Potential risks of viral infections in xenotransplantation

Biofabrication of Poly(glycerol sebacate) Scaffolds Functionalized with a Decellularized Bone Extracellular Matrix for Bone Tissue Engineering

The microarchitecture of bone tissue engineering (BTE) scaffolds has been shown to have a direct effect on the osteogenesis of mesenchymal stem cells (MSCs) and bone tissue regeneration. Poly(glycerol sebacate) (PGS) is a promising polymer that can be tailored to have specific mechanical properties, as well as be used to create microenvironments that are relevant in the context of BTE applications. In this study, we utilized PGS elastomer for the fabrication of a biocompatible and bioactive scaffold for BTE, with tissue-specific cues and a suitable microstructure for the osteogenic lineage commitment of MSCs. In order to achieve this, the PGS was functionalized with a decellularized bone (deB) extracellular matrix (ECM) (14% and 28% by weight) to enhance its osteoinductive potential. Two different pore sizes were fabricated (small: 100-150 μm and large: 250-355 μm) to determine a preferred pore size for in vitro osteogenesis. The decellularized bone ECM functionalization of the PGS not only improved initial cell attachment and osteogenesis but also enhanced the mechanical strength of the scaffold by up to 165 kPa. Furthermore, the constructs were also successfully tailored with an enhanced degradation rate/pH change and wettability. The highest bone-inserted small-pore scaffold had a 12% endpoint weight loss, and the pH was measured at around 7.14. The in vitro osteogenic differentiation of the MSCs in the PGS-deB blends revealed a better lineage commitment of the small-pore-sized and 28% (w/w) bone-inserted scaffolds, as evidenced by calcium quantification, ALP expression, and alizarin red staining. This study demonstrates a suitable pore size and amount of decellularized bone ECM for osteoinduction via precisely tailored PGS elastomer BTE scaffolds.

Fibrin-based tissue engineering: comparison of different methods of autologous fibrinogen isolation

OBJECTIVE

This study is focussed on the optimal method of autologous fibrinogen isolation with regard to the yield and the use as a scaffold material. This is particularly relevant for pediatric patients with strictly limited volumes of blood.

MATERIALS AND METHODS

The following isolation methods were evaluated: cryoprecipitation, ethanol (EtOH) precipitation, ammonium sulfate [(NH(4))(2)SO(4))] precipitation, ammonium sulfate precipitation combined with cryoprecipitation, and polyethylene glycol precipitation combined with cryoprecipitation. Fibrinogen yields were quantified spectrophotometrically and by electrophoretic analyses. To test the influence of the different isolation methods on the microstructure of the fibrin gels, scanning electron microscopy (SEM) was used and the mechanical strength of the cell-free and cell-seeded fibrin gels was tested by burst strength measurements. Cytotoxicity assays were performed to analyze the effect of various fibrinogen isolation methods on proliferation, apoptosis, and necrosis. Tissue development and cell migration were analyzed in all samples using immunohistochemical techniques. The synthesis of collagen as an extracellular matrix component by human umbilical cord artery smooth muscle cells in fibrin gels was measured using hydroxyproline assay.

RESULTS

Compared to cryoprecipitation, all other considered methods were superior in quantitative analyses, with maximum fibrinogen yields of ∼80% of total plasma fibrinogen concentration using ethanol precipitation. SEM imaging demonstrated minor differences in the gel microstructure. Ethanol-precipitated fibrin gels exhibited the best mechanical properties. None of the isolation methods had a cytotoxic effect on the cells. Collagen production was similar in all gels except those from ammonium sulfate precipitation. Histological analysis showed good cell compatibility for ethanol-precipitated gels.

CONCLUSION

The results of the present study demonstrated that ethanol precipitation is a simple and effective method for isolation of fibrinogen and a suitable alternative to cryoprecipitation. This technique allows minimization of the necessary blood volume for fibrinogen isolation, particularly important for pediatric applications, and also has no negative influence on microstructure, mechanical properties, cell proliferation, or tissue development.

New concepts in organ transplantation

Major progress has been made in clinical transplantation over recent years due to close cooperation between clinical specialists and academic investigators. High success rates are evident by longer patient and graft survivals. Treatment procedures have been integrated into fixed protocols utilizing new chemical immunosuppressive reagents that have improved the management of transplanted patients. Further developments in organ transplantation through better surgical techniques have allowed grafts of pancreas, lungs, and intestine. Current transplant medicine has, however, its limitations, especially in the context of the donor organ shortage, the toxicity of immunosuppressive drugs, the chronic rejection activity, and the inability to produce a state of immunologic tolerance. This paper sought to review new concepts in organ transplantation, especially concerning immunologic tolerance and the organ donor shortage.

Osteogenic stem cells and orthopedic engineering: summary and update

The use of osteogenic stem cells or osteoprogenitors to reconstruct skeletal tissues is a popular area of research investigation with high potential for successful use of tissue-engineering principles in orthopedics. Recent studies demonstrate the migration of marrow-derived stem cells to skeletal sites and the proliferation and differentiation at local tissue sites and support possibilities for assessing the successful uses of human osteoprogenitors in the treatment of bone deficiency diseases. In addition, the development of gene therapy procedures in these and other conditions is now considered an achievable goal with the use of these primitive marrow cells.