Tissue engineering and 3D printing of bioartificial pancreas for regenerative medicine in diabetes

3D printing and bioprinting in the battle against diabetes and its chronic complications

Diabetes is a metabolic disorder characterized by high blood sugar. Uncontrolled blood glucose affects the circulatory system in an organism by intervening blood circulation. The high blood glucose can lead to macrovascular (large blood vessels) and microvascular (small blood vessels) complications. Due to this, the vital organs (notably brain, eyes, feet, heart, kidneys, lungs and nerves) get worsen in diabetic patients if not treated at the earliest. Therefore, acquiring treatment at an appropriate time is very important for managing diabetes and other complications that are caused due to diabetes. The root cause for the occurrence of various health complications in diabetic patients is the uncontrolled blood glucose levels. This review presents a consolidated account of the applications of various types of three-dimensional (3D) printing and bioprinting technologies in treating diabetes as well as the complications caused due to impaired blood glucose levels. Herein, the development of biosensors (for the diagnosis), oral drug formulations, transdermal drug carriers, orthotic insoles and scaffolds (for the treatment) are discussed. Next to this, the fabrication of 3D bioprinted organs and cell-seeded hydrogels (pancreas engineering for producing insulin and bone engineering for managing bone defects) are explained. As the final application, 3D bioprinting of diabetic disease models for high-throughput screening of ant-diabetic drugs are discussed. Lastly, the challenges and future perspective associated with the use of 3D printing and bioprinting technologies against diabetes and its related chronic complications have been put forward.

Innovations in bio-engineering and cell-based approaches to address immunological challenges in islet transplantation

Human allogeneic pancreatic islet transplantation is a life-changing treatment for patients with severe Type 1 Diabetes (T1D) who suffer from hypoglycemia unawareness and high risk of severe hypoglycemia. However, intensive immunosuppression is required to prevent immune rejection of the graft, that may in turn lead to undesirable side effects such as toxicity to the islet cells, kidney toxicity, occurrence of opportunistic infections, and malignancies. The shortage of cadaveric human islet donors further limits islet transplantation as a treatment option for widespread adoption. Alternatively, porcine islets have been considered as another source of insulin-secreting cells for transplantation in T1D patients, though xeno-transplants raise concerns over the risk of endogenous retrovirus transmission and immunological incompatibility. As a result, technological advancements have been made to protect transplanted islets from immune rejection and inflammation, ideally in the absence of chronic immunosuppression, to improve the outcomes and accessibility of allogeneic islet cell replacement therapies. These include the use of microencapsulation or macroencapsulation devices designed to provide an immunoprotective environment using a cell-impermeable layer, preventing immune cell attack of the transplanted cells. Other up and coming advancements are based on the use of stem cells as the starting source material for generating islet cells 'on-demand'. These starting stem cell sources include human induced pluripotent stem cells (hiPSCs) that have been genetically engineered to avoid the host immune response, curated HLA-selected donor hiPSCs that can be matched with recipients within a given population, and multipotent stem cells with natural immune privilege properties. These strategies are developed to provide an immune-evasive cell resource for allogeneic cell therapy. This review will summarize the immunological challenges facing islet transplantation and highlight recent bio-engineering and cell-based approaches aimed at avoiding immune rejection, to improve the accessibility of islet cell therapy and enhance treatment outcomes. Better understanding of the different approaches and their limitations can guide future research endeavors towards developing more comprehensive and targeted strategies for creating a more tolerogenic microenvironment, and improve the effectiveness and sustainability of islet transplantation to benefit more patients.

Advances in secondary prevention mechanisms of macrovascular complications in type 2 diabetes mellitus patients: a comprehensive review

Type 2 diabetes mellitus (T2DM) poses a significant global health burden. This is particularly due to its macrovascular complications, such as coronary artery disease, peripheral vascular disease, and cerebrovascular disease, which have emerged as leading contributors to morbidity and mortality. This review comprehensively explores the pathophysiological mechanisms underlying these complications, protective strategies, and both existing and emerging secondary preventive measures. Furthermore, we delve into the applications of experimental models and methodologies in foundational research while also highlighting current research limitations and future directions. Specifically, we focus on the literature published post-2020 concerning the secondary prevention of macrovascular complications in patients with T2DM by conducting a targeted review of studies supported by robust evidence to offer a holistic perspective.

