and medium texture. Cell number and viability of the cells were increasing during the time course of experiments on every texture. TGFß1 was lowest expressed on the fine and medium texture indicating a trend for decreased fibrotic activity. For silicone surfaces produced with the salt-loss technique, we were able to show an antifibrotic effect of smaller sized pores. These findings underline the hypothesis of a key role of the implant surface and the pore size and pore structure in preventing capsular contracture.

Hypoxia-induced epithelial-mesenchymal transition and fibrosis for the development of breast capsular contracture

Fibrosis has been considered as a major cause of capsular contracture. Hypoxia has widely emerged as one of the driving factors for fibrotic diseases. The aim of this study was to examine the association between hypoxia-induced fibrosis and breast capsular contracture formation. Fibrosis, epithelial-mesenchymal transition (EMT), expression levels of hypoxia-inducible factor-1α (HIF-1α), vimentin, fibronectin, and matrix metalloproteinase-9 (MMP-9) in tissues from patients with capsular contracture were determined according to the Baker classification system. Normal breast skin cells in patients with capsular contracture after implant-based breast surgery and NIH3T3 mouse fibroblasts were cultured with cobalt chloride (CoCl₂) to mimic hypoxic conditions. Treatment responses were determined by detecting the expression of HIF-1α, vimentin, fibronectin, N-cadherin, snail, twist, occludin, MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1) and -2, as well as phosphorylated ERK. The expression levels of HIF-1α, vimentin, fibronectin, and fibrosis as well as EMT were positively correlated with the severity of capsular contracture. MMP-9 expression was negatively correlated the Baker score. Hypoxia up-regulated the expression of HIF-1α, vimentin, fibronectin, N-cadherin, snail, twist, TIMP-1 and -2, as well as phosphorylated ERK in normal breast skin cells and NIH3T3. Nonetheless, the expression levels of MMP-9 and occludin were down-regulated in response to CoCl₂ treatment. This study is the first to demonstrate the association of hypoxia-induced fibrosis and capsular contracture.

The aetiopathogenesis of capsular contracture: A systematic review of the literature

BACKGROUND

Capsular contracture is the most frequent complication after breast augmentation or reconstruction with breast implants. The immune system plays a prominent role in capsular contracture formation, albeit to an unknown extent. Bacterial contamination in situ has been hypothesized to be causative for capsular contracture. How this relates to the immunological processes involved is unknown. This article aims to provide an overview of immunological and bacterial factors involved in development of capsular contracture.

MATERIALS AND METHODS

We undertook a systematic literature review focused on immunological factors and microbiota in relation to capsular contraction around implants. This systematic review was performed in accordance with the PRISMA guidelines. PubMed, EMBASE, and the Cochrane databases were searched from inception up to October 2016. Included studies were assessed for the following variables: subject characteristics, number of capsules, primary indication for surgery, surgical procedure, follow-up or implant duration, study methods, type of antibiotics or medical therapies and outcomes related to microbiota and immunological factors.

RESULTS

Data on immunological factors and bacterial contamination were retrieved from 64 included studies. Notably the presence of macrophages and Staphylococcus epidermidis within capsules was often associated with capsular contracture.

CONCLUSION

This review provides a clear overview of the immunological factors associated with capsular contracture and provides a hypothetical immunological model for development of the disease. Furthermore, an overview of bacterial contamination and associations with capsular contracture has been provided. Follow-up research may result in clinical recommendations to prevent capsular contracture.

Effects of Medical Chitosan on Capsular Formation Following Silicone Implant Insertion in a Rabbit Model

BACKGROUND

Capsular contracture is a serious complication that occurs after breast implant surgery. This study was performed to confirm that medical chitosan (MC) affects capsule formation and elucidates a possible mechanism.

MATERIALS AND METHODS

In this study, we used 18 female adult New Zealand White rabbits. In each rabbit, two silicone implants were placed under the pectoralis muscle layer on both sides (one side was included in the experimental group and the other side was included in the control group). MC was applied around the silicone implant of the experiment group, while the control group received no treatment. The capsular thickness was calculated by Masson's trichrome stain. The expression of MMPs and TIMPs were determined by real-time PCR, Western blotting, and immunohistochemistry.

