3D patterned stem cell differentiation using thermo-responsive methylcellulose hydrogel molds

Biocompatibility of Veratric Acid-Encapsulated Chitosan/Methylcellulose Hydrogel: Biological Characterization, Osteogenic Efficiency with In Silico Molecular Modeling

The limitations of graft material, and surgical sites for autografts in bone defects treatment have become a significant challenge in bone tissue engineering. Phytocompounds markedly affect bone metabolism by activating the osteogenic signaling pathways. The present study investigated the biocompatibility of the bio-composite thermo-responsive hydrogels consisting of chitosan (CS), and methylcellulose (MC) encapsulated with veratric acid (VA) as a restorative agent for bone defect treatment. The spectroscopy analyses confirmed the formation of CS/MC hydrogels and VA encapsulated CS/MC hydrogels (CS/MC-VA). Molecular analysis of the CS-specific MC decamer unit with VA complex exhibited a stable integration in the system. Further, Runx2 (runt-related transcription factor 2) was found in the docking mechanism with VA, indicating a high binding affinity towards the functional site of the Runx2 protein. The formulated CS/MC-VA hydrogels exhibited biocompatibility with the mouse mesenchymal stem cells, while VA promoted osteogenic differentiation in the stem cells, which was verified by calcium phosphate deposition through the von Kossa staining. The study results suggest that CS/MC-VA could be a potential therapeutic alternative source for bone regeneration.

Sequential Assembly of Mutually Interactive Supramolecular Hydrogels and Fabrication of Multi-Domain Materials

A two-component self-sorting hydrogel based on acylhydrazide and carboxylic acid derivatives of 1,3:2,4-dibenzylidene-d-sorbitol (DBS-CONHNH₂ and DBS-COOH) is reported. A heating-cooling cycle induces the self-assembly of DBS-CONHNH₂ , followed by the self-assembly of DBS-COOH induced by decreasing pH. Although the networks are formed sequentially, there is spectroscopic evidence of interactions between them, which impact on the mechanical properties and significantly enhance the ability of these low-molecular-weight gelators (LMWGs) to form gels when mixed. The DBS-COOH network can be switched "off" and "on" within the two-component gel through a pH change. By using a photo-acid generator, the two-component gel can be prepared combining the thermal trigger with photo-irradiation. Photo-patterned self-assembly of DBS-COOH within a pre-formed DBS-CONHNH₂ gel under a mask yields spatially controlled multi-domain gels. Different gel domains can have different functions, for example, controlling the rate of release of heparin incorporated into the gel, or directing gold nanoparticle assembly. Such photo-patterned multi-component hydrogels have potential applications in regenerative medicine or bio-nano-electronics.

Efficient generation of human primordial germ cell-like cells from pluripotent stem cells in a methylcellulose-based 3D system at large scale

Background

The mechanisms underlying human germ cell development and infertility remain largely unknown due to bioethical issues and the shortage of experimental materials. Therefore, an effective in vitro induction system of human primordial germ-like cells (hPGCLCs) from human pluripotent stem cells (hPSC) is in high demand. The current strategies used for the generation of hPGCLCs are not only costly but also difficult to perform at a large scale, thereby posing barriers to further research. In this study, we attempted to solve these problems by providing a new 3D culture system for hPGCLC differentiation.

Methods

The efficiency and relative yield of a methylcellulose (MC)-based 3D hPGCLC induction system were first compared with that of a conventional U96 system. Then, we examined the gene expression of germ cell marker genes and the key epigenetic modifications of the EpCAM-/INTEGRINα6-high cells from the 3D MC induction system and the U96 system via quantitative PCR and immunofluorescence. Finally, the reliability of the MC-based 3D hPGCLC induction system was evaluated via the generation of induced pluripotent stem cells (iPSCs) from the testicular cells of one patient with obstructive azoospermia (OA) and followed by the subsequent differentiation of iPSCs into the germ cell lineage.

Results

In the present study, we demonstrated that the 3D MC induction system combined with low-cell attachment plates facilitated the generation of hPGCLCs at a large scale. We found that the hPGCLCs generated via the MC system shared similar characteristics to that via the U96 system in terms of the gene expression profiles, germ cell-specific markers, epigenetic modification states and cellular states. In addition, hPGCLCs from iPSCs derived from one OA patient were generated with high efficiency via the present 3D MC induction system.

Discussion

The in vitro induction of hPGCLCs from human embryonic stem cells (hESCs)/human induced pluripotent stem cells (hiPSCs) has significant implications in exploring the underlying mechanisms of the origin and specification of hPGCs and the epigenetic programming of the human germ line as well as treating male infertility. Here, we developed a simple and efficient 3D induction system to generate hPGCLCs from hESCs/hiPSCs at a large scale, which facilitated the study of human germ cell development and stem cell-based reproductive medicine.

Exploiting Advanced Hydrogel Technologies to Address Key Challenges in Regenerative Medicine

Regenerative medicine aims to tackle a panoply of challenges from repairing focal damage to articular cartilage to preventing pathological tissue remodeling after myocardial infarction. Hydrogels are water-swollen networks formed from synthetic or naturally derived polymers and are emerging as important tools to address these challenges. Recent advances in hydrogel chemistries are enabling researchers to create hydrogels that can act as 3D ex vivo tissue models, allowing them to explore fundamental questions in cell biology by replicating tissues' dynamic and nonlinear physical properties. Enabled by cutting edge techniques such as 3D bioprinting, cell-laden hydrogels are also being developed with highly controlled tissue-specific architectures, vasculature, and biological functions that together can direct tissue repair. Moreover, advanced in situ forming and acellular hydrogels are increasingly finding use as delivery vehicles for bioactive compounds and in mediating host cell response. Here, advances in the design and fabrication of hydrogels for regenerative medicine are reviewed. It is also addressed how controlled chemistries are allowing for precise engineering of spatial and time-dependent properties in hydrogels with a look to how these materials will eventually translate to clinical applications.

Biomimetic hydrogels direct spinal progenitor cell differentiation and promote functional recovery after spinal cord injury

OBJECTIVE

Demyelination that results from disease or traumatic injury, such as spinal cord injury (SCI), can have a devastating effect on neural function and recovery. Many researchers are examining treatments to minimize demyelination by improving oligodendrocyte availability in vivo. Transplantation of stem and oligodendrocyte progenitor cells is a promising option, however, trials are plagued by undirected differentiation. Here we introduce a biomaterial that has been optimized to direct the differentiation of neural progenitor cells (NPCs) toward oligodendrocytes as a cell delivery vehicle after SCI.

APPROACH

A collagen-based hydrogel was modified to mimic the mechanical properties of the neonatal spinal cord, and components present in the developing extracellular matrix were included to provide appropriate chemical cues to the NPCs to direct their differentiation toward oligodendrocytes. The hydrogel with cells was then transplanted into a unilateral cervical contusion model of SCI to examine the functional recovery with this treatment. Six behavioral tests and histological assessment were performed to examine the in vivo response to this treatment.

MAIN RESULTS

Our results demonstrate that we can achieve a significant increase in oligodendrocyte differentiation of NPCs compared to standard culture conditions using a three-component biomaterial composed of collagen, hyaluronic acid, and laminin that has mechanical properties matched to those of neonatal neural tissue. Additionally, SCI rats with hydrogel transplants, with and without NPCs, showed functional recovery. Animals transplanted with hydrogels with NPCs showed significantly increased functional recovery over six weeks compared to the media control group.

SIGNIFICANCE

The three-component hydrogel presented here has the potential to provide cues to direct differentiation in vivo to encourage regeneration of the central nervous system.