Deconstructing, Replicating, and Engineering Tissue Microenvironment for Stem Cell Differentiation

Temporal control in shell-core structured nanofilm for tracheal cartilage regeneration: synergistic optimization of anti-inflammation and chondrogenesis

Cartilage tissue engineering offers hope for tracheal cartilage defect repair. Establishing an anti-inflammatory microenvironment stands as a prerequisite for successful tracheal cartilage restoration, especially in immunocompetent animals. Hence, scaffolds inducing an anti-inflammatory response before chondrogenesis are crucial for effectively addressing tracheal cartilage defects. Herein, we develop a shell-core structured PLGA@ICA-GT@KGN nanofilm using poly(lactic-co-glycolic acid) (PLGA) and icariin (ICA, an anti-inflammatory drug) as the shell layer and gelatin (GT) and kartogenin (KGN, a chondrogenic factor) as the core via coaxial electrospinning technology. The resultant PLGA@ICA-GT@KGN nanofilm exhibited a characteristic fibrous structure and demonstrated high biocompatibility. Notably, it showcased sustained release characteristics, releasing ICA within the initial 0 to 15 days and gradually releasing KGN between 11 and 29 days. Subsequent in vitro analysis revealed the potent anti-inflammatory capabilities of the released ICA from the shell layer, while the KGN released from the core layer effectively induced chondrogenic differentiation of bone marrow stem cells (BMSCs). Following this, the synthesized PLGA@ICA-GT@KGN nanofilms were loaded with BMSCs and stacked layer by layer, adhering to a 'sandwich model' to form a composite sandwich construct. This construct was then utilized to repair circular tracheal defects in a rabbit model. The sequential release of ICA and KGN facilitated by the PLGA@ICA-GT@KGN nanofilm established an anti-inflammatory microenvironment before initiating chondrogenic induction, leading to effective tracheal cartilage restoration. This study underscores the significance of shell-core structured nanofilms in temporally regulating anti-inflammation and chondrogenesis. This approach offers a novel perspective for addressing tracheal cartilage defects, potentially revolutionizing their treatment methodologies.

Engineered adult stem cells: Current clinical trials status of disease treatment

Regenerative medicine is an interdisciplinary field involving the process of replacing and regenerating cells/tissues or organs by integrating medicine, science, and engineering principles to enhance the intrinsic regenerative capacity of the host. Recently, engineered adult stem cells have gained attention for their potential use in regenerative medicine by reducing inflammation and modulating the immune system. This chapter introduces adult stem cell engineering and chimeric antigen receptor T cells (CAR T) gene therapy and summarises current engineered stem cell- and extracellular vesicles (EVs)-focused clinical trial studies that provide the basis for the proposal of a personalised medicine approach to diseases diagnosis and treatment.

Implantation with SHED sheet induced with homogenate protein of spinal cord promotes functional recovery from spinal cord injury in rats

Introduction: After spinal cord injury (SCI) occurs, the lesion is in a growth inhibitory microenvironment that severely hinders neural regeneration. In this microenvironment, inhibitory factors are predominant and factors that promote nerve regeneration are few. Improving neurotrophic factors in the microenvironment is the key to treating SCI.

Methods: Based on cell sheet technology, we designed a bioactive material with a spinal cord‐like structure –SHED sheet induced with homogenate protein of spinal cord (hp–SHED sheet). Hp–SHED sheet was implanted into the spinal cord lesion for treating SCI rats with SHED suspensions as a control to investigate the effects on nerve regeneration.

Results: Hp–SHED sheet revealed a highly porous three–dimensional inner structure, which facilitates nerve cell attachment and migration. Hp-SHED sheet in vivo restored sensory and motor functions in SCI rats by promoting nerve regeneration, axonal remyelination, and inhibiting glial scarring.

