Regeneration of elastic fibers by three-dimensional culture on a collagen scaffold and the addition of latent TGF-ß binding protein 4 to improve elastic matrix deposition.

The objective of this study was to investigate the effects of latent TGF-ß binding protein 4 (LTBP-4) on elastic fiber regeneration in three-dimensional cultures of human dermal fibroblasts (HDFs). Appropriate collagen scaffold for elastic fiber regeneration was also examined. Collagen sponges cross-linked at 120 °C and composed of small pores (25 µm on average) was favorable for elastic fiber regeneration by HDFs. Addition of LTBP-4, followed by culture for 21 days, accelerated elastic fiber accumulation within the scaffolds. Conditioned scaffolds containing either HDFs or LTBP-4-built mature elastic fibers were implanted between the dermis and the cutaneous muscle of mice. The combined use of HDFs and LTBP-4 resulted in thicker tissues containing elastic fibers. These results indicate that weakly cross-linked collagen sponges can be used as scaffolds for regenerating elastic fibers both in vitro and in vivo, and that the addition of LTBP-4 accelerates the deposition of both elastin and fibrillin-1, and increases cell proliferation. These techniques may be useful for generating cutaneous or cardiovascular tissue equivalents; furthermore, they may serve as a useful method for the three-dimensional analyses of drugs used to treat skin diseases or to examine the microstructure of elastin networks.

Preparation of collagen/gelatin sponge scaffold for sustained release of bFGF.

Artificial dermis (AD) has been used to regenerate dermis-like tissues in the treatment of full-thickness skin defects, but it takes 2 or 3 weeks to complete dermal regeneration. Our previous study demonstrated that injection of basic fibroblast growth factor (bFGF)-impregnated gelatin microspheres (MS) into the AD accelerates the regeneration of dermis-like tissue. However, injection of gelatin MS before clinical use is complicated and time consuming. This study investigated a new scaffold, in which collagen and gelatin are integrated, and which is capable of sustained bFGF release. We produced collagen/gelatin sponges with a gelatin concentration of 0wt%, 10wt%, 30wt%, and 50wt%. The mean pore size in each sponge decreased with the gelatin concentration. In an in vitro study, proliferation of fibroblasts in each sponge was not significantly different over 7 days of culture. As for in vivo sustained release of bFGF, a radioisotope study demonstrated that retention of bFGF in gelatin 10wt% and 30wt% sponges was significantly larger than that in gelatin 0wt% sponge. The collagen/gelatin sponges were grafted on full-thickness skin defects created on a rabbit ear, and we evaluated regeneration of dermis-like tissue by measuring the amount of hemoglobin and size of dermis-like tissue on histological sections. Seven days after implantation, the amount of hemoglobin in dermis-like tissue in gelatin 10wt% sponge was significantly larger than those in control and gelatin 50wt% sponge. Twenty-eight days after implantation, the area of dermis-like tissue in gelatin 10wt% sponge was significantly larger than those in the other specimens. We conclude that the collagen sponge integrated with 10wt% gelatin has the most potential for sustained release of bFGF and that the combination of collagen/gelatin 10wt% sponge and bFGF is a promising therapeutic modality for the treatment of full-thickness skin defects.

In vivo culturing of a bilayered dermal substitute with adipo-stromal cells.

BACKGROUND: Skin grafting is an important procedure to cover skin defects. Recently, cultured epidermal sheets and bilayered cultured skin have been used clinically, but they lack subcutaneous tissue. The objective of this study was to produce a bilayered dermal substitute with adipose tissue simultaneously in vivo. MATERIALS AND METHODS: We disseminated adipo-stromal cells on one side of a collagen sponge at a density of 1,0 x 10(5)cells/cm(2) and incubated overnight. Then, we turned over the sponge and disseminated dermal fibroblasts and keratinocytes at a density of 1,0 x 10(6)cells/cm(2) on the other side of the sponge. Finally, we cultured this for 1 wk and implanted it on the backs of severe combined immunodeficiency mice with or without basic FGF. RESULTS: Six weeks after implantation, specimens were harvested. Macroscopically, the formed tissue in the bFGF-administered group was thick, and the epidermal component, the dermal component, and adipose tissue were formed in the cross section. The thickness of newly formed tissue in bFGF-administered group was significantly greater than that in the group without bFGF administration. The area of the newly formed capillaries in the bFGF-administered group was significantly larger than that in the group without bFGF administration. CONCLUSIONS: We could produce a thick composite tissue in vivo, combining three kinds of human cells, collagen scaffold, and bFGF. This composite graft was thicker than the bilayered dermal substitute and could be a substitute for a skin flap.

