biology project and need support to help me learn.
I need someone’s expertise on checking the introduction draft I have for my senior thesis. I need them to improve it and make it a very legit paper. they should also check for plagiarism and correct anything that is considered plagiarism(VERY IMPORTANT). The word count should not decrease. I do not want my paper to be summarized or shortened in any way.
Requirements: no less than 7 pages
INTRODUCTION
The somatosensory system is part of the nervous system responsible for processing sensory information related to touch, temperature, pain, and proprioception (the sense of the body’s position and movement in space). The process begins with specialized sensory receptors called mechanoreceptors, thermoreceptors, and nociceptors, which are located in the skin, muscles, and joints. These receptors respond to different types of stimuli and send electrical signals, called action potentials, to the spinal cord and brain. The signals travel through specialized nerve fibers, known as sensory neurons, which are organized into bundles called nerves. The nerves carrying sensory information from the skin, muscles, and joints enter the spinal cord through the dorsal root ganglion. Once inside the spinal cord, the sensory information is processed and then transmitted to several brain regions, including those responsible for pain perception. The group of special interneurons responsible for processing and transmission of sensory information in the brainstem is spinal sensory interneurons (INs) (Todd A. J., 2010). The information processed by the sensory interneurons allows us to perceive sensations such as touch, pressure, temperature, pain, and the position and movement of our body in space. This somatosensory system is essential for our ability to interact with the environment, detect potential threats, and perform motor tasks with precision.
Sensory interneurons are located in the dorsal horn of the spinal cord. Sensory interneurons are of different varieties which can be recognized by a combination of transcription factor expression and their origin in the developing dorsal spinal cord. These interneurons play a key role in sensory processing and integration within the somatosensory system. They help to filter and amplify sensory information, allowing us to perceive and respond to environmental stimuli. They also play a role in modulating pain perception and controlling reflexes and motor responses to sensory stimuli. Overall, sensory interneurons are essential for the proper functioning of the somatosensory system and play a critical role in our ability to perceive and respond to sensory stimuli. When these neurons are damaged in injuries such as spinal cord injuries (SCIs), patients lose various sensations along with the ability to move coordinately due to damage to both the sensory and the motor system.
According to the World Health Organization (WHO), it is estimated that approximately 250,000 to 500,000 people suffer from spinal cord injury (SCI) worldwide each year. These estimates are based on available data from various countries, and the actual number of cases may be higher due to under-reporting and a lack of reliable data from some regions. SCI is a serious and often life-altering condition that can result in long-term disability and reduced quality of life. According to a study by Lee et al. (2020), individuals with spinal cord injuries may experience a variety of physical and psychological challenges, including loss of motor function, chronic pain, and depression. The global burden of SCI is significant in terms of human suffering and loss of productivity but also the economic costs of medical care, rehabilitation, and ongoing support for individuals with SCI and their families.
According to the National Institute of Neurological Disorders and Stroke (2019), spinal cord injury can be classified into two main types of complete and incomplete based on the degree of damage to the spinal cord and the resulting loss of sensory and motor function. A complete spinal cord injury results in the total loss of sensory and motor function below the level of the injury. There is no feeling or movement below the level of injury, while an incomplete spinal cord injury results in partial loss of sensory and/or motor function below the level of the injury. There are different types of incomplete spinal cord injuries. In patients with anterior cord syndrome damage to the front of the spinal cord results in loss of motor function and pain and temperature sensation. Those suffering from central cord syndrome experience damage to the center of the spinal cord resulting in weakness and loss of function in the arms and hands. The brown-Séquard syndrome is a condition in which damage to one side of the spinal cord causes weakness and loss of function on that side of the body, as well as a loss of pain and temperature sensation on the opposite side of the body. Damage to the lower end of the spinal cord, known as conus medullaris syndrome, can lead to various symptoms, including bladder and bowel dysfunction, weakness in the legs, and loss of sensation in the area where one would be sitting on a saddle. The neurological disorder known as cauda equina syndrome is characterized by damage to the nerve roots located at the lower end of the spinal cord, which results in a variety of symptoms including lower limb weakness, urinary and fecal incontinence, and sensory loss in the perianal region, or saddle area.
The severity and extent of a spinal cord injury can vary depending on the location and nature of the injury. It is important to note that each individuals injury and resulting disability will be unique.
There have been some studies investigating the potential for stem cell-based therapies to promote the regeneration of sensory interneurons in mouse models of spinal cord injury.