Discussion: Hp–SHED sheet maximally mimics the microenvironment of the natural spinal cord and facilitate cell survival and differentiation. Hp–SHED sheet could release more neurotrophins and the sustained action of neurotrophins improves the pathological microenvironment, which effectively promotes nerve regeneration, axonal extension, and inhibits glial scarring, thereby promoting the in situ centralis neuroplasticity. Hp–SHED sheet therapy is a promising strategy for effective treatment of SCI based on neurotrophins delivery.

Carboxymethyl Chitosan and Gelatin Hydrogel Scaffolds Incorporated with Conductive PEDOT Nanoparticles for Improved Neural Stem Cell Proliferation and Neuronal Differentiation

Tissue engineering scaffolds provide biological and physiochemical cures to guide tissue recovery, and electrical signals through the electroactive materials possess tremendous potential to modulate the cell fate. In this study, a novel electroactive hydrogel scaffold was fabricated by assembling poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles on a carboxymethyl chitosan/gelatin (CMCS/Gel) composite hydrogel surface via in situ chemical polymerization. The chemical structure, morphology, conductivity, porosity, swelling rate, in vitro biodegradation, and mechanical properties of the prepared hydrogel samples were characterized. The adhesion, proliferation, and differentiation of neural stem cells (NSCs) on conductive hydrogels were investigated. The CMCS/Gel-PEDOT hydrogels exhibited high porosity, excellent water absorption, improved thermal stability, and adequate biodegradability. Importantly, the mechanical properties of the prepared hydrogels were similar to those of brain tissue, with electrical conductivity up to (1.52 ± 0.15) × 10^-3 S/cm. Compared to the CMCS/Gel hydrogel, the incorporation of PEDOT nanoparticles significantly improved the adhesion of NSCs, and supported long-term cell growth and proliferation in a three-dimensional (3D) microenvironment. In addition, under the differentiation condition, the conductive hydrogel also significantly enhanced neuronal differentiation with the up-regulation of β-tubulin III expression. These results suggest that CMCS/Gel-PEDOT hydrogels may be an attractive conductive substrate for further studies on neural tissue repair and regeneration.

The Bumpy Road to Stem Cell Therapies: Rational Design of Surface Topographies to Dictate Stem Cell Mechanotransduction and Fate

Cells sense and respond to a variety of physical cues from their surrounding microenvironment, and these are interpreted through mechanotransductive processes to inform their behavior. These mechanisms have particular relevance to stem cells, where control of stem cell proliferation, potency, and differentiation is key to their successful application in regenerative medicine. It is increasingly recognized that surface micro- and nanotopographies influence stem cell behavior and may represent a powerful tool with which to direct the morphology and fate of stem cells. Current progress toward this goal has been driven by combined advances in fabrication technologies and cell biology. Here, the capacity to generate precisely defined micro- and nanoscale topographies has facilitated the studies that provide knowledge of the mechanotransducive processes that govern the cellular response as well as knowledge of the specific features that can drive cells toward a defined differentiation outcome. However, the path forward is not fully defined, and the "bumpy road" that lays ahead must be crossed before the full potential of these approaches can be fully exploited. This review focuses on the challenges and opportunities in applying micro- and nanotopographies to dictate stem cell fate for regenerative medicine. Here, key techniques used to produce topographic features are reviewed, such as photolithography, block copolymer lithography, electron beam lithography, nanoimprint lithography, soft lithography, scanning probe lithography, colloidal lithography, electrospinning, and surface roughening, alongside their advantages and disadvantages. The biological impacts of surface topographies are then discussed, including the current understanding of the mechanotransductive mechanisms by which these cues are interpreted by the cells, as well as the specific effects of surface topographies on cell differentiation and fate. Finally, considerations in translating these technologies and their future prospects are evaluated.

