3D hydrogel/ bioactive glass scaffolds in bone tissue engineering: Status and future opportunities

Repairing significant bone defects remains a critical challenge, raising the clinical demand to design novel bone biomaterials that incorporate osteogenic and angiogenic properties to support the regeneration of vascularized bone. Bioactive glass scaffolds can stimulate angiogenesis and osteogenesis. In addition, natural or synthetic polymers exhibit structural similarity with extracellular matrix (ECM) components and have superior biocompatibility and biodegradability. Thus, there is a need to prepare composite scaffolds of hydrogels for vascularized bone, which incorporate to improve the mechanical properties and bioactivity of natural polymers. In addition, those composites' 3-dimensional (3D) form offer regenerative benefits such as direct doping of the scaffold with ions. This review presents a comprehensive discussion of composite scaffolds incorporated with BaG, focusing on their effects on osteo-inductivity and angiogenic properties. Moreover, the adaptation of the ion-doped hydrogel composite scaffold into a 3D scaffold for the generation of vascularized bone tissue is exposed. Finally, we highlight the challenges and future of manufacturing such biomaterials.

Engineering organ-on-a-chip systems to model viral infections

Infectious diseases remain a public healthcare concern worldwide. Amidst the pandemic of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 infection, increasing resources have been diverted to investigate therapeutics targeting the COVID-19 spike glycoprotein and to develop various classes of vaccines. Most of the current investigations employ two-dimensional (2D) cell culture and animal models. However, 2D culture negates the multicellular interactions and three-dimensional (3D) microenvironment, and animal models cannot mimic human physiology because of interspecies differences. On the other hand, organ-on-a-chip (OoC) devices introduce a game-changer to model viral infections in human tissues, facilitating high-throughput screening of antiviral therapeutics. In this context, this review provides an overview of thein vitroOoC-based modeling of viral infection, highlighting the strengths and challenges for the future.

Effect of COVID-19 on Serum Activity of Liver Enzymes: Is This Associated with Severity and Mortality Rate?

Introduction Coronavirus disease 2019 (COVID-19) is a viral infection caused by a novel coronavirus known as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease raises an enormous public health challenge for the international community. Liver enzymes have been reported to be frequently elevated in hospitalized patients with severe COVID-19 disease.

Materials and Methods This article is a narrative review of abnormal liver tests and liver injury as a manifestation of progression to severe pneumonia. We collected data from the PubMed database (National Library of Medicine, Bethesda, Maryland, United States). We used the search term “abnormal liver test” and relevant records were measured. The review article was organized thematically.

Results This narrative review aims to summarize the available clinical data on abnormal liver enzymes in coronavirus infection and its association with the risk of mortality, severer pneumonia, and systemic inflammation. Some clinical studies refer to abnormal liver tests and liver injury as a manifestation of progression to severe pneumonia. Recent research verified the relationship between hepatic liver enzyme activities and liver damage in patients with COVID-19, which suggested that it might reflect the infection severity and the mortality risk. Thus, this review investigated the correlation between liver serum enzymes level and the severity of COVID-19 patients, by reviewing investigating the relationship between the illness severity in COVID-19 patients with abnormal liver tests, liver pathology, and markers of inflammation.

Conclusion In the current pandemic of SARS-CoV-2, abnormalities of liver enzyme tests were commonly observed in patients with COVID-19. However, because of multiorgan damages that observed in COVID-19 patients, various issues should be considered such as the pathology and pathophysiology of the liver tissue, especially on the activation process of the immune response and cytokine storm to prevent the severity of the disease.

Comparative Study of the Characterisation and Extraction Techniques of Polyphenolic Compounds from Acacia seyal gum

Abstract

Acacia seyal gum is an abundant source of natural polyphenolic compounds (NPPCs) and antioxidant activity with numerous benefits and is often used in cancer treatment. The type of extraction technique can significantly impact the yield and isolation of NPPCs from Acacia seyal gum (ASG). The traditional use of maceration extraction reportedly yields fewer NPPCs.

Objectives

This study investigates five extraction techniques for NPPCs and ASG antioxidant activity, namely: homogenisation, shaking, ultrasonication, magnetic stirring, and maceration.

Materials and Methods

The evaluation of the antioxidant activity (AoA) of the extracted NPPCs from ASG used five assays, namely: Total Flavonoids Content (TFC), Folin-Ciocalteu index (FCI), 2,2-Diphenyl-1-Picrylhydrazyl radical scavenging activity (DPPH), Ferric Reducing Antioxidant Power (FRAP), and Cupric Reducing Antioxidant Capacity (CUPRAC).