Toward a 3D Printed Perfusable Islet Embedding Structure: Technical Notes and Preliminary Results

To date, islet transplantation to treat type 1 diabetes mellitus remains unsuccessful in long-term follow-up, mainly due to failed engraftment and reconstruction of the islet niche. Alternative approaches, such as islet embedding structures (IESs) based on 3D printing have been developed. However, most of them have been implanted subcutaneously and only a few are intended for direct integration into the vascular system through anastomosis. In this study, we 3D printed a proof-of-concept IES using gelatin methacrylate biocompatible ink. This structure consisted of a branched vascular system surrounding both sides of a central cavity dedicated to islets of Langerhans. Furthermore, we designed a bioreactor optimized for these biological structures. This bioreactor allows seeding and perfusion experiments under sterile and physiological conditions. Preliminary experiments aimed to analyze if the vascular channel could successfully be seeded with mature endothelial cells and the central cavity with rat islets. Subsequently, the structures were used for a humanized model seeding human endothelial progenitor cells (huEPC) within the vascular architecture and human islets co-cultured with huEPC within the central cavity. The constructs were tested for hemocompatibility, suture strength, and anastomosability. The 3D printed IES appeared to be hemocompatible and anastomosable using an alternative cuff anastomosis in a simple ex vivo perfusion model. While rat islets alone could not successfully be embedded within the 3D printed structure for 3 days, human islets co-cultivated with huEPC successfully engrafted within the same time. This result emphasizes the importance of co-culture, nursing cells, and islet niche. In conclusion, we constructed a proof-of-concept 3D printed islet embedding device consisting of a vascular channel that is hemocompatible and perspectively anastomosable to clinical scale blood vessels. However, there are numerous limitations in this model that need to be overcome to transfer this technology to the bedside.

Recent trends of 3D printing based on starch-hydrocolloid in food, biomedicine and environment

People are exploring the potential application of 3D printing in food, biomedicine and environment, but it is urgent to find suitable bio-ink. Bio-ink compounded with starch and hydrocolloid can not only improve the rheology, structure and printability of starch-based edible bio-ink, but also endow it with other functional characteristics, so that it can be applied to food, biomedicine and even the environment, and meet the strategic needs of national health, green and sustainable development. In this paper, hydrocolloids are reviewed as potential means to regulate the physicochemical properties of starch, which endows it with good printability and presents excellent printing products. The specific applications of the bio-ink in the fields of food, biomedicine and environment in hypoglycemic, lipid-lowering, swallowable food, delivery, intelligent materials, and bio-sensor are also discussed. Then, the challenges and future development trends of realizing large-scale application are prospected. Proper physicochemical properties of starch-hydrocolloid are positively correlated with printability. The presentation of excellent printability has realized the application in different fields, not only satisfies most people, but also create benefits for some specific people. This review is expected to provide some theoretical guidance for the further development of 3D printing technology and its large-scale application.

Recent Advances in Decellularized Extracellular Matrix-Based Bioinks for 3D Bioprinting in Tissue Engineering

In recent years, three-dimensional (3D) bioprinting has been widely utilized as a novel manufacturing technique by more and more researchers to construct various tissue substitutes with complex architectures and geometries. Different biomaterials, including natural and synthetic materials, have been manufactured into bioinks for tissue regeneration using 3D bioprinting. Among the natural biomaterials derived from various natural tissues or organs, the decellularized extracellular matrix (dECM) has a complex internal structure and a variety of bioactive factors that provide mechanistic, biophysical, and biochemical signals for tissue regeneration and remodeling. In recent years, more and more researchers have been developing the dECM as a novel bioink for the construction of tissue substitutes. Compared with other bioinks, the various ECM components in dECM-based bioink can regulate cellular functions, modulate the tissue regeneration process, and adjust tissue remodeling. Therefore, we conducted this review to discuss the current status of and perspectives on dECM-based bioinks for bioprinting in tissue engineering. In addition, the various bioprinting techniques and decellularization methods were also discussed in this study.

Microneedle Patches Loaded with Nanovesicles for Glucose Transporter-Mediated Insulin Delivery

Glucose-responsive insulin delivery systems that mimic insulin secretion activity in the pancreas show great potential to improve clinical therapeutic outcomes for people with type 1 and advanced type 2 diabetes. Here, we report a glucose-responsive insulin delivery microneedle (MN) array patch that is loaded with red blood cell (RBC) vesicles or liposome nanoparticles containing glucose transporters (GLUTs) bound with glucosamine-modified insulin (Glu-Insulin). In hyperglycemic conditions, high concentrations of glucose in interstitial fluid can replace Glu-Insulin via a competitive interaction with GLUT, leading to a quick release of Glu-Insulin and subsequent regulation of blood glucose (BG) levels in vivo. To prolong the effective glucose-responsive insulin release from MNs, additional free Glu-Insulin, which serves as "stored insulin", is loaded after RBC vesicles or liposome nanoparticles bound with Glu-Insulin. In the streptozotocin (STZ)-induced type 1 diabetic mouse model, this smart GLUT-based insulin patch can effectively control BG levels without causing hypoglycemia.

