Regeneration of Volumetric Muscle Loss Using MSCs Encapsulated in PRP-Derived Fibrin Microbeads

Volumetric muscle loss (VML) is one of the major types of soft tissue injury frequently encountered worldwide. In case of VML, the endogenous regenerative capacity of the skeletal muscle tissue is usually not sufficient for complete healing of the damaged area resulting in permanent functional musculoskeletal impairment. Therefore, the development of new tissue engineering approaches that will enable functional skeletal muscle regeneration by overcoming the limitations of current clinical treatments for VML injuries has become a critical goal. Platelet-rich plasma (PRP) is an inexpensive and relatively effective blood product with a high concentration of platelets containing various growth factors and cytokines involved in wound healing and tissue regeneration. Due to its autologous nature, PRP has been a safe and widely used treatment option for various wound types for many years. Recently, PRP-based biomaterials have emerged as a promising approach to promote muscle tissue regeneration upon injury. This chapter describes the use of PRP-derived fibrin microbeads as a versatile encapsulation matrix for the localized delivery of mesenchymal stem cells and growth factors to treat VML using tissue engineering strategies.

Magnetic biocomposite scaffold based on decellularized tendon ECM and MNP-deposited halloysite nanotubes: physicochemical, thermal, rheological, mechanical andin vitrobiological evaluations

The development of new three-dimensional biomaterials with advanced versatile properties is critical to the success of tissue engineering (TE) applications. Here, (a) bioactive decellularized tendon extracellular matrix (dECM) with a sol-gel transition feature at physiological temperature, (b) halloysite nanotubes (HNT) with known mechanical properties and bioactivity, and (c) magnetic nanoparticles (MNP) with superparamagnetic and osteogenic properties were combined to develop a new scaffold that could be used in prospective bone TE applications. Deposition of MNPs on HNTs resulted in magnetic nanostructures without agglomeration of MNPs. A completely cell-free, collagen- and glycosaminoglycan- rich dECM was obtained and characterized. dECM-based scaffolds incorporated with 1%, 2% and 4% MNP-HNT were analysed for their physical, chemical, andin vitrobiological properties. Fourier-transform infrared spectroscopy, x-ray powder diffractometry and vibrating sample magnetometry analyses confirmed the presence of dECM, HNT and MNP in all scaffold types. The capacity to form apatite layer upon incubation in simulated body fluid revealed that dECM-MNP-HNT is a bioactive material. Combining dECM with MNP-HNT improved the thermal stability and compressive strength of the macroporous scaffolds upto 2% MNP-HNT.In vitrocytotoxicity and hemolysis experiments showed that the scaffolds were essentially biocompatible. Human bone marrow mesenchymal stem cells adhered and proliferated well on the macroporous constructs containing 1% and 2% MNP-HNT; and remained metabolically active for at least 21 din vitro. Collectively, the findings support the idea that magnetic nanocomposite dECM scaffolds containing MNP-HNT could be a potential template for TE applications.

Decellularized Bone Matrix/45S5 Bioactive Glass Biocomposite Hydrogel-Based Constructs with Angiogenic and Osteogenic Properties: Ex Ovo and Ex Vivo Evaluations

Decellularized extracellular matrix is often used to create an in vivo-like environment that supports cell growth and proliferation, as it reflects the micro/macrostructure and molecular composition of tissues. On the other hand, bioactive glasses (BG) are surface-reactive glass-ceramics that can convert to hydroxyapatite in vivo and promote new bone formation. This study is designed to evaluate the key properties of a novel angiogenic and osteogenic biocomposite graft made of bovine decellularized bone matrix (DBM) hydrogel and 45S5 BG microparticles (10 and 20 wt%) to combine the existing superior properties of both biomaterial classes. Morphological, physicochemical, mechanical, and thermal characterizations of DBM and DBM/BG composite hydrogels are performed. Their in vitro biocompatibility is confirmed by cytotoxicity and hemocompatibility analyses. Ex vivo chick embryo aortic arch and ex ovo chick chorioallantoic membrane (CAM) assays reveal that the present pro-angiogenic property of DBM hydrogels is enhanced by the incorporation of BG. Histochemical stainings (Alcian blue and Alizarin red) and digital image analysis of ossification on hind limbs of embryos used in the CAM model reveal the osteogenic potential of biomaterials. The findings support the notion that the developed DBM/BG composite hydrogel constructs have the potential to be a suitable graft for bone repair.