Results

To minimise the dataset dimensionality requires Principal Component Analysis. The ultrasonic and maceration techniques were the best techniques to extract NPPCs and examine the AoA of ASG, with a high correlation between the NPPCs and AoA. However, the maceration process was slow (12 h) compared to ultrasonication (1 h). Slow extraction can result in a decline of the NPPCs due to polyphenol oxidase-enzyme and impact productivity.

Conclusions

These findings provide an essential guide for the choice of extraction techniques for the effective extraction of NPPCs from ASG and other plant materials.

Coaxial 3D bioprinting of tri-polymer scaffolds to improve the osteogenic and vasculogenic potential of cells in co-culture models

The crosstalk between osteoblasts and endothelial cells is critical for bone vascularization and regeneration. Here, we used a coaxial 3D bioprinting method to directly print an osteon-like structure by depositing angiogenic and osteogenic bioinks from the core and shell regions of the coaxial nozzle, respectively. The bioinks were made up of gelatin, gelatin methacryloyl (GelMA), alginate, and hydroxyapatite (HAp) nanoparticles and were loaded with human umbilical vascular endothelial cells (HUVECs) and osteoblasts (MC3T3) in the core and shell regions, respectively. Conventional monoaxial 3D bioprinting was used as a control method, where the hydrogels, HAp nanoparticles, MC3T3 cells, and HUVECs were all mixed in one bioink and printed from the core nozzle. As a result, the bioprinted scaffolds were composed of cell-laden fibers with either a core-shell or homogenous structure, providing a non-contact (indirect) or contact (direct) co-culture of MC3T3 cells and HUVECs, respectively. Both structures supported the 3D culture of HUVECs and osteoblasts over a long period. The scaffolds also supported the expression of osteogenic and angiogenic factors. However, the gene expression was significantly higher for the core-shell structure than the homogeneous structure due to the well-defined distribution of osteoblasts and endothelial cells and the formation of vessel-like structures in the co-culture system. Our results indicated that the coaxial bioprinting technique, with the ability to create a non-contact co-culture of cells, can provide a more efficient bioprinting strategy for printing highly vascularized and bioactive bone structures.

Engineering viral genomics and nano-liposomes in microfluidic platforms for patient-specific analysis of SARS-CoV-2 variants

New variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are continuing to spread globally, contributing to the persistence of the COVID-19 pandemic. Increasing resources have been focused on developing vaccines and therapeutics that target the Spike glycoprotein of SARS-CoV-2. Recent advances in microfluidics have the potential to recapitulate viral infection in the organ-specific platforms, known as organ-on-a-chip (OoC), in which binding of SARS-CoV-2 Spike protein to the angiotensin-converting enzyme 2 (ACE2) of the host cells occurs. As the COVID-19 pandemic lingers, there remains an unmet need to screen emerging mutations, to predict viral transmissibility and pathogenicity, and to assess the strength of neutralizing antibodies following vaccination or reinfection. Conventional detection of SARS-CoV-2 variants relies on two-dimensional (2-D) cell culture methods, whereas simulating the micro-environment requires three-dimensional (3-D) systems. To this end, analyzing SARS-CoV-2-mediated pathogenicity via microfluidic platforms minimizes the experimental cost, duration, and optimization needed for animal studies, and obviates the ethical concerns associated with the use of primates. In this context, this review highlights the state-of-the-art strategy to engineer the nano-liposomes that can be conjugated with SARS-CoV-2 Spike mutations or genomic sequences in the microfluidic platforms; thereby, allowing for screening the rising SARS-CoV-2 variants and predicting COVID-19-associated coagulation. Furthermore, introducing viral genomics to the patient-specific blood accelerates the discovery of therapeutic targets in the face of evolving viral variants, including B1.1.7 (Alpha), B.1.351 (Beta), B.1.617.2 (Delta), c.37 (Lambda), and B.1.1.529 (Omicron). Thus, engineering nano-liposomes to encapsulate SARS-CoV-2 viral genomic sequences enables rapid detection of SARS-CoV-2 variants in the long COVID-19 era.

Role of biomaterials in the diagnosis, prevention, treatment, and study of corona virus disease 2019 (COVID-19)

Recently emerged novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the resulting corona virus disease 2019 (COVID-19) led to urgent search for methods to prevent and treat COVID-19. Among important disciplines that were mobilized is the biomaterials science and engineering. Biomaterials offer a range of possibilities to develop disease models, protective, diagnostic, therapeutic, monitoring measures, and vaccines. Among the most important contributions made so far from this field are tissue engineering, organoids, and organ-on-a-chip systems, which have been the important frontiers in developing tissue models for viral infection studies. Also, due to low bioavailability and limited circulation time of conventional antiviral drugs, controlled and targeted drug delivery could be applied alternatively. Fortunately, at the time of writing this paper, we have two successful vaccines and new at-home detection platforms. In this paper, we aim to review recent advances of biomaterial-based platforms for protection, diagnosis, vaccination, therapeutics, and monitoring of SARS-CoV-2 and discuss challenges and possible future research directions in this field.

