Introduction of N-cadherin-binding motif to alginate hydrogels for controlled stem cell differentiation

Blastocyst-Inspired Hydrogels to Maintain Undifferentiation of Mouse Embryonic Stem Cells

Stem cell fate is determined by specific niches that provide multiple physical, chemical, and biological cues. However, the hierarchy or cascade of impact of these cues remains elusive due to their spatiotemporal complexity. Here, anisotropic silk protein nanofiber-based hydrogels with suitable cell adhesion capacity are developed to mimic the physical microenvironment inside the blastocele. The hydrogels enable mouse embryonic stem cells (mESCs) to maintain stemness in vitro in the absence of both leukemia inhibitory factor (LIF) and mouse embryonic fibroblasts (MEFs), two critical factors in the standard protocol for mESC maintenance. The mESCs on hydrogels can achieve superior pluripotency, genetic stability, developmental capacity, and germline transmission to those cultured with the standard protocol. Such biomaterials establish an improved dynamic niche through stimulating the secretion of autocrine factors and are sufficient to maintain the pluripotency and propagation of ESCs. The mESCs on hydrogels are distinct in their expression profiles and more resemble ESCs in vivo. The physical cues can thus initiate a self-sustaining stemness-maintaining program. In addition to providing a relatively simple and low-cost option for expansion and utility of ESCs in biological research and therapeutic applications, this biomimetic material helps gain more insights into the underpinnings of early mammalian embryogenesis.

You Talking to Me? Cadherin and Integrin Crosstalk in Biomaterial Design

While much work has been done in the design of biomaterials to control integrin-mediated adhesion, less emphasis has been put on functionalization of materials with cadherin ligands. Yet, cell-cell contacts in combination with cell-matrix interactions are key in driving embryonic development, collective cell migration, epithelial to mesenchymal transition, and cancer metastatic processes, among others. This review focuses on the incorporation of both cadherin and integrin ligands in biomaterial design, to promote what is called the "adhesive crosstalk." First, the structure and function of cadherins and their role in eliciting mechanotransductive processes, by themselves or in combination with integrin mechanosensing, are introduced. Then, biomaterials that mimic cell-cell interactions, and recent applications to get insights in fundamental biology and tissue engineering, are critically discussed.

ChondroGELesis: Hydrogels to harness the chondrogenic potential of stem cells

The extracellular matrix is a highly complex microenvironment, whose various components converge to regulate cell fate. Hydrogels, as water-swollen polymer networks composed by synthetic or natural materials, are ideal candidates to create biologically active substrates that mimic these matrices and target cell behaviour for a desired tissue engineering application. Indeed, the ability to tune their mechanical, structural, and biochemical properties provides a framework to recapitulate native tissues. This review explores how hydrogels have been engineered to harness the chondrogenic response of stem cells for the repair of damaged cartilage tissue. The signalling processes involved in hydrogel-driven chondrogenesis are also discussed, identifying critical pathways that should be taken into account during hydrogel design.

Composition and Mechanism of Three-Dimensional Hydrogel System in Regulating Stem Cell Fate

Three-dimensional (3D) hydrogel systems integrating different types of stem cells and scaffolding biomaterials have an important application in tissue engineering. The biomimetic hydrogels that pattern cell suspensions within 3D configurations of biomaterial networks allow for the transport of bioactive factors and mimic the stem cell niche in vivo, thereby supporting the proliferation and differentiation of stem cells. The composition of a 3D hydrogel system determines the physical and chemical characteristics that regulate stem cell function through a biological mechanism. Here, we discuss the natural and synthetic hydrogel compositions that have been employed in 3D scaffolding, focusing on their characteristics, fabrication, biocompatibility, and regulatory effects on stem cell proliferation and differentiation. We also discuss the regulatory mechanisms of cell-matrix interaction and cell-cell interaction in stem cell activities in various types of 3D hydrogel systems. Understanding hydrogel compositions and their cellular mechanisms can yield insights into how scaffolding biomaterials and stem cells interact and can lead to the development of novel hydrogel systems of stem cells in tissue engineering and stem cell-based regenerative medicine. Impact statement Three-dimensional hydrogel system of stem cell mimicking the stemcell niche holds significant promise in tissue engineering and regenerative medicine. Exactly how hydrogel composition regulates stem cell fate is not well understood. This review focuses on the composition of hydrogel, and how the hydrogel composition and its properties regulate the stem cell adhesion, growth, and differentiation. We propose that cell-matrix interaction and cell-cell interaction are important regulatory mechanisms in stem cell activities. Our review provides key insights into how the hydrogel composition regulates the stem cell fate, untangling the engineering of three-dimensional hydrogel systems for stem cells.

