3D ECM-rich environment sustains the identity of naive human iPSCs

Harnessing developmental dynamics of spinal cord extracellular matrix improves regenerative potential of spinal cord organoids

Neonatal spinal cord tissues exhibit remarkable regenerative capabilities as compared to adult spinal cord tissues after injury, but the role of extracellular matrix (ECM) in this process has remained elusive. Here, we found that early developmental spinal cord had higher levels of ECM proteins associated with neural development and axon growth, but fewer inhibitory proteoglycans, compared to those of adult spinal cord. Decellularized spinal cord ECM from neonatal (DNSCM) and adult (DASCM) rabbits preserved these differences. DNSCM promoted proliferation, migration, and neuronal differentiation of neural progenitor cells (NPCs) and facilitated axonal outgrowth and regeneration of spinal cord organoids more effectively than DASCM. Pleiotrophin (PTN) and Tenascin (TNC) in DNSCM were identified as contributors to these abilities. Furthermore, DNSCM demonstrated superior performance as a delivery vehicle for NPCs and organoids in spinal cord injury (SCI) models. This suggests that ECM cues from early development stages might significantly contribute to the prominent regeneration ability in spinal cord.

Effect of chitin-architected spatiotemporal three-dimensional culture microenvironments on human umbilical cord-derived mesenchymal stem cells

Mesenchymal stem cell (MSC) transplantation has been explored for the clinical treatment of various diseases. However, the current two-dimensional (2D) culture method lacks a natural spatial microenvironment in vitro. This limitation restricts the stable establishment and adaptive maintenance of MSC stemness. Using natural polymers with biocompatibility for constructing stereoscopic MSC microenvironments may have significant application potential. This study used chitin-based nanoscaffolds to establish a novel MSC three-dimensional (3D) culture. We compared 2D and 3D cultured human umbilical cord-derived MSCs (UCMSCs), including differentiation assays, cell markers, proliferation, and angiogenesis. When UCMSCs are in 3D culture, they can differentiate into bone, cartilage, and fat. In 3D culture condition, cell proliferation is enhanced, accompanied by an elevation in the secretion of paracrine factors, including vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF), Interleukin-6 (IL-6), and Interleukin-8 (IL-8) by UCMSCs. Additionally, a 3D culture environment promotes angiogenesis and duct formation with HUVECs (Human Umbilical Vein Endothelial Cells), showing greater luminal area, total length, and branching points of tubule formation than a 2D culture. MSCs cultured in a 3D environment exhibit enhanced undifferentiated, as well as higher cell activity, making them a promising candidate for regenerative medicine and therapeutic applications.

Advances in the application of extracellular vesicles derived from three-dimensional culture of stem cells

Stem cells (SCs) have been used therapeutically for decades, yet their applications are limited by factors such as the risk of immune rejection and potential tumorigenicity. Extracellular vesicles (EVs), a key paracrine component of stem cell potency, overcome the drawbacks of stem cell applications as a cell-free therapeutic agent and play an important role in treating various diseases. However, EVs derived from two-dimensional (2D) planar culture of SCs have low yield and face challenges in large-scale production, which hinders the clinical translation of EVs. Three-dimensional (3D) culture, given its ability to more realistically simulate the in vivo environment, can not only expand SCs in large quantities, but also improve the yield and activity of EVs, changing the content of EVs and improving their therapeutic effects. In this review, we briefly describe the advantages of EVs and EV-related clinical applications, provide an overview of 3D cell culture, and finally focus on specific applications and future perspectives of EVs derived from 3D culture of different SCs.