CRISPR/Cas9 mediated GFP-human dentin matrix protein 1 (DMP1) promoter knock-in at the ROSA26 locus in mesenchymal stem cell for monitoring osteoblast differentiation

BACKGROUND

Dentin matrix protein 1 (DMP1) is highly expressed in mineralized tooth and bone, playing a critical role in mineralization and phosphate metabolism. One important role for the expression of DMP1 in the nucleus of preosteoblasts is the up-regulation of osteoblast-specific genes such as osteocalcin and alkaline phosphatase¹ . The present study aimed to investigate the potential application of human DMP1 promoter as an indicator marker of osteoblastic differentiation.

METHODS

In the present study, we developed DMP1 promoter-DsRed-GFP knock-in mesenchymal stem cell (MSCs) via the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system that enabled automatic detection of osteoblast differentiation. With the application of a homology-directed knock-in strategy, a 2-kb fragment of DMP1 promoter, which was inserted upstream of the GFP and DsRed reporter cassette, was integrated into the human ROSA locus to generate double fluorescent cells. We further differentiated MSCs under osteogenic media to monitor the fate of MSCs. First, cells were transfected using CRISPR/Cas9 plasmids, which culminated in MSCs with a green fluorescence intensity, then GFP-positive cells were selected using puromycin. Second, the GFP-positive MSCs were differentiated toward osteoblasts, which demonstrated an increased red fluorescence intensity. The osteoblast differentiation of MSCs was also verified by performing alkaline phosphatase and Alizarin Red assays.

RESULTS

We have exploited the DMP1 promoter as a predictive marker of MSC differentiation toward osteoblasts. Using the CRISPR/Cas9 technology, we have identified a distinctive change in the fluorescence intensities of GFP knock-in (green) and osteoblast differentiated MSCs ² .

CONCLUSIONS

The data show that DMP1-DsRed-GFP knock-in MSCs through CRISPR/Cas9 technology provide a valuable indicator for osteoblast differentiation. Moreover, The DMP1 promoter might be used as a predictive marker of MSCs differentiated toward osteoblasts.

Cell-cell interaction in a coculture system consisting of CRISPR/Cas9 mediated GFP knock-in HUVECs and MG-63 cells in alginate-GelMA based nanocomposites hydrogel as a 3D scaffold

The interaction between osteogenic and angiogenic cells through a coculturing system in biocompatible materials has been considered for successfully engineering vascularized bone tissue equivalents. In this study, we developed a hydrogel-blended scaffold consisted of gelatin methacryloyl (GelMA) and alginate enriched with hydroxyapatite nanoparticles (HAP) to model an in vitro prevascularized bone construct. The hydrogel-based scaffold revealed a higher mechanical stiffness than those of pure (GelMA), alginate, and (GelMA+ HAP) hydrogels. In the present study, we generated a green fluorescent protein (GFP) knock-in umbilical vein endothelial cells (HUVECs) cell line using the CRISPR/Cas9 technology. The GFP was inserted into the human-like ROSA locus of HUVECs genome. HUVECs expressing GFP were cocultured with OB-like cells (MG-63) within three-dimensionally (3D) fabricated hydrogel to investigate the response of cocultured osteoblasts and endothelial cells in a 3D structure. Cell viability under the 3D cocultured gel was higher than the 3D monocultured. Compared to the 3D monocultured condition, the cells were aligned and developed into the vessel-like structures. During 14 days of culture periods, the cells displayed actin protrusions by the formation of spike-like filopodia in the 3D cocultured model. Angiogenic and osteogenic-related genes such as CD31, vWF, and osteocalcin showed higher expression in the cocultured versus the monocultured. These results have collectively indicated that the 3D cocultured hydrogel facilitates interaction among cells, thereby having a greater effect on angiogenic and osteogenic properties in the absence of induction media.

