Ear Hypertrophic Scar Research Articles

Development of a bioactive silk fibroin bilayer scaffold for wound healing and scar inhibition

In cases of deep skin defects, spontaneous tissue regeneration and excessive collagen deposition lead to hyperplastic scars. Conventional remedial action after scar formation is limited with a high recurrence rate. In this study, we designed a new artificial skin bilayer using silk fibroin nanofibers films (SNF) as the epidermis, and silk fibroin (SF) / hyaluronic acid (HA) scaffold as the dermal layer. The regenerated SF film was used as a binder to form a functional SNF-SF-HA bilayer scaffold. The bilayer scaffold showed high porosity, hydrophilicity, and strength, and retained its shape over 30 days in PBS. In vitro, human umbilical vein endothelial cells were seeded into the bilayer scaffold and showed superior cell viability. In vivo analyses using the rabbit ear hypertrophic scar (HS) model indicated that the bilayer scaffold not only supported the reconstruction of new tissue, but also inhibited scar formation. The scaffold possibly achieved scar inhabitation by reducing wound contraction, weakening inflammatory reactions, and regulating collagen deposition and type conversion, which was partly observed through the downregulation of type I collagen, transforming growth factor-β, and α-smooth muscle actin. This study describes a new strategy to expand the application of silk-based biomaterials for the treatment of hyperplastic skin scars.

CO2 fractional laser-assisted transdermal delivery of silk nanofiber carriers in a rabbit ear hypertrophic scar model.

Hypertrophic scars are skin fibrotic diseases, characterized by fibroblast hyperproliferation and excessive accumulation of extracellular matrix. However, topical drug application for hypertrophic scars are unsatisfactory. The purpose of this study was to explore the permeability of silk nanofiber hydrogels (SNFs) loaded with rhodamine 6G (R6G) and rhodamine 110 (R110) mediated by CO2 fractional laser irradiation into hypertrophic scar tissues. In this work, R6G and R110 were chosen as hydrophilic and hydrophobic model molecules. They were loaded inside SNFs. In vivo rabbit ear hypertrophic scars were treated with CO2 fractional laser irradiation and then R6G/R110-laden SNFs were applied to the scars to evaluate their synergetic effect on drug penetration efficiency. Their permeability was quantified by fluorescence intensity and measured by confocal laser scanning microscopy on days 1, 3, 5 and 7. More specifically, the thermal coagulation zone (CZ) and its surrounding area (peri-CZ) caused by the thermal coagulation of the laser were discussed separately. Our data indicated that the SNFs promoted the penetration of R6G but not that of R110 in the peri-CZ on day 1 when combined with laser irradiation. Interestingly, both R6G and R110 were abundant in the CZ and remained stable on days 1, 3 and 5. Moreover, rapid re-epithelialization hindered the long-term permeability of both drugs. Combining CO2 fractional laser irradiation with SNF drug delivery could improve the efficiency of hydrophilic drug delivery within 24h before total re-epithelialization.

Pigment epithelium-derived factor attenuates angiogenesis and collagen deposition in hypertrophic scars.

Scar forming wounds are often characterized by higher levels of vascularity than non-scarring wounds and normal skin, and inhibition of angiogenesis has been shown to inhibit scar formation in some model systems. The rabbit ear hypertrophic scar (HS) model has been widely used to study the mechanisms that underlie the development of HS as well as the effectiveness of various treatments. Although the rabbit ear HS model is well characterized in terms of scar formation, the rate and level of angiogenesis has not been investigated in this model, and the cause-effect relationship between angiogenesis and rabbit HSs has not been examined. In the current study, full-thickness excisional wounds were created on the ventral side of New Zealand White rabbit ears to induce HS formation, and the dynamic pattern of angiogenesis and the expression of angiogenic regulatory factors were examined over time. Blood vessel density was found to peak at 2.7% on day 14 post-wounding, decreasing to 1.7% by day 28. mRNA levels of the proangiogenic factor VEGF-A peaked at day 14, while the expression of the antiangiogenic factors pigment epithelium-derived factor (PEDF) and thrombospondin 1 (TSP1) peaked at day 28 post-wounding. To examine whether inhibition of angiogenesis influences HS formation in this model, wounds were treated with exogenous soluble antiangiogenic agents including recombinant PEDF (rPEDF) and a functional PEDF peptide (PEDF-335). rPEDF and PEDF-335 were administered intradermally from day 4 post-wounding every 3 days until day 19. Intradermal injection of rPEDF or PEDF-335 both led to decreased angiogenesis and decreased collagen deposition at the wound site. The results support the utility of antiangiogenic therapies, including rPEDF/PEDF-335, as a potential new strategy for the prevention or treatment of HSs.

