Analyzing the role of extracellular matrix during nervous system development to advance new regenerative strategies

An overview of latest advances in exploring bioactive peptide hydrogels for neural tissue engineering

Neural tissue engineering holds great potential in addressing current challenges faced by medical therapies employed for the functional recovery of the brain. In this context, self-assembling peptides have gained considerable interest owing to their diverse physicochemical properties, which enable them to closely mimic the biophysical characteristics of the native ECM. Additionally, in contrast to synthetic polymers, which lack inherent biological signaling, peptide-based nanomaterials could be easily designed to present essential biological cues to the cells to promote cellular adhesion. Moreover, injectability of these biomaterials further widens their scope in biomedicine. In this context, hydrogels obtained from short bioactive peptide sequences are of particular interest owing to their facile synthesis and highly tunable properties. In spite of their well-known advantages, the exploration of short peptides for neural tissue engineering is still in its infancy and thus detailed discussion is required to evoke interest in this direction. This review provides a general overview of various bioactive hydrogels derived from short peptide sequences explored for neural tissue engineering. The review also discusses the current challenges in translating the benefits of these hydrogels to clinical practices and presents future perspectives regarding the utilization of these hydrogels for advanced biomedical applications.

Appropriate Scaffold Selection for CNS Tissue Engineering

Cellular transplantation, due to the low regenerative capacity of the Central Nervous System (CNS), is one of the promising strategies in the treatment of neurodegenerative diseases. The design and application of scaffolds mimicking the CNS extracellular matrix features (biochemical, bioelectrical, and biomechanical), which affect the cellular fate, are important to achieve proper efficiency in cell survival, proliferation, and differentiation as well as integration with the surrounding tissue. Different studies on natural materials demonstrated that hydrogels made from natural materials mimic the extracellular matrix and supply microenvironment for cell adhesion and proliferation. The design and development of cellular microstructures suitable for neural tissue engineering purposes require a comprehensive knowledge of neuroscience, cell biology, nanotechnology, polymers, mechanobiology, and biochemistry. In this review, an attempt was made to investigate this multidisciplinary field and its multifactorial effects on the CNS microenvironment. Many strategies have been used to simulate extrinsic cues, which can improve cellular behavior toward neural lineage. In this study, parallel and align, soft and injectable, conductive, and bioprinting scaffolds were reviewed which have indicated some successes in the field. Among different systems, three-Dimensional (3D) bioprinting is a powerful, highly modifiable, and highly precise strategy, which has a high architectural similarity to tissue structure and is able to construct controllable tissue models. 3D bioprinting scaffolds induce cell attachment, proliferation, and differentiation and promote the diffusion of nutrients. This method provides exceptional versatility in cell positioning that is very suitable for the complex Extracellular Matrix (ECM) of the nervous system.

The influence of microenvironment and extracellular matrix molecules in driving neural stem cell fate within biomaterials

Transplantation of stem cells is a promising potential therapy for central nervous system disease and injury. The capacity for self-renewal, proliferation of progenitor cells, and multi-lineage potential underscores the need for controlling stem cell fate. Furthermore, transplantation within a hostile environment can lead to significant cell death and limited therapeutic potential. Tissue-engineered materials have been developed to both regulate stem cell fate, increase transplanted cell viability, and improve therapeutic outcomes. Traditionally, regulation of stem cell differentiation has been driven through soluble signals, such as growth factors. While these signals are important, insoluble factors from the local microenvironment or extracellular matrix (ECM) molecules also contribute to stem cell activity and fate. Understanding the microenvironment factors that influence stem cell fate, such as mechanical properties, topography, and presentation of specific ECM ligands, is necessary for designing improved biomaterials. Here we review some of the microenvironment factors that regulate stem cell fate and how they can be incorporated into biomaterials as part of potential CNS therapies.

Neural stem cell heterogeneity in the mammalian forebrain

The brain was long considered an organ that underwent very little change after development. It is now well established that the mammalian central nervous system contains neural stem cells that generate progeny that are capable of making new neurons, astrocytes, and oligodendrocytes throughout life. The field has advanced rapidly as it strives to understand the basic biology of these precursor cells, and explore their potential to promote brain repair. The purpose of this review is to present current knowledge about the diversity of neural stem cells in vitro and in vivo, and highlight distinctions between neural stem cell populations, throughout development, and within the niche. A comprehensive understanding of neural stem cell heterogeneity will provide insights into the cellular and molecular regulation of neural development and lifelong neurogenesis, and will guide the development of novel strategies to promote regeneration and neural repair.