Astrocytes, essential components of the central nervous system (CNS), perform diverse functions such as providing structural support, maintaining ion homeostasis, forming a glial scar after injury, contributing to the blood-brain barrier, and providing neuroprotection, tasks that are critical to proper CNS function. Astrocytes comprise of the soma with radially arranged extendable processes. They display distinctive morphological characteristics to perform their specific functions successfully. Abnormalities in astrocyte morphology have been linked to various neurological disorders. Despite their acknowledged significance, our comprehension of astrocytes remains incomplete, particularly regarding their intricate morphology. In the past, astrocytes were visualized using fluorescence microscopy. Using dye has several disadvantages, including increased chances of photobleaching, perturbations to the system, and not allowing continuous monitoring. This greatly limits the amount of morphological information that can be extracted. To address these challenges, we utilized quantitative phase imaging (QPI), a label-free imaging method that produces 2D and 3D refractive index profiles, allowing us to extract and quantify a plethora of morphological information. In our study, we investigated the impact of silicon nanowire (SiNW) substrates on rat cortical astrocyte morphology, aiming to understand how this substrate influences astrocyte morphology compared to traditional glass substrates. The novelty lies in utilizing QPI to image astrocytes on nanostructured substrates such as SiNW substrates. Astrocytes cultured on SiNW substrates displayed a “star-like” morphology typically found in vivo. This leads to several opportunities for future studies such as quantification of morphological features of astrocytes on SiNW substrates.
Astrocytes play a critical role in regulating brain physiology at ionic, synaptic and whole-organ level. Their function is mainly controlled by ionic signalings, in particular Ca2+ signaling, that mediate cell-cell communication. Infrared pulsed stimulation is a label-free tool that has been previously used to modulate neuronal firing. Here we present the use of infrared pulsed light to stimulate ionic astrocytic signaling in order to modulate astroglial physiology. We present infrared pulsed stimulation as a powerful technique to understand astrocytic function and dysfunction.
We have shown previously that astrocytes are independently sensitive to IR exposure in the context of infrared neural stimulation (INS). More recently, our advances have identified some physiological basis of astrocytic sensitivity to INS. Single pulse INS evokes intracellular calcium signaling primarily mediated through inositol-triphosphate receptor (IP¬3R) activation, rather than thermally sensitive transient receptor protein (TRP) pathways. Interestingly, different dosing strategies for IR appear to evoke different physiology. Our findings suggest that tailoring irradiation parameters with INS may be used for preferentially drive separate physiological responses in astrocytes, and possibly other cell types.
In mammals, neurons are accompanied by numerous cell types, including microglia, oligodendrocytes, and astrocytes. These cells work cohesively to stabilize the neuronal microenvironments and ensure cellular functionality is unperturbed. Studies involving infrared neural stimulation (INS) have been focused on neuronal-type cellular responses, while the effects on non-neuronal cells have been largely unexplored. Astrocytes, in particular, play a key role in maintaining extracellular ion and neurotransmitter concentrations, maintaining osmotic balance, preserving synaptic connectivity, and in mediating neurovascular coupling responses in the brain. Previous work has speculated whether astrocytes are affected by INS in the brain. Here, we characterize the effect of INS on astrocytes using calcium dynamics in response to varying optical parameters and explore whether astrocytic response is driven by neuronal activity or directly by transient thermal energy deposition. Using video-rate calcium-fluorescence multiphoton imaging and nonlinear microscopy of cultured cells, we found that calcium activity in astrocytes is sensitive to infrared light independent of neuronal presence. These cells exhibited similar time-dependent behavior as reported in previous in vivo studies. Success in eliciting calcium responses from a cell, as well as response amplitude, appears to correlate with radiant exposure. The duration and shape of such responses are variable from cell to cell, with some responses aligning with previous observations. Our results suggest that collateral activation of non-neuronal cells, particularly in astrocytes, may play a role when applying INS in vivo.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.