Glial-restricted progenitor cells: a cure for diseased brain?

The central nervous system (CNS) is home to neuronal and glial cells. Traditionally, glia was disregarded as just the structural support across the brain and spinal cord, in striking contrast to neurons, always considered critical players in CNS functioning. In modern times this outdated dogma is continuously repelled by new evidence unravelling the importance of glia in neuronal maintenance and function. Therefore, glia replacement has been considered a potentially powerful therapeutic strategy. Glial progenitors are at the center of this hope, as they are the source of new glial cells. Indeed, sophisticated experimental therapies and exciting clinical trials shed light on the utility of exogenous glia in disease treatment. Therefore, this review article will elaborate on glial-restricted progenitor cells (GRPs), their origin and characteristics, available sources, and adaptation to current therapeutic approaches aimed at various CNS diseases, with particular attention paid to myelin-related disorders with a focus on recent progress and emerging concepts. The landscape of GRP clinical applications is also comprehensively presented, and future perspectives on promising, GRP-based therapeutic strategies for brain and spinal cord diseases are described in detail.

Mesenchymal stem cell engineering by ARCA analog-capped mRNA

We previously have shown that mRNA-based engineering may enhance mesenchymal stem cell (MSC) trafficking. However, optimal conditions for in vitro mRNA engineering of MSCs are unknown. Here, we investigated several independent variables: (1) transfection factor (Lipofectamine 2000 vs. TransIT), (2) mRNA purification method (spin column vs. high-performance liquid chromatography [HPLC] column), and (3) mRNA capping (ARCA vs. β-S-ARCA D1 and β-S-ARCA D2). Dependent variables included protein production based on mRNA template (measured by the bioluminescence of reporter gene luciferase over hours), MSC metabolic activity corresponding with their wellbeing measured by CCK-8 over days, and endogenous expression of genes by RT-qPCR related to innate intracellular immune response and decapping at two time points: days 2 and 5. We have found that Lipofectamine 2000 outperforms TransIT, and used it throughout the study. Then, we showed that mRNA must be purified by HPLC to be relatively neutral to MSCs in terms of metabolic activity and endogenous protein production. Ultimately, we demonstrated that β-S-ARCA D1 enables higher protein production but at the cost of lower MSC metabolic activity, with no impact on RT-qPCR results. Thus Lipofectamine 2000-based in vitro transfection of HPLC-purified and ARCA- or β-S-ARCA D1-capped mRNA is optimal for MSC engineering.

Low-intensity illumination for lensless digital holographic microscopy with minimized sample interaction

Exposure to laser light alters cell culture examination via optical microscopic imaging techniques based on label-free coherent digital holography. To mitigate this detrimental feature, researchers tend to use a broader spectrum and lower intensity of illumination, which can decrease the quality of holographic imaging due to lower resolution and higher noise. We study the lensless digital holographic microscopy (LDHM) ability to operate in the low photon budget (LPB) regime to enable imaging of unimpaired live cells with minimized sample interaction. Low-cost off-the-shelf components are used, promoting the usability of such a straightforward approach. We show that recording data in the LPB regime (down to 7 µW of illumination power) does not limit the contrast or resolution of the hologram phase and amplitude reconstruction compared to regular illumination. The LPB generates hardware camera shot noise, however, to be effectively minimized via numerical denoising. The ability to obtain high-quality, high-resolution optical complex field reconstruction was confirmed using the USAF 1951 amplitude sample, phase resolution test target, and finally, live glial restricted progenitor cells (as a challenging strongly absorbing and scattering biomedical sample). The proposed approach based on severely limiting the photon budget in lensless holographic microscopy method can open new avenues in high-throughout (optimal resolution, large field-of-view, and high signal-to-noise-ratio single-hologram reconstruction) cell culture imaging with minimized sample interaction.

A methylcellulose/agarose hydrogel as an innovative scaffold for tissue engineering

In situ crosslinked materials are the main interests of both scientific and industrial research. Methylcellulose (MC) aqueous solution is one of the representatives that belongs to this family of thermosensitive materials. At room temperature, MC is a liquid whereupon during temperature increase up to 37 °C, it crosslinks physically and turns into a hydrogel. This feature makes it unique, especially for tissue engineering applications. However, the crosslinking rate of MC alone is relatively slow considering tissue engineering expectations. According to these expectations, the crosslinking should take place slowly enough to allow for complete injection and fill the injury avoiding clogging in the needle, and simultanously, it should be sufficiently fast to prevent it from relocation from the lesion. One of the methods to overcome this problem is MC blending with another substance that increases the crosslinking rate of MC. In these studies, we used agarose (AGR). These studies aim to investigate the effect of different AGR amounts on MC crosslinking kinetics, and thermal, viscoelastic, and biological properties. Differential Scanning Calorimetry (DSC) and dynamic mechanical analysis (DMA) measurements proved that AGR addition accelerates the beginning of MC crosslinking. This phenomenon resulted from AGR's greater affinity to water, which is crucial in this particular crosslinking part. In vitro tests, carried out using the L929 fibroblast line and mesenchymal stem cells (MSCs), confirmed that most of the hydrogel samples were non-cytotoxic in contact with extracts and directly with cells. Not only does this type of thermosensitive hydrogel system provide excellent mechanical and biological cues but also its stimuli-responsive character provides more novel functionalities for designing innovative scaffold/cell delivery systems for tissue engineering applications.