One study published in 2018 in the journal Cell Stem Cell demonstrated that transplantation of mouse embryonic stem cell-derived neural progenitors into the spinal cord of mice with SCI resulted in the formation of functional neurons that were able to integrate into the host spinal cord circuitry and contribute to the restoration of motor function (Lu et al., 2018). However, this study did not investigate the regeneration of the sensory circuitry and the restoration of sensory function in mice, and the translation of these findings to humans would require further research.
The paper “Deriving Dorsal Spinal Sensory Interneurons from Human Pluripotent Stem Cells” describes a study in which the butler lab successfully derived sensory interneurons from human pluripotent stem cells in vitro. The researchers used a combination of small molecules and growth factors to direct the differentiation of the stem cells into sensory interneurons. They found that the derived sensory interneurons exhibited molecular and functional properties characteristic of endogenous dorsal spinal sensory interneurons (Gupta et al., 2018). Overall, this study provides proof of concept for deriving functional sensory interneurons from human pluripotent stem cells, which has potential implications for the development of cell-based therapies for spinal cord injury and other neurological disorders.
Following the publication of the last scientific paper mentioned, Dr. Gupta and Butler lab developed two directed differentiation protocols to produce sensory spinal interneurons from human embryonic stem cells and induced pluripotent stem cells.
The first protocol involves using retinoic acid to induce pain, itch, and heat-mediating interneurons, while the second protocol uses retinoic acid and bone morphogenetic protein 4 to induce proprioceptive and mechanosensory interneurons in the stem cell cultures. These protocols are seen as an important step in the development of therapies to restore sensation in patients with spinal cord injuries. While these protocols were the important first steps, they are far from recapitulating the full repertoire of sensory interneurons observed in the spinal cord. For example, the protocol published earlier by the Butler lab uses neuroectoderm to induce sensory interneurons that result in the generation of 4 classes of INs instead of 6 (Gupta et. al., 2018). Recently, studies from the butler lab have shown that when mouse stem cells were directed toward another intermediate cell type called neuromesodermal progenitors (NMPs), this leads to the generation of a full complement of sensory interneurons (6 classes of INs). We have recently identified conditions to generate NMPs from the human embryonic stem cell as well and identified that human NMPs also can generate all 6 classes of sensory INs. However, it remains to be determined why these two protocols differ in their capacity to induce different classes of INs and if the INs generated through different protocols are molecularly and functionally similar.
Thus, in my BRIDGES thesis with Dr. Gupta, in the lab of Dr. Samantha Butler, I aim to characterize the differentiation path taken by stem cells when directed by different protocols using RNA-Seq analysis. I will also analyze if INs generated through these protocols are functionally similar using virally encoded calcium sensors that monitor neuronal activity in real time.
References
Todd A. J. (2010). Neuronal circuitry for pain processing in the dorsal horn.?Nature reviews. Neuroscience,?11(12), 823??836.
World Health Organization. (2022). Spinal cord injury. Fact sheet.
Lu, P., Wang, Y., Graham, L., McHale, K., Gao, M., Wu, D., Brock, J., Blesch, A., & Rosenzweig, E. S. (2018). Long-distance growth and connectivity of neural stem cells after severe spinal cord injury. Cell Stem Cell, 22(2), 206-210. doi: 10.1016/j.stem.2018.01.017
Gupta, Sandeep & Sivalingam, Daniel & Hain, Samantha & Makkar, Christian & Sosa, Enrique & Clark, Amander & Butler, Samantha. (2018). Deriving Dorsal Spinal Sensory Interneurons from Human Pluripotent Stem Cells. Stem Cell Reports. 10. 10.1016/j.stemcr.2017.12.012.
Gupta, Sandeep & Yamauchi, Ken & Novitch, Bennett & Butler, Samantha. (2021). Derivation of dorsal spinal sensory interneurons from human pluripotent stem cells. STAR Protocols. 2. 100319. 10.1016/j.xpro.2021.100319.
National Institute of Neurological Disorders and Stroke. (2019). Spinal Cord Injury: Hope Through Research.
Lee, Y.-I., Lee, Y.-S., & Kim, Y.-H. (2020). Spinal cord injury: A review of current therapy, future treatments, and basic science frontiers. Experimental Neurobiology, 29(4), 205-213.
SpinalCord.com. Spinal Cord Injury: Types of Spinal Cord Injuries. Spinal Cord Injury | Types of Spinal Cord Injuries | SpinalCord.com. [Accessed 2020 Feb25].
https://www.spinalcord.com/types-of-spinal-cord-injuries
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