Liposome-encapsulated statins reduce hypertrophic scarring through topical application.

Hypertrophic scar is an important clinical problem with limited therapeutic options. Aside from their roles as 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, statins have also been demonstrated to decrease scarring by reducing connective tissue growth factor (CTGF) expression. However, poor penetrative ability limits their utility as topical treatments for hypertrophic scar. Here, we aim to develop novel statin formulations using liposomes to enhance dermal penetrative ability and to evaluate their efficacy against formation of hypertrophic scar utilizing our validated rabbit ear hypertrophic scar model. Liposomal simvastatin or pravastatin were compounded using a novel, flexible liposomal formulation and applied topically to rabbit ear hypertrophic scars daily from postoperation day (POD) 14 until POD 25. Scar color, including erythema and melanin, was measured using reflectance spectrophotometry on POD 28, and scar tissue was harvested for evaluation of scar elevation index as well as gene and protein expression. Human foreskin fibroblasts were also treated with statin formulations and CCN2 expression was determined by quantitative PCR. Both simvastatin and pravastatin were efficiently encapsulated in liposomes, forming nanometer-scale particles possessing highly negative charges. Topical treatment with liposomal simvastatin and pravastatin at 6.5% concentration significantly reduced scar elevation index and decreased type I/III collagen content and myofibroblast persistence in the wound. The erythema/vascularity of scars was reduced by liposomal statin treatment, with concomitant decrease of CD31 expression as measured histologically. Expression levels of transcripts encoding CTGF, collagen I, and collagen III collagen in scar tissue were also decreased by liposomal pravastatin treatment, as were myofibroblast persistence and the type I/III collagen ratio as assessed by immunofluorescence and picrosirus red staining, respectively. Treatment of human foreskin fibroblasts with simvastatin or with liposome-encapsulated pravastatin resulted in decreased expression of transcript encoding CTGF. Overall, our novel statin formulations encapsulated in liposomes were successfully delivered through topical application, significantly reducing hypertrophic scarring in a rabbit ear model.

Anti-inflammatory effects of ginsenoside Rg3 on the hypertrophic scar formation via the NF-κB/IκB signaling pathway in rabbit ears.

The anti-inflammatory effects of Rg3 on the hypertrophic scar (HS) formation remain relatively obscure. Hence, this study aimed to explore the anti-inflammatory effects of Rg3 on the HS formation using a rabbit ear model and we assessed the involvement of the NF-κ B/IκB signaling pathway in this process. We constructed the Newland white rabbit ear HS model and treated it with Rg3. Using histological analyses, we evaluated scar hypertrophy based on the hematoxylin and eosin staining. The degree of scarring was evaluated using the scar elevation index (SEI). In addition, collagen I and collagen III expression levels were assessed by immunohistochemistry, while fibroblast apoptosis was examined using TUNEL assays. While MPO, IL-1β, IL-6, and TNF-α concentrations were quantified using ELISA, NF-κB and p-IκB activities were respectively measured using electrophoretic mobility shift assays (EMSAs) and western blots. SEI measurements and histological characteristics revealed that Rg3 could suppress the HS formation. Moreover, Rg3 could inhibit the HS formation by decreasing collagen I and collagen III synthesis and inducing fibroblast apoptosis. Besides, Rg3 treatment markedly inhibited the inflammatory cytokine production and ameliorated neutrophil infiltration. Notably, this study revealed that Rg3 inhibited NF-κB activation and the activity of p-IκB. Furthermore, this study suggested that the ability of Rg3 to decrease the scar formation might result from its ability to inhibit inflammation by modulating the NF-κB/IκB signaling. Overall, the findings of this study could support the use of Rg3 to prevent the HS formation.