Manganese-Labeled Alginate Hydrogels for Image-Guided Cell Transplantation

Cell transplantation has been studied extensively as a therapeutic strategy for neurological disorders. However, to date, its effectiveness remains unsatisfactory due to low precision and efficacy of cell delivery; poor survival of transplanted cells; and inadequate monitoring of their fate in vivo. Fortunately, different bio-scaffolds have been proposed as cell carriers to improve the accuracy of cell delivery, survival, differentiation, and controlled release of embedded stem cells. The goal of our study was to establish hydrogel scaffolds suitable for stem cell delivery that also allow non-invasive magnetic resonance imaging (MRI). We focused on alginate-based hydrogels due to their natural origin, biocompatibility, resemblance to the extracellular matrix, and easy manipulation of gelation processes. We optimized the properties of alginate-based hydrogels, turning them into suitable carriers for transplanted cells. Human adipose-derived stem cells embedded in these hydrogels survived for at least 14 days in vitro. Alginate-based hydrogels were also modified successfully to allow their injectability via a needle. Finally, supplementing alginate hydrogels with Mn ions or Mn nanoparticles allowed for their visualization in vivo using manganese-enhanced MRI. We demonstrated that modified alginate-based hydrogels can support therapeutic cells as MRI-detectable matrices.

Myelin-Independent Therapeutic Potential of Canine Glial-Restricted Progenitors Transplanted in Mouse Model of Dysmyelinating Disease

BACKGROUND

Dysfunction of glia contributes to the deterioration of the central nervous system in a wide array of neurological disorders, thus global replacement of glia is very attractive. Human glial-restricted precursors (hGRPs) transplanted intraventricularly into neonatal mice extensively migrated and rescued the lifespan in half of the studied mice, whereas mouse GRPs (mGRPs) presented no therapeutic benefit. We studied in the same experimental setting canine GRPs (cGRP) to determine whether their therapeutic potential falls between hGRPs and mGRPs. Additional motivation for the selection of cGRPs was a potential for use in veterinary medicine.

METHODS

cGRPs were extracted from the brain of dog fetuses. The cells were transplanted into the anterior or posterior aspect of the lateral ventricle (LV) of neonatal, immunodeficient, dysmyelinated mice (Mbpshi, Rag2 KO; shiv/rag2). Outcome measures included early cell biodistribution, animal survival and myelination assessed with MRI, immunohistochemistry and electron microscopy.

RESULTS

Grafting of cGRP into posterior LV significantly extended animal survival, whereas no benefit was observed after anterior LV transplantation. In contrast, myelination of the corpus callosum was more prominent in anteriorly transplanted animals.

CONCLUSIONS

The extended survival of animals after transplantation of cGRPs could be explained by the vicinity of the transplant near the brain stem.

Mesenchymal stem cells in glioblastoma therapy and progression: How one cell does it all

Mesenchymal stem cells (MSCs) are among the most investigated and applied somatic stem cells in experimental therapies for the regeneration of damaged tissues. Moreover, as it was recently postulated, MSCs may demonstrate anti-tumor properties. Glioblastoma (GBM) is a grade IV central nervous system tumor with no available effective therapy and an inevitably fatal prognosis. Experimental studies utilizing MSCs in GBM treatment resulted in numerous controversies. Native MSCs were shown to exert anti-GBM activity by controlling angiogenesis, regulating cell cycle, and inducing apoptosis. They also were used as sensitizing factors and vehicles delivering various anti-cancer compounds. On the other hand, some experiments revealed significant risks related to MSC-based therapies for GBM, such as enhancement of tumor cell proliferation, invasion, and aggressiveness. The following review elaborates on all mentioned contradictory data and provides a realistic, current clinical perspective on MSCs' potential in GBM treatment.

PTD4 Peptide Increases Neural Viability in an In Vitro Model of Acute Ischemic Stroke

Ischemic stroke is a disturbance in cerebral blood flow caused by brain tissue ischemia and hypoxia. We optimized a multifactorial in vitro model of acute ischemic stroke using rat primary neural cultures. This model was exploited to investigate the pro-viable activity of cell-penetrating peptides: arginine-rich Tat(49–57)-NH₂ (R⁴⁹KKRRQRRR⁵⁷-amide) and its less basic analogue, PTD4 (Y⁴⁷ARAAARQARA⁵⁷-amide). Our model included glucose deprivation, oxidative stress, lactic acidosis, and excitotoxicity. Neurotoxicity of these peptides was excluded below a concentration of 50 μm, and PTD4-induced pro-survival was more pronounced. Circular dichroism spectroscopy and molecular dynamics (MD) calculations proved potential contribution of the peptide conformational properties to neuroprotection: in MD, Tat(49–57)-NH₂ adopted a random coil and polyproline type II helical structure, whereas PTD4 adopted a helical structure. In an aqueous environment, the peptides mostly adopted a random coil conformation (PTD4) or a polyproline type II helical (Tat(49–57)-NH₂) structure. In 30% TFE, PTD4 showed a tendency to adopt a helical structure. Overall, the pro-viable activity of PTD4 was not correlated with the arginine content but rather with the peptide’s ability to adopt a helical structure in the membrane-mimicking environment, which enhances its cell membrane permeability. PTD4 may act as a leader sequence in novel drugs for the treatment of acute ischemic stroke.

