Biomimetic Polyphosphate Materials: Toward Application in Regenerative Medicine.

Global Challenges in Stem Cell Research and the Many Roads Ahead

PurposeOrganoids are three-dimensional cultures of stem cells in an environment similar to the body’s extracellular matrix. This is also a novel development in the realm of regenerative medicine. Stem cells can begin to develop into 3D structures by modifying signaling pathways. To form organoids, stem cells are transplanted into the extracellular matrix. Organoids have provided the required technologies to reproduce human tissues. As a result, it might be used in place of animal models in scientific study. The key goals of these investigations are research into viral and genetic illnesses, malignancies, and extracellular vesicles, pharmaceutical discovery, and organ transplantation. Organoids can help pave the road for precision medicine through genetic editing, pharmaceutical development, and cell therapy.MethodsPubMed, Google Scholar, and Scopus were used to search for all relevant papers written in English (1907–2021). The study abstracts were scrutinized. Studies on the use of stem-cell-derived organoids in regenerative medicine, organoids as 3D culture models for EVs analysis, and organoids for precision medicine were included. Articles with other irrelevant aims, meetings, letters, commentaries, congress and conference abstracts, and articles with no available full texts were excluded.ResultsAccording to the included studies, organoids have various origins, types, and applications in regenerative and precision medicine, as well as an important role in studying extracellular vesicles.ConclusionOrganoids are considered a bridge that connects preclinical studies to clinical ones. However, the lack of a standardized protocol and other barriers addressed in this review, hinder the vast use of this technology.Lay SummaryOrganoids are 3D stem cell propagations in biological or synthetic scaffolds that mimic ECM to allow intercellular or matrix-cellular crosstalk. Because these structures are similar to organs in the body, they can be used as research models. Organoids are medicine’s future hope for organ transplantation, tumor biobank formation, and the development of precision medicine. Organoid models can be used to study cell-to-cell interactions as well as effective factors like inflammation and aging. Bioengineering technologies are also used to define the size, shape, and composition of organoids before transforming them into precise structures. Finally, the importance of organoid applications in regenerative medicine has opened a new window for a better understanding of biological research, as discussed in this study.

Lentivirus Immobilization to Nanoparticles for Enhanced and Localized Delivery From Hydrogels

Chapter 4 - Biomimetic routes to micro/nanofabrication: Morphogenetically active high-energy inorganic polyphosphate nano/microparticles

Exosomes and exosome-loaded scaffolds: Characterization and application in modern regenerative medicine

Dental pulp stem cells (DPSCs) are a promising source of cells for numerous and varied regenerative medicine applications. Their natural function in the production of odontoblasts to create reparative dentin support applications in dentistry in the regeneration of tooth structures. However, they are also being investigated for the repair of tissues outside of the tooth. The ease of isolation of DPSCs from discarded or removed teeth offers a promising source of autologous cells, and their similarities with bone marrow stromal cells (BMSCs) suggest applications in musculoskeletal regenerative medicine. DPSCs are derived from the neural crest and, therefore, have a different developmental origin to BMSCs. These differences from BMSCs in origin and phenotype are being exploited in neurological and other applications. This review briefly highlights the source and functions of DPSCs and then focuses on in vivo applications across the breadth of regenerative medicine.

Recent advances in stem cell technologies have enabled the application of three-dimensional neural organoids for exploring the mechanisms of neurodevelopment and regenerative medicine. Over the past decade, series of studies have been carried out to investigate the cellular and molecular events of human neurogenesis using animal models, while the species differences between animal models and human being prevent a full understanding of human neurogenesis. Human neural organoids provide a new model system for gaining a more complete understanding of human neural development and their applications in regenerative medicine. In this chapter, the recent advances of the neural organoids of the brain and retina as well as their applications in neurodevelopment and regenerative medicine are reviewed.

Mesenchymal stem cells (MSCs) have been widely used in the fields of tissue engineering and regenerative medicine due to their self-renewal capabilities and multipotential differentiation assurance. However, capitalizing on specific factors to precisely guide MSC behaviors is the cornerstone of biomedical applications. Fortunately, several key biophysical and biochemical cues of biomaterials that can synergistically regulate cell behavior have paved the way for the development of cell-instructive biomaterials that serve as delivery vehicles for promoting MSC application prospects. Therefore, the identification of these cues in guiding MSC behavior, including cell migration, proliferation, and differentiation, may be of particular importance for better clinical performance. This review focuses on providing a comprehensive and systematic understanding of biophysical and biochemical cues, as well as the strategic engineering of these signals in current scaffold designs, and we believe that integrating biophysical and biochemical cues in next-generation biomaterials would potentially help functionally regulate MSCs for diverse applications in regenerative medicine and cell therapy in the future.