Topical Oxandrolone Reduces Ear Hypertrophic Scar Formation in Rabbits

Wound healing is a complex process. Despite extensive studies, hypertrophic and keloid scars still occur, and can be functionally and cosmetically problematic. In an attempt to prevent hypertrophic scar formation, the effects of topical oxandrolone, using hyaluronic acid as a biomaterial, were studied on ear wounds in rabbits. Deep second-degree burns were inflicted on each ear in 10 New Zealand rabbits. On the left ears, considered the control side, hyaluronic acid gel was applied, whereas on the right ears, the study side, a combination of oxandrolone and hyaluronic acid was applied. Dressings were changed every 2 days for 2 weeks. At week 10, biopsy specimens from the postburn scars were harvested for histologic and immunohistochemical examinations. Fourteen wounds were studied, half on the control side and half on the study side. Six hypertrophic scars were encountered on the control side and only one scar was encountered on the study side. In addition, an increased degree of inflammation, an increased amount of collagen and fibroblast cellularity, increased vascularization, and increased myofibroblast activity were observed on the control side. Topical administration of oxandrolone using hyaluronic acid as a biomaterial led to better healing and prevented hypertrophic scar formation.

Early intervention of fractional carbon dioxide laser on fresh traumatic scar

To determine the combined therapeutic effect of fractional carbon dioxide laser and silicone gel on fresh traumatic scars using a rabbit ear hypertrophic scar (EHS) model, as well as on human subjects. The rabbit EHS model was established by punching four circular wounds in each ear and respectively treated with carbon dioxide laser, silicone gel, and the combination of both, while one wound was left untreated. In addition, a validation group of five rabbits was also included wherein the wounds were treated with triamcinolone, IFN-α, and normal saline, with one untreated control. The gross hyperplasic changes and the histological features were analyzed, and the scar elevation index (SEI) was calculated for each treatment group. In the rabbit model, the untreated control wounds showed hypertrophic growth, whereas triamcinolone or IFN-α showed an inhibitory effect, similar to that on hypertrophic scars in humans, thereby proving the feasibility of our animal model. The SEI peaked 2 months after treatment and was respectively 2.28 ± 0.56, 1.85 ± 0.33, 1.91 ± 0.34, and 1.45 ± 0.22 in the untreated control, and the silicone, laser, and combined treatment groups, clearly indicating a significant therapeutic effect of the combined treatment modality (p < 0.01). The fibroblast and microvascular counts also showed similar trends in each group. Early application of fractional carbon dioxide laser can prevent hypertrophic scars; the combined use of laser and silicone gel was more effective with less recovery time, thereby worthy of clinical promotion.

Effects of low concentration 5-fluorouracil and triamcinolone acetonide on ear hypertrophic scar in a rat model

Objective To explore the effect of low concentration 5-fluorouracil combined with triamcinolone acetonide on rabbit ear hypertrophic scar model. Methods White rabbits post-traumatic scars were randomly divided into A , B , C and D groups, each group contained 18 cases. Group A was given triamcinolone acetonide and low concentration 5-fluorouracil, Group B was given low concentration 5 - fluorouracil, Group C was given triamcinolone acetonide and Group D was used as the control group. The dynamic changes of the scar were observed by naked eyes, hematoxylin-eosin (HE) staining and van Gieson (VG) staining through microscope. Vascular endothelial growth factor (VEGF) and CD34 were detected and compared within 4 groups by immunohistochemical staining. Results We successfully established a rabbit ear scar model. It was observed that the scars of Groups A, B and C had been shorter and flatter than Group D, close to the normal tissue. In HE and VG staining, the number of fibroblasts, inflammatory cells, blood vessels in groups A, B and C had been decreased, compared with Group D. Immunohistochemical results showed that the positive rates of VEGF and CD34 from the most to the lest were Groups D, B, C and A. The scar proliferation index from the most to the lest were Groups D, B, C and A. Conclusions The effect of low concentration 5-fluorouracil in treatment of the rabbit ear hypertrophic scar is better than that of triamcinolone acetonide. Low concentration 5-fluorouracil combined with triamcinolone acetonide has a synergistic effect in treatment of hypertrophic scar, which has better effect than that of low concentration 5-fluorouracil or triamcinolone acetonide alone. Key words: Hypertrophic scar; 5-fluorouracil; Triamcinolone acetonide; Vascular endothelial growth factor; CD34

Experimental Study of 5-fluorouracil Encapsulated Ethosomes Combined with CO2 Fractional Laser to Treat Hypertrophic Scar

