Ad-Dressing Stem Cells: Hydrogels for Encapsulation

Modern advances in spinal cord regeneration: hydrogel combined with neural stem cells

Severe spinal cord injuries (SCI) lead to loss of functional activity of the body below the injury site, affect a person's ability to self-care and have a direct impact on performance. Due to the structural features and functional role of the spinal cord in the body, the consequences of SCI cannot be completely overcome at the expense of endogenous regenerative potential and, developing over time, lead to severe complications years after injury. Thus, the primary task of this type of injury treatment is to create artificial conditions for the regenerative growth of damaged nerve fibers through the area of the SCI. Solving this problem is possible using tissue neuroengineering involving the technology of replacing the natural tissue environment with synthetic matrices (for example, hydrogels) in combination with stem cells, in particular, neural/progenitor stem cells (NSPCs). This approach can provide maximum stimulation and support for the regenerative growth of axons of damaged neurons and their myelination. In this review, we consider the currently available options for improving the condition after SCI (use of NSC transplantation or/and replacement of the damaged area of the SCI with a matrix, specifically a hydrogel). We emphasise the expediency and effectiveness of the hydrogel matrix + NSCs complex system used for the reconstruction of spinal cord tissue after injury. Since such a complex approach (a combination of tissue engineering and cell therapy), in our opinion, allows not only to creation of conditions for supporting endogenous regeneration or mechanical reconstruction of the spinal cord, but also to strengthen endogenous regeneration, prevent the spread of the inflammatory process, and promote the restoration of lost reflex, motor and sensory functions of the injured area of spinal cord.

A clinical feasible stem cell encapsulation ensures an improved wound healing

Cell encapsulation has proven to be promising in stem cell therapy. However, there are issues needed to be addressed, including unsatisfied yield, unmet clinically friendly formulation, and unacceptable viability of stem cells after cryopreservation and thawing. We developed a novel biosynsphere technology to encapsulate stem cells in clinically-ready biomaterials with controlled microsphere size. We demonstrated that biosynspheres ensure the bioviability and functionality of adipose-derived stromal cells (ADSCs) encapsulated, as delineated by a series of testing procedures. We further demonstrated that biosynspheres protect ADSCs from the hardness of clinically handling such as cryopreservation, thawing, high-speed centrifugation and syringe/nozzle injection. In a swine full skin defect model, we showed that biosynspheres were integrated to the destined tissues and promoted the repair of injured tissues with an accelerating healing process, less scar tissue formation and normalized deposition of collagen type I and type III, the ratio similar to that found in normal skin. These findings underscore the potential of biosynsphere as an improved biofabrication technology for tissue regeneration in clinical setting.

Adhesive and biodegradable membranes made of sustainable catechol-functionalized marine collagen and chitosan

We describe bioadhesive membranes developed from marine renewable biomaterials, namely chitosan and collagen extracted from fish skins. Collagen was functionalized with catechol groups (Coll-Cat) to provide the membranes with superior adhesive properties in a wet environment and blended with chitosan to improve the mechanical properties. The blended membranes were compared to chitosan and chitosan blended with unmodified collagen in terms of surface morphology, wettability, weight loss, water uptake, mechanical and adhesive properties. The metabolic activity, the viability and the morphology of L929 fibroblastic cells seeded on these membranes were also assessed. Our results show that the functionalization with catechol groups improves the adhesive and mechanical properties of the membranes and enhances cell attachment and proliferation. These data suggest that the developed marine origin-raw membranes present a potential towards the restoration of the structural and functional properties of damaged soft tissues.

Potential Role of Growth Factors Controlled Release in Achieving Enhanced Neuronal Trans-differentiation from Mesenchymal Stem Cells for Neural Tissue Repair and Regeneration

With an increase in the incidence of neurodegenerative diseases, a need to replace incapable conventional methods has arisen. To overcome this burden, stem cells therapy has emerged as an efficient treatment option. Endeavours to accomplish this have paved the path to neural regeneration through efficient neuronal transdifferentiation. Despite their potential, the use of stem cells still entails several limitations, such as low differentiation efficiency and difficulties in guiding differentiation. The process of neural differentiation through the stem cells is achieved through the use of chemical inducers or growth factors and their direct introduction reduces their bioavailability in the system. To address these limitations, neural regeneration ventures require growth factors to be effectively implemented on stem cells in order to produce functional neuronal precursor cells. An efficient technique to achieve it is through the delivery of growth factors via microcarriers for their sustained release. It ensures the presence of commensurable concentration even at later stages of neuronal transdifferentiation. Nanofibers and nanoparticles, along with liposomes and such, have been used to implement this. The interaction between such carriers and the growth factors is mainly electrostatic. Such interaction enables them to form a stable assembly through immobilisation of the growth factor either onto their surfaces or within the core of their structures. The rate of sustained release depends upon the release kinetics associated with the polymeric structure employed and its interaction with the encapsulated growth factor. The sustained release ensures that the stem cells immerse under the effect of the growth factors for a prolonged period, ultimately aiding in the formation of cells showing ample characteristics of neuron precursors. This review analyses the various carriers that have been employed for the release of growth factors in an orderly fashion and their constituents, along with the advantages and the limitations they pose in delivering the growth factors for facilitating the process of neuronal transdifferentiation.