Biomimetic mineralization of platelet lysate/oxidized dextran cryogel as a macroporous 3D composite scaffold for bone repair

Scaffold development approaches using autologous sources for tissue repair are of great importance in obtaining bio-active/-compatible constructs. Platelet-rich plasma (PRP) containing various growth factors and platelet lysate (PL) derived from PRP are autologous products that have the potential to accelerate the tissue repair response by inducing a transient inflammatory event. Considering the regenerative capacity of PRP and PL, PRP/PL-based scaffolds are thought to hold great promise for tissue engineering as a natural source of autologous growth factors and a provider of mechanical support for cells. Here, a bio-mineralized PRP-based scaffold was developed using oxidized dextran (OD) and evaluated for future application in bone tissue engineering. Prepared PL/OD scaffolds were incubated in simulated body fluid (SBF) for 7, 14 and 21 d periods. Mineralized PL/OD scaffolds were characterized using Fourier transform infrared spectroscopy, x-ray diffraction spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis, porosity and compression tests. SEM and energy-dispersive x-ray spectroscopy analyses revealed mineral accumulation on the PL/OD scaffold as a result of SBF incubation.In vitrocytotoxicity andin vitrohemolysis tests revealed that the scaffolds were non-toxic and hemocompatible. Additionally, human osteoblasts (hOBs) exhibited good attachment and spreading behavior on the scaffolds and maintained their viability throughout the culture period. The alkaline phosphatase activity assay and calcium release results revealed that PL/OD scaffolds preserved the osteogenic properties of hOBs. Overall, findings suggest that mineralized PL/OD scaffold may be a promising scaffold for bone tissue engineering.

Encapsulation of MSCs in PRP-Derived Fibrin Microbeads

Platelet-rich plasma (PRP) is a highly concentrated platelet-containing blood plasma that incorporates a significant amount of growth factors and cytokines needed to accelerate the tissue repair process. PRP has been used effectively for many years in the treatment of various wounds by direct injection into the target tissue or impregnation with scaffold or graft materials. Since autologous PRP can be obtained by simple centrifugation, it is an attractive and inexpensive product for use in repairing damaged soft tissues. Cell-based regenerative approaches, which draw attention in the treatment of tissue and organ injuries, are based on the principle of delivering stem cells to damaged sites by various means, including encapsulation. Current biopolymers used in cell encapsulation have some advantages with some limitations. By adjusting its physicochemical properties, PRP-derived fibrin can become an efficient matrix material for encapsulating stem cells. This chapter covers the fabrication protocol of PRP-derived fibrin microbeads and their use to encapsulate stem cells as a general bioengineering platform for prospective regenerative medical applications.

Bioactive composite hydrogels as 3D mesenchymal stem cell encapsulation environment for bone tissue engineering: in vitro and in vivo studies

Although decellularized bone matrix (DBM) has often been used in scaffold form for osteogenic applications, its use as a stem cell encapsulation matrix adaptable to surgical shaping procedures has been neglected. This study aimed to investigate the feasibility of utilizing solubilized DBM and nanohydroxyapatite (nHAp)-incorporated DBM hydrogels as encapsulation matrix for bone marrow-derived MSCs (BM-MSCs). First, DBM and DBM/nHAp hydrogels were assessed by physical, chemical, turbidimetric, thermal, and mechanical methods; then, in vitro cytocompatibility and in vitro hemocompatibility were investigated. An in vivo study was performed to evaluate the osteogenic properties of hydrogels alone or with BM-MSCs encapsulated in them. The findings revealed that hydrogels retained high levels of collagen and glycosaminoglycans after successful decellularization. They were found to be cytocompatible and hemocompatible in vitro, and were able to gel with sufficient mechanical stability at physiological temperature. BM-MSCs survived in culture for at least 2 weeks as metabolically active when encapsulated in both DBM and DBM/nHAp. Preliminary in vivo study showed that DBM-nHAp has higher osteogenicity than DBM. Moreover, BM-MSC encapsulated DMB/nHAp showed predominant bone-like tissue formation at 30 days in the rat ectopic site compared to its cell-free form.