Generation of Artificial Blastoids Combining miR-200-Mediated Reprogramming and Mechanical Cues

In vitro-generated blastocyst-like structures are of great importance since they recapitulate specific features or processes of early embryogenesis, thus avoiding ethical concerns as well as increasing scalability and accessibility compared to the use of natural embryos. Here, we combine cell reprogramming and mechanical stimuli to create 3D spherical aggregates that are phenotypically similar to those of natural embryos. Specifically, dermal fibroblasts are reprogrammed, exploiting the miR-200 family property to induce a high plasticity state in somatic cells. Subsequently, miR-200-reprogrammed cells are either driven towards the trophectoderm (TR) lineage using an ad hoc induction protocol or encapsulated into polytetrafluoroethylene micro-bioreactors to maintain and promote pluripotency, generating inner cell mass (ICM)-like spheroids. The obtained TR-like cells and ICM-like spheroids are then co-cultured in the same micro-bioreactor and, subsequently, transferred to microwells to encourage blastoid formation. Notably, the above protocol was applied to fibroblasts obtained from young as well as aged donors, with results that highlighted miR-200's ability to successfully reprogram young and aged cells with comparable blastoid rates, regardless of the donor's cell age. Overall, the approach here described represents a novel strategy for the creation of artificial blastoids to be used in the field of assisted reproduction technologies for the study of peri- and early post-implantation mechanisms.

ECM-derived biomaterials for regulating tissue multicellularity and maturation

Recent breakthroughs in developing human-relevant organotypic models led to the building of highly resemblant tissue constructs that hold immense potential for transplantation, drug screening, and disease modeling. Despite the progress in fine-tuning stem cell multilineage differentiation in highly controlled spatiotemporal conditions and hosting microenvironments, 3D models still experience naive and incomplete morphogenesis. In particular, existing systems and induction protocols fail to maintain stem cell long-term potency, induce high tissue-level multicellularity, or drive the maturity of stem cell-derived 3D models to levels seen in their in vivo counterparts. In this review, we highlight the use of extracellular matrix (ECM)-derived biomaterials in providing stem cell niche-mimicking microenvironment capable of preserving stem cell long-term potency and inducing spatial and region-specific differentiation. We also examine the maturation of different 3D models, including organoids, encapsulated in ECM biomaterials and provide looking-forward perspectives on employing ECM biomaterials in building more innovative, transplantable, and functional organs.

Cell cycle control by cell-matrix interactions

Cell adhesion to the extracellular matrix (ECM) is required for normal cell cycle progression and accurate cell division. However, how cell adhesion to the wide range of ECM proteins found in human tissues influences the cell cycle is not fully understood. The composition and physical properties of the ECM can have profound effects on cell proliferation but can also promote cell cycle exit and quiescence. Furthermore, during tumor development and progression, changes in the ECM can drive both cancer cell proliferation and dormancy. Cell-matrix adhesion is primarily sensed via integrin-associated adhesion complexes, which in turn are regulated by the cell cycle machinery. In particular, cyclin-dependent kinase 1 (CDK1) has been shown to play a crucial role in regulating adhesion complexes during interphase and entry into mitosis. These reciprocal links between cell cycle progression and cell-matrix interactions are now being identified.

Self-renewing human naïve pluripotent stem cells dedifferentiate in 3D culture and form blastoids spontaneously

Human naïve pluripotent stem cells (hnPSCs) can generate integrated models of blastocysts termed blastoids upon switch to inductive medium. However, the underlying mechanisms remain obscure. Here we report that self-renewing hnPSCs spontaneously and efficiently give rise to blastoids upon three dimensional (3D) suspension culture. The spontaneous blastoids mimic early stage human blastocysts in terms of structure, size, and transcriptome characteristics and are capable of progressing to post-implantation stages. This property is conferred by the glycogen synthase kinase-3 (GSK3) signalling inhibitor IM-12 present in 5iLAF self-renewing medium. IM-12 upregulates oxidative phosphorylation-associated genes that underly the capacity of hnPSCs to generate blastoids spontaneously. Starting from day one of self-organization, hnPSCs at the boundary of all 3D aggregates dedifferentiate into E5 embryo-like intermediates. Intermediates co-express SOX2/OCT4 and GATA6 and by day 3 specify trophoblast fate, which coincides with cavity and blastoid formation. In summary, spontaneous blastoid formation results from 3D culture triggering dedifferentiation of hnPSCs into earlier embryo-like intermediates which are then competent to segregate blastocyst fates.