Harnessing the Stem Cell Niche in Regenerative Medicine: Innovative Avenue to Combat Neurodegenerative Diseases

Regenerative medicine harnesses the body's innate capacity for self-repair to restore malfunctioning tissues and organs. Stem cell therapies represent a key regenerative strategy, but to effectively harness their potential necessitates a nuanced understanding of the stem cell niche. This specialized microenvironment regulates critical stem cell behaviors including quiescence, activation, differentiation, and homing. Emerging research reveals that dysfunction within endogenous neural stem cell niches contributes to neurodegenerative pathologies and impedes regeneration. Strategies such as modifying signaling pathways, or epigenetic interventions to restore niche homeostasis and signaling, hold promise for revitalizing neurogenesis and neural repair in diseases like Alzheimer's and Parkinson's. Comparative studies of highly regenerative species provide evolutionary clues into niche-mediated renewal mechanisms. Leveraging endogenous bioelectric cues and crosstalk between gut, brain, and vascular niches further illuminates promising therapeutic opportunities. Emerging techniques like single-cell transcriptomics, organoids, microfluidics, artificial intelligence, in silico modeling, and transdifferentiation will continue to unravel niche complexity. By providing a comprehensive synthesis integrating diverse views on niche components, developmental transitions, and dynamics, this review unveils new layers of complexity integral to niche behavior and function, which unveil novel prospects to modulate niche function and provide revolutionary treatments for neurodegenerative diseases.

A Self-Regenerating Artificial Cell, that is One Step Closer to Living Cells: Challenges and Perspectives

Controllable, self-regenerating artificial cells (SRACs) can be a vital advancement in the field of synthetic biology, which seeks to create living cells by recombining various biological molecules in the lab. This represents, more importantly, the first step on a long journey toward creating reproductive cells from rather fragmentary biochemical mimics. However, it is still a difficult task to replicate the complex processes involved in cell regeneration, such as genetic material replication and cell membrane division, in artificially created spaces. This review highlights recent advances in the field of controllable, SRACs and the strategies to achieve the goal of creating such cells. Self-regenerating cells start by replicating DNA and transferring it to a location where proteins can be synthesized. Functional but essential proteins must be synthesized for sustained energy generation and survival needs and function in the same liposomal space. Finally, self-division and repeated cycling lead to autonomous, self-regenerating cells. The pursuit of controllable, SRACs will enable authors to make bold advances in understanding life at the cellular level, ultimately providing an opportunity to use this knowledge to understand the nature of life.

Environmentally Tolerant Ionic Hydrogel with High Power Density for Low-Grade Heat Harvesting

Harvesting low-grade heat by an ionic hydrogel thermoelectric generator (ITEG) into useful electricity is promising to power flexible electronics. However, the poor environmental tolerance of the ionic hydrogel limits its application. Herein, we demonstrate an ITEG with high thermoelectric properties, as well as excellent capabilities of water retention, freezing resistance, and self-regeneration. The obtained ITEG can maintain the original water content at ambient conditions (302 K, 65% relative humidity (RH)) for 7 days and keep unfreezing at a low temperature (253 K). It can even be self-regenerated and recovered to its original state after a water loss in high-temperature conditions. Furthermore, a high ionic Seebeck coefficient of 11.3 mV K^-1 and an impressive power density of 167.90 mW m^-2 are achieved under a temperature difference of 20 K. A high power density of 60.00 mW m^-2 can also be maintained even at 258 K. After drying and regeneration, ITEG-re could even exhibit a higher ionic Seebeck coefficient of 11.8 mV K^-1. Successful lighting of light-emitting diodes (LEDs) and charging of capacitors demonstrate the great potential of ITEG to provide continuous energy supply for powering flexible electronics.