Advances in Regenerative Medicine and Biomaterials

The low regenerative potential of the human body hinders proper regeneration of dysfunctional or lost tissues and organs due to trauma, congenital defects, and diseases. Tissue or organ transplantation has hence been a major conventional option for replacing the diseased or dysfunctional body parts of the patients. In fact, a great number of patients on waiting lists would benefit tremendously if tissue and organs could be replaced with biomimetic spare parts on demand. Herein, regenerative medicine and advanced biomaterials strive to reach this distant goal. Tissue engineering aims to create new biological tissue or organ substitutes, and promote regeneration of damaged or diseased tissue and organs. This approach has been jointly evolving with the major advances in biomaterials, stem cells, and additive manufacturing technologies. In particular, three-dimensional (3D) bioprinting utilizes 3D printing to fabricate viable tissue-like structures (perhaps organs in the future) using bioinks composed of special hydrogels, cells, growth factors, and other bioactive contents. A third generation of multifunctional biomaterials could also show opportunities for building biomimetic scaffolds, upon which to regenerate stem cells in vivo. Besides, decellularization technology based on isolation of extracellular matrix of tissue and organs from their inhabiting cells is presented as an alternative to synthetic biomaterials. Today, the gained knowledge of functional microtissue engineering and biointerfaces, along with the remarkable advances in pluripotent stem cell technology, seems to be instrumental for the development of more realistic microphysiological 3D in vitro tissue models, which can be utilized for personalized disease modeling and drug development. This chapter will discuss the recent advances in the field of regenerative medicine and biomaterials, alongside challenges, limitations, and potentials of the current technologies.

Fabrication and Molecular Modeling of Navette-Shaped Fullerene Nanorods Using Tobacco Mosaic Virus as a Nanotemplate

To date, metallization studies have been performed with the nanometer-scale template, Tobacco Mosaic Virus (TMV). Here we show that fullerenes as well can be deposited on TMV coat protein in a controlled manner. Two methods were followed for the coating process. First, underivatized fullerene was dispersed in different solvents to bring the underivatized fullerene and wild-type TMV together. Improved depositions were obtained with the fullerene dicarboxylic derivative synthesized via the Bingel method. The form of the coating was analyzed by transmission electron microscopy. Our results demonstrate that the coating efficiency with the carboxy derivative was much better compared to the underivatized fullerene. The goal of coupling a carbon nanoparticle to a biological molecule, the viral coat of TMV, was achieved with the carboxy derivative of fullerene, resulting in the production of navette-shaped nanorods. The interactions between carboxyfullerenes and TMV were investigated through modeling with computational simulations and Gaussian-based density functional theory (DFT) calculations using the Gaussian09 program package. The theoretical calculations supported the experimental findings. This inexpensive and untroublesome method promises new fullerene hybrid nanomaterials in particular shapes and structures.

Decellularized liver ECM-based 3D scaffolds: Compositional, physical, chemical, rheological, thermal, mechanical, and in vitro biological evaluations

The extracellular matrix (ECM) is involved in many critical cellular interactions through its biological macromolecules. In this study, a macroporous 3D scaffold originating from decellularized bovine liver ECM (dL-ECM), with defined compositional, physical, chemical, rheological, thermal, mechanical, and in vitro biological properties was developed. First, protocols were determined that effectively remove cells and DNA while ECM retains biological macromolecules collagen, elastin, sGAGs in tissue. Rheological analysis revealed the elastic properties of pepsin-digested dL-ECM. Then, dL-ECM hydrogel was neutralized, molded, formed into macroporous (~100-200 μm) scaffolds in aqueous medium at 37 °C, and lyophilized. The scaffolds had water retention ability, and were mechanically stable for at least 14 days in the culture medium. The findings also showed that increasing the dL-ECM concentration from 10 mg/mL to 20 mg/mL resulted in a significant increase in the mechanical strength of the scaffolds. The hemolysis test revealed high in vitro hemocompatibility of the dL-ECM scaffolds. Studies investigating the viability and proliferation status of human adipose stem cells seeded over a 2-week culture period have demonstrated the suitability of dL-ECM scaffolds as a cell substrate. Prospective studies may reveal the extent to which 3D dL-ECM sponges have the potential to create a biomimetic environment for cells.