Raw materials, such as collagen and chitosan, obtained from by-products from the food industry (beef hides and crustacean exoskeletons), can be used to obtain collagen–chitosan composite biomaterials, with potential applications in regenerative medicine. Functionalization of these composite biomaterials is a possibility, thus, resulting in a molecule with potential applications in regenerative medicine, namely clotrimazole (a molecule with antibacterial, antifungal, and antitumor activity), at a mass ratio (collagen–chitosan–clotrimazole) of 1:1:0.1. This functionalized composite biomaterial has great potential for application in regenerative medicine, due to the following properties: (1) it is porous, and the pores formed are interconnected, due to the use of a mass ratio between collagen and chitosan of 1:1; (2) the size of the formed pores is between 500–50 μm; (3) between collagen and chitosan, hydrogen bonds are formed, which ensure the unity of composite biomaterial; (4) the functionalized bio-composite exhibits in vitro antimicrobial activity for Candida albicans, Staphylococcus aureus, and Staphylococcus aureus MRSA; for the latter microorganism, the antimicrobial activity is equivalent to that of the antibiotic Minocycline; (5) the proliferation tests performed on a standardized line of normal human cells with simple or composite materials obtained by lyophilization do not show cytotoxicity in the concentration range studied (10–500) μg/mL.

In this talk, I will discuss two applications of biomedical fluid mechanics in urology and regenerative medicine, and present new theoretical models developed alongside complementary experimental approaches. Throughout the talk, I will highlight how the derivation and exploitation of reduced models that retain the essential physics, while remaining tractable, can provide mechanistic insights into these biomedical fluid flows, and discuss how the resulting insights can be exploited to drive new healthcare innovations. The first application will show how a detailed understanding of the fluid mechanics associated with medical devices used to treat kidney stones can be exploited to guide innovations in device operation and design with enhanced mass transport properties. The second application in regenerative medicine considers the complex interplay of cells, biomaterials, and bioreactors and microfluidic systems required for tissue growth, repair and regeneration. I will show how insights into the wealth of fluid mechanics challenges encountered in regenerative medicine, including fluid-structure interactions, reactive multiphase flows, and advective transport, can guide the development of new regenerative medicine therapies and protocols.

Decellularized extracellular matrix hydrogel (dECM-G) has demonstrated its significant tissue-specificity, high biocompatibility, and versatile utilities in tissue engineering. However, the low mechanical stability and fast degradation are major drawbacks for its application in three-dimensional (3D) printing. Herein, we report a hybrid hydrogel system consisting of dECM-Gs and photocrosslinkable gelatin methacrylate (GelMA), which resulted in significantly improved printability and structural fidelity. These premixed hydrogels retained high bioactivity and tissue-specificity due to their containing dECM-Gs. More specifically, it was realized that the hydrogel containing dECM-G derived from porcine peripheral nerves (GelMA/pDNM-G) effectively facilitated neurite growth and Schwann cell migration from two-dimensional cultured dorsal root ganglion explants. The nerve cells were also encapsulated in the GelMA/pDNM-G hydrogel for 3D culture or underwent cell-laden bioprinting with high cell viability. The preparation of such GelMA/dECM-G hydrogels enabled the recapitulation of functional tissues through extrusion-based bioprinting, which holds great potential for applications in regenerative medicine. Impact statement Tissue-derived decellularized matrices have drawn broad interests for their versatile applications in tissue engineering and regenerative medicine, especially the decellularized peripheral nerve matrix, which can effectively facilitate axonal extension, remyelination, and neural functional restoration after peripheral nerve injury. However, neither decellularized porcine nerve matrix (pDNM) nor pDNM hydrogel (pDNM-G) can be directly used in three-dimensional printing for personalized nerve constructs or cell transplantation. This work developed a hybrid hydrogel consisting of decellularized extracellular matrix hydrogel (dECM-G) and photocrosslinkable gelatin methacrylate (GelMA), which resulted in significantly improved printability and structural fidelity. The GelMA/pDNM-G hydrogel retained high bioactivity and tissue-specificity due to its dECM-G content. Such hybrid hydrogel systems built up a springboard in advanced biomaterials for neural tissue engineering, as well as a promising strategy for dECM containing bioprinting.

