Newer approaches to dry eye therapy: Nanotechnology, regenerative medicine, and tissue engineering

Definitive treatment of dry eye disease (DED), one of the commonest ocular surface disorders, has remained elusive despite several recent advances in better diagnostics and the introduction of newer therapeutic molecules. The current treatment paradigms rely heavily on lubricating eye drops and anti-inflammatory agents that may need to be used long-term and are mainly palliative. Research is ongoing not only for a curative treatment option but also to improve the potency and efficacy of existing drug molecules through better formulations and delivery platforms. In the past two decades, significant advancement has been made in terms of preservative-free formulations, biomaterials such as nanosystems and hydrogels, stem cell therapy, and creation of a bioengineered lacrimal gland. This review comprehensively summarizes the newer approaches to DED treatment, which are biomaterials such as nanosystems, hydrogels, and contact lenses for drug delivery, cell and tissue-based regenerative therapy for damaged lacrimal gland and ocular surface, and tissue engineering for developing artificial lacrimal gland. Also, their potential efficacies in animal models or in vitro studies and possible limitations are discussed. The ongoing research looks promising and needs to be supported with clinical efficacy and safety studies for human use

4D Printing for Vascular Tissue Engineering: Progress and Challenges

The hierarchical network of blood vessels comprises the larger vessels (veins and arteries), the smaller ones (venules and arterioles), and the thinnest capillaries. The proper functioning of most tissues in the body relies on vascularization, which is meant for the diffusion of gases, nutrients, and harmful waste. However, it is known that cell survival is compromised as the diffusion of oxygen is limited beyond 100–200 µm and damage can occur at any level of the complex system of the vascular network, as is the case in cardiovascular, musculoskeletal, and neurovascular diseases that recur and progress with age. These may prove fatal, hence the need for vascular tissue engineering (VTE) arises. VTE mainly focuses on the fabrication of vascular constructs using natural, synthetic material, or a combination of both using various techniques. The construct is expected to integrate and anastomose with the host vasculature. 4D bioprinting is an emerging field that allows the fabrication of hollow tubes employing different materials that respond to different stimuli. This review is a comprehensive summary of the major techniques employed in VTE and the recent technique of 4D bioprinting foreseen to revolutionize the field

Development of an in vitro 3D Printed Liver Sinusoid Model

Liver is one of the most remarkable organs of the human body as it performs various vital functions namely metabolism of fats and carbohydrates, drugs, detoxification, production of bile and has a capacity to regenerate. The intricate functional units of the liver called the sinusoids are of immense interest as they are early targets of many drugs and toxicants as well as have been reported to play a significant role in initiating liver regeneration and contribute to the pathophysiology of many liver diseases. Thus, understanding the functioning of these microvascular structures can be instrumental in providing us a multitude of information. Furthermore, as this area is targeted by many drugs and toxicants replicating the sinusoid in vitro can provide us with accurate drug testing devices as well as help in development of newer and more effective drugs. Here, we present a 3D printed liver sinusoidal model that contains a biomimetic liver decellularized extracellular matrix hydrogel to support the culture of hepatocytes. The prepared hydrogel has a potential to provide cells an environment similar to the native microenvironment of the sinusoids. The microarchitecture is mimicked by preparing a 3D printed scaffold emulating the native sinusoid to a certain extent. This is the first liver sinusoid model which has liver dECM gel to support the hepatocytes and thus has tremendous potential of becoming a device which can be used for drug testing as well as for studying the complex pathophysiology of life threatening liver diseases such as cirrhosis, fibrosis etc

Development of Invitro 3D Bronchi Model Using Novel Decellularized Smooth Muscle Matrix