ObjectiveThis study is designed to explore permeability of ethosomes encapsulated with 5-florouracil (5-FU) mediated by CO2 fractional laser on hypertrophic scar tissues. Moreover, therapeutic and duration effect of CO2 fractional laser combined with 5-FU encapsulated ethosomes in rabbit ear hypertrophic scar model will be evaluated.MethodsThe permeated amount of 5-FU and retention contents of 5-FU were both determined by high-performance liquid chromatography (HPLC). Fluorescence intensities of ethosomes encapsulated with 5-FU (5E) labeled with Rodanmin 6GO (Rho) were measured by confocal laser scanning microscopy (CLSM). The permeability promotion of 5E labeled with Rho in rabbit ear hypertrophic scar mediated by CO2 fractional laser was evaluated at 0 h, 6 h, 12 h, 24 h, 3 days and 7 days after the irradiation. The opening rates of the micro-channels were calculated according to CLSM. The therapeutic effect of 5EL was evaluated on rabbit ear hypertrophic scar in vivo. Relative thickness of rabbit ear hypertrophic scar before and after the treatment was measured by caliper method. Scar elevation index (SEI) of rabbit ear hypertrophic scar was measured using H&E staining.ResultsThe data showed that the penetration amount of 5EL group was higher than 5E group (4.15 ± 2.22 vs. 0.73 ± 0.33; p < 0.05) after 1-h treatment. Additionally, the penetration amount of 5EL was higher than that of the 5E group (107.61 ± 13.27 vs. 20.73 ± 3.77; p < 0.05) after 24-h treatment. The retention contents of the 5EL group also showed higher level than 5E group (24.42 ± 4.37 vs.12.25 ± 1.64; p < 0.05). The fluorescence intensity of Rho in hypertrophic scar tissues of the 5EL group was higher than that of the 5E group at different time points (1, 6, and 24 h). The opening rates of the micro-channels were decreased gradually within 24 h, and micro-channels were closed completely 3 days after the irradiation by CO2 fractional laser. The relative thickness and SEI of rabbit ear hypertrophic scar after 7 days of treatment in the 5EL group were significantly lower than the 5E group.ConclusionCO2 fractional laser combined with topical 5E can be effective in the treatment of hypertrophic scar in vivo and supply a novel therapy method for human hypertrophic scar.

Enhanced in vivo delivery of 5-fluorouracil by ethosomal gels in rabbit ear hypertrophic scar model.

Applying Ethosomal Gels (EGs) in transdermal drug delivery systems has evoked considerable interest because of their good water-solubility and biocompatibility. However, there has not been an explicit description of applying EGs as a vehicle for hypertrophic scars treatment. Here, a novel transdermal EGs loaded with 5-fluorouracil (5-FU EGs) was successfully prepared and characterized. The stability assay in vitro revealed that 5-FU EGs stored for a period of 30 days at 4 ± 1 °C had a better size stability than that at 25 ± 1 °C. Furthermore, using confocal laser scanning microscopy, EGs labeled with Rhodamine 6 G penetrated into the deep dermis of the hypertrophic scar within 24 h in the rabbit ear hypertrophic model suggested that the EGs were an optional delivery carrier through scar tissues. In addition, the value of the Scar Elevation Index (SEI) of 5-FU EGs group in the rabbit ear scar model was lower than that of 5-FU Phosphate Buffered Saline gel and Control groups. To conclude, these results suggest that EGs delivery system loaded 5-fluorouracil is a perfect candidate drug for hypertrophic scars therapy in future.

Endostar Injection Inhibits Rabbit Ear Hypertrophic Scar Formation

This study aims to investigate the effect of Endostar injection on the rabbit ear hypertrophic scar formation and expand the use of Endostar. The rabbit ear hypertrophic scar models were established 4 weeks postoperation and were treated with Endostar injection; the control group was injected with saline, once a week, 3 times totally. At the seventh week, the scar tissue was harvested and processed with hematoxylin and eosin (HE) staining and CD34 immunohistochemistry and cell apoptosis assay. In addition, the endothelial cell was cultured and seeded on Martrigel with different concentrations of Endostar to observe the vessel tube formation. The results showed that the volume of the hypertrophic scar with Endostar injection was greatly reduced compared with what was seen in the control group; meanwhile, HE staining showed that the cell number decreased and collagen density became looser. In addition, the CD34 staining indicated that microvessel formation in the study group also decreased and cell apoptosis increased. In vitro, the addition of Endostar could reduce vessel tube formation in a dose-dependent manner. In conclusion, the Endostar is effective for hypertrophic scar inhibition and could be a potential tool to treat scars.