Evaluation of nanofiber-based polyglycolic acid scaffolds for improved chondrocyte retention and in vivo bioengineered cartilage regeneration

The significance of nanofiber polyglycolic acid for promoting tissue repair in a rat subcutaneous implantation model

Among various biomaterials, we focused on nanofiber-based polyglycolic acid (PGA) fabric and examined the dynamics of cells that migrate within the non-woven fabric after implantation. The efficacy of nano-PGA as a tissue reinforcement in the process of subcutaneous tissue repair was immunohistochemically investigated. Two types of clinically available PGA non-woven sheet (nano-PGA: fiber diameter = 2.0 μm, conventional PGA: fiber diameter = 14.2 μm) were used and subcutaneously implanted in rats. Samples were collected 3 days, and 1, 2, 3, and 4 weeks after the implantation to perform histological and immunohistochemical (CD68, CD163, α-SMA, Type I collagen, CD34, MCP-1, IL-6, TNF-α, TGF-β, VEGF, IgG) examinations to assess the expression of molecules related to inflammation or tissue repair. Immunohistochemical analysis in nano-PGA revealed that the intensity and positive cells (CD68, MCP-1, IL-6, TNF-α) significantly increased which indicated an early inflammatory response. This was followed by phagocytosis of nano-PGA with foreign body giant cells and CD68+ macrophages. Finally, the number of proliferating cells (CD163, α-SMA, TGF-β) and angiogenesis (CD34, VEGF) for tissue repair promoted the formation of collagen fibers (type I collagen). Unlike nano-PGA, implantation of conventional PGA sheet resulted in a prolonged inflammatory response and was characterized by the presence of discontinuous collagen fibers with many foreign body giant cells, which did not lead to tissue repair. Nano-PGA sheets demonstrated a better tissue compatibility compared with conventional PGA by inducing early polarization to M2 phenotype macrophages, which triggered subsequent angiogenesis and tissue repair in the subcutaneous tissue.

Surface modification of the cubic micro-cartilage by collagenase treatment and its efficacy in cartilage regeneration for ear tissue engineering

BACKGROUND

In order to enhance cartilage regeneration, surface modification of the cubic micro-cartilage with the collagenase treatment was tested and its efficacy to tissue engineer ear cartilage was investigated.

MATERIALS AND METHODS

Harvested cubic micro-cartilages were treated with collagenase with different digestion time (0, 15, 60, and 120 min). Histological, ultrastructural (SEM and TEM), and Western blot analyses were carried out. Subsequently, A total of 45 dogs were used to tissue engineer ear cartilage. Using collagenase-treated micro-cartilage, the ear cartilage regeneration with the prepared dilution (8, 12.5, 25, 50, 100%) of micro-cartilage block seeding was performed to determine the minimum amount of cartilage tissue required for ear tissue-engineering (n = 6 at each point in each group). At 10 weeks after surgery, samples were resected and subjected to histochemical and immune-histological evaluation for cartilage regeneration.

RESULTS

In vitro study on micro-cartilage morphology and western blot analysis showed that collagenase digestion was optimal at 60 min for cartilage regeneration. In vivo evaluation on the reduced proportions of micro-cartilage block seeding onto implant scaffolds under 60-min collagenase digestion determined the minimum amount of cartilage tissue necessary to initiate a one-step ear cartilage regeneration in a canine autologous model, which was 12.5-25% of the original ear size.

CONCLUSION

Tissue-engineering ear cartilage from limited volume of donor cartilage can possibly be achieved by the collagenase treatment on micro-cartilage to expand cartilage regeneration capacity, application of cytokine sustained-release system, and seeding on a suitable ear scaffold material.

Ethanol treatment of nanoPGA/PCL composite scaffolds enhances human chondrocyte development in the cellular microenvironment of tissue-engineered auricle constructs

