Alkaline phosphatase dual-binding sites for collagen dictate cell migration and microvessel assembly in vitro

Collagen-mediated cardiovascular calcification

Cardiovascular calcification is a pathological process commonly observed in the elderly. Based on the location of the calcification, cardiovascular calcification can be classified into two main types: vascular calcification and valvular calcification. Collagen plays a critical role in the development of cardiovascular calcification lesions. The content and type of collagen are the result of a dynamic balance between synthesis and degradation. Unregulated processes can lead to adverse outcomes. During cardiovascular calcification, collagen not only serves as a scaffold for ectopic mineral deposition but also acts as a signal transduction pathway that mediates calcification by guiding the aggregation and nucleation of matrix vesicles and promoting the proliferation, migration and phenotypic changes of cells involved in the lesion. This review provides an overview of collagen subtypes in the cardiovascular system under physiological conditions and discusses their distribution. Additionally, we introduce pathological changes and mechanisms of collagen in blood vessels and heart valves. Then, the formation process and characteristic stages of cardiovascular calcification are described. Finally, we highlight the role of collagen in cardiovascular calcification, explore strategied for mediating calcification, and suggest potential directions for future research.

Amniotic membrane, a novel bioscaffold in cardiac diseases: from mechanism to applications

Cardiovascular diseases represent one of the leading causes of death worldwide. Despite significant advances in the diagnosis and treatment of these diseases, numerous challenges remain in managing them. One of these challenges is the need for replacements for damaged cardiac tissues that can restore the normal function of the heart. Amniotic membrane, as a biological scaffold with unique properties, has attracted the attention of many researchers in recent years. This membrane, extracted from the human placenta, contains growth factors, cytokines, and other biomolecules that play a crucial role in tissue repair. Its anti-inflammatory, antibacterial, and wound-healing properties have made amniotic membrane a promising option for the treatment of heart diseases. This review article examines the applications of amniotic membrane in cardiovascular diseases. By focusing on the mechanisms of action of this biological scaffold and the results of clinical studies, an attempt will be made to evaluate the potential of using amniotic membrane in the treatment of heart diseases. Additionally, the existing challenges and future prospects in this field will be discussed.

A 3D Bioprinted Cortical Organoid Platform for Modeling Human Brain Development

The ability to promote three-dimensional (3D) self-organization of induced pluripotent stem cells into complex tissue structures called organoids presents new opportunities for the field of developmental biology. Brain organoids have been used to investigate principles of neurodevelopment and neuropsychiatric disorders and serve as a drug screening and discovery platform. However, brain organoid cultures are currently limited by a lacking ability to precisely control their extracellular environment. Here, this work employs 3D bioprinting to generate a high-throughput, tunable, and reproducible scaffold for controlling organoid development and patterning. Additionally, this approach supports the coculture of organoids and vascular cells in a custom architecture containing interconnected endothelialized channels. Printing fidelity and mechanical assessments confirm that fabricated scaffolds closely match intended design features and exhibit stiffness values reflective of the developing human brain. Using organoid growth, viability, cytoarchitecture, proliferation, and transcriptomic benchmarks, this work finds that organoids cultured within the bioprinted scaffold long-term are healthy and have expected neuroectodermal differentiation. Lastly, this work confirms that the endothelial cells (ECs) in printed channel structures can migrate toward and infiltrate into the embedded organoids. This work demonstrates a tunable 3D culturing platform that can be used to create more complex and accurate models of human brain development and underlying diseases.