Robust Self-Regeneratable Stiff Living Materials Fabricated from Microbial Cells

Living systems have not only the exemplary capability to fabricate materials (e.g. wood, bone) under ambient conditions but they also consist of living cells that imbue them with properties like growth and self-regeneration. Like a seed that can grow into a sturdy living wood, we wondered: can living cells alone serve as the primary building block to fabricate stiff materials? Here we report the fabrication of stiff living materials (SLMs) produced entirely from microbial cells, without the incorporation of any structural biopolymers (e.g. cellulose, chitin, collagen) or biominerals (e.g. hydroxyapatite, calcium carbonate) that are known to impart stiffness to biological materials. Remarkably, SLMs are also lightweight, strong, resistant to organic solvents and can self-regenerate. This living materials technology can serve as a powerful biomanufacturing platform to design and develop advanced structural and cellular materials in a sustainable manner.

Cell Proliferation to Evaluate Preliminarily the Presence of Enduring Self-Regenerative Antioxidant Activity in Cerium Doped Bioactive Glasses

(1) Background: a cell evaluation focused to verify the self-regenerative antioxidant activity is performed on cerium doped bioactive glasses. (2) Methods: the glasses based on 45S5 Bioglass^®, are doped with 1.2 mol%, 3.6 mol% and 5.3 mol% of CeO₂ and possess a polyhedral shape (~500 µm²). Glasses with this composition inhibit oxidative stress by mimicking catalase enzyme (CAT) and superoxide dismutase (SOD) activities; moreover, our previous cytocompatibility tests (neutral red (NR), 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Bromo-2-deoxyUridine (BrdU)) reveal that the presence of cerium promotes the absorption and vitality of the cells. The same cytocompatibility tests were performed and repeated, in two different periods (named first and second use), separated from each other by four months. (3) Results: in the first and second use, NR tests indicate that the presence of cerium promotes once again cell uptake and viability, especially after 72 h. A decrease in cell proliferation it is observed after MTT and BrdU tests only in the second use. These findings are supported by statistically significant results (4) Conclusions: these glasses show enhanced proliferation, both in the short and in the long term, and for the first time such large dimensions are studied for this kind of study. A future prospective is the implantation of these bioactive glasses as bone substitute in animal models.

Hydro-Assisted Self-Regenerating Brominated N-Alkylated Thiophene Diketopyrrolopyrrole Dye Nanofibers-A Sustainable Synthesis Route for Renewable Air Filter Materials

With rising global concerns over the alarming levels of particulate pollution, a sustainable air quality management is the need of the hour. Air filtration research has gained momentum in recent years. However, the research perspective is still blinkered toward formulating new fiber systems for the energy-intensive electrospinning process to fabricate high quality factor air filters. A holistic approach on sustainable air filtration models is still lacking. The air filter model presented in this work uses a simple process involving water-induced self-organization and self-regeneration of nanofibers, and an easy recycling route after the filter life that not only facilitates reuse of the microfibrous scaffold holding the nanofibers but also allows renewal of nanofibers. Three generations of air filters are fabricated and tested, all having high particulate matter (PM)-adsorbing tendency, high filtration efficiency (>95%), and high Young's modulus (≈5 GPa). The renewable air filters offer a sustainable alternative to the present cost-intensive electrospun air filters.

Self-Regeneration Performance and Characterization of Silver-Containing Activated Carbon Fibers Coated by Titanium Dioxide

In this study, wood-based activated carbon fibers (WACF) were modified by Ag nanoparticles (AgNPs) and TiO₂ films. The coating of TiO₂ films decreased the AgNPs agglomeration and exfoliation on WACF. As the soaking concentration of AgNO₃ solution (S_conc) increased, AgNPs size and content increased, while the pore volume (especially micropore volume) of fibers reduced. However, at higher S_conc in the range of 0.2 to0.4 mol/L, only slight variations in AgNPs content and pore structure were observable for WACF/TiO₂/Ag (Ag-containing WACF coated by TiO₂ film). WACF/TiO₂/Ag-0.1 (0.1 was the soaking concentration of AgNO₃ solution, mol/L) represented the best self-regeneration performance under the visible light irradiation. The self-regeneration performance of WACF/TiO₂/Ag was determined by the synergistic effects of two factors: adsorption and photodegradation. The abundant pores of WACF/TiO₂/Ag-0.1 increased the methylene blue (MB) concentration of TiO₂ surrounding and facilitated the MB photodegradation. Meanwhile, their suitable Ag content enhanced MB photodegradation. Furthermore, the principal pathway of a chemical reaction between Ag⁺ and WACF was interpreted based on the data of surface elemental constituents and surface functional groups.