Microenvironment Influences on Human Umbilical Cord Mesenchymal Stem Cell-Based Bone Regeneration

The microenvironment, or niche, regulates stem cell fate and improves differentiation efficiency. Human umbilical cord mesenchymal stem cells (hUC-MSCs) are ideal cell source for bone tissue engineering. However, the role of the microenvironments in hUC-MSC-based bone regeneration is not yet fully understood. This study is aimed at investigating the effects of the in vitro culture microenvironment (hUC-MSCs, nano-hydroxyapatite/collagen/poly (L-lactide) (nHAC/PLA), osteogenic media (OMD), and recombinant human bone morphogenetic protein-7 (rhBMP-7)) and the in vivo transplanted microenvironment (ectopic and orthotopic) on bone regeneration ability of hUC-MSCs. The isolated hUC-MSCs showed self-renewal potential and MSCs' characteristics. In the in vitro two-dimensional culture microenvironment, OMD or OMD with rhBMP-7 significantly enhanced hUC-MSCs' osteocalcin immunofluorescence staining, alkaline phosphatase, and Alizarin red staining; OMD with rhBMP-7 exhibited the highest ALP secretion and mineralized matrix formation. In the in vitro three-dimensional culture microenvironment, nHAC/PLA supported hUC-MSCs' adhesion, proliferation, and differentiation; the microenvironment containing OMD or OMD and rhBMP-7 shortened cell proliferation progression and made osteogenic differentiation progression advance; rhBMP-7 significantly attenuated the inhibiting effect of OMD on hUC-MSCs' proliferation and significantly enhanced the promoting effect of OMD on gene expression and protein secretion of osteogenic differentiation markers, calcium and phosphorous concentration, and mineralized matrix formation. The in vitro three-dimensional culture microenvironment containing OMD and rhBMP-7 induced hUC-MSCs to form the most new bones in ectopic or orthotopic microenvironment as proved by microcomputed tomography and hematoxylin and eosin staining, but bone formation in orthotopic microenvironment was significantly higher than that in ectopic microenvironment. The results indicated that the combination of in vitro hUC-MSCs+nHAC/PLA+OMD+rhBMP-7 microenvironment and in vivo orthotopic microenvironment provided a more optimized niche for bone regeneration of hUC-MSCs. This study elucidates that hUC-MSCs and their local microenvironment, or niche, play an important role in hUC-MSC-based bone regeneration. The endogenously produced BMP may serve an important regulatory role in the process.

Effect of tissue microenvironment on fibrous capsule formation to biomaterial-coated implants

Within tissue exposed to the systemic immune system, lymphocytes and fibroblasts act against biomaterials via the development of a fibrous capsule, known as the foreign body reaction (FBR). Inspired by the natural tolerance that the uterine cavity has to foreign bodies, our study explores the role of microenvironment across classical (subcutaneous) and immune privileged (uterine) tissues in the development of the FBR. As a model biomaterial, we used electrospun fibers loaded with sclerosing agents to provoke scar tissue growth. Additionally, we integrated these materials onto an intrauterine device as a platform for intrauterine biomaterial studies. Polyester materials in vitro achieved drug release up to 10 days, greater pro-inflammatory and pro-healing cytokine expression, and the addition of gelatin enabled greater fibroblast attachment. We observed the materials that induced the greatest FBR in the mouse, had no effect when inserted at the utero-tubal junction of non-human primates. These results suggest that the FBR varies across different tissue microenvironments, and a dampened fibrotic response exists in the uterine cavity, possibly due to immune privilege. Further study of immune privileged tissue factors on biomaterials could broaden our understanding of the FBR and inform new methods for achieving biocompatibility in vivo.