Oxygen is the most important necessity for keeping us all alive. Lungs, in our body allows oxygen into our body. Any damage to this vital organ could be fatal. Incidences of tracheal and bronchial injuries are at a rise with increase in the number of road traffic accidents. Apart from traffic accidents, accidents that involve chest crashing, gun wounds, knife penetrations on chest area also damages the respiratory tract causing either blunt or penetrating injuries. Most of the injuries due to blunt trauma encompasses damage or rupture of trachea and mainstem bronchi. Not only injuries, several other conditions like tumors in the airway or congenital malformations like severe respiratory stenosis, bronchomalacia and bronchial atresia etc. also cause tracheobronchial damages. The theraupeutic approaches for all the cases are not well defined and may vary based on the site, extent of lesion and the severity of damage. There are problems associated with the traditional surgical approches and hence researchers are finding and developing new ways to overcome the complications and also to minimize the organ- demand and supply curve. In this thesis, we made an attempt to develop smooth muscle layer of the bronchi which is the part of the major project lab engineered bronchi which structurally and functionally mimics the native bronchi. Herein, we designed and fabricated a bioreactor using 3D printing technology and used this construct for development of smooth muscle layer of the bronchi model. To support the cells in the construct, we decellularized caprine smooth muscle and prepared its hydogel. Mesenchymal stem cells were embedded into the pre-gel and was incorporated into the printed bioreactor. In this process, we also tried to study the differentiation of MSC into smooth muscle cells in the decellularized smooth muscle matrix which stands as novelty in this project

Tissue-Specific Bioink from Xenogeneic Sources for 3D Bioprinting of Tissue Constructs

3D bioprinting brings new aspirations to the tissue engineering and regenerative medicine research community. However, despite its huge potential, its growth towards translation is severely impeded due to lack of suitable materials, technological barrier, and appropriate validation models. Recently, the use of decellularized extracellular matrices (dECM) from animal sources is gaining attention as printable bioink as it can provide a microenvironment close to the native tissue. Hence, it is worth exploring the use of xenogeneic dECM and its translation potential for human application. However, extensive studies on immunogenicity, safety-related issues, and animal welfare-related ethics are yet to be streamlined. In addition, the regulatory concerns need to be addressed with utmost priority in order to expedite the use of xenogeneic dECM bioink for 3D bioprinted implantable tissues for human welfare

Oxidative stress physiology in Scylla serrata for environmental health assessment

The oxidative stress (OS) condition and antioxidant level as a function of pH, few major elements, temperature, turbidity, organic carbon, sediment, and water salinity are vital to understanding the redox homeostasis of inhabiting animals. These parameters are also used to monitor environmental health. A spatiotemporal redox antioxidant system, followed by discriminant function analysis about the aforementioned abiotic factors, was investigated in the muscle, gill, and hepatopancreas of the mud crab, Scylla serrata, sampled from the Indian coastal belt along the Bay of Bengal (Tamil Nadu and Odisha) and the Arabian Sea (Gujarat) as a measure of environmental health assessment. Results revealed that the redox homeostasis of mud crabs significantly varied with seasonal fluctuations of abiotic factors and sediment chemistry. The level of superoxide dismutase and the non-protein-SH group were negatively correlated, whereas other antioxidant molecules with lipid peroxidation levels were positively correlated with abiotic factors. Only the activities of glutathione peroxidase and glutathione reductase were strongly correlated with all the abiotic factors. The hepatopancreas was found to be the most susceptible organ to OS. The lipid peroxidation level was 20–25 times higher in hepatopancreatic tissue than that in other tissues. The antioxidant level was elevated to 200% during the summer compared to the rainy season. Thus, the results of redox homeostasis in S. serrata may be useful for monitoring the ecotoxic effects of estuarine and marine environments and managing the inhabiting species

3D Bioprinting of Multi-Material Decellularized Liver Matrix Hydrogel at Physiological Temperatures

Bioprinting is an acclaimed technique that allows the scaling of 3D architectures in an organized pattern but suffers from a scarcity of appropriate bioinks. Decellularized extracellular matrix (dECM) from xenogeneic species has garnered support as a biomaterial to promote tissue-specific regeneration and repair. The prospect of developing dECM-based 3D artificial tissue is impeded by its inherent low mechanical properties. In recent years, 3D bioprinting of dECM-based bioinks modified with additional scaffolds has advanced the development of load-bearing constructs. However, previous attempts using dECM were limited to low-temperature bioprinting, which is not favorable for a longer print duration with cells. Here, we report the development of a multi-material decellularized liver matrix (dLM) bioink reinforced with gelatin and polyethylene glycol to improve rheology, extrudability, and mechanical stability. This shear-thinning bioink facilitated extrusion-based bioprinting at 37 °C with HepG2 cells into a 3D grid structure with a further enhancement for long-term applications by enzymatic crosslinking with mushroom tyrosinase. The heavily crosslinked structure showed a 16-fold increase in viscosity (2.73 Pa s−1) and a 32-fold increase in storage modulus from the non-crosslinked dLM while retaining high cell viability (85–93%) and liver-specific functions. Our results show that the cytocompatible crosslinking of dLM bioink at physiological temperatures has promising applications for extended 3D-printing procedures. © 2022 by the authors

