Effects of heat shock on survival, proliferation and differentiation of mouse neural stem cells

Thermosensitive receptors in neural stem cells link stress-induced hyperthermia to impaired neurogenesis via microglial engulfment

Social stress impairs hippocampal neurogenesis and causes psychiatric disorders such as depression. Recent studies have highlighted the significance of increased body temperature in stress responses; however, whether and how social stress–induced hyperthermia affects hippocampal neurogenesis remains unknown. Here, using transgenic mice in which the thermosensitive transient receptor potential vanilloid 4 (TRPV4) is conditionally knocked out in Nestin-expressing neural stem cells (NSCs), we found that social defeat stress (SDS)–induced hyperthermia activates TRPV4 in NSCs in the dentate gyrus and thereby impairs hippocampal neurogenesis. Specifically, SDS activated TRPV4 in NSCs and induced the externalization of phosphatidylserine in NSCs, which was recognized by the brain-resident macrophage, microglia, and promoted the microglial engulfment of NSCs. SDS-induced impairment of hippocampal neurogenesis was ameliorated by NSC-specific knockout of TRPV4 or pharmacological removal of microglia. Thus, this study reveals a previously unknown role of thermosensitive receptors expressed by NSCs in stress responses.

Increased Ruminoreticular Temperature and Body Activity after Foot-and-Mouth Vaccination in Pregnant Hanwoo (Bos taurus coreanae) Cows

How does vaccination against foot-and-mouth disease (FMD) affect pregnant cows? Vaccination is the most effective method of preventing the spread of FMD, but it is linked to sporadic side effects, such as abortion and premature birth, which result in economic loss. In this study, ruminoreticular temperature and body activity were measured before and after FMD vaccination using a ruminoreticular biocapsule sensor in Hanwoo cows at different stages of pregnancy. Compared to the unvaccinated groups, the ruminoreticular temperature increased 12 h after vaccination in the vaccinated groups. This increase in temperature is significantly correlated to vaccination. Compared to the nonpregnant and early pregnancy groups, the ruminoreticular temperature of the late pregnancy group increased sharply by more than 40 °C. Moreover, in nonpregnant and early pregnancy groups, a rapid increase in body activity was observed after FMD vaccinations. Of the 73 pregnant vaccinated cows in the study, a total of five cases had side effects (four abortions and one premature birth). Therefore, changes in the ruminoreticular temperature and activity in pregnant cows can be used as raw data to further clarify the association of FMD vaccination with the loss of a fetus and possibly predict abortion, miscarriage, and premature birth following FMD vaccination.

Heat shock response enhanced by cell culture treatment in mouse embryonic stem cell-derived proliferating neural stem cells

Cells have a regulatory mechanism known as heat shock (HS) response, which induces the expression of HS genes and proteins in response to heat and other cellular stresses. Exposure to moderate HS results in beneficial effects, such as thermotolerance and promotes survival, whereas excessive HS causes cell death. The effect of HS on cells depends on both exogenous factors, including the temperature and duration of heat application, and endogenous factors, such as the degree of cell differentiation. Neural stem cells (NSCs) can self-renew and differentiate into neurons and glial cells, but the changes in the HS response of symmetrically proliferating NSCs in culture are unclear. We evaluated the HS response of homogeneous proliferating NSCs derived from mouse embryonic stem cells during the proliferative phase and its effect on survival and cell death in vitro. The number of adherent cells and the expression ratios of HS protein (Hsp)40 and Hsp70 genes after exposure to HS for 20 min at temperatures above 43°C significantly increased with the extension of the culture period before exposure to HS. In contrast, caspase activity was significantly decreased by extension of the culture period before exposure to HS and suppressed the decrease in cell viability. These results suggest that the culture period before HS remarkably affects the HS response, influencing the expression of HS genes and cell survival of proliferating NSCs in culture.

