Exploitation of fibrin-based signaling niche for deriving progenitors from human adipose-derived mesenchymal stem cells towards potential neural engineering applications

A hybrid construct of decellularized matrix and fibrin for differentiating adipose stem cells into insulin-producing cells, an optimized in vitro assessment

The generation of insulin-producing cells (IPCs) is an attractive approach for replacing damaged β cells in diabetic patients. In the present work, we introduced a hybrid platform of decellularized amniotic membrane (dAM) and fibrin encapsulation for differentiating adipose tissue-derived stem cells (ASCs) into IPCs. ASCs were isolated from healthy donors and characterized. Human AM was decellularized, and its morphology, DNA, collagen, glycosaminoglycan (GAG) contents, and biocompatibility were evaluated. ASCs were subjected to four IPC differentiation methods, and the most efficient method was selected for the experiment. ASCs were seeded onto dAM, alone or encapsulated in fibrin gel with various thrombin concentrations, and differentiated into IPCs according to a method applying serum-free media containing 2-mercaptoethanol, nicotinamide, and exendin-4. PDX-1, GLUT-2 and insulin expression were evaluated in differentiated cells using real-time PCR. Structural integrity and collagen and GAG contents of AM were preserved after decellularization, while DNA content was minimized. Cultivating ASCs on dAM augmented their attachment, proliferation, and viability and enhanced the expression of PDX-1, GLUT-2, and insulin in differentiated cells. Encapsulating ASCs in fibrin gel containing 2 mg/ml fibrinogen and 10 units/ml thrombin increased their differentiation into IPCs. dAM and fibrin gel synergistically enhanced the differentiation of ASCs into IPCs, which could be considered an appropriate strategy for replacing damaged β cells.

Regulatory mechanisms of stem cell differentiation: Biotechnological applications for neurogenesis

The world population's life expectancy is growing, and neurodegenerative disorders common in old age require more efficient therapies. In this context, neural stem cells (NSCs) are imperative for the development and maintenance of the functioning of the nervous system and have broad therapeutic applicability for neurodegenerative diseases. Therefore, knowing all the mechanisms that govern the self-renewal, differentiation, and cell signaling of NSC is necessary. This review will address some of these aspects, including the role of growth and transcription factors, epigenetic modulators, microRNAs, and extracellular matrix components. Furthermore, differentiation and transdifferentiation processes will be addressed as therapeutic strategies showing their significance for stem cell-based therapy.

In vivo neural tissue engineering using adipose-derived mesenchymal stem cells and fibrin matrix

BACKGROUND

The multipotency of adipose-derived mesenchymal stem cells (ADMSC) could be an advantage to regenerate tissues with multiple cell types. However, due to the hostile nature, trauma sites like spinal cord injury can augment the ADMSC differentiation into undesirable lineages. Immersing pre-differentiated neural progenitors in a biomimetic niche during delivery could guard them against any undesired differentiation or death.

OBJECTIVE

The study proposes using an insoluble cell-specific fibrin niche for in vitro differentiation of rat ADMSCs to neural progenitor cells (NPCs) and oligodendrocyte progenitor cells (OPCs). Further, the study explores fibrin hydrogel for in vivo progenitor cell delivery, and that can aid post-transplant survival/differentiation.

DESIGN

The in vitro experiments analyzed for differentiation-specific markers to establish derivation of rADMSCs to rNPCs and rOPCs. The derived progenitors, tagged with fluorescent tracker dye were delivered in rat T10 contusion SCI using fibrin hydrogel. After 28 days, imaged the experiment site to determine cell survival, immunostained the tissues to identify differentiation of transplanted cells, and evaluated the effect of fibrin and cells on regulating the injury-associated immune response.

RESULTS

The study demonstrated fibrin niche aided stable differentiation of rat ADMSCs into neural progenitors. Fibrin matrix holds up the delivered progenitor cells in the SCI site. The H&E stained tissues revealed regulated cavitation, astrogliosis, and inflammation in test tissues. Progression of transplanted cells into oligodendrocytes upon delivering a mixture of rNPCs, rOPCs, and fibrin is evident.

CONCLUSION

Fibrin niche-based derivation of neural progenitors from ADMSC seems valuable for transplantation using fibrin hydrogel. It is a promising strategy for extensive study towards further development of translational stem cell-based neural replacement therapy.