Imunofan-RDKVYR Peptide-Stimulates Skin Cell Proliferation and Promotes Tissue Repair

Regeneration and wound healing are vital to tissue homeostasis and organism survival. One of the biggest challenges of today's science and medicine is finding methods and factors to stimulate these processes in the human body. Effective solutions to promote regenerative responses will accelerate advances in tissue engineering, regenerative medicine, transplantology, and a number of other clinical specialties. In this study, we assessed the potential efficacy of a synthetic hexapeptide, RDKVYR, for the stimulation of tissue repair and wound healing. The hexapeptide is marketed under the name "Imunofan" (IM) as an immunostimulant. IM displayed stability in aqueous solutions, while in plasma it was rapidly bound by albumins. Structural analyses demonstrated the conformational flexibility of the peptide. Tests in human fibroblast and keratinocyte cell lines showed that IM exerted a statistically significant (p < 0.05) pro-proliferative activity (30-40% and 20-50% increase in proliferation of fibroblast and keratinocytes, respectively), revealed no cytotoxicity over a vast range of concentrations (p < 0.05), and had no allergic properties. IM was found to induce significant transcriptional responses, such as enhanced activity of genes involved in active DNA demethylation (p < 0.05) in fibroblasts and activation of genes involved in immune responses, migration, and chemotaxis in adipose-derived stem cells derived from surgery donors. Experiments in a model of ear pinna injury in mice indicated that IM moderately promoted tissue repair (8% in BALB/c and 36% in C57BL/6 in comparison to control).

Methacrylated gellan gum and hyaluronic acid hydrogel blends for image-guided neurointerventions

Mn-Based gellan gum hydrogels for cell delivery and real-time tracking on image-guided neuro-procedures.

Epigenetic inhibitor zebularine activates ear pinna wound closure in the mouse

BACKGROUND

Most studies on regenerative medicine focus on cell-based therapies and transplantations. Small-molecule therapeutics, though proved effective in different medical conditions, have not been extensively investigated in regenerative research. It is known that healing potential decreases with development and developmental changes are driven by epigenetic mechanisms, which suggests epigenetic repression of regenerative capacity.

METHODS

We applied zebularine, a nucleoside inhibitor of DNA methyltransferases, to stimulate the regenerative response in a model of ear pinna injury in mice.

FINDINGS

We observed the regeneration of complex tissue that was manifested as improved ear hole repair in mice that received intraperitoneal injections of zebularine. Six weeks after injury, the mean hole area decreased by 83.2 ± 9.4% in zebularine-treated and by 43.6 ± 15.4% in control mice (p < 10^-30). Combined delivery of zebularine and retinoic acid potentiated and accelerated this effect, resulting in complete ear hole closure within three weeks after injury. We found a decrease in DNA methylation and transcriptional activation of neurodevelopmental and pluripotency genes in the regenerating tissues.

INTERPRETATION

This study is the first to demonstrate an effective induction of complex tissue regeneration in adult mammals using zebularine. We showed that the synergistic action of an epigenetic drug (zebularine) and a transcriptional activator (retinoic acid) could be effectively utilized to induce the regenerative response, thus delineating a novel pharmacological strategy for regeneration. The strategy was effective in the model of ear pinna regeneration in mice, but zebularine acts on different cell types, therefore, a similar approach can be tested in other tissues and organs.

SOD1/Rag2 Mice with Low Copy Number of SOD1 Gene as a New Long-Living Immunodeficient Model of ALS

The most recent research concerning amyotrophic lateral sclerosis (ALS) emphasizes the role of glia in disease development. Thus, one can suspect that the effective therapeutic strategy in treatment of ALS would be replacement of defective glia. One of the basic problems with human glial progenitors (hGRPs) replacement strategies is the time needed for the cells to become fully functional in vivo. The lifespan of most popular high copy number SOD1 mutant mice might be too short to acknowledge benefits of transplanted cells. We focused on developing immunodeficient rag2-/- model of ALS with lower number of transgene copies and longer lifespan. The obtained hSOD1/rag2 double mutant mice have been characterized. QPCR analysis revealed that copy number of hSOD1 transgene varied in our colony (4-8 copies). The difference in transgene copy number may be translated to significant impact on the lifespan. The death of long- and short-living hSOD1/rag2 mice is preceded by muscular weakness as early as one month before death. Importantly, based on magnetic resonance imaging we identified that mutant mice demonstrated abnormalities within the medullar motor nuclei. To conclude, we developed long-living double mutant hSOD1/rag2 mice, which could be a promising model for testing therapeutic utility of human stem cells.