A High-Performance Self-Regenerating Solar Evaporator for Continuous Water Desalination

Emerging solar desalination by interfacial evaporation shows great potential in response to global water scarcity because of its high solar-to-vapor efficiency, low environmental impact, and off-grid capability. However, solute accumulation at the heating interface has severely impacted the performance and long-term stability of current solar evaporation systems. Here, a self-regenerating solar evaporator featuring excellent antifouling properties using a rationally designed artificial channel-array in a natural wood substrate is reported. Upon solar evaporation, salt concentration gradients are formed between the millimeter-sized drilled channels (with a low salt concentration) and the microsized natural wood channels (with a high salt concentration) due to their different hydraulic conductivities. The concentration gradients allow spontaneous interchannel salt exchange through the 1-2 µm pits, leading to the dilution of salt in the microsized wood channels. The drilled channels with high hydraulic conductivities thus function as salt-rejection pathways, which can rapidly exchange the salt with the bulk solution, enabling the real-time self-regeneration of the evaporator. Compared to other salt-rejection designs, the solar evaporator exhibits the highest efficiency (≈75%) in a highly concentrated salt solution (20 wt% NaCl) under 1 sun irradiation, as well as long-term stability (over 100 h of continuous operation).

Bone regeneration after sinonasal mucocele marsupialization: What really happens over time?

OBJECTIVE

To evaluate the necessity of reconstructing the eroded bony boundaries after mucocele marsupialization when the mucoperiosteum has been spared.

STUDY DESIGN

Retrospective review of 308 patients treated for a sinonasal mucocele. Of these, 116 showed areas of bone reabsorption in their preoperative computed tomography (CT) scan.

METHODS

Of 116 patients showing one or more areas of bone reabsorption who underwent marsupialization of the mucocele, whether using a purely endonasal endoscopic approach or a combined approach, the common factor was that the mucoperiosteum of the paranasal sinus had always been spared and the eroded bone had never been reconstructed. After rigorous selection, 12 adult patients were enrolled to undergo a postoperative CT scan in order to verify what had happened to the eroded bone at least 3 years following the surgical marsupialization of the mucocele.

RESULTS

In 66,6% of patients, the postoperative CT scan showed complete self-reconstruction of bone that had previously been eroded by the mucocele. No enophthalmus, meningocele, or other facial deformities were noted in our selection group, despite not having undergone surgical reconstruction of the bone.

CONCLUSIONS

Even taking into account the small number of patients enrolled in the present study, indications are that there is no need to reconstruct the eroded bone, as would appear from our results that sparing the mucoperiosteum is enough to enable the bone to regenerate. Nevertheless, larger scale studies of the subject are merited.

Platelet-derived growth factor BB gene-released scaffolds: biosynthesis and characterization

Tissue engineering generally requires three basic elements; stem/progenitor cells, inductive agents and a biomaterial scaffold; the latter is one of the key components which directly influences cellular activity and matrix formation. Commonly used scaffolds to repair defects in general do not induce stem cell recruitment, which is an essential element to tissue regeneration. In this study, fabrication of a scaffold which is capable of restoring damaged tissue through the recruitment of mesenchymal stem cells (MSCs) by gene therapy of the gene encoding platelet-derived growth factor-B (PDGF-B) was investigated. PDGF-B adenovirus (AdPDGF) was combined into novel mesoporous bioglass-silk fibrin scaffolds, which were characterized for their controlled release and sustained bioactivity. Our results demonstrate that these scaffolds can release PDGF-B adenovirus for up to 3 weeks and increase MSC recruitment, both in vitro and following subcutaneous implantation in mice. Osseous calvarial defects in mice further demonstrate the ability of these scaffolds to enhance tissue regeneration through stem cell homing. This study demonstrates the potent ability of host stem cells to regenerate tissue defects through recruitment of MSCs via gene therapy. Copyright © 2013 John Wiley & Sons, Ltd.