Therapeutical growth in oligodendroglial fate induction via transdifferentiation of stem cells for neuroregenerative therapy

The merits of stem cell therapy and research are undisputed due to their widespread usage in the treatment of neurodegenerative diseases and demyelinating disorders. Cell replacement therapy especially revolves around stem cells and their induction into different cell lineages both adult and progenitor - belonging to each germ layer, prior to transplantation or disease modeling studies. The nervous system is abundant in glial cells and among these are oligodendrocytes capable of myelinating new-born neurons and remyelination of axons with lost or damaged myelin sheath. But demyelinating diseases generate tremendous deficit between myelin loss and recovery. To compensate for this loss, analyze the defects in remyelination mechanisms as well as to trigger full recovery in such patients mesenchymal stem cells (MSCs) have been induced to transdifferentiate into oligodendrocytes. But such experiments are riddled with problems like prolonged, tenuous and complicated protocols that stretch longer than the time taken for the spread of demyelination-associated after-effects. This review delves into such protocols and the combinations of different molecules and factors that have been recruited to derive bona fide oligodendrocytes from in vitro differentiation of embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs) and MSCs with special focus on MSC-derived oligodendrocytes.

Biomaterial-based strategies for in vitro neural models

In vitro models have been used as a complementary tool to animal studies in understanding the nervous system's physiological mechanisms and pathological disorders, while also serving as platforms to evaluate the safety and efficiency of therapeutic candidates. Following recent advances in materials science, micro- and nanofabrication techniques and cell culture systems, in vitro technologies have been rapidly gaining the potential to bridge the gap between animal and clinical studies by providing more sophisticated models that recapitulate key aspects of the structure, biochemistry, biomechanics, and functions of human tissues. This was made possible, in large part, by the development of biomaterials that provide cells with physicochemical features that closely mimic the cellular microenvironment of native tissues. Due to the well-known material-driven cellular response and the importance of mimicking the environment of the target tissue, the selection of optimal biomaterials represents an important early step in the design of biomimetic systems to investigate brain structures and functions. This review provides a comprehensive compendium of commonly used biomaterials as well as the different fabrication techniques employed for the design of neural tissue models. Furthermore, the authors discuss the main parameters that need to be considered to develop functional platforms not only for the study of brain physiological functions and pathological processes but also for drug discovery/development and the optimization of biomaterials for neural tissue engineering.

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.

Optimizing fibrin hydrogel toward effective neural progenitor cell delivery in spinal cord injury

Transplantation of neural progenitor cell (NPC) possessing the potential to differentiate into neurons may guard against spinal cord injury (SCI)- associated neuronal trauma. We propose that autologous-like NPC may reduce post-transplant immune response. The study used the rat SCI model to prove this concept. For isolation and expansion of rat NPC for cell-based SCI therapy, thein vitroprotocol standardized with human NPC seemed suitable. The primary aim of this study is to select a cell/neural tissue-compatible biomaterial for improving NPC survivalin vivo. The composition of the fibrin hydrogel is adjusted to obtain degradable, porous, and robust fibrin strands for supporting neural cell attachment, migration, and tissue regeneration. This study employed NPC culture to evaluate the cytocompatibility and suitability of the hydrogel, composed by adding graded concentrations of thrombin to a fixed fibrinogen concentration. The microstructure evaluation by scanning electron microscope guided the selection of a suitable composition for delivering the embedded cells. On adding more thrombin, fibrinogen clotted quickly but reduced porosity, pore size, and fiber strand thickness. The high activity of thrombin also affected NPC morphology and thein vitrocell survival. The selected hydrogel carried viable NPC and retained them at the injury site post-transplantation. The fibrin hydrogel played a protective role throughout the transfer process by providing cell attachment sites and survival signals. The fibrin and NPC together regulated the immune response at the SCI site reducing ED1^+ve/ED2^+vemacrophages in the early period of 8-16 d after injury. Migration ofβ-III tubulin^+veneural-like cells into the fibrin-injected control SCI is evident. The continuous use of a non-neurotoxic fibrin matrix could be a convenient strategy forin vitroNPC preparation, minimally invasive cell delivery, and better transplantation outcome.