Regenerative medicine technologies applied to transplant medicine. An update

Regenerative medicine (RM) is changing how we think and practice transplant medicine. In regenerative medicine, the aim is to develop and employ methods to regenerate, restore or replace damaged/diseased tissues or organs. Regenerative medicine investigates using tools such as novel technologies or techniques, extracellular vesicles, cell-based therapies, and tissue-engineered constructs to design effective patient-specific treatments. This review illustrates current advancements in regenerative medicine that may pertain to transplant medicine. We highlight progress made and various tools designed and employed specifically for each tissue or organ, such as the kidney, heart, liver, lung, vasculature, gastrointestinal tract, and pancreas. By combing both fields of transplant and regenerative medicine, we can harbor a successful collaboration that would be beneficial and efficacious for the repair and design of de novo engineered whole organs for transplantations.

Pierre Robin Sequence and 3D Printed Personalized Composite Appliances in Interdisciplinary Approach

This paper introduces a complex novel concept and methodology for the creation of personalized biomedical appliances 3D-printed from certified biocompatible photopolymer resin Dental LT Clear (V2). The explained workflow includes intraoral and CT scanning, patient virtualization, digital appliance design, additive manufacturing, and clinical application with evaluation of the appliance intended for patients with cranio-facial syndromes. The presented concept defines virtual 3D fusion of intraoral optical scan and segmented CT as sufficient and accurate data defining the 3D surface of the face, intraoral and airway morphology necessary for the 3D design of complex personalized intraoral and extraoral parts of the orthopedic appliance. A central aspect of the concept is a feasible utilization of composite resin for biomedical prototyping of the sequence of marginally different appliances necessary to keep the pace with the patient rapid growth. Affordability, noninvasiveness, and practicality of the appliance update process shall be highlighted. The methodology is demonstrated on a particular case of two-year-old infant with Pierre Robin sequence. Materialization by additive manufacturing of this photopolymer provides a highly durable and resistant-to-fracture two-part appliance similar to a Tübingen palatal plate, for example. The paper concludes with the viability of the described method and material upon interdisciplinary clinical evaluation of experts from departments of orthodontics and cleft anomalies, pediatric pneumology and phthisiology, and pediatric otorhinolaryngology.

Hyaluronic acid methacrylate/pancreatic extracellular matrix as a potential 3D printing bioink for constructing islet organoids

Islet transplantation has poor long-term efficacy because of the lack of extracellular matrix support and neovascularization; this limits its wide application in diabetes research. In this study, we develop a 3D-printed islet organoid by combining a pancreatic extracellular matrix (pECM) and hyaluronic acid methacrylate (HAMA) as specific bioinks. The HAMA/pECM hydrogel was validated in vitro to maintain islet cell adhesion and morphology through the Rac1/ROCK/MLCK signaling pathway, which helps improve islet function and activity. Further, in vivo experiments confirmed that the 3D-printed islet-encapsulated HAMA/pECM hydrogel increases insulin levels in diabetic mice, maintains blood glucose levels within a normal range for 90 days, and rapidly secretes insulin in response to blood glucose stimulation. In addition, the HAMA/pECM hydrogel can facilitate the attachment and growth of new blood vessels and increase the density of new vessels. Meanwhile, the designed 3D-printed structure was conducive to the formation of vascular networks and it promoted the construction of 3D-printed islet organoids. In conclusion, our experiments optimized the HAMA/pECM bioink composition and 3D-printed structure of islet organoids with promising therapeutic effects compared with the HAMA hydrogel group that can be potentially used in clinical applications to improve the effectiveness and safety of islet transplantation in vivo. STATEMENT OF SIGNIFICANCE: The extraction process of pancreatic islets can easily cause damage to the extracellular matrix and vascular system, resulting in poor islet transplantation efficiency. We developed a new tissue-specific bioink by combining pancreatic extracellular matrix (pECM) and hyaluronic acid methacrylate (HAMA). The islet organoids constructed by 3D printing can mimic the microenvironment of the pancreas and maintain islet cell adhesion and morphology through the Rac1/ROCK/MLCK signaling pathway, thereby improving islet function and activity. In addition, the 3D-printed structures we designed are favorable for the formation of new blood vessel networks, bringing hope for the long-term efficacy of islet transplantation.

Engineering Islets From Stem Cells: The Optimal Solution for the Treatment of Diabetes?

Diabetes is a metabolic disease characterized by insulin deficiency. Bioengineering of stem cells with the aim to restore insulin production and glucose regulation has the potential to cure diabetic patients. In this review, we focus on the recent developments for bioengineering of induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and pancreatic progenitor cells in view of generating insulin producing and glucose regulating cells for β-cell replacement therapies. Recent clinical trials using islet cells derived from stem cells have been initiated for the transplantation into diabetic patients, with crucial bottlenecks of tumorigenesis, post-transplant survival, genetic instability, and immunogenicity that should be further optimized. As a new approach given high expectations, bioengineered islets from stem cells occupies considerable potential for the future clinical application and addressing the treatment dilemma of diabetes.