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Undergraduate Research Opportunities Program

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Now showing 1 - 5 of 5
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The effects of AT-RvD1 delivery on SPM metabolism, myeloid recruitment, and myogenesis in a murine model of Volumetric Muscle Loss injury

2022-05 , Pittman, Frank S.

Volumetric Muscle Loss injury (VML) is the partial ablation of skeletal muscle, usually on the extremities, sustained through traumatic or surgical means, such as motor vehicle accidents, military combat, or surgical resection. The frank loss of musculature characteristic of VML sufficiently disrupts or eliminates the wound’s endogenous repair mechanisms such that healing becomes virtