Evaluation and biological characterization of bilayer gelatin/chondroitin-6-sulphate/hyaluronic acid membrane

The Era of Biomaterials: Smart Implants?

Conditions, accidents, and aging processes have brought with them the need to develop implants with higher technology that allow not only the replacement of missing tissue but also the formation of tissue and the recovery of its function. The development of implants is due to advances in different areas such as molecular-biochemistry (which allows the understanding of the molecular/cellular processes during tissue repair), materials engineering, tissue regeneration (which has contributed advances in the knowledge of the properties of the materials used for their manufacture), and the so-called intelligent biomaterials (which promote tissue regeneration through inductive effects of cell signaling in response to stimuli from the microenvironment to generate adhesion, migration, and cell differentiation processes). The implants currently used are combinations of biopolymers with properties that allow the formation of scaffolds with the capacity to mimic the characteristics of the tissue to be repaired. This review describes the advances of intelligent biomaterials in implants applied in different dental and orthopedic problems; by means of these advances, it is expected to overcome limitations such as additional surgeries, rejections and infections in implants, implant duration, pain mitigation, and mainly, tissue regeneration.

Rete ridges: Morphogenesis, function, regulation, and reconstruction

Rete ridges (RRs) are distinct undulating microstructures at the junction of the dermis and epidermis in the skin of humans and certain animals. This structure is essential for enhancing the mechanical characteristics of skin and preserving homeostasis. With the development of tissue engineering and regenerative medicine, artificial skin grafts have made great progress in the field of skin healing. However, the restoration of RRs has been often disregarded or absent in artificial skin grafts, which potentially compromise the efficacy of tissue repair and regeneration. Therefore, this review collates recent research advances in understanding the structural features, function, morphogenesis, influencing factors, and reconstruction strategies pertaining to RRs. In addition, the preparation methods and limitations of tissue-engineered skin with RRs are discussed. STATEMENT OF SIGNIFICANCE: The technology for the development of tissue-engineered skin (TES) is widely studied and reported; however, the preparation of TES containing rete ridges (RRs) is often ignored, with no literature reviews on the structural reconstruction of RRs. This review focuses on the progress pertaining to RRs and focuses on the reconstruction methods for RRs. In addition, it discusses the limitations of existing reconstruction methods. Therefore, this review could be a valuable reference for transferring TES with RR structure from the laboratory to clinical applications in skin repair.

A hybrid scaffold of gelatin glycosaminoglycan matrix and fibrin as a carrier of human corneal fibroblast cells

A hybrid scaffold of gelatin-glycosaminoglycan matrix and fibrin (FGG) has been synthesized to improve the mechanical properties, degradation time and cell response of fibrin-like scaffolds. The FGG scaffold was fabricated by optimizing some properties of fibrin-only gel and gelatin-glycosaminoglycan (GG) scaffolds. Mechanical analysis of optimized fibrin-only gel showed the Young module and tensile strength of up to 72 and 121 KPa, respectively. Significantly, the nine-fold increase in the Young modulus and a seven-fold increase in tensile strength was observed when fibrin reinforced with GG scaffold. Additionally, the results demonstrated that the degradation time of fibrin was enhanced successfully up to 7 days which was much longer time compared to fibrin-only gel with 38 h of degradation time. More than 45% of FGG initial mass was preserved on day 7 in the presence of aprotinin. Human corneal fibroblast cells (HCFCs) were seeded on the FGG, fibrin-only gel and GG scaffolds for 5 days. The FGG scaffold showed excellent cell viability over 5 days, and the proliferation of HCFCs also increased significantly in comparison with fibrin-only gel and GG scaffolds. The FGG scaffold illustrates the great potential to use in which appropriate stability and mechanical properties are essential to tissue functionality.

