Porcine arterial ECM hydrogel: Designing an in vitro angiogenesis model for long-term high-throughput research

Hydrogel-Encapsulated Pancreatic Islet Cells as a Promising Strategy for Diabetic Cell Therapy

Islet transplantation has now become a promising treatment for insulin-deficient diabetes mellitus. Compared to traditional diabetes treatments, cell therapy can restore endogenous insulin supplementation, but its large-scale clinical application is impeded by donor shortages, immune rejection, and unsuitable transplantation sites. To overcome these challenges, an increasing number of studies have attempted to transplant hydrogel-encapsulated islet cells to treat diabetes. This review mainly focuses on the strategy of hydrogel-encapsulated pancreatic islet cells for diabetic cell therapy, including different cell sources encapsulated in hydrogels, encapsulation methods, hydrogel types, and a series of accessorial manners to improve transplantation outcomes. In addition, the formation and application challenges as well as prospects are also presented.

Self-Organization of Long-Lasting Human Endothelial Capillary-Like Networks Guided by DLP Bioprinting

Tissue engineering holds great promise for regenerative medicine, drug discovery, and as an alternative to animal models. However, as soon as the dimensions of engineered tissue exceed the diffusion limit of oxygen and nutriments, a necrotic core forms leading to irreversible damage. To overcome this constraint, the establishment of a functional perfusion network is essential. In this work, digital light processing bioprinting is used to encapsulate endothelial progenitor cells (EPCs) in 3D light-cured hydrogel scaffolds to guide them toward vascular network formation. In these scaffolds, EPCs proliferate and self-organize within a few days into branched tubular structures with predefined geometry, forming capillary-like vascular tubes or trees of diameters in the range of 10 to 100 µm. Presenting a confluent monolayer wall of cells strongly connect by tight junctions around a central lumen-like space, these structures can be microinjected with a fluorescent dye and are stable for several weeks in vitro. These endothelial structures can be recovered and manipulated in an alginate patch without altering their shape or viability. This approach opens new opportunities for future applications, such as stacking with other cell sheets or multicellular constructs to yield bioengineered tissue with higher complexity and functionality.

In Vitro Models of Blood and Lymphatic Vessels-Connecting Tissues and Immunity

Blood and lymphatic vessels are regulators of physiological processes, including oxygenation and fluid transport. Both vessels are ubiquitous throughout the body and are critical for sustaining tissue homeostasis. The complexity of each vessel's processes has limited the understanding of exactly how the vessels maintain their functions. Both vessels have been shown to be involved in the pathogenesis of many diseases, including cancer metastasis, and it is crucial to probe further specific mechanisms involved. In vitro models are developed to better understand blood and lymphatic physiological functions and their mechanisms. In this review, blood and lymphatic in vitro model systems, including 2D and 3D designs made using Transwells, microfluidic devices, organoid cultures, and various other methods, are described. Models studying endothelial cell-extracellular matrix interactions, endothelial barrier properties, transendothelial transport and cell migration, lymph/angiogenesis, vascular inflammation, and endothelial-cancer cell interactions are particularly focused. While the field has made significant progress in modeling and understanding lymphatic and blood vasculature, more models that include coculture of multiple cell types, complex extracellular matrix, and 3D morphologies, particularly for models mimicking disease states, will help further the understanding of the role of blood and lymphatic vasculature in health and disease.

Extracellular Matrix Hydrogels Originated from Different Organs Mediate Tissue-Specific Properties and Function

Porcine extracellular matrix (pECM)-derived hydrogels were introduced, in recent years, aiming to benefit the pECM’s microstructure and bioactivity, while controlling the biomaterial’s physical and mechanical properties. The use of pECM from different tissues, however, offers tissue-specific features that can better serve different applications. In this study, pECM hydrogels derived from cardiac, artery, pancreas, and adipose tissues were compared in terms of composition, structure, and mechanical properties. While major similarities were demonstrated between all the pECM hydrogels, their distinctive attributes were also identified, and their substantial effects on cell-ECM interactions were revealed. Furthermore, through comprehensive protein and gene expression analyses, we show, for the first time, that each pECM hydrogel supports the spontaneous differentiation of induced pluripotent stem cells towards the resident cells of its origin tissue. These findings imply that the origin of ECM should be carefully considered when designing a biomedical platform, to achieve a maximal bioactive impact.

Sulfated glycosaminoglycans in decellularized placenta matrix as critical regulators for cutaneous wound healing

Perinatal-related tissues, such as the placenta, umbilical cord, and amniotic membrane, are generally discarded after delivery and are increasingly attracting attention as alternative sources for decellularized extracellular matrix (dECM) isolation. Recent studies indicate that glycosaminoglycans (GAGs) in the dECM play key roles during tissue regeneration. However, the dECM is organ specific, and the glycosaminoglycanomics of dECMs from perinatal tissues and the regulatory function of GAGs have been poorly investigated. In this study, we explored the glycosaminoglycanomics of dECMs from the placenta, umbilical cord and amniotic membrane. We hypothesized that the therapeutic effects of dECMs are related to the detailed composition of GAGs. Hydrogels of dECM derived from perinatal tissues were generated, and glycosaminoglycanomics analysis was employed to identify the cues that promote tissue repair and regeneration in a murine cutaneous wound-healing model. We utilized highly sensitive liquid chromatography-tandem mass spectrometry for glycosaminoglycanomics analysis. Our results revealed that placenta-derived dECM (PL-dECM) hydrogel has higher contents of chondroitin sulfate (CS) and heparan sulfate (HS). In addition, molecular imaging showed that the PL-dECM hydrogel exerted the best anti-inflammatory and proangiogenic effects in the skin wound healing model. Further in vitro analyses demonstrated that CS with 6-O-sulfo group (CS-6S) has an anti-inflammatory effect, while HS with 6-O-sulfo group (HS-6S) plays a crucial role in angiogenesis. In conclusion, this study highlights the critical roles of GAGs in perinatal tissue-derived dECMs by promoting angiogenesis and inhibiting inflammation and indicates that it is feasible to utilize 6-sulfated GAG-enriched placental dECM hydrogel as an attractive candidate for tissue engineering and drug delivery.

Extracellular matrix grafts: From preparation to application (Review)

Recently, the increasing emergency of traffic accidents and the unsatisfactory outcome of surgical intervention are driving research to seek a novel technology to repair traumatic soft tissue injury. From this perspective, decellularized matrix grafts (ECM-G) including natural ECM materials, and their prepared hydrogels and bioscaffolds, have emerged as possible alternatives for tissue engineering and regenerative medicine. Over the past decades, several physical and chemical decellularization methods have been used extensively to deal with different tissues/organs in an attempt to carefully remove cellular antigens while maintaining the non-immunogenic ECM components. It is anticipated that when the decellularized biomaterials are seeded with cells in vitro or incorporated into irregularly shaped defects in vivo, they can provide the appropriate biomechanical and biochemical conditions for directing cell behavior and tissue remodeling. The aim of this review is to first summarize the characteristics of ECM-G and describe their major decellularization methods from different sources, followed by analysis of how the bioactive factors and undesired residual cellular compositions influence the biologic function and host tissue response following implantation. Lastly, we also provide an overview of the in vivoapplication of ECM-G in facilitating tissue repair and remodeling.