Cryopreservation of heat-shocked canine adipose-derived mesenchymal stromal cells with 10% dimethyl sulfoxide and 40% serum results in better viability, proliferation, anti-oxidation, and in-vitro differentiation

Cryopreserved canine adipose-derived mesenchymal stromal cells (Ad-MSCs) can be used instantly in dogs for clinical uses. However, cryopreservation results in a reduction of the cellular viability, proliferation, and anti-oxidation of post-thawed Ad-MSCs. Therefore, there is a need for in-vitro procedure to improve post-thawed Ad-MSCs' viability, proliferation, anti-oxidation, and differentiation capacity. In this study, fresh-Ad-MSCs were activated with heat shock, hypoxia (5% O₂), or hypoxia (5% O₂) + heat shock treatments. The results showed that compared to the other treatments, heat shock significantly improved the proliferation rate, anti-oxidation, heat shock proteins and growth factors expressions of canine-fresh-Ad-MSCs. Consequently, fresh-Ad-MSCs were heat-shocked and then cryopreserved with different combinations of dimethyl sulfoxide (Me₂SO) and fetal bovine serum (FBS) to determine the combination that could effectively preserve the cellular viability, proliferation, anti-oxidation and differentiation capacity of Ad-MSCs after cryopreservation. We found that C-HST-Ad-MSCs cryopreserved with 10% Me₂SO + 40% FBS presented significantly (p < 0.05) improved cellular viability, proliferation rate, anti-oxidant capacity, and differentiation potential as compared to C-HST-Ad-MSCs cryopreserved with 1% Me₂SO + 10% FBS or 1% Me₂SO alone or control. We concluded, heat shock treatment is much better to enhance the characteristics of fresh-Ad-MSCs than other treatments, moreover, C-HST-Ad-MSCs in 10% Me₂SO + 40% FBS showed better results compared to other cryopreserved groups. However, future work is required to optimize the expression of heat shock proteins, which would further improve the characteristics of fresh- and cryopreserved-HST-Ad-MSCs and reduce the dependency on Me₂SO and FBS.

Hydroxysafflor yellow A (HSYA) alleviates apoptosis and autophagy of neural stem cells induced by heat stress via p38 MAPK/MK2/Hsp27-78 signaling pathway

This study aimed to explore mechanisms of the effects of hydroxysafflor yellow A (HSYA) on neural stem cells (NSCs) after heat stress (HS). Rat NSCs cells were cultured at 42 °C to impose heat stress. Cell counting kit-8 and Edu assay were used to analyze NSC proliferation. Annexin V/PI apoptosis kit was used to detect NSC apoptosis. Expression and phosphorylation of autophagy and apoptosis-associated proteins were determined by western blotting. We showed that HSYA significantly promoted proliferation and attenuated apoptosis of NSCs after heat stress. HSYA also increased Bcl-2 expression but decreased the expression of Bax and cleaved caspase-3 in NSCs induced by heat stress. In addition, HSYA decreased p38 and Hsp27-78 phosphorylation and MK-2 expression after heat stress, which was consistent with NSCs treated with SB203850 treatment or p38 knockdown. Furthermore, we demonstrated that heat stress increased LC3-II expression and mTOR phosphorylation, and decreased the expression of p62 in NSCs, while HSYA, SB203850 treatment or p38 knockdown reversed these alterations. In conclusion, HSYA significantly reversed the apoptosis and autophagy of NSCs induced by heat stress (P < 0.05), via downregulating MK2 expression and p38 and Hsp27-78 phosphorylation.