Key components of engineering vascularized 3-dimensional bioprinted bone constructs

Vascularization has a pivotal role in engineering successful tissue constructs. However, it remains a major hurdle of bone tissue engineering, especially in clinical applications for the treatment of large bone defects. Development of vascularized and clinically-relevant engineered bone substitutes with sufficient blood supply capable of maintaining implant viability and supporting subsequent host tissue integration remains a major challenge. Since only cells that are 100-200 µm from blood vessels can receive oxygen through diffusion, engineered constructs that are thicker than 400 µm face a challenging oxygenation problem. Following implantation in vivo, spontaneous ingrowth of capillaries in thick engineered constructs is too slow. Thus, it is critical to provide optimal conditions to support vascularization in engineered bone constructs. To achieve this, an in-depth understanding of the mechanisms of angiogenesis and bone development is required. In addition, it is also important to mimic the physiological milieu of native bone to fabricate more successful vascularized bone constructs. Numerous applications of engineered vascularization with cell-and/or microfabrication-based approaches seek to meet these aims. Three-dimensional (3D) printing promises to create patient-specific bone constructs in the future. In this review, we discuss the major components of fabricating vascularized 3D bioprinted bone constructs, analyze their related challenges, and highlight promising future trends.

Evaluation of testis hormonal and histopathological alterations in type I and type II diabetic rats

BACKGROUND

Diabetes is a devastating metabolic disease that causes long-term damage to various organs. An important leading complication of diabetes is a degenerative effect on the reproductive system including infertility and gonadal dysfunction. This study aimed to evaluate the effects of experimental type I and II diabetes on the levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone.

METHODS

Male Wistar rats were randomly divided into four separate groups: (1) type I diabetes (T1DM), (2) type II diabetes (T2DM), (3) cetrorelix acetate-treated nondiabetic control group, and (4) normal untreated group (n = 6). T1DM was experimentally induced by a single injection of alloxan (135 mg/kg) while T2DM was induced by feeding the animals with drinking water enriched with fructose (10%). Cetrorelix acetate (100 mg/kg, intraperitoneal for 1 week) treatment group was used as a positive control. All rats were killed and blood and testes were collected after 8 weeks of the study. The effects of induced diabetes on the levels of blood glucose and insulin were assessed. The levels of sex hormones and insulin were determined by radioimmunoassay. Histological staining was used to check abnormal patterns of testicular morphology, the diameter of seminiferous tubules, testicular diameter, and germinal layer thickness.

RESULTS

A significant reduction in the testosterone, FSH, and LH levels were observed in T1DM, T2DM, and also in cetrorelix acetate-treated groups. Analysis of testicular histology sections revealed significantly reduced thickness of cell layer in T1DM and cetrorelix acetate-treated groups compared with the T2DM group. In T2DM, the cell numbers, the thickness of cell layer, the diameter of seminiferous tubules, and weight of testicles were slightly increased. In contrast, total tubules of empty seminiferous increased significantly in T1D and cetrorelix treated groups compared with the control group.

CONCLUSION

Overall, diabetes can induce hypothalamus-pituitary-gonad axis dysfunction, affects hormonal secretion, and causes histological damage to testes, collectively leading to deleterious effects on male fertility.

Exosomes: Nanoparticulate tools for RNA interference and drug delivery

Exosomes are naturally occurring extracellular vesicles released by most mammalian cells in all body fluids. Exosomes are known as key mediators in cell‐cell communication and facilitate the transfer of genetic and biochemical information between distant cells. Structurally, exosomes are composed of lipids, proteins, and also several types of RNAs which enable these vesicles to serve as important disease biomarkers. Moreover, exosomes have emerged as novel drug and gene delivery tools owing to their multiple advantages over conventional delivery systems. Recently, increasing attention has been focused on exosomes for the delivery of drugs, including therapeutic recombinant proteins, to various target tissues. Exosomes are also promising vehicles for the delivery of microRNAs and small interfering RNAs, which is usually hampered by rapid degradation of these RNAs, as well as inefficient tissue specificity of currently available delivery strategies. This review highlights the most recent accomplishments and trends in the use of exosomes for the delivery of drugs and therapeutic RNA molecules.

Exosomes as nanocarriers for siRNA delivery: paradigms and challenges

Exosomes are nano-sized vesicles that facilitate intercellular communications through carrying genetic materials and functional biomolecules. Owing to their unique size and structure, exosomes have emerged as a useful tool to overcome the limitations of siRNA delivery. The use of exosomes as siRNA delivery vehicles lacks certain disadvantages of the existing foreign delivery systems such as viruses, polycationic polymers and liposomes, and introduces several advantages including inherent capacity to pass through biological barriers and escape from phagocytosis by the reticuloendothelial system, as well as being biocompatible, non-toxic, and immunologically inert. Different strategies have been employed to harness exosome-based delivery systems, including surface modification with targeting ligands, and using exosome-display technology, virus-modified exosomes, and exosome-mimetic vesicles. The present review provides a capsule summary of the recent advances and current challenges in the field of exosome-mediated siRNA delivery.