A major obstacle for tissue engineering ear-shaped cartilage is poorly developed tissue comprising cell-scaffold constructs. To address this issue, bioresorbable scaffolds of poly-ε-caprolactone (PCL) and polyglycolic acid nanofibers (nanoPGA) were evaluated using an ethanol treatment step before auricular chondrocyte scaffold seeding, an approach considered to enhance scaffold hydrophilicity and cartilage regeneration. Auricular chondrocytes were isolated from canine ears and human surgical samples discarded during otoplasty, including microtia reconstruction. Canine chondrocytes were seeded onto PCL and nanoPGA sheets either with or without ethanol treatment to examine cellular adhesion in vitro. Human chondrocytes were seeded onto three-dimensional bioresorbable composite scaffolds (PCL with surface coverage of nanoPGA) either with or without ethanol treatment and then implanted into athymic mice for 10 and 20 weeks. On construct retrieval, scanning electron microscopy showed canine auricular chondrocytes seeded onto ethanol-treated scaffolds in vitro developed extended cell processes contacting scaffold surfaces, a result suggesting cell-scaffold adhesion and a favorable microenvironment compared to the same cells with limited processes over untreated scaffolds. Adhesion of canine chondrocytes was statistically significantly greater (p ≤ 0.05) for ethanol-treated compared to untreated scaffold sheets. After implantation for 10 weeks, constructs of human auricular chondrocytes seeded onto ethanol-treated scaffolds were covered with glossy cartilage while constructs consisting of the same cells seeded onto untreated scaffolds revealed sparse connective tissue and cartilage regeneration. Following 10 weeks of implantation, RT-qPCR analyses of chondrocytes grown on ethanol-treated scaffolds showed greater expression levels for several cartilage-related genes compared to cells developed on untreated scaffolds with statistically significantly increased SRY-box transcription factor 5 (SOX5) and decreased interleukin-1α (inflammation-related) expression levels (p ≤ 0.05). Ethanol treatment of scaffolds led to increased cartilage production for 20- compared to 10-week constructs. While hydrophilicity of scaffolds was not assessed directly in the present findings, a possible factor supporting the summary data is that hydrophilicity may be enhanced for ethanol-treated nanoPGA/PCL scaffolds, an effect leading to improvement of chondrocyte adhesion, the cellular microenvironment and cartilage regeneration in tissue-engineered auricle constructs.

A biodegradable soy protein isolate-based waterborne polyurethane composite sponge for implantable tissue engineering

A biodegradable soy protein isolate-based waterborne polyurethane composite sponge (SWPU) was prepared from soy protein isolate (SPI) and polyurethane prepolymer (PUP) by a process involving chemical reaction and freeze-drying. Effects of SPI content (0, 10%, 30%, 50%, 70%) on the micro-structure and physical properties of the composite sponges were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The results showed that the reaction between -NCO of PUP and -NH₂ of SPI formed porous SPI-based WPU composite sponges. The results of the water absorption ratio measurement, solvent resistance measurement and compressive testing showed that water absorption, hydrophilicity, and tensile strength in the dry state of the composite sponges increased with the increase of SPI content. Especially, the tensile strength ranged from 0.3 MPa to 5.5 MPa with the increase in SPI content. The cytocompatibility and biodegradability of the composite sponges were evaluated by in vitro cell culture and in vivo implantation experiments. The results indicated that a certain SPI content in the sponges could promote the adhesion, growth, and proliferation of cells, enhance the cytocompatibility and accelerate the degradation speed of composite sponges. During the in vivo implanting period within 9 months, SWPU-50 sponge containing 50% of SPI brought out the lowest activated inflammatory reaction, most newly-regenerated blood capillaries, and best histocompatibility. All results indicated that SWPU-50 composite sponges had greatest potential for tissue engineering.

Nonwoven membranes for tissue engineering: an overview of cartilage, epithelium, and bone regeneration

Scaffold-type biomaterials are crucial for application in tissue engineering. Among them, the use of a nonwoven scaffold has grown in recent years and has been widely investigated for the regeneration of different types of tissues. Several polymers, whether they are synthetic, biopolymers or both, have been used to produce a scaffold that can mimic the natural tissue to which it will be applied to. The scaffolds used in tissue engineering must be biocompatible and allow cell adhesion and proliferation to be applied in tissue engineering. In addition, the scaffolds should maintain the mechanical properties and architecture of the desired tissue. Nonwoven fabrics have produced good results and are more extensively applied for the regeneration of cartilage, epithelial and bone tissues. Recent advances in tissue engineering have shown promising results, however, no ideal material or standardization parameters and characteristics of the materials were obtained. The present review provides an overview of the application of nonwoven scaffolds, including the main results obtained regarding the properties of the biomaterials and their applications in vitro and in vivo, focusing on the cartilaginous, the epithelium, and bone tissue regeneration.

