(Georgia Institute of Technology, 2022-05)
Garcia, Violet
Peripheral nerve injury currently has a poor prognosis that often results in motor deficits such as discoordination and co-contraction of muscle antagonists (Brushart, 2011; Horstman et al., 2019). Because of this, studying the effects of peripheral nerve injury on the morphology and functional connectivity of the central nervous system (CNS) is of utmost importance. Our study centers around the anatomical changes that occur after peripheral nerve injury in the rat spinal cord, namely the degradation of Ia input defined by the expression of the vesicular glutamate transporter 1 (VGLUT1). This study is based on the proposed microglia-dependent mechanism of permanent synaptic loss from the Rotterman et al. (2019) paper. We ask if 1) we can suppress microglia accumulation with minocycline, a tetracycline antibiotic, and 2) if using minocycline can help preserve the Ia sensory afferent synapses after nerve injury. We first retrogradely labeled the medial gastrocnemius motor pool in 15 adult Wistar rats. One week later, we transected the medial gastrocnemius nerve in the left hindlimb. Rats were either treated with vehicle or minocycline for 14 days following injury. Control animals were also produced. At 14 days post injury, animals were perfused, spinal cords were collected and subsequently sectioned. Using immunohistochemistry (IHC), we labeled VGLUT1 synapses on these injured motor neurons and imaged them with confocal microscopy for subsequent reconstruction and analysis. We found four main results: 1) treatment with minocycline for 14 days after nerve injury does not seem to prevent microglia proliferation, 2) the chromalytic reaction (somatic expansion) that commonly occurs after axotomy did not seem to occur in the minocycline- treated animals, 3) there was partial preservation of somatic VGLUT1 synapses in the minocycline-treatment animals, and 4) there was complete dendritic VGLUT1 synapse preservation in the minocycline-treated animals. Although there were limitations to the study with regards to the methods of counting microglia, the study produced robust conclusions that will aid in the development of further research. Future studies should be conducted on the efficacy of minocycline preserving the synapses, the molecular mechanisms underlying minocycline’s effects, and the potential recovery of nerve function.
(Georgia Institute of Technology, 2021-05)
Pfahl, Emily Lynn
Oxaliplatin (OX) is a widely used chemotherapy compound used in the treatment of colorectal cancers (CRCs). Patients treated with OX often exhibit severe side effects, including motor dysfunction and imbalance, potentially influenced by the inability of sensory neurons, including muscle spindle afferents (MSAs), to repetitively fire, which is needed to properly encode information about limb movement. Even though OX is prescribed in a majority of CRCs, it is currently unknown how the compound causes the aforementioned side effects. The aim of the present study was to determine if OX acts through modification of the voltage-gated potassium channel Kv3.3, which is hypothesized to promote repetitive firing. To test this hypothesis, the soleus nerve and muscle were isolated from control mice. A series of ramp and triangular stretches were applied to the muscles, and afferent firing responses were recorded. A synthetic Kv3.3-knockdown line of mice was created using Kv3.3 siRNA (ThermoFischer Scientific). The soleus nerve and muscle were isolated from these mice, the same stretches were applied to the muscle, and MSA recordings were taken and compared to the control MSA responses. Preliminary data suggest that afferent responses to stretch are altered in the Kv3.3-knockdown mice, but as of this time, not enough data has been collected to make statistically significant claims. Future work will focus on collecting enough Kv3.3-knockdown data to perform statistical analyses on the data, as well as on performing immunohistochemical (IHC) staining of tissue from knockdown animals to ensure silencing of Kv3.3.
(Georgia Institute of Technology, 2020-05)
Palanivel, Shivani
Neural stem cells (NSCs) are important multipotent adult stem cells capable of
self-renewal and differentiation into various cell types present in the central nervous system. Studying the characteristics of NSCs and their differentiation offers insights into developmental mechanisms and allows us to assess their utility in vitro disease modeling and neurotoxicological research.
This study investigates the properties of NSC during propagation and differentiation in culture. Neurospheres, formed from NSC aggregates, were cultured and examined for morphology and growth rate by cell counting and size analysis. Neurospheres were induced to differentiate toward neural network formation. The expression of markers of NSC and astrocytes in neurospheres during differentiation was detected by immunostaining methods. NSC multiplied with an exponential proliferation rate accompanied by a steady increase in neurosphere diameter. The neurosphere cells expressed Nestin, an NSC/ progenitor cell marker, when cultured in self-renewal media, and displayed pronounced GFAP expression after induction of differentiation indicating a prevalence of astrocytes. Further studies will provide better understanding of NSC characteristics that may be applied for the advancement of stem cell therapy to help combat neurodegenerative diseases.