Mesenchymal stem cells can survive on the extracellular matrix-derived decellularized bovine articular cartilage scaffold

OBJECTIVE S

The scarcity of articular cartilage defect to repair due to absence of blood vessels and tissue engineering is one of the promising approaches for cartilage regeneration. The objective of this study was to prepare an extracellular matrix derived decellularized bovine articular cartilage scaffold and investigate its interactions with seeded rat bone marrow mesenchymal stem cells (BM-MSCs).

MATERIALS AND METHODS

Bovine articular cartilage that was cut into pieces with 2 mm thickness, were decellularized by combination of physical and chemical methods including snap freeze-thaw and treatment with sodium dodecyl sulfate (SDS). The scaffolds were then seeded with 1, 1'-dioctadecyl-3, 3, 3', 3'-tetramethylindocarbocyanine perchlorate (DiI) labeled BM-MSCs and cultured for up to two weeks.

RESULTS

Histological studies of decellularized bovine articular cartilage showed that using 5 cycles of snap freeze-thaw in liquid nitrogen and treatment with 2.5% SDS for 4 hr led to the best decellularization, while preserving the articular cartilage structure. Adherence and penetration of seeded BM-MSCs on to the scaffold were displayed by histological and florescence examinations and also confirmed by electron microscopy.

CONCLUSION

ECM-derived decellularized articular cartilage scaffold provides a suitable environment to support adhesion and maintenance of cultured BM-MSCs and could be applied to investigate cellular behaviors in this system and may also be useful for studies of cartilage tissue engineering.

Elevated microRNA-181c and microRNA-30d levels in the enlarged amygdala of the valproic acid rat model of autism

Autism spectrum disorders are severe neurodevelopmental disorders, marked by impairments in reciprocal social interaction, delays in early language and communication, and the presence of restrictive, repetitive and stereotyped behaviors. Accumulating evidence suggests that dysfunction of the amygdala may be partially responsible for the impairment of social behavior that is a hallmark feature of ASD. Our studies suggest that a valproic acid (VPA) rat model of ASD exhibits an enlargement of the amygdala as compared to controls rats, similar to that observed in adolescent ASD individuals. Since recent research suggests that altered neuronal development and morphology, as seen in ASD, may result from a common post-transcriptional process that is under tight regulation by microRNAs (miRs), we examined genome-wide transcriptomics expression in the amygdala of rats prenatally exposed to VPA, and detected elevated miR-181c and miR-30d expression levels as well as dysregulated expression of their cognate mRNA targets encoding proteins involved in neuronal system development. Furthermore, selective suppression of miR-181c function attenuates neurite outgrowth and branching, and results in reduced synaptic density in primary amygdalar neurons in vitro. Collectively, these results implicate the small non-coding miR-181c in neuronal morphology, and provide a framework of understanding how dysregulation of a neurodevelopmentally relevant miR in the amygdala may contribute to the pathophysiology of ASD.

Scaffolds derived from cancellous bovine bone support mesenchymal stem cells' maintenance and growth

Since bone defects can lead to various disabilities, in recent years, many increasing attempts have been made in bone tissue engineering. In this regard, scaffolds have attracted a lot of attention as three dimensional substrates for cell attachment which improve successful tissue engineering. The aim of the present study was to provide an interconnected porous scaffold to facilitate cell infiltration. To do so, cancellous bone from bovine femur was dissected in fragments and decellularized by physicochemical methods, including snap freeze/thaw, rinsing in hot water and treatment with different solutions of sodium dodecyl sulfate (SDS). Histological analysis and 4',6-diamidino-2-phenylindole staining revealed that the best results were obtained after treatment with 2.5%, 5%, and 8% SDS for 8, 3, or 1 h respectively, which significantly removed bone cells with intact trabeculae geometry. Further characterization of decellularized scaffolds by the compression tests also revealed no significant difference between elastic modulus values of the three different SDS treatments. Moreover, studying the ratio of bone trabeculae to bone surfaces (BT/BS) as assessed by Clemex vision software 3.5 showed that treatment with 2.5% SDS for 8 h resulted in a BT/BS score in the range of native bone and therefore this treatment was used for further experiments. Histological studies and scanning electron microscopy revealed rat mesenchymal stem cells integration, adhesion, and maintenance during the 2 and 7 d of culture in vitro. In conclusion, the present results support the effective role of SDS in cancellous bovine bone decellularization and also propensity of treated samples in providing a suitable three-dimentional environment to support the maintenance and growth of mesenchymal stem cells.