Tailoring the gelatin/chitosan electrospun scaffold for application in skin tissue engineering: an in vitro study

The nanofibrous structure containing protein and polysaccharide has good potential in tissue engineering. The present work aims to study the role of chitosan in gelatin/chitosan nanofibrous scaffolds fabricated through electrospinning process under optimized condition. The performance of chitosan in gelatin/chitosan nanofibrous scaffolds was evaluated by mechanical tests, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and in vitro cell culture on scaffolds with different gelatin/chitosan blend ratios. To assay the influence of chitosan ratio on biocompatibility of the electrospun gelatin/chitosan scaffolds for skin tissue engineering, the culturing of the human dermal fibroblast cells (HDF) on nanofibers in terms of attachment, morphology and proliferation was evaluated. Morphological observation showed that HDF cells were attached and spread well on highly porous gelatin/chitosan nanofibrous scaffolds displaying spindle-like shapes and stretching. The fibrous morphologies of electrospun gelatin/chitosan scaffolds in culture medium were maintained during 7 days. Cell proliferation on electrospun gelatin/chitosan scaffolds was quantified by MTS assay, which revealed the positive effect of chitosan content (around 30%) as well as the nanofibrous structure on the biocompatibility (cell proliferation and attachment) of substrates.

Gelatin-chondroitin-6-sulfate-hyaluronic acid scaffold seeded with vascular endothelial growth factor 165 modified hair follicle stem cells as a three-dimensional skin substitute

INTRODUCTION

In the field of skin tissue engineering, gelatin-chondroitin-6-sulfate-hyaluronic acid (Gel-C6S-HA) stents are a suitable bio skin substitute. The purpose was to investigate the effect of genetically-modified hair follicle stem cells (HFSCs), combined with Gel-C6S-HA scaffolds, on the vascularization of tissue-engineered skin.

METHODS

Three-dimensional (3D) Gel-C6S-HA scaffolds were prepared by freeze-drying. Vascular endothelial growth factor (VEGF) 165 gene-modified rat HFSCs (rHFSCs) were inoculated into the scaffolds and cultured for 7 days. Two bilateral full-thickness skin defects were created on the back of 18 Sprague-Dawley rats. Rats were randomly divided into four groups: Group A, HFSCs transduced with VEGF165 seeded onto Gel-C6S-HA scaffolds; Group B, HFSCs transduced with empty vector seeded onto Gel-C6S-HA scaffolds; Group C, Gel-C6S-HA scaffold only; Group D, Vaseline gauze dressing. These compositions were implanted onto the defects and harvested at 7, 14 and 21 days. Wound healing was assessed and compared among groups according to hematoxylin-eosin staining, CD31 expression, alpha smooth muscle actin (α-SMA) and major histocompatibility complex class I (MHC-I) immunohistochemistry, and microvessel density (MVD) count, to evaluate the new blood vessels.

RESULTS

SEM revealed the Gel-C6S-HA scaffold was spongy and 3D, with an average pore diameter of 133.23 ± 43.36 μm. Cells seeded on scaffolds showed good adherent growth after 7 days culture. No significant difference in rHFSC morphology, adherence and proliferative capacity was found before and after transfection (P >0.05). After 14 and 21 days, the highest rate of wound healing was observed in Group A (P <0.05). Histological and immunological examination showed that after 21 days, MVD also reached a maximum in Group A (P <0.05). Therefore, the number of new blood vessels formed within the skin substitutes was greatest in Group A, followed by Group B. In Group C, only trace amounts of mature subcutaneous blood vessels were observed, and few subcutaneous tissue cells migrated into the scaffolds.

CONCLUSIONS

Tissue-engineered skin constructs, using 3D Gel-C6S-HA scaffolds seeded with VEGF165-modified rHFSCs, resulted in promotion of angiogenesis during wound healing and facilitation of vascularization in skin substitutes. This may be a novel approach for tissue-engineered skin substitutes.

Properties of newly-synthesized cationic semi-interpenetrating hydrogels containing either hyaluronan or chondroitin sulfate in a methacrylic matrix

Extracellular matrix components such as hyaluronan (HA) and chondroitin sulfate (CS) were combined with a synthetic matrix of p(HEMA-co-METAC) (poly(2-hydroxyethylmethacrylate-co-2-methacryloxyethyltrimethylammonium)) at 1% and 2% w/w concentration following a previously developed procedure. The resulting semi-interpenetrating hydrogels were able to extensively swell in water incrementing their dry weight up to 13 fold depending on the glycosamminoglycan content and nature. When swollen in physiological solution, materials water uptake significantly decreased, and the differences in swelling capability became negligible. In physiological conditions, HA was released from the materials up to 38%w/w while CS was found almost fully retained. Materials were not cytotoxic and a biological evaluation, performed using 3T3 fibroblasts and an original time lapse videomicroscopy station, revealed their appropriateness for cell adhesion and proliferation. Slight differences observed in the morphology of adherent cells suggested a better performance of CS containing hydrogels.