Decellularized Cell Culture ECMs Act as Cell Differentiation Inducers

Decellularized tissues and organs have aroused considerable interest for developing functional bio-scaffolds as natural templates in tissue engineering applications. More recently, the use of natural extracellular matrix (ECM) extracted from the in vitro cell cultures for cellular applications have come into question. It is well known that the microenvironment largely defines cellular properties. Thus, we have anticipated that the ECMs of the cells with different potency levels should likely possess different effects on cell cultures. To test this, we have comparatively evaluated the differentiative effects of ECMs derived from the cultures of human somatic dermal fibroblasts, human multipotent bone marrow mesenchymal stem cells, and human induced pluripotent stem cells on somatic dermal fibroblasts. Although challenges remain, the data suggest that the use of cell culture-based extracellular matrices perhaps may be considered as an alternative approach for the differentiation of even somatic cells into other cell types.

Preliminary assessment of an injectable extracellular matrix from decellularized bovine myocardial tissue

The goal of this study was to develop an injectable form of decellularized bovine myocardial tissue matrix which could retain high levels of functional ECM molecules, and could gel at physiological temperature. Dissected ventricular tissue was processed by a detergent-based protocol, lyophilized, enzymatically-digested, and neutralized to form the injectable myocardial matrix (IMM). Histochemical analysis, DNA quantification, and agarose gel electrophoresis demonstrated the efficiency of the applied protocol. Chemical, thermal, morphological, and rheological characterization; protein and sulfated glycosaminoglycan (sGAG) content analysis were performed, in vitro biological properties were evaluated. An in vivo histocompatibility and biodegradability study was performed. Histochemistry revealed complete removal of myocardial cells. DNA content analysis revealed a significant decrease (87%) in the nuclear material, while protein and sGAG contents were highly preserved following decellularization. Soluble IMM was capable of turning into gel form at ∼37 °C, indicating selfassembling property. In vitro findings showed the biomaterial was noncytotoxic, nonhemolytic, and supported the attachment and proliferation of mesenchymal stem cells. In vivo study demonstrated IMM was well-tolerated by rats receiving subcutaneous injection. This work demonstrates that the IMM from decellularized bovine myocardial tissue has the potential for use as a feasible regenerative biomaterial in prospective tissue engineering and regenerative medicine studies.

Magneto-sensitive decellularized bone matrix with or without low frequency-pulsed electromagnetic field exposure for the healing of a critical-size bone defect

Bioactive ECM-based materials mimic the complex composition and structure of natural tissues. Decellularized cancellous bone matrix (DBM) has potential for guiding new bone formation and accelerating the regeneration process. On the other hand, low frequency-pulsed electromagnetic field (LF-PEMF) has been shown to enhance the regeneration capacity of bone defects. The present study sought to explore the feasibility of using DBM and DBM/MNP, and LF-PEMF for treating critical-size bone defects. Firstly, decellularization protocol was optimized to obtain a bioactive DBM, then MNPs were incorporated. Later, the physical, chemical and biological properties of DBM and DBM/MNP were assessed in vitro. MNPs homogeneously distributed into the DBM were not found to be toxic to human osteoblast cultures. Finally, an in vivo study was carried out with DBM and DBM/MNP composites in a bilateral critical-size rat cranial defect model (n = 48) with or without LF-PEMF exposure for 45 and 90 days. The histomorphometric and radiographic evaluations revealed that, while the collagen (positive control) and Sham (negative control) groups showed high incidence of fibrous connective tissue together with low level of osteogenic activity, both the DBM and DBM/MNP-grafted groups significantly promoted new bone tissue formation and angiogenesis, by the appropriate use of LF-PEMF for 90 days.

Development of a multicellular 3D-bioprinted microtissue model of human periodontal ligament-alveolar bone biointerface: Towards a pre-clinical model of periodontal diseases and personalized periodontal tissue engineering