RESULTS

Compared to the control group, the capsular thickness of the MC group was significantly reduced at 4, 8, and 12 weeks after the operation (4 week: 229.3 ± 72.2 vs 76.1 ± 12.6 µm, p < 0.05; 8 week: 326.0 ± 53.8 vs 155.4 ± 61.7 µm, p < 0.0.5; 12 week: 151.2 ± 52.5 vs 60.0 ± 22.0 µm, p < 0.05). Compared to the control group, the MC group had significantly lower expressions of TIMP-1 and TIMP-2 (p < 0.05). However, compared to the control group, there was no statistically significant difference in the expressions of MMP-2 and MMP-9 in the experiment group (p > 0.05).

CONCLUSION

MC reduced the risk of developing capsular contracture around silicone implants, possibly by blocking the signaling pathway of TIMPs.

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Effect of Antiadhesion Barrier Solution and Fibrin on Capsular Formation After Silicone Implant Insertion in a White Rat Model

INTRODUCTION

One of the most serious complications of breast reconstruction and augmentation using silicone implants is capsular contracture. Several preventive treatments, including vitamin E, steroids, antibiotics, and cysteinyl leukotriene inhibitors, have been studied, and their clinical effects have been reported. However, the problem of capsular contracture has not yet been completely resolved. This study was performed to compare anti-adhesion barrier solution (AABS) and fibrin in their ability to prevent fibrotic capsule formation and simultaneously evaluated their effect when used in combination by capsular thickness analysis and quantitative analysis of matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), and type I collagen within the fibrous capsule.

MATERIALS AND METHODS

This study used female six-week-old Sprague-Dawley rats. Eighty rats were equally subdivided into the four following groups: AABS-treated, fibrin-treated, AABS and fibrin combined-treated, and untreated control groups. Each rat received two silicone chips under the panniculus carnosus muscle layer. The test materials were applied around the silicon chips. Four weeks later, the implantation sites including the skin and muscle were excised to avoid the risk of losing the fibrous capsule around the implants. The capsular thickness was analyzed by Masson's trichrome stain. Quantitative analysis of type I collagen, MMPs, and TIMPs was performed by real-time PCR, Western blot, and zymography.

RESULTS

The mean capsular thickness was 668.10 ± 275.12 μm in the control group, 356.97 ± 112.11 μm in the AABS-treated group, 525.96 ± 130.97 μm in the fibrin-treated group, and 389.24 ± 130.51 μm in the AABS and fibrin combined-treated group. Capsular thickness was significantly decreased in all experimental groups (p < 0.05). Capsular thickness was greater in the fibrin-treated group than in the AABS-treated group (p < 0.05). There was no statistically significant difference in capsular thickness between the AABS and fibrin combined-treated group and the AABS- or fibrin-treated group (p > 0.05). Compared to the control group, the experimental groups had significantly lower expressions of type I collagen and MMP-1 (p < 0.05), but there was no statistically significant difference in expressions of type I collagen and MMP-1 between the AABS-, fibrin-, and AABS and fibrin combined-treated groups (p > 0.05). The expressions of MMP-2 and TIMP-2 were not significantly different between the control and the experimental groups (p > 0.05).

CONCLUSION

AABS is more effective in reducing capsular thickness compared with fibrin treatment in a white rat model.

Capsular contracture by silicone breast implants: possible causes, biocompatibility, and prophylactic strategies

The most common implanted material in the human body consists of silicone. Breast augmentation and breast reconstruction using silicone-based implants are procedures frequently performed by reconstructive and aesthetic surgeons. A main complication of this procedure continues to be the development of capsular contracture (CC), displaying the result of a fibrotic foreign body reaction after the implantation of silicone. For many years, experimental and clinical trials have attempted to analyze the problem of its etiology, treatment, and prophylaxis. Different theories of CC formation are known; however, the reason why different individuals develop CC in days or a month, or only after years, is unknown. Therefore, we hypothesize that CC formation, might primarily be induced by immunological mechanisms along with other reasons. This article attempts to review CC formation, with special attention paid to immunological and inflammatory reasons, as well as actual prophylactic strategies. In this context, the word “biocompatibility” has been frequently used to describe the overall biological innocuousness of silicone in the respective studies, although without clear-cut definitions of this important feature. We have therefore developed a new five-point scale with distinct key points of biocompatibility. Hence, this article might provide the basis for ongoing discussion in this field to reduce single-publication definitions as well as increase the understanding of biocompatibility.