SDF-1 Functionalized Hydrogel Microcarriers for Skin Flap Repair

Critically sized skin flaps used to treat skin defects often suffer from necrosis due to insufficient blood supply. Hence there is an urgent need to improve the survival rate of skin flaps by promoting local angiogenesis. The delivery of growth factor loaded microcarriers have shown promise in enhancing defect repair, however, their rapid clearance from the defect site limits their regenerative potential. Thus, it is critical to develop microcarriers which can promote the sustained release of bioactive factors to effectively stimulate tissue repair. This study aimed to develop a stromal cell-derived factor 1 (SDF-1) loaded microcarrier coated with Matrigel (MC@SDF-1@Mat) to promote skin flap repair. SEM imaging showed that the surface of the microcarrier was coated by a porous Matrigel film. The drug release experiment showed that the Matrigel-coated microcarriers enhanced the sustained release of the model drug methylene blue when compared to uncoated group. MC@SDF-1@Mat significantly promoted the proliferation, migration, and angiogenesis of HUVECs via CCK-8, wound healing assay, and tube formation assay, respectively. Moreover, the murine random skin flap model was further established and treated. It was found that the flap necrosis area in the MC@SDF-1@Mat treated group was significantly reduced. H&E and Masson staining showed the histological structure and collagen organization exhibited a normal phenotype in the MC@SDF-1@Mat treated group. Additionally, CD31 immunohistochemical analysis showed that the MC@SDF-1@Mat treated group exhibited the greatest degree of neovascularization. In conclusion, our SDF-1 functionalized gelatin-based hydrogel microcarrier has potential clinical applications in promoting skin flap repair and drug delivery.

Cell-assembled extracellular matrix (CAM): a human biopaper for the biofabrication of pre-vascularized tissues able to connect to the host circulationin vivo

When considering regenerative approaches, the efficient creation of a functional vasculature, that can support the metabolic needs of bioengineered tissues, is essential for their survival after implantation. However, it is widely recognized that the post-implantation microenvironment of the engineered tissues is often hypoxic due to insufficient vascularization, resulting in ischemia injury and necrosis. This is one of the main limitations of current tissue engineering applications aiming at replacing significant tissue volumes. Here, we have explored the use of a new biomaterial, the cell-assembled extracellular matrix (CAM), as a biopaper to biofabricate a vascular system. CAM sheets are a unique, fully biological and fully human material that has already shown stable long-term implantation in humans. We demonstrated, for the first time, the use of this unprocessed human ECM as a microperforated biopaper. Using microvalve dispensing bioprinting, concentrated human endothelial cells (30 millions ml^-1) were deposited in a controlled geometry in CAM sheets and cocultured with HSFs. Following multilayer assembly, thick ECM-based constructs fused and supported the survival and maturation of capillary-like structures for up to 26 d of culture. Following 3 weeks of subcutaneous implantation in a mice model, constructs showed limited degradative response and the pre-formed vasculature successfully connected with the host circulatory system to establish active perfusion.This mechanically resilient tissue equivalent has great potential for the creation of more complex implantable tissues, where rapid anastomosis is sine qua non for cell survival and efficient tissue integration.

Vascularization strategies in tissue engineering approaches for soft tissue repair

Insufficient vascularization during tissue repair is often associated with poor clinical outcomes. This is a concern especially when patients have critical-sized injuries, where the size of the defect restricts vascularity, or even in small defects that have to be treated under special conditions, such as after radiation therapy (relevant to tumor resection) that hinders vascularity. In fact, poor vascularization is one of the major obstacles for clinical application of tissue engineering methods in soft tissue repair. As a key issue, lack of graft integration, caused by inadequate vascularization after implantation, can lead to graft failure. Moreover, poor vascularization compromises the viability of cells seeded in deep portions of scaffolds/graft materials, due to hypoxia and insufficient nutrient supply. In this article we aim to review vascularization strategies employed in tissue engineering techniques to repair soft tissues. For this purpose, we start by providing a brief overview of the main events during the physiological wound healing process in soft tissues. Then, we discuss how tissue repair can be achieved through tissue engineering, and considerations with regards to the choice of scaffold materials, culture conditions, and vascularization techniques. Next, we highlight the importance of vascularization, along with strategies and methods of prevascularization of soft tissue equivalents, particularly cell-based prevascularization. Lastly, we present a summary of commonly used in vitro methods during the vascularization of tissue-engineered soft tissue constructs.