Continuous tuneable droplet ejection via pulsed surface acoustic wave jetting

We report a miniaturised platform for continuous production of single or multiple liquid droplets with diameters between 60 and 500 μm by interfacing a capillary-driven self-replenishing liquid feed with pulsed excitation of focussed surface acoustic waves (SAWs). The orifice-free operation circumvents the disadvantages of conventional jetting systems, which are often prone to clogging that eventuates in rapid degradation of the operational performance. Additionally, we show the possibility for flexibly tuning the ejected droplet size through the pulse width duration, thus avoiding the need for a separate device for every different droplet size required, as is the case for systems in which the droplet size is set by nozzles and orifices, as well as preceding ultrasonic jetting platforms where the droplet size is controlled by the operating frequency. Further, we demonstrate that cells can be jetted and hence printed onto substrates with control over the cell density within the droplets down to single cells. Given that the jetting does not lead to significant loss to the cell's viability or ability to proliferate, we envisage that this versatile jetting method can potentially be exploited with further development for cell encapsulation, dispensing and 3D bioprinting applications.

Direct exposure to mild heat promotes proliferation and neuronal differentiation of neural stem/progenitor cells in vitro

Heat acclimation in rats is associated with enhanced neurogenesis in thermoregulatory centers of the hypothalamus. To elucidate the mechanisms for heat acclimation, we investigated the effects of direct mild heat exposure on the proliferation and differentiation of neural stem/progenitor cells (NSCs/NPCs). The NSCs/NPCs isolated from forebrain cortices of 14.5-day-old rat fetuses were propagated as neurospheres at either 37.0°C (control) or 38.5°C (mild heat exposure) for four days, and the effects on proliferation were investigated by MTS cell viability assay, measurement of neurosphere diameter, and counting the total number of cells. The mRNA expressions of heat shock proteins (HSPs) and brain-derived neurotrophic factor (BDNF), cAMP response element-binding (CREB) protein and Akt phosphorylation levels, and intracellular reactive oxygen species (ROS) levels were analyzed using real time PCR, Western blotting and CM-H₂DCFDA assay respectively. Heat exposure under proliferation condition increased NSC/NPC viability, neurosphere diameter, and cell count. BDNF mRNA expression, CREB phosphorylation, and ROS level were also increased by heat exposure. Heat exposure increased HSP27 mRNA expression concomitant with enhanced p-Akt level. Moreover, treatment with LY294002 (a PI3K inhibitor) abolished the effects of heat exposure on NSC/NPC proliferation. Furthermore, heat exposure under differentiation conditions increased the proportion of cells positive for Tuj1 (a neuronal marker). These findings suggest that mild heat exposure increases NSC/NPC proliferation, possibly through activation of the Akt pathway, and also enhances neuronal differentiation. Direct effects of temperature on NSCs/NPCs may be one of the mechanisms involved in hypothalamic neurogenesis in heat-acclimated rats. Such heat-induced neurogenesis could also be an effective therapeutic strategy for neurodegenerative diseases.

Strain-Rate Dependency of Axonal Tolerance for Uniaxial Stretching

This study aims to clarify the relation between axonal deformation and the onset of axonal injury. Firstly, to examine the influence of strain rate on the threshold for axonal injury, cultured neurons were subjected to 12 types of stretching (strains were 0.10, 0.15, and 0.20 and strain rates were 10, 30, 50, and 70 s^-1). The formation of axonal swellings and bulbs increased significantly at strain rates of 50 and 30 s^-1 with strains of 0.15 and 0.20, respectively, even though those formations did not depend on strain rates in cultures exposed to a strain of 0.10. Then, to examine the influence of the strain along an axon on axonal injury, swellings were measured at every axonal angle in the stretching direction. The axons that were parallel to stretching direction were injured the most. Finally, we proposed an experimental model that subjected an axon to more accurate strain. This model observed the process of axonal injury formation by detecting the same neuron before and after stretching. These results suggest that the strain-rate dependency of axonal tolerance is induced by a higher magnitude of loading strain and an experiment focusing on axonal strain is required for obtaining more detailed injury criteria for an axon.

