The Utility of Silk-elastin Hydrogel as a New Material for Wound Healing.

Cutaneous ulcers are treated with dressing materials and/or ointments to keep the wound in an appropriately moist environment. However, chronic cutaneous ulcers commonly have bacterial colonization that can cause local infection in such an environment. Therefore, the dressing materials and/or ointments should have antibacterial potency to treat chronic ulcers. Acute cutaneous wounds, by contrast, heal rapidly without local infection. The aim of treating acute cutaneous wounds is therefore not only wound closure but also preventing scar contracture after wound healing. However, no dressing materials or ointments available at present are simultaneously effective for preventing infection in chronic ulcers and reducing wound contracture in acute ulcers. Silk-elastin is a recombinant protein polymer with repeating units of silk-like and elastin-like blocks. Silk-elastin solution can self-assemble from a liquid to a hydrogel. We preliminarily reported that silk-elastin hydrogels have the potential to accelerate wound healing in decubitus ulcers of diabetic mice, which are animal models of severe, intractable cutaneous ulcers. In the present study, we examined the effects of silk-elastin hydrogels in chronic and acute ulcer models in comparison with conventional products (carboxymethyl cellulose gel). Silk-elastin hydrogels resulted in significantly higher epithelialization rates than conventional hydrogels in both the chronic and acute ulcer models and significantly larger areas of granulation tissue in acute ulcer models. These results show that silk-elastin hydrogel is a promising material for promoting the healing of cutaneous wounds, including decubitus ulcers, chronic ulcers, and acute ulcers.

An exploratory clinical study on the safety and efficacy of an autologous fibroblast-seeded artificial skin cultured with animal product-free medium in patients with diabetic foot ulcers.

Cultured dermal substitutes have been used for the treatment of chronic skin ulcers; however, the biological risks of animal-derived materials in the culture process such as foetal bovine serum (FBS) have been reported. In this study, we prepared an autologous fibroblast-seeded artificial dermis (AFD) using animal-product-free medium supplemented with 2% patient autologous serum and without any animal-derived materials such as trypsin in the culturing process. We applied the AFD in five patients with diabetic ulcers and investigated its safety and efficacy. As the primary endpoint, we defined 'wound bed improvement' according to the percentage of granulation area to the whole wound area on day 21, and 60% or higher was regarded as improved. The mean age of the patients was 60·6 years and the mean duration of the ulcer was 22·6 months. In the evaluation of the primary endpoint, the 'wound bed' was improved in all patients [proportion of improvement: 100%, 95% confidence interval (CI): 48% to 100%]. Three patients had complete wound healing within 12 weeks after application and two patients had >80% wound healing at 12 weeks. Side effects were not serious. Our AFD may be a safe and effective treatment of diabetic ulcers.

Evaluation of a novel collagen-gelatin scaffold for achieving the sustained release of basic fibroblast growth factor in a diabetic mouse model.

The objective of this study was to evaluate the ability of a scaffold, collagen-gelatin sponge (CGS), to release basic fibroblast growth factor (bFGF) in a sustained manner, using a pressure-induced decubitus ulcer model involving genetically diabetic mice. We confirmed that CGSs impregnated with a bFGF concentration of up to 50 µg/cm(2) were able to sustain the release of bFGF throughout their biodegradation. We prepared decubitus ulcers on diabetic mice. After debriding the ulcers, we implanted CGSs (diameter 8 mm) impregnated with normal saline solution (NSS) or bFGF solution (7, 14, 28 or 50 µg/cm(2)). At 1 and 2 weeks after implantation, the mice were sacrificed and tissue specimens were obtained. The wound area, neoepithelium length and numbers and total area of newly formed capillaries were evaluated. The CGSs impregnated with NSS became infected and degraded, whereas the CGSs impregnated with 7 or 14 µg/cm(2) bFGF displayed accelerated dermis-like tissue formation and the CGSs impregnated with 14 µg/cm(2) bFGF produced significant improvements in the remaining wound area, neoepithelium length and numbers and total area of newly formed capillaries compared with the NSS group. No significant difference was observed between the NSS and 50 µg/cm(2) bFGF groups. CGSs impregnated with 7-14 µg/cm(2) bFGF accelerated wound healing, and an excess amount of bFGF did not increase the wound-healing efficacy of the CGSs. Our CGS is a scaffold that can release positively charged growth factors such as bFGF in a sustained manner and shows promise as a scaffold for skin regeneration.

Novel collagen/gelatin scaffold with sustained release of basic fibroblast growth factor: clinical trial for chronic skin ulcers.