Identification of molecular phenotypic descriptors of breast capsular contracture formation using informatics analysis of the whole genome transcriptome

Breast capsular contracture formation following silicone implant augmentation/reconstruction is a common complication that remains poorly understood. The aim of this study was to identify potential biomarkers implicated in breast capsular contracture formation by using, for the first time, whole genome arrays. Biopsy samples were taken from 18 patients (23 breast capsules) with Baker Grade I-II (Control) and Baker Grade III-IV (Contracted). Whole genome microarrays were performed and six significantly dysregulated genes were selected for further validation with quantitative reverse transcriptase polymerase chain reaction and immunohistochemistry. Hematoxylin and eosin was also carried out to compare the histological characteristics of control and contracted samples. Microarray results showed that aggrecan, tissue inhibitor of metalloproteinase 4 (TIMP4), and tumor necrosis factor superfamily (ligand) member 11 were significantly down-regulated in contracted capsules; while matrix metallopeptidase 12, serum amyloid A 1, and interleukin 8 (IL8) were significantly up-regulated. The dysregulation of aggrecan, tumor necrosis factor superfamily (ligand) member 11, TIMP4, and IL8 was validated by quantitative reverse transcriptase polymerase chain reaction (p < 0.05). Immunohistochemistry confirmed an increased protein expression for IL8 and matrix metallopeptidase 12 in contracted capsules (p < 0.05), and decreased protein expression of TIMP4 (p < 0.05). This study has shown, for the first time, a number of unique biomarkers of significance in capsular contracture formation. IL8 and TIMP4 may serve as potential key diagnostic, therapeutic, and prognostic biomarkers in capsular contracture formation.

Bed isolation in experimental flap studies in rats: a dispensable procedure

Review of the literature regarding rodent experimental flap models reveals fundamental differences in applied surgical procedures. Although some authors isolate the flap from its wound bed, others do not. This study was planned to investigate to what extent the insertion of a silicone sheet affects physiological wound healing in experimental flap surgery. An extended epigastric adipocutaneous flap (6 × 10 cm) was raised in 16 male Lewis rats. In the control group (group C), flaps were immediately inset without any intervention. In the experimental group (group M), a silicone sheet barrier was placed between the flap and the wound bed. Mean flap survival area and flap perfusion were evaluated. Microvessel density was visualized by immunohistochemistry, and semiquantitative real-time polymerase chain reaction addressed differential gene expression. All animals were investigated on postoperative day 5. Flap survival area and flap perfusion were found to be similar. Immunohistochemistry, however, demonstrated a significantly increased number of CD31-positive small vessels in group C. The insertion of the silicone sheet barrier (group M) was accompanied by a significantly enhanced expression of proinflammatory genes and a suppression of proangiogenic genes. Our results show that although the silicone membrane has no influence on the surgical outcome in terms of flap survival and perfusion, it does lead to significant molecular alterations in pathways involved in physiological wound healing. These alterations are artificially induced by the foreign body material and conceal the true driving forces of the healing process. As the latter might include relevant therapeutic targets to ameliorate surgical results, we regard wound bed isolation as a dispensable procedure in the study of rodent flap models.

Focus on collagen: in vitro systems to study fibrogenesis and antifibrosis state of the art

Fibrosis represents a major global disease burden, yet a potent antifibrotic compound is still not in sight. Part of the explanation for this situation is the difficulties that both academic laboratories and research and development departments in the pharmaceutical industry have been facing in re-enacting the fibrotic process in vitro for screening procedures prior to animal testing. Effective in vitro characterization of antifibrotic compounds has been hampered by cell culture settings that are lacking crucial cofactors or are not holistic representations of the biosynthetic and depositional pathway leading to the formation of an insoluble pericellular collagen matrix. In order to appreciate the task which in vitro screening of antifibrotics is up against, we will first review the fibrotic process by categorizing it into events that are upstream of collagen biosynthesis and the actual biosynthetic and depositional cascade of collagen I. We point out oversights such as the omission of vitamin C, a vital cofactor for the production of stable procollagen molecules, as well as the little known in vitro tardy procollagen processing by collagen C-proteinase/BMP-1, another reason for minimal collagen deposition in cell culture. We review current methods of cell culture and collagen quantitation vis-à-vis the high content options and requirements for normalization against cell number for meaningful data retrieval. Only when collagen has formed a fibrillar matrix that becomes cross-linked, invested with ligands, and can be remodelled and resorbed, the complete picture of fibrogenesis can be reflected in vitro. We show here how this can be achieved. A well thought-out in vitro fibrogenesis system represents the missing link between brute force chemical library screens and rational animal experimentation, thus providing both cost-effectiveness and streamlined procedures towards the development of better antifibrotic drugs.