Nanoscale and Macroscale Scaffolds with Controlled-Release Polymeric Systems for Dental Craniomaxillofacial Tissue Engineering

Tremendous progress in stem cell biology has resulted in a major current focus on effective modalities to promote directed cellular behavior for clinical therapy. The fundamental principles of tissue engineering are aimed at providing soluble and insoluble biological cues to promote these directed biological responses. Better understanding of extracellular matrix functions is ensuring optimal adhesive substrates to promote cell mobility and a suitable physical niche to direct stem cell responses. Further, appreciation of the roles of matrix constituents as morphogen cues, termed matrikines or matricryptins, are also now being directly exploited in biomaterial design. These insoluble topological cues can be presented at both micro- and nanoscales with specific fabrication techniques. Progress in development and molecular biology has described key roles for a range of biological molecules, such as proteins, lipids, and nucleic acids, to serve as morphogens promoting directed behavior in stem cells. Controlled-release systems involving encapsulation of bioactive agents within polymeric carriers are enabling utilization of soluble cues. Using our efforts at dental craniofacial tissue engineering, this narrative review focuses on outlining specific biomaterial fabrication techniques, such as electrospinning, gas foaming, and 3D printing used in combination with polymeric nano- or microspheres. These avenues are providing unprecedented therapeutic opportunities for precision bioengineering for regenerative applications.

Long-Term Comparison between Human Normal Conchal and Microtia Chondrocytes Regenerated by Tissue Engineering on Nanofiber Polyglycolic Acid Scaffolds

BACKGROUND

Previous regeneration studies of auricle-shaped cartilage by tissue engineering leave unresolved whether the chondrocyte phenotype from human auricular chondrocytes seeded onto polymeric scaffolds is retained over the long term and whether microtia remnants may be a viable cell source for auricular reconstruction.

METHODS

Chondrocytes were isolated from human ears, either normal conchal ear or microtia cartilage remnants, expanded in vitro, and seeded onto nanoscale-diameter polyglycolic acid sheets. These tissue-engineered constructs were implanted into athymic mice for up to 40 weeks. At harvest times of 5, 10, 20, and 40 weeks, samples were documented by gross morphology, histology, and reverse transcription-quantitative polymerase chain reaction analysis.

RESULTS

Neocartilages generated from the two types of surgical tissues were similar in appearance of their extracellular matrices and positive staining for elastin and proteoglycans. In the 5- to 40-week time interval, there was an increasing trend in gene expression for type II collagen, elastin, and sex determining region Y box 5, important to normal cartilage phenotype, and a decreasing trend in gene expression for type III collagen, a fibroblast and dedifferentiation marker. Over 40 weeks of implantation, the original nanoscale-diameter polyglycolic acid scaffold dimensions (1 cm × 1 cm × 80 µm) were generally maintained in tissue-engineered cartilage length and width, and thickness was statistically significantly increased.

CONCLUSIONS

Auricular cartilage can be regenerated over the long term (40 weeks) from surgical remnants by tissue-engineering techniques incorporating nanoscale-diameter polyglycolic acid scaffolds. Based on the present assays, microtia neocartilage very closely resembles tissue-engineered cartilage regenerated from chondrocytes isolated from normal conchal cartilage.

The prospective opportunities offered by magnetic scaffolds for bone tissue engineering: a review

Magnetic scaffolds are becoming increasingly attractive in tissue engineering, due to their ability to enhance bone tissue formation by attracting soluble factors, such as growth factors, hormones and polypeptides, directly to the implantation site, as well as their potential to improve the fixation and stability of the implant. Moreover, there is increasing evidence that the synergistic effects of magnetic scaffolds and magnetic fields can promote bone repair and regeneration. In this manuscript we review the recent innovations in bone tissue engineering that exploit magnetic biomaterials combined with static magnetic fields to enhance bone cell adhesion and proliferation, and thus bone tissue growth.

Soy protein-modified waterborne polyurethane biocomposites with improved functionality

Soy protein isolate-modified waterborne polyurethane biocomposites exhibited improved cytocompatibility and biodegradability.

Nasal ectomesenchymal stem cells: multi-lineage differentiation and transformation effects on fibrin gels

Ectomesenchymal stem cells (EMSCs) are novel adult stem cells derived from the cranial neural crest. However, their stemness and multi-lineage differentiation potential on three-dimensional fibrin gels has not yet been explored. The objective of this study was to investigate induced differentiation of EMSCs on fibrin gels and their remodeling effects on the scaffolds during the induced differentiation process. The results indicated that CD133(+)/nestin(+)/CD44(+) EMSCs were extensively distributed in the lamina propria of the nasal mucosa. The passaged cells could be induced to differentiate to a greater degree into neurons, Schwann cells and osteoblasts on three-dimensional fibrin gels than on two-dimensional glass slides. More importantly, the induced Schwann cells and osteoblasts exerted channelized and calcified remodeling effects, respectively, on the fibrin gels. Thus, these reshaped scaffolds have desirable biological properties, such as good cell adhesion, biocompatibility and guidance over the cell behavior, providing a tissue-committed niche for specific tissue generation.