Evaluation of functions and tissue compatibility of poly (D,L-lactic-co-glycolic acid) seeded with human dermal fibroblasts

Recent advances on biomedical applications of scaffolds in wound healing and dermal tissue engineering

The tissue engineering field has developed in response to the shortcomings related to the replacement of the tissues lost to disease or trauma: donor tissue rejection, chronic inflammation and donor tissue shortages. The driving force behind the tissue engineering is to avoid the mentioned issues by creating the biological substitutes capable of replacing the damaged tissue. This is done by combining the scaffolds, cells and signals in order to create the living, physiological, three-dimensional tissues. A wide variety of skin substitutes are used in the treatment of full-thickness injuries. Substitutes made from skin can harbour the latent viruses, and artificial skin grafts can heal with the extensive scarring, failing to regenerate structures such as glands, nerves and hair follicles. New and practical skin scaffold materials remain to be developed. The current article describes the important information about wound healing scaffolds. The scaffold types which were used in these fields were classified according to the accepted guideline of the biological medicine. Moreover, the present article gave the brief overview on the fundamentals of the tissue engineering, biodegradable polymer properties and their application in skin wound healing. Also, the present review discusses the type of the tissue engineered skin substitutes and modern wound dressings which promote the wound healing.

Biodegradation and Biocompatibility of Poly L-lactic Acid Implantable Mesh

Purpose

The purpose of this study was to evaluate the biodegradation and biocompatibility of poly L-lactic acid (PLLA) implantable mesh under in vitro and in vivo conditions.

Methods

PLLA mesh was examined for changes in weight and tensile strength. The histology of the tissue around the PLLA implant was also evaluated.

Results

The weight and tensile strength of the PLLA prosthesis was stable for 180 days. In addition, the surface of the PLLA mesh was not digested under in vitro or in vivo conditions as determined by scanning electron microscope. Histologically, there were no significant changes in the diameters of implanted PLLA mesh and subtype fibers over the course of 180 days. Likewise, there were no significant changes in the number of inflammatory and mast cells after 180 days, nor was there an increase in the percentage of collagen surrounding the PLLA mesh.

Conclusions

The results indicate that PLLA prostheses have good rigidity and biocompatibility in vivo and in vitro.

Electrospun 3D Fibrous Scaffolds for Chronic Wound Repair

Chronic wounds are difficult to heal spontaneously largely due to the corrupted extracellular matrix (ECM) where cell ingrowth is obstructed. Thus, the objective of this study was to develop a three-dimensional (3D) biodegradable scaffold mimicking native ECM to replace the missing or dysfunctional ECM, which may be an essential strategy for wound healing. The 3D fibrous scaffolds of poly(lactic acid-co-glycolic acid) (PLGA) were successfully fabricated by liquid-collecting electrospinning, with 5~20 µm interconnected pores. Surface modification with the native ECM component aims at providing biological recognition for cell growth. Human dermal fibroblasts (HDFs) successfully infiltrated into scaffolds at a depth of ~1400 µm after seven days of culturing, and showed significant progressive proliferation on scaffolds immobilized with collagen type I. In vivo models showed that chronic wounds treated with scaffolds had a faster healing rate. These results indicate that the 3D fibrous scaffolds may be a potential wound dressing for chronic wound repair.

Regeneration of full-thickness skin defects using umbilical cord blood stem cells loaded into modified porous scaffolds

In this study, we have demonstrated the ability of cord blood (CB)-derived unrestricted somatic stem cells (USSCs) and chitosan-modified poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) scaffold to promote skin regeneration. Afterward, the scaffolds were evaluated by structural, microscopic, physical, and mechanical assays and cell culture analyses. Results of structural, physical, and mechanical analyses also showed a good resilience and compliance with movement as a skin graft. Cellular experiments showed a better cell adhesion, growth, and proliferation inside the modified scaffolds compared with unmodified ones. In animal models with histological examinations, all groups, excluding the control group especially the groups treated with stem cells, exhibited the most pronounced effect on wound closure, with the statistically significant improvement in wound healing being seen at postoperative day 21. These data suggest that chitosan-modified PHBV scaffold loaded with CB-derived USSCs could significantly contribute to wound repair and be potentially used in the tissue engineering.

The healing effect of unrestricted somatic stem cells loaded in collagen-modified nanofibrous PHBV scaffold on full-thickness skin defects

Unrestricted somatic stem cells (USSCs) loaded in nanofibrous PHBV scaffold can be used for skin regeneration when grafted into full-thickness skin defects of rats. Nanofibrous PHBV scaffolds were designed using electrospinning method and then, modified with the immobilized collagen via the plasma method. Afterward, the scaffolds were evaluated using scanning electron microscopy, physical and mechanical assays. In this study; nanofibrous PHBV scaffolds loaded with and without USSCs were grafted into the skin defects. The wounds were subsequently investigated at 21 days after grafting. Results of mechanical and physical analyses showed good resilience and compliance to movement as a skin graft. In animal models; all study groups excluding the control group exhibited the most pronounced effect on wound closure, with the statistically significant improvement in wound healing being seen on post-operative Day 21. Histological and immunostaining examinations of healed wounds from all groups, especially the groups treated with stem cells, showed a thin epidermis plus recovered skin appendages in the dermal layer. Thus, the graft of collagen-coated nanofibrous PHBV scaffold loaded with USSC showed better results during the healing process of skin defects in rat model.

PLLA-collagen and PLLA-gelatin hybrid scaffolds with funnel-like porous structure for skin tissue engineering

In skin tissue engineering, a three-dimensional porous scaffold is necessary to support cell adhesion and proliferation and to guide cells moving into the repair area in the wound healing process. Structurally, the porous scaffold should have an open and interconnected porous architecture to facilitate homogenous cell distribution. Moreover, the scaffolds should be mechanically strong to protect deformation during the formation of new skin. In this study, the hybrid scaffolds were prepared by forming funnel-like collagen or gelatin sponge on a woven poly(l-lactic acid) (PLLA) mesh. The hybrid scaffolds combined the advantages of both collagen or gelatin (good cell-interactions) and PLLA mesh (high mechanical strength). The hybrid scaffolds were used to culture dermal fibroblasts for dermal tissue engineering. The funnel-like porous structure promoted homogeneous cell distribution and extracellular matrix production. The PLLA mesh reinforced the scaffold to avoid deformation. Subcutaneous implantation showed that the PLLA-collagen and PLLA-gelatin scaffolds promoted the regeneration of dermal tissue and epidermis and reduced contraction during the formation of new tissue. These results indicate that funnel-like hybrid scaffolds can be used for skin tissue regeneration.

Polymer carriers for drug delivery in tissue engineering

Growing demand for tissues and organs for transplantation and the inability to meet this need using by autogeneic (from the host) or allogeneic (from the same species) sources has led to the rapid development of tissue engineering as an alternative. Tissue engineering aims to replace or facilitate the regrowth of damaged or diseased tissue by applying a combination of biomaterials, cells and bioactive molecules. This review focuses on synthetic polymers that have been used for tissue growth scaffold fabrication and their applications in both cell and extracellular matrix support and controlling the release of cell growth and differentiation supporting drugs.