Incorporation of basic fibroblast growth factor into preconfluent cultured skin substitute to accelerate neovascularisation and skin reconstruction after transplantation.

Cultured skin substitutes (CSS) with both epidermal and dermal components seem to be ideal, but they have not been widely used clinically, partly because it takes several weeks to produce them. Decreasing the number of seeding cells may reduce the period required for production, but it still takes a long time before the cells become confluent and neovascularisation is completed in CSS after grafting. As we have already succeeded in reducing the number of seeded keratinocytes in this study, we first attempted to reduce the number of seeded fibroblasts. Consequently, preconfluent CSS with 10 x 10(3) cells/cm2 of fibroblasts combined with 100 x 10(3) cells/cm2 of keratinocytes could be successfully grafted on to full-thickness wounds. bFGF-impregnated gelatin microspheres were then added to the preconfluent CSS before grafting. Incorporation of bFGF significantly accelerated neovascularisation and increased epidermal thickness, cellular components, and thickness of the dermis. The incorporation of bFGF makes CSS a potential therapeutic approach for management of skin wounds.

Handling characteristics of poly(L-lactide-co-epsilon-caprolactone) monofilament suture.

A monofilament suture made of poly(L-lactide-co-epsilon-caprolactone) was examined by several mechanical tests to evaluate handling characteristics for tight tying. Six types of other monofilament sutures were also examined for comparisons. Two of these were nonabsorbable, while the others were absorbable sutures. Sutures consisting of glicolide were strongest among all the sutures examined. On the other hand, PROLENE and P(LA/CL) sutures showed high knot-pull strength despite low straight pull strength. Untying performance was evaluated by viscoelasticity, bending plasticity and tying test. A good correlation between tan delta and bending plasticity index was observed and the poly(L-lactide-co-epsilon-caprolactone) suture exhibited high tan delta, high bending plasticity and good resistance against untying.

Viability and function of autologous and allogeneic fibroblasts seeded in dermal substitutes after implantation.

BACKGROUND: Fibroblast-seeded collagen sponges have been used for the treatment of skin defects and skin ulcers. However, the viability of the fibroblasts after implantation is still unknown. The objective of this study was to investigate the viability and distribution of autologous and allogeneic fibroblasts after implantation and to clarify which type is more effective for wound healing. MATERIALS AND METHODS: Skin samples of Hartley guinea pigs were retrieved and autologous fibroblasts were isolated and cultured. Fibroblasts isolated from the skin of a Strain2 guinea pig were used as allogeneic fibroblasts. Three full-thickness wounds were created on the backs of guinea pigs and an acellular collagen sponge, a collagen sponge seeded with autologous fibroblasts, and a collagen sponge seeded with allogeneic fibroblasts were transplanted. Before implantation, fibroblasts were labeled with PKH26. The guinea pigs were sacrificed 1, 2, and 3 weeks after implantation. The epithelization and contraction of the wounds were assessed, and the viability and distribution of the seeded fibroblasts were observed in cross sections. RESULTS: Three weeks after implantation, the PKH26-labeled autologous and allogeneic fibroblasts remained viable. In the wounds covered with the autologous fibroblast-seeded collagen sponge, the epithelization was fastest, and the percent wound contraction was smallest. In contrast, in the wounds covered with allogeneic fibroblasts, the epithelization was slowest and the percent contraction was largest. CONCLUSION: The allogeneic fibroblasts seeded in the collagen sponge survived and remained viable on the grafted area, but did not accelerate wound healing.