While periodontal (PD) disease is among principal causes of tooth loss worldwide, regulation of concomitant soft and mineralized PD tissues, and PD pathogenesis have not been completely clarified yet. Besides, relevant pre-clinical models and in vitro platforms have limitations in simulating human physiology. Here, we have harnessed three-dimensional bioprinting (3DBP) technology for developing a multi-cellular microtissue model resembling PD ligament-alveolar bone (PDL-AB) biointerface for the first time. 3DBP parameters were optimized; the physical, chemical, rheological, mechanical, and thermal properties of the constructs were assessed. Constructs containing gelatin methacryloyl (Gel-MA) and hydroxyapatite-magnetic iron oxide nanoparticles showed higher level of compressive strength when compared with that of Gel-MA constructs. Bioprinted self-supporting microtissue was cultured under flow in a microfluidic platform for >10 days without significant loss of shape fidelity. Confocal microscopy analysis indicated that encapsulated cells were homogenously distributed inside the matrix and preserved their viability for >7 days under microfluidic conditions. Immunofluorescence analysis showed the cohesion of stromal cell surface marker-1+ human PDL fibroblasts containing PDL layer with the osteocalcin+ human osteoblasts containing mineralized layer in time, demonstrating some permeability of the printed constructs to cell migration. Preliminary tetracycline interaction study indicated the uptake of model drug by the cells inside the 3D-microtissue. Also, the non-toxic levels of tetracycline were determined for the encapsulated cells. Thus, the effects of tetracyclines on PDL-AB have clinical significance for treating PD diseases. This 3D-bioprinted multi-cellular periodontal/osteoblastic microtissue model has potential as an in vitro platform for studying processes of the human PDL.

Mesenchymal Stem Cells for Coronavirus (COVID-19)-Induced Pneumonia: Revisiting the Paracrine Hypothesis with New Hopes?

Mesenchymal stem cells (MSCs) bear a promising potential for regenerative medicine therapies and they repair damaged tissue through secretion of immune modulatory and anti-inflammatory molecules acting in a paracrine fashion. Coronavirus disease 2019 (COVID-19) has spread all over the world with high morbidity and mortality rates and there is no specific treatment for this infection. A recent study published in the journal reports that MSC infusion is safe and effective in patients suffering from COVID-19 induced pneumonia. In the light of this study and previous reports, we make additional comments about possible therapeutic effects of MSCs in COVID-19 infection.

Bioethical issues in genome editing by CRISPR-Cas9 technology

Genome editing technologies have led to fundamental changes in genetic science. Among them, CRISPR-Cas9 technology particularly stands out due to its advantages such as easy handling, high accuracy, and low cost. It has made a quick introduction in fields related to humans, animals, and the environment, while raising difficult questions, applications, concerns, and bioethical issues to be discussed. Most concerns stem from the use of CRISPR-Cas9 to genetically alter human germline cells and embryos (called germline genome editing). Germline genome editing leads to serial bioethical issues, such as the occurrence of undesirable changes in the genome, from whom and how informed consent is obtained, and the breeding of the human species (eugenics). However, the bioethical issues that CRISPR-Cas9 technology could cause in the environment, agriculture and livestock should also not be forgotten. In order for CRISPR-Cas9 to be used safely in all areas and to solve potential issues, worldwide legislation should be prepared, taking into account the opinions of both life and social scientists, policy makers, and all other stakeholders of the sectors, and CRISPR-Cas9 applications should be implemented according to such legislations. However, these controls should not restrict scientific freedom. Here, various applications of CRISPR-Cas9 technology, especially in medicine and agriculture, are described and ethical issues related to genome editing using CRISPR-Cas9 technology are discussed. The social and bioethical concerns in relation to human beings, other organisms, and the environment are addressed.

Macroporous elastic cryogels based on platelet lysate and oxidized dextran as tissue engineering scaffold: In vitro and in vivo evaluations

In this study, three-dimensional macroporous cryogels were developed from platelet lysate (PL) and different concentrations of oxidized dextran (OD; 0.5, 1, 2, 4%). Subsequently, PL/OD scaffolds were characterized for potential use in tissue engineering applications. The pore size and morphology of the resulting cryogels were visualized using scanning electron microscopy (SEM). The pore size distributions were determined using mercury intrusion porosimetry (MIP). In vitro hydrolytic degradation, water uptake, mechanical properties and hemocompatibility were investigated. Extraction test was carried out to evaluate potential in vitro toxic effects of the PL/OD. The in vitro adhesion, proliferation, chondrogenic differentiation, and extracellular matrix production of human adipose stem cells (hASCs) on PL/OD cryogels were evaluated. In vivo biodegradation of the cryogels was investigated at the subcutaneous dorsal site of rats. SEM and MIP results indicated that PL/OD had a macroporous pore structure with pore sizes ranging between 10 and 200 μm. The cryogels completely degraded within 90-240 days post-implantation, depending on OD concentration. Histochemical analysis revealed high levels of cell and tissue infiltration into the pores of PL/OD. In vitro cytotoxicity findings indicated that the extracts of PL/OD_0.5, PL/OD₁ and PL/OD₂ showed no cytotoxic effect, whereas that of PL/OD₄ exhibited a moderate cytotoxic effect on cell cultures. hASCs seeded on PL/OD₂ retained their viability and showed extensive spreading and filopodia formation after 7 days. PL/OD₂ also supported the chondrogenesis of hASCs in the presence of chondro-inductive factors. Given all the results, PL/OD could have potential as a scaffold for tissue engineering applications.