Fabrication and biocompatibility of novel bilayer scaffold for skin tissue engineering applications

In this study, a novel bilayer scaffold composed of electrospun polycaprolactone and poly(lacto-co-glycolic acid) (PCL/PLGA) membrane and glutaraldehyde (3.5% v/v) cross-linked chitosan/gelatin hydrogel was fabricated using two methods: electrospinning of the membrane onto the lyophilized hydrogel (BS-1) and membrane underlaying and casting method (BS-2). The morphology of the fabricated scaffolds was examined by scanning electron microscope (SEM). Mechanical strength, porosity, swelling capacity, and biodegradation rates of the scaffolds were also characterized. The in vitro biocompatibility of the materials was investigated by assessing cytotoxicity and cell proliferation on the material was measured using MTT assay. In addition, cell adhesion on the material was investigated by SEM. The BS-2 was grafted in Sprague-Dawley rats to determine its in vivo behavior and biocompatibility. The experimental results showed that the addition of the membrane layer to the hydrogel decreased swelling and degradation rates and provided ease of handling during implantation. Grafted BS-2 showed normal wound healing and no major inflammatory reaction was observed.

Potential applications of natural origin polymer-based systems in soft tissue regeneration

Despite the many advances in tissue engineering approaches, scientists still face significant challenges in trying to repair and replace soft tissues. Nature-inspired routes involving the creation of polymer-based systems of natural origins constitute an interesting alternative route to produce novel materials. The interest in these materials comes from the possibility of constructing multi-component systems that can be manipulated by composition allowing one to mimic the tissue environment required for the cellular regeneration of soft tissues. For this purpose, factors such as the design, choice, and compatibility of the polymers are considered to be key factors for successful strategies in soft tissue regeneration. More recently, polysaccharide-protein based systems have being increasingly studied and proposed for the treatment of soft tissues. The characteristics, properties, and compatibility of the resulting materials investigated in the last 10 years, as well as commercially available matrices or those currently under investigation are the subject matter of this review.

Regulation of adult human mesenchymal stem cells into osteogenic and chondrogenic lineages by different bioreactor systems

The aim of this study was to examine the feasibility of expanding and regulating mesenchymal stem cells (MSCs) from isolated adult human bone marrow mononuclear cells, seeded on gelatin-hyaluronic acid biomatrices, and then to quantitatively compare the gene expression in three different culture systems. Individual and interactive effects of model system parameters on construct structure, function, and molecular properties were evaluated. The results showed that these adult human MSCs even at old age not only expressed primitive mesenchymal cell markers but also maintained a high level of colony-forming efficiency and were capable of differentiating into osteoblasts, chondrocytes, and adipocytes upon appropriate inductions. After 21 days of culture, we found that the osteoblastic and chondrocytic lineage gene expression were earlier and higher expressed in spinner flask bioreactor culture group when compared with the static culture and rotating wall vessel reactor culture. The osteogenic lineage proteins type I collagen, alkaline phosphatase, and osteocalcin were strongly stained in histological sections of spinner flask bioreactor culture, whereas these were less detected in the other two groups, especially in rotating wall vessel reactor culture. As for the markers associated with the chondrogenic lineage differentiation proteins, type II collagen was apparently expressed in spinner flask culture group, while the expression of proteoglycans (aggreacan, decorin) in three culture conditions took the lead of each other. We conclude that the spinner flask bioreactor with appropriate induction medium reported in this study may be used to rapidly expand adult MSCs and is likely to possess better induction results toward osteoblastic and chondrocytic lineages.

Smart biomaterials for tissue engineering of cartilage

Biological regeneration using cartilage tissue engineering in which cells are grown on biomaterial scaffolds and then implanted into the cartilage defects could provide new treatment options for articular cartilage defects. This review aims to give an overview of the wide variety of biomaterials that are currently developed as scaffolds for cartilage tissue engineering. Emphasis will be placed on the current development of the materials that are able to direct cell differentiation and metabolism. These so-called "smart" biomaterials are produced by modifying the physical properties of the scaffolds using peptide sequences and most importantly by developing materials that can deliver proteins to enhance tissue regeneration. Besides providing drug delivery systems, the materials respond to environmental stimuli or release their cargo on cellular demand. However, critical issues remain, such as the transferability of basic science insights to clinical products and the applicability of certain data sets to human patients.