Neural progenitor cell proliferation in the hypothalamus is involved in acquired heat tolerance in long-term heat-acclimated rats

Constant exposure to moderate heat facilitates progenitor cell proliferation and neuronal differentiation in the hypothalamus of heat-acclimated (HA) rats. In this study, we investigated neural phenotype and responsiveness to heat in HA rats’ hypothalamic newborn cells. Additionally, the effect of hypothalamic neurogenesis on heat acclimation in rats was evaluated. Male Wistar rats (5 weeks old) were housed at an ambient temperature (T_a) of 32°C for 6 days (STHA) or 40 days (LTHA), while control (CN) rats were kept at a T_a of 24°C for 6 days (STCN) or 40 days (LTCN). Bromodeoxyuridine (BrdU) was intraperitoneally injected daily for five consecutive days (50 mg/kg/day) after commencing heat exposure. The number of hypothalamic BrdU-immunopositive (BrdU+) cells in STHA and LTHA rats was determined immunohistochemically in brain samples and found to be significantly greater than those in respective CN groups. In LTHA rats, approximately 32.6% of BrdU+ cells in the preoptic area (POA) of the anterior hypothalamus were stained by GAD67, a GABAergic neuron marker, and 15.2% of BrdU+ cells were stained by the glutamate transporter, a glutamatergic neuron marker. In addition, 63.2% of BrdU+ cells in the POA were immunolabeled with c-Fos. Intracerebral administration of the mitosis inhibitor, cytosine arabinoside (AraC), interfered with the proliferation of neural progenitor cells and acquired heat tolerance in LTHA rats, whereas the selected ambient temperature was not changed. These results demonstrate that heat exposure generates heat responsive neurons in the POA, suggesting a pivotal role in autonomic thermoregulation in long-term heat-acclimated rats.

Remote Control of Cellular Functions: The Role of Smart Nanomaterials in the Medicine of the Future

The remote control of cellular functions through smart nanomaterials represents a biomanipulation approach with unprecedented potential applications in many fields of medicine, ranging from cancer therapy to tissue engineering. By actively responding to external stimuli, smart nanomaterials act as real nanotransducers able to mediate and/or convert different forms of energy into both physical and chemical cues, fostering specific cell behaviors. This report describes those classes of nanomaterials that have mostly paved the way to a "wireless" control of biological phenomena, focusing the discussion on some examples close to the clinical practice. In particular, magnetic fields, light irradiation, ultrasound, and pH will be presented as means to manipulate the cellular fate, due to the peculiar physical/chemical properties of some smart nanoparticles, thus providing realistic examples of "nanorobots" approaching the visionary ideas of Richard Feynman.

Fixed, low radiant exposure vs. incremental radiant exposure approach for diode laser hair reduction: a randomized, split axilla, comparative single-blinded trial

BACKGROUND

Diode lasers are the most commonly used treatment modalities for unwanted hair reduction. Only a few controlled clinical trials but not a single randomized controlled trial (RCT) compared the impact of various laser parameters, especially radiant exposure, onto efficacy, tolerability and safety of laser hair reduction.

OBJECTIVE

To compare the safety, tolerability and mid-term efficacy of fixed, low and incremental radiant exposures of diode lasers (800 nm) for axillary hair removal, we conducted an intrapatient, left-to-right, patient- and assessor-blinded and controlled trial.

METHODS

Diode laser (800 nm) treatments were evaluated in 39 study participants (skin type II-III) with unwanted axillary hairs. Randomization and allocation to split axilla treatments were carried out by a web-based randomization tool. Six treatments were performed at 4- to 6-week intervals with study subjects blinded to the type of treatment. Final assessment of hair reduction was conducted 6 months after the last treatment by means of blinded 4-point clinical scale using photographs. The primary endpoint was reduction in hair growth, and secondary endpoints were patient-rated tolerability and satisfaction with the treatment, treatment-related pain and adverse effects.