Chronic skin ulcers such as diabetic ulcers and venous leg ulcers are increasing and are a costly problem in healthcare. We have developed a novel artificial dermis, collagen/gelatin sponge (CGS), which is capable of sustained release of basic fibroblast growth factor (bFGF) for more than 10 days. The objective of this study was to investigate the safety and efficacy of CGS impregnated with bFGF in the treatment of chronic skin ulcers. Patients with chronic skin ulcers that had not healed in at least 4 weeks were treated with CGS impregnated with bFGF at 7 or 14 µg/cm(2) after debridement, and the wound bed improvement was assessed 14 days after application. Wound bed improvement was defined as a granulated and epithelialized area on day 14 with a proportion to the baseline wound area after debridement of 50% or higher. The wound area, the wound area on day 14, and the granulation area on day 14 were independently measured by blinded reviewers in a central review using digital images of wounds taken with a calibrator. Patients were followed up until 28 days after application to observe the adverse reactions related to the application of CGS. From May 2010 to June 2011, 17 patients were enrolled and, in 16 patients, the wound bed improved. Among the randomized patients in step 2, no significant difference was seen between the low-dose group and the high-dose group. No serious adverse reactions were observed. Adverse reactions with a clear causal relationship to the study treatment were mild and patients quickly recovered from them. This study is the first-in-man clinical trial of CGS and showed the safety and efficacy of CGS impregnated with bFGF in the treatment of chronic skin ulcers. This combination therapy could be a promising therapy for chronic skin ulcers.

Efficacy of novel collagen/gelatin scaffold with sustained release of basic fibroblast growth factor for dermis-like tissue regeneration.

We have developed collagen/gelatin sponges (CGS) with a gelatin concentration of 10 wt% to sustain the release of basic fibroblast growth factor (bFGF). The objective of this study is to elucidate the efficacy of CGS impregnated with different concentrations of bFGF, using mouse skin defects. CGSs impregnated with normal saline solution (NSS) or bFGF solution (1, 7, 14, or 50 µg/cm) were implanted into full-thickness skin defects on the backs of mice. The wound area, neoepithelium length, and total area of newly formed capillaries in CGS were evaluated. The group of CGS with 7-µg/cm bFGF was significantly superior to the NSS group in all evaluated items. CGS impregnated with the appropriate dosage of bFGF accelerates dermis-like tissue formation 2 or 3 times earlier than existing artificial dermis. The combination of CGS and bFGF could solve the problem of the existing artificial dermis and be very promising for the treatment of skin defects.

Collagen-gelatin scaffold impregnated with bFGF accelerates palatal wound healing of palatal mucosa in dogs.

BACKGROUND: We have developed a collagen-gelatin sponge (CGS) as a scaffold capable of the sustained release of bFGF to improve the healing process of the existing collagen scaffold. The aim of this study was to evaluate the efficacy of CGS impregnated with basic fibroblast growth factor (bFGF) in palatal wound healing in beagles. MATERIALS AND METHODS: Four standardized 6 mm diameter full-thickness wounds were made in the palate of each dog and covered with CGS impregnated with normal saline or bFGF at concentrations of 1 µg/cm2, 7 µg/cm2 and 14 µg/cm2. One and 2 wk after surgery, the wound area, neoepithelium length, thickness, area of regenerated submucosal tissue, and the number and total area of neoformed capillaries were evaluated. RESULTS: Two weeks after implantation, wounds treated with bFGF 7 µg/cm2 and 14 µg/cm2 were completely epithelized, while the length of the neoformed epithelium was significantly longer in the 7 µg/cm2 group. Groups impregnated with bFGF 7 µg/cm2 and 14 µg/cm2 showed promoted regeneration of submucosal tissue 2 wk later. The number and area of neoformed capillaries were significantly higher in the bFGF 7 µg/cm2 group than in other groups. We conclude that palatal wound healing in the bFGF 7 µg/cm2 group was promoted with good neovascularization and showed less contracture than other groups. CONCLUSIONS: Our new collagen-gelatin scaffold, CGS, impregnated with bFGF, could be a promising treatment to accelerate the regeneration of palatal mucosa.

The utilization of animal product-free media and autologous serum in an autologous dermal substitute culture.

BACKGROUND: Cultured dermal substitutes are used for the treatment of skin ulcers. However, the biological risks of fetal bovine serum (FBS) in the culture process have been reported. The use of the patient's autologous serum (AS) is another possibility, but the amount available is limited. In this study, we examined whether animal product-free media (HFDM-1) supplemented with 2% AS could support the growth of autologous fibroblasts in primary culture and their dissemination to dermal substitutes. MATERIALS AND METHODS: We cultured autologous fibroblasts using HFDM-1 with 2% AS, Dulbecco's modified eagle medium (DMEM) with 10% FBS, and DMEM with 10% human serum (HS). Then, we disseminated and cultured the cells for 10 d. The fibroblast proliferation and concentrations of vascular endothelial growth factor (VEGF) and transforming growth factor ß1 (TGF-ß1) in each medium, as well as the deposition of human type I collagen into dermal substitutes were examined. RESULTS: The number of fibroblasts cultured in HFDM-1 with AS was highest. After seeding, the number of fibroblasts cultured in DMEM with HS was higher than those in DMEM with FBS and HFDM-1 with AS, but no significant difference was found between these two media. The VEGF concentration in DMEM with HS was also larger, but no significant difference was found between two other media. No significant difference was observed in TGF-ß1 concentration or the deposition of collagen. CONCLUSIONS: This study shows that HFDM-1 with 2% AS can be used to produce cultured dermal substitutes instead of DMEM with 10% FBS.