Bioengineered gastrointestinal (GI) tracts have potential applications in regenerative medicine and disease modeling. Methods for engineering tubular GI tracts containing natural extracellular matrix (ECM) are currently limited. Here, the fabrication of collagen tubes with designed shapes by using lipid bilayer supported droplet networks is reported. Droplets containing cells and collagen are arrayed in lipid‐containing oil to form droplet networks, which undergo thermal gelation to provide continuous collagen tubes. A variety of tubular GI tissues are fabricated. For example, human intestinal organoids embedded in the collagen tubes migrate to the luminal surfaces and fuse to form a continuous epithelial layer, mimicking aspects of intestinal tissue structure. Fibroblasts embedded in the collagen induce a cell density dependent contraction of the tubes. Complex tubular structures are produced by patterning droplets containing different densities of fibroblasts. The fibroblast‐containing collagen tubes are seeded with various epithelial cells at their luminal surfaces to form gastric and colonic tissues, which comprise monolayers or multilayers of epithelial cells and fibroblast‐containing subepithelial layers. The engineered gastric tissues are susceptible to infection with Helicobacter pylori. The versatile technique allows the construction of tubular GI tracts containing ECM and layered structures, with broad potential applications in disease research and regenerative medicine.

Exosomes are membrane‐bound nanovesicles containing complex cargoes including proteins, lipids, and nucleic acids (mRNAs and microRNAs), which can be derived from most cells. Increasing evidence has implicated exosomes as key players in intercellular and even interorganismal communications. Exosomes confer stability and can direct their cargoes to specific cell types for promoting cell growth and tissue regeneration. Exosome cargoes also appear to act in a combinatorial manner to communicate directives to other cells. This Review focuses on recent developments and findings of exosomes applied towards applications in tissue engineering and regenerative medicine, including healing of the skin, cardiovascular, skeletal, nervous, and visceral systems. The underlying mechanisms of action of exosomes in tissue regeneration are also discussed. In addition, we highlight examples whereby exosomes have been integrated with hydrogels for biofabrication and other related biomedical utilities such as drug delivery.

In view of the very expensive modern healthcare system, sudden loss or failure of organs and tissues could pose a very difficult and costly medical problem to patients. Further, the limited supply of organs globally that a patient can afford for replacement in the event of an organ failure makes the problem even more challenging and complicated. These medical and healthcare challenges have triggered research and developments into tissue engineering to advance the field of regenerative medicine. Especially, the research focus has been on the design, development and optimization of a cell-scaffold-microenvironment to promote the regeneration of various types of tissue including skin, cartilage, bone, tendon and cardiac tissue, to name a few. Studies have been undertaken to produce functional three-dimensional (3D) tissue substitutes or constructs that are based on bio scaffolds from the ground up. To this end, bioprinting strategies have been considered for fabrication of complex 3D functional living tissues or artificial organs. Here, we describe some notable advances in laser bioprinting enabled tissue engineering, which is a rapidly emerging field in 3D bio fabrication technology for applications in regenerative medicine.

Endometrial organoids (EOs) have gained attention as a promising in vitro model for investigating uterine physiology, reproductive disorders, and embryo-maternal interactions, providing an alternative to in vivo studies while minimizing ethical concerns. Despite their increasing use across species, a well-characterized rat EO model is limited. We established and validated a rat EO platform that recapitulates the structural and functional characteristics of the native endometrium. We established and validated a rat EO platform that recapitulates the structural and functional characteristics of the native endometrium. Organoids were generated from epithelial-rich stem-cell populations isolated from adult female rats and cultured in 3D Matrigel. EO formation efficiency was assessed in relation to plasma progesterone concentration, and organoids were evaluated for long-term viability, cryopreservation tolerance, and morphological consistency over serial passages. Functional relevance was examined by real-time polymerase chain reaction and RNA sequencing of sex steroid hormone receptors (progesterone receptor and estrogen receptor α) and CD34. GFP (Green Fluorescent Protein)-labeled EOs were transplanted into the uterine lumen of wild-type rats to evaluate engraftment and persistence. Rat EOs displayed morphological and molecular characteristics comparable to native uterine tissue, maintaining viability and integrity over multiple passages and after cryopreservation. Immunohistochemical analyses using epithelial (E-cadherin), stromal (Vimentin), and proliferative (Ki-67) markers confirmed the presence of multiple cell types resembling those in native uterine tissue. Formation efficiency positively correlated with circulating progesterone concentrations. Gene expression confirmed key endometrial markers, including hormone receptors and stromal-associated genes. GFP-expressing EOs successfully engrafted into wild-type uterine lumens and persisted long term, demonstrating functional and structural compatibility with the in vivo uterine environment. The rat EO model developed here provides a physiologically relevant platform for studying endometrial biology, enabling research on reproductive mechanisms and disease modeling. Its ability to mimic and engraft in the uterine environment suggests applications in regenerative medicine and therapeutic transplantation. This rat EO model provides a physiologically relevant platform for studying uterine biology and reproductive mechanisms without extensive animal use. Its ability to mimic and engraft in the uterine environment supports potential applications in disease modeling, drug testing, and regenerative medicine.