RESULTS

Excellent reduction in axillary hairs (≥ 76%) at 6-month follow-up visit after receiving fixed, low and incremental radiant exposure diode laser treatments was obtained in 59% and 67% of study participants respectively (Z value: 1.342, P = 0.180). Patients reported lower visual analogue scale (VAS) pain score on the fixed (4.26) than on the incremental radiant exposure side (5.64) (P < 0.0003). The only side-effect was mild and transient erythema. Subjects better tolerated the fixed, low radiant exposure protocol (P = 0.03). The majority of the study participants were satisfied with both treatments.

CONCLUSION

Both low and incremental radiant exposures produced similar hair reduction and high and comparable patient satisfaction. However, low radiant exposure diode laser treatments were less painful and better tolerated.

Induction of neurite outgrowth in PC12 cells treated with temperature-controlled repeated thermal stimulation

To promote the functional restoration of the nervous system following injury, it is necessary to provide optimal extracellular signals that can induce neuronal regenerative activities, particularly neurite formation. This study aimed to examine the regulation of neuritogenesis by temperature-controlled repeated thermal stimulation (TRTS) in rat PC12 pheochromocytoma cells, which can be induced by neurotrophic factors to differentiate into neuron-like cells with elongated neurites. A heating plate was used to apply thermal stimulation, and the correlation of culture medium temperature with varying surface temperature of the heating plate was monitored. Plated PC12 cells were exposed to TRTS at two different temperatures via heating plate (preset surface temperature of the heating plate, 39.5°C or 42°C) in growth or differentiating medium for up to 18 h per day. We then measured the extent of growth, neuritogenesis, or acetylcholine esterase (AChE) activity (a neuronal marker). To analyze the mechanisms underlying the effects of TRTS on these cells, we examined changes in intracellular signaling using the following: tropomyosin-related kinase A inhibitor GW441756; p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580; and MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor U0126 with its inactive analog, U0124, as a control. While a TRTS of 39.5°C did not decrease the growth rate of cells in the cell growth assay, it did increase the number of neurite-bearing PC12 cells and AChE activity without the addition of other neuritogenesis inducers. Furthermore, U0126, and SB203580, but not U0124 and GW441756, considerably inhibited TRTS-induced neuritogenesis. These results suggest that TRTS can induce neuritogenesis and that participation of both the ERK1/2 and p38 MAPK signaling pathways is required for TRTS-dependent neuritogenesis in PC12 cells. Thus, TRTS may be an effective technique for regenerative neuromedicine.

Pluripotent stem cell-derived neural stem cells: From basic research to applications

Basic research on pluripotent stem cells is designed to enhance understanding of embryogenesis, whereas applied research is designed to develop novel therapies and prevent diseases. Attainment of these goals has been enhanced by the establishment of embryonic stem cell lines, the technological development of genomic reprogramming to generate induced-pluripotent stem cells, and improvements in vitro techniques to manipulate stem cells. This review summarizes the techniques required to generate neural cells from pluripotent stem cells. In particular, this review describes current research applications of a simple neural differentiation method, the neural stem sphere method, which we developed.

Genetic, epigenetic, and environmental contributions to neural tube closure

The formation of the embryonic brain and spinal cord begins as the neural plate bends to form the neural folds, which meet and adhere to close the neural tube. The neural ectoderm and surrounding tissues also coordinate proliferation, differentiation, and patterning. This highly orchestrated process is susceptible to disruption, leading to neural tube defects (NTDs), a common birth defect. Here, we highlight genetic and epigenetic contributions to neural tube closure. We describe an online database we created as a resource for researchers, geneticists, and clinicians. Neural tube closure is sensitive to environmental influences, and we discuss disruptive causes, preventative measures, and possible mechanisms. New technologies will move beyond candidate genes in small cohort studies toward unbiased discoveries in sporadic NTD cases. This will uncover the genetic complexity of NTDs and critical gene-gene interactions. Animal models can reveal the causative nature of genetic variants, the genetic interrelationships, and the mechanisms underlying environmental influences.