Enhanced regeneration of osteochondral defects by using an aggrecanase-1 responsively degradable and N-cadherin mimetic peptide-conjugated hydrogel loaded with BMSCs

Due to the poor self-repair capabilities of articular cartilage, chondral or osteochondral injuries are difficult to be recovered. In this study, an N-cadherin mimetic peptide sequence HAVDIGGGC (HAV) was conjugated to direct cell-cell interactions, and an aggrecanase-1 cleavable peptide sequence CRDTEGE-ARGSVIDRC (ACpep) was used to crosslink hyperbranched PEG-based multi-acrylate polymer (HBPEG) with cysteamine-modified chondroitin sulfate (Cys-CS), obtaining an aggrecanase-1 responsively degradable and HAV-conjugated hydrogel ((HAV-HBPEG)-CS-ACpep). A HBPEG-CS-ACpep hydrogel without the HAV motif was also prepared. The two hydrogels exhibited similar equilibrium swelling ratios, elastic moduli and pore sizes after lyophilization, indicating the negligible influence of conjugated HAV on the crosslinking networks and mechanical properties of the hydrogels. After being degraded in PBS, aggrecanase-1 (ADAMTS4) and trypsin, the HBPEG-CS-ACpep hydrogel exhibited significantly decreased elastic moduli with a much lower value when incubated in enzyme solutions. The two hydrogels could maintain the viability of encapsulated bone marrow-derived mesenchymal stem cells (BMSCs), and the (HAV-HBPEG)-CS-ACpep hydrogel better promoted the cell-cell interactions. After being implanted into osteochondral defects in rabbits for 18 weeks, the two cell-laden hydrogel groups achieved better repair effects than the blank control group. Moreover, hyaline cartilage was formed in the (HAV-HBPEG)-CS-ACpep/BMSCs hydrogel group, while a hybrid of hyaline cartilage and fibrocartilage was found in the HBPEG-CS-ACpep/BMSCs hydrogel group.

Effect of RGD content in poly(ethylene glycol)-crosslinked poly(methyl vinyl ether-alt-maleic acid) hydrogels on the expansion of ovarian cancer stem-like cells

The extracellular matrix (ECM) affects cell behaviors, such as survival, proliferation, motility, invasion, and differentiation. The arginine-glycine-aspartic acid (RGD) sequence is present in several ECM proteins, such as fibronectin, collagen type I, fibrinogen, laminin, vitronectin, and osteopontin. It is very critical to develop ECM-like substrates with well-controlled features for the investigation of influence of RGD on the behavior of tumor cells. In this study, poly(ethylene glycol) (PEG)-crosslinked poly(methyl vinyl ether-alt-maleic acid) (P(MVE-alt-MA)) hydrogels (PEMM) with different RGD contents were synthesized, fully characterized, and established as in vitro culture platforms to investigate the effects of RGD content on cancer stem cell (CSC) enrichment. The morphology, proliferation, and viability of SK-OV-3 ovarian cancer cells cultured on hydrogels with different RGD contents, the expression of CSC markers and malignant signaling pathway-related genes, and drug resistance were systematically evaluated. The cell aggregates formed on the hydrogel surface with a lower RGD content acquired certain CSC-like properties, thus drug resistance was enhanced. In contrast, the drug sensitivity of cells on the higher RGD content surface increased because of less CSC-like properties. However, the presence of RGD in the stiff hydrogels (PEMM2) had less effect on the stemness expression than did its presence in the soft hydrogels (PEMM1). The results suggest that RGD content and matrix stiffness can lead to synergetic effects on the expression of cancer cell stemness and the epithelial-mesenchymal transition (EMT), interleukin-6 (IL-6), and Wnt pathways.