3D Bioprinting of Tissue Models with Customized Bioinks

The ordered assembly of multicellular structures mimicking native tissues has lately come into prominence for various applications of biomedicine. In this respect, three-dimensional bioprinting (3DP) of cells and other biologics through additive manufacturing techniques has brought the possibility to develop functional in vitro tissue models and perhaps creating de novo transplantable tissues or organs in time. Bioinks, which can be defined as the printable analogues of the extracellular matrix, represent the foremost component of 3DP. In this chapter, we attempt to elaborate the major classes of bioinks which are prevalently being evaluated for the 3DP of a wide range of tissue models.

Autologous protein-based scaffold composed of platelet lysate and aminated hyaluronic acid

This study describes a protein-based scaffold using platelet rich plasma (PRP), aminated hyaluronic acid (HA-NH₂) and Genipin for potential use in regenerative applications as an autologous tissue engineering scaffold. Human PRP was subjected to three freeze-thaw cycles for obtaining platelet lysates (PL). HA-NH₂ was synthesized from hyaluronic acid. PL/HA-NH₂ scaffolds were fabricated using different concentrations of genipin (0.05, 0.1 and 0.2%) and HA-NH₂ (10, 20 and 30 mg/mL). Mechanical, physical, and chemical properties of the scaffolds were comprehensively investigated. The compressive test findings revealed that crosslinking with 0.1 and 0.2% genipin improved the mechanical properties of the scaffolds. SEM evaluations showed that the scaffolds exhibited an interconnected and macroporous structure. Besides, porosimetry analysis indicated a wide distribution of the scaffold pore-size. Rheological findings demonstrated that the G' values were higher than the G″ values, indicating that PL/HA-NH₂ scaffolds had typical viscoelastic properties. In vitro biocompatibility studies showed that the scaffolds were both cytocompatible and hemocompatible. Alamar Blue test indicated that human adipose mesenchymal stem cells (hASCs) were able to attach, spread and proliferate on the scaffolds for 21 days-duration. Our findings clearly indicate that PL/HA-NH₂ can be a promising autologous candidate scaffold for tissue engineering applications.

Mesenchymal stem cell transplantation in polytrauma: Evaluation of bone and liver healing response in an experimental rat model

PURPOSE

Trauma is the most common cause of death of young people in the world. As known, mesenchymal stem cells (MSCs) accelerate tissue regeneration mechanisms. In our study, we aimed to investigate the effects of MSCs transplantation on the healing of liver and bone tissue by considering trauma secondary inflammatory responses.

METHODS

56 adult Wistar-albino rats were divided into two groups: the polytrauma (liver and bone) (n = 28), and the liver trauma group (n = 28). At 36 h and 5th day after surgery, both rats with polytrauma and with isolated liver injury received either intravenous (IV) or intraperitoneal (IP) injections of MSCs (one million cells per kg body weight). Untreated groups received IV and IP saline injections. At day 21 after surgery, liver, tibia and fibula of the subjects were excised and evaluated for histopathologic and histomorphometric examination. Additionally, whole blood count (white blood cells, hemoglobin and platelets), C-reactive protein (CRP), glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin, blood gas, and trauma markers interleukin-1B (IL-1B), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF alpha) levels were investigated.

RESULTS

In general, MSC transplantations were well tolerated by the subjects. It was found that ALT, CRP, albumin were significantly lower in rats which received MSCs (p < 0.001). Inflammation of the liver and bone tissue in the MSC-injected rats were significantly lower than that of the untreated groups.

CONCLUSIONS

Herewith we have shown that MSC infusion in posttraumatic rats leads to less aggressive and more effective consequences on liver and bone tissue healing. Human MSC treatment for trauma is still in early stages of development; thus standard protocols, and patient inclusion criteria should be established beforehand clinical trials.