Recent Advancements in Molecular Therapeutics for Corneal Scar Treatment

The process of corneal wound healing is complex and induces scar formation. Corneal scarring is a leading cause of blindness worldwide. The fibrotic healing of a major ocular wound disrupts the highly organized fibrillar collagen arrangement of the corneal stroma, rendering it opaque. The process of regaining this organized extracellular matrix (ECM) arrangement of the stromal layer to restore corneal transparency is complicated. The surface retention capacity of ocular drugs is poor, and there is a large gap between suitable corneal donors and clinical requirements. Therefore, a more efficient way of treating corneal scarring is needed. The eight major classes of interventions targeted as therapeutic tools for healing scarred corneas include those based on exosomes, targeted gene therapy, microRNAs, recombinant viral vectors, histone deacetylase inhibitors, bioactive molecules, growth factors, and nanotechnology. This review highlights the recent advancements in molecular therapeutics to restore a cornea without scarring. It also provides a scope to overcome the limitations of present studies and perform robust clinical research using these strategies. © 2022 by the authors

Indirect 3D Bioprinting of a Robust Trilobular Hepatic Construct with Decellularized Liver Matrix Hydrogel

The liver exhibits complex geometrical morphologies of hepatic cells arranged in a hexagonal lobule with an extracellular matrix (ECM) organized in a specific pattern on a multi-scale level. Previous studies have utilized 3D bioprinting and microfluidic perfusion systems with various biomaterials to develop lobule-like constructs. However, they all lack anatomical relevance with weak control over the size and shape of the fabricated structures. Moreover, most biomaterials lack liver-specific ECM components partially or entirely, which might limit their biomimetic mechanical properties and biological functions. Here, we report 3D bioprinting of a sacrificial PVA framework to impart its trilobular hepatic structure to the decellularized liver extracellular matrix (dLM) hydrogel with polyethylene glycol-based crosslinker and tyrosinase to fabricate a robust multi-scale 3D liver construct. The 3D trilobular construct exhibits higher crosslinking, viscosity (182.7 ± 1.6 Pa·s), and storage modulus (2554 ± 82.1 Pa) than non-crosslinked dLM. The co-culture of HepG2 liver cells and NIH 3T3 fibroblast cells exhibited the influence of fibroblasts on liver-specific activity over time (7 days) to show higher viability (90–91.5%), albumin secretion, and increasing activity of four liver-specific genes as compared to the HepG2 monoculture. This technique offers high lumen patency for the perfusion of media to fabricate a densely populated scaled-up liver model, which can also be extended to other tissue types with different biomaterials and multiple cells to support the creation of a large functional complex tissue. © 2022 by the authors

Recent advances in additive manufacturing of patient-specific devices for dental and maxillofacial rehabilitation

ObjectivesCustomization and the production of patient-specific devices, tailoring the unique anatomy of each patient's jaw and facial structures, are the new frontiers in dentistry and maxillofacial surgery. As a technological advancement, additive manufacturing has been applied to produce customized objects based on 3D computerized models. Therefore, this paper presents advances in additive manufacturing strategies for patient-specific devices in diverse dental specialties.MethodsThis paper overviews current 3D printing techniques to fabricate dental and maxillofacial devices. Then, the most recent literature (2018–2023) available in scientific databases reporting advances in 3D-printed patient-specific devices for dental and maxillofacial applications is critically discussed, focusing on the major outcomes, material-related details, and potential clinical advantages.ResultsThe recent application of 3D-printed customized devices in oral prosthodontics, implantology and maxillofacial surgery, periodontics, orthodontics, and endodontics are presented. Moreover, the potential application of 4D printing as an advanced manufacturing technology and the challenges and future perspectives for additive manufacturing in the dental and maxillofacial area are reported.SignificanceAdditive manufacturing techniques have been designed to benefit several areas of dentistry, and the technologies, materials, and devices continue to be optimized. Image-based and accurately printed patient-specific devices to replace, repair, and regenerate dental and maxillofacial structures hold significant potential to maximize the standard of care in dentistry