Modulating Alginate Hydrogels for Improved Biological Performance as Cellular 3D Microenvironments

The rational choice and design of biomaterials for biomedical applications is crucial for successful in vitro and in vivo strategies, ultimately dictating their performance and potential clinical applications. Alginate, a marine-derived polysaccharide obtained from seaweeds, is one of the most widely used polymers in the biomedical field, particularly to build three dimensional (3D) systems for in vitro culture and in vivo delivery of cells. Despite their biocompatibility, alginate hydrogels often require modifications to improve their biological activity, namely via inclusion of mammalian cell-interactive domains and fine-tuning of mechanical properties. These modifications enable the addition of new features for greater versatility and control over alginate-based systems, extending the plethora of applications and procedures where they can be used. Additionally, hybrid systems based on alginate combination with other components can also be explored to improve the mimicry of extracellular microenvironments and their dynamics. This review provides an overview on alginate properties and current clinical applications, along with different strategies that have been reported to improve alginate hydrogels performance as 3D matrices and 4D dynamic systems.

Design of modular gellan gum hydrogel functionalized with avidin and biotinylated adhesive ligands for cell culture applications

This article proposes the coupling of the recombinant protein avidin to the polysaccharide gellan gum to create a modular hydrogel substrate for 3D cell culture and tissue engineering. Avidin is capable of binding biotin, and thus biotinylated compounds can be tethered to the polymer network to improve cell response. The avidin is successfully conjugated to gellan gum and remains functional as shown with fluorescence titration and electrophoresis (SDS-PAGE). Self-standing hydrogels were formed using bioamines and calcium chloride, yielding long-term stability and adequate stiffness for 3D cell culture, as confirmed with compression testing. Human fibroblasts were successfully cultured within the hydrogel treated with biotinylated RGD or biotinylated fibronectin. Moreover, human bone marrow stromal cells were cultured with hydrogel treated with biotinylated RGD over 3 weeks. We demonstrate a modular and inexpensive hydrogel scaffold for cell encapsulation that can be equipped with any desired biotinylated cell ligand to accommodate a wide range of cell types.

The Investigation of LRP5-Loaded Composite with Sustained Release Behavior and Its Application in Bone Repair

Low-density lipoprotein receptor-related protein 5 (LRP5) plays a vital role in bone formation and regeneration. In this study, we developed an injectable and sustained-release composite loading LRP5 which could gelatinize in situ. The sustained release of the composite and its efficacy in bone regeneration were evaluated. Sodium alginate, collagen, hydroxyapatite, and LRP5 formed the composite LRP5-Alg/Col/HA. It was found that the initial setting time and final setting time of LRP5-Alg/Col/HA containing 4% alginate were suitable for surgical operation. When the composite was loaded with 40 μg/mL LRP5, LRP5-Alg/Col/HA did not exhibit a burst-release behavior and could sustainably release LRP5 up to 21 days. Up to 18 days, LRP5 released from LRP5-Alg/Col/HA still present the binding activity with DKK1 (Wnt signaling pathway antagonist) and could increase the downstream β-catenin mRNA in bone marrow mesenchymal stem cells. Moreover, LRP5-Alg/Col/HA was found to significantly increase bone mineral density in the defect area after 6 weeks’ implantation of LRP5-Alg/Col/HA into the rats’ calvarial defect area. H&E staining detection demonstrated that LRP5-Alg/Col/HA could mediate the formation of a new bone tissue. Therefore, we concluded that Alg/Col/HA was a suitable sustained-release carrier for LRP5 and LRP5-Alg/Col/HA had a significant effect on repairing bone defects and could be a good bone regeneration material.