Encapsulation of bone marrow-MSCs in PRP-derived fibrin microbeads and preliminary evaluation in a volumetric muscle loss injury rat model: modular muscle tissue engineering

Repair of volumetric muscle loss (VML) injuries is a complicated endeavour which necessitates the collaborative use of different regenerative approaches and technologies. Herein is proposed the development of fibrin-based microbeads (FMs) alone or as a bone marrow mesenchymal stem cell (MSC) encapsulation matrix for modular muscle engineering. FMs were generated through the ionotropic gelation of alginate and fibrinogen obtained from the platelet-rich plasma of whole blood, and then removing the alginate by citrate treatment. FMs were first characterized by FT-IR, SEM and water uptake tests. Then, the stability of FMs and the mitochondrial dehydrogenase activity of the MSCs encapsulated in FMs were evaluated under in vitro culture conditions. Eventually, the regenerative capacity of the cell-devoid and MSCs-encapsulated FMs was evaluated in a rat VML injury model involving 8 × 4×4 mm³-size bilateral defects in the biceps femoris muscles. The histochemical, immunohistochemical and semi-quantitative histomorphological scoring results retrieved at 30, 60 and 180 days demonstrated that the cell-devoid FMs supported muscle regeneration to a great extent. Moreover, MSCs-encapsulated FMs were more effective in shortening the regeneration period of the injured tissue of the rat VML, resulting in good myofibre orientation, while the Sham group resulted in incomplete repair with fibrotic scar tissue formations.

Osteogenic differentiation of encapsulated rat mesenchymal stem cells inside a rotating microgravity bioreactor: in vitro and in vivo evaluation

The objective of this study is to evaluate the in vitro and in vivo osteogenic potential of rat bone marrow mesenchymal stem cells (BM-MSCs) using chitosan/hydroxyapatite (C/HAp) microbeads as encapsulation matrix under osteoinductive medium and dynamic culture conditions. The degradation characteristics of C/HAp microbeads were evaluated under in vitro and in vivo conditions for 180 days. BM-MSCs were encapsulated in C/HAp microbeads with > 85% viability, and were cultured in a slow turning lateral vessel-type rotating bioreactor simulating microgravity conditions for 28 days, under the effect of osteogenic inducers. MTT assay showed that the metabolic activity of encapsulated cells was preserved > 80% after a week. In vitro experiments confirmed that the encapsulated BM-MSCs differentiated into osteoblastic cells, formed bone-like tissue under osteogenic microgravity bioreactor conditions. Preliminary in vivo study indicated C/HAp microbeads containing BM-MSCs were able to repair the surgically-created small bone defects in the rat femur. BM-MSCs-C/HAp composite microbeads may have potential for modular bone regeneration.

Decellularization of Bovine Small Intestinal Submucosa

Decellularization technology promises to overcome some of the significant limitations in the regenerative medicine field by providing functional biocompatible grafts. The technique involves removal of the cells from the biological tissues or organs for further use in tissue engineering and clinical interventions. There are significant differences between decellularization protocols due to the intrinsic properties of different tissue types and purpose of use. This multistep, chemical-solution-based protocol is optimized for the preparation of decellularized bovine small intestinal submucosa (SIS).

Intrinsically Conductive Polymer Nanocomposites for Cellular Applications

Intrinsically conductive polymer nanocomposites have a remarkable potential for cellular applications such as biosensors, drug delivery systems, cell culture systems and tissue engineering biomaterials. Intrinsically conductive polymers transmit electrical stimuli between cells, and induce regeneration of electroactive tissues such as muscle, nerve, bone and heart. However, biocompatibility and processability are common issues for intrinsically conductive polymers. Conductive polymer composites are gaining importance for tissue engineering applications due to their excellent mechanical, electrical, optical and chemical functionalities. Here, we summarize the different types of intrinsically conductive polymers containing electroactive nanocomposite systems. Cellular applications of conductive polymer nanocomposites are also discussed focusing mainly on poly(aniline), poly(pyrrole), poly(3,4-ethylene dioxythiophene) and poly(thiophene).