Advances in 3D bioprinting technology for cardiac tissue engineering and regeneration

Cardiovascular disease is still one of the leading causes of death in the world, and heart transplantation is the current major treatment for end-stage cardiovascular diseases. However, because of the shortage of heart donors, new sources of cardiac regenerative medicine are greatly needed. The prominent development of tissue engineering using bioactive materials has creatively laid a direct promising foundation. Whereas, how to precisely pattern a cardiac structure with complete biological function still requires technological breakthroughs. Recently, the emerging three-dimensional (3D) bioprinting technology for tissue engineering has shown great advantages in generating micro-scale cardiac tissues, which has established its impressive potential as a novel foundation for cardiovascular regeneration. Whether 3D bioprinted hearts can replace traditional heart transplantation as a novel strategy for treating cardiovascular diseases in the future is a frontier issue. In this review article, we emphasize the current knowledge and future perspectives regarding available bioinks, bioprinting strategies and the latest outcome progress in cardiac 3D bioprinting to move this promising medical approach towards potential clinical implementation.

Organ-on-a-Chip systems for new drugs development

Research on alternatives to the use of animal models and cell cultures has led to the creation of organ-on-a-chip systems, in which organs and their physiological reactions to the presence of external stimuli are simulated. These systems could even replace the use of human beings as subjects for the study of drugs in clinical phases and have an impact on personalized therapies. Organ-on-a-chip technology present higher potential than traditional cell cultures for an appropriate prediction of functional impairments, appearance of adverse effects, the pharmacokinetic and toxicological profile and the efficacy of a drug. This potential is given by the possibility of placing different cell lines in a three-dimensional-arranged polymer piece and simulating and controlling specific conditions. Thus, the normal functioning of an organ, tissue, barrier, or physiological phenomenon can be simulated, as well as the interrelation between different systems. Furthermore, this alternative allows the study of physiological and pathophysiological processes. Its design combines different disciplines such as materials engineering, cell cultures, microfluidics and physiology, among others. This work presents the main considerations of OoC systems, the materials, methods and cell lines used for their design, and the conditions required for their proper functioning. Examples of applications and main challenges for the development of more robust systems are shown. This non-systematic review is intended to be a reference framework that facilitates research focused on the development of new OoC systems, as well as their use as alternatives in pharmacological, pharmacokinetic and toxicological studies.

A State-of-the-Art of Functional Scaffolds for 3D Nervous Tissue Regeneration

Exploring and developing multifunctional intelligent biomaterials is crucial to improve next-generation therapies in tissue engineering and regenerative medicine. Recent findings show how distinct characteristics of in situ microenvironment can be mimicked by using different biomaterials. In vivo tissue architecture is characterized by the interconnection between cells and specific components of the extracellular matrix (ECM). Last evidence shows the importance of the structure and composition of the ECM in the development of cellular and molecular techniques, to achieve the best biodegradable and bioactive biomaterial compatible to human physiology. Such biomaterials provide specialized bioactive signals to regulate the surrounding biological habitat, through the progression of wound healing and biomaterial integration. The connection between stem cells and biomaterials stimulate the occurrence of specific modifications in terms of cell properties and fate, influencing then processes such as self-renewal, cell adhesion and differentiation. Recent studies in the field of tissue engineering and regenerative medicine have shown to deal with a broad area of applications, offering the most efficient and suitable strategies to neural repair and regeneration, drawing attention towards the potential use of biomaterials as 3D tools for in vitro neurodevelopment of tissue models, both in physiological and pathological conditions. In this direction, there are several tools supporting cell regeneration, which associate cytokines and other soluble factors delivery through the scaffold, and different approaches considering the features of the biomaterials, for an increased functionalization of the scaffold and for a better promotion of neural proliferation and cells-ECM interplay. In fact, 3D scaffolds need to ensure a progressive and regular delivery of cytokines, growth factors, or biomolecules, and moreover they should serve as a guide and support for injured tissues. It is also possible to create scaffolds with different layers, each one possessing different physical and biochemical aspects, able to provide at the same time organization, support and maintenance of the specific cell phenotype and diversified ECM morphogenesis. Our review summarizes the most recent advancements in functional materials, which are crucial to achieve the best performance and at the same time, to overcome the current limitations in tissue engineering and nervous tissue regeneration.