Osteogenic differentiation of mesenchymal stem cells using hybrid nanofibers with different configurations and dimensionality

Novel, hybrid fibrinogen/polylactic acid (FBG/PLA) nanofibers with different configuration (random vs aligned) and dimensionality (2-D vs 3-D environment) were used to control the overall behavior and the osteogenic differentiation of human adipose-derived mesenchymal stem cells (ADMSCs). Aligned nanofibers in both the 2-D and 3-D configurations are proved to be favored for osteodifferentiation. Morphologically, we found that on randomly configured nanofibers, the cells developed a stellate-like morphology with multiple projections; however, time-lapse analysis showed significantly diminished cell movements. Conversely, an elongated cell shape with advanced cell spreading and extended actin cytoskeleton accompanied with significantly increased cell mobility were observed when cells attached on aligned nanofibers. Moreover, a clear tendency for higher alkaline phosphatase activity was also found on aligned fibers when ADMSCs were switched to osteogenic induction medium. The strongest accumulation of Alizarin red (AR) and von Kossa stain at 21 days of culture in osteogenic medium were found on 3-D aligned constructs while the rest showed lower and rather undistinguishable activity. Quantitative reverse transcription-polymerase chain reaction analysis for Osteopontin (OSP) and RUNX 2 generally confirmed this trend showing favorable expression of osteogenic genes activity in 3-D environment particularly in aligned configuration. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2065-2074, 2017.

A comparative study on the in vitro cytotoxic responses of two mammalian cell types to fullerenes, carbon nanotubes and iron oxide nanoparticles

The present study was designed to evaluate and compare the time- and dose-dependent cellular response of human periodontal ligament fibroblasts (hPDLFs), and mouse dermal fibroblasts (mDFs) to three different types of nanoparticles (NPs); fullerenes (C₆₀), single walled carbon nanotubes (SWCNTs) and iron (II,III) oxide (Fe₃O₄) nanoparticles via in vitro toxicity methods, and impedance based biosensor system. NPs were characterized according to their morphology, structure, surface area, particle size distribution and zeta potential by using transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller, dynamic light scattering and zeta sizer analyses. The Mössbauer spectroscopy was used in order to magnetically characterize the Fe₃O₄ NPs. The hPDLFs and mDFs were exposed to different concentrations of the NPs (0.1, 1, 10, 50 and 100 μg/mL) for predetermined time intervals (6, 24 and 48 h) under controlled conditions. Subsequently, NP exposed cells were tested for viability, membrane leakage and generation of intracellular reactive oxygen species. Additional to in vitro cytotoxicity assays, the cellular responses to selected NPs were determined in real time using an impedance based biosensor system. Taken together, information obtained from all experiments suggests that toxicity of the selected NPs is cell type, concentration and time dependent.

Polycation-coated polyanion microspheres of urease for urea hydrolysis

Urease (EC 3.5.1.5) was immobilized within polyanionic carboxymethylcellulose/alginate (CMC/Alg) microspheres coated with a cationic polysaccharide, chitosan (C). Coating with chitosan improved the mechanically durability of the polyanionic microspheres, as well as increased enzyme immobilization yield [approximately 0.4 mg.mL-1 gel]. The effects of chitosan coating and CMC/Alg ratio on the water uptake and spherical morphology of the microspheres were investigated. The optimal pH of urease was not extensively affected by the immobilization procedure. However, the optimal temperature of urease activity increased upto 60 and 65 degrees C within CMC/Alg and C(CMC/Alg) microspheres, respectively, while the optimum for the free enzyme was 50 degrees C. The half life (t1/2) and deactivation rate constant (kd) of free urease were 79 min and 8.77 x 10(-3) min-1, respectively, whilst the t1/2 and kd values of urease within polyanion and polycation-coated polyanion microspheres were 142 min and 4.88 x 10(-3).min-1, and 179 min and 3.87 x 10(-3).min-1, at 80 degrees C, respectively. While the activation energy of the hydrolysis reaction of free urease was found to be 11.86 kJ.M-1.dm-3, it increased to 18.91 and 20.02 kJ.M-1.dm-3, for the immobilized urease within CMC/Alg and C(CMC/Alg) microspheres, respectively. The free enzyme exhibited K(m) and Vmax values of 2.85 mM.dm-3 and 31.9 mM.dm-3.s-1.g-1p-1, respectively, whilst the K(m) and Vmax for urease within polyanion and polycation-coated polyanion microspheres were 3.94 mM.dm-3 and 73.4 mM.dm-3.s-1.g-1.p-1, and 4.22 mM.dm-3 and 81.4 mM.dm-3.s-1.g-1.p-1, in the same order. C(CMC/Alg) microspheres showed a nearly stable urease activity of around 80-85% of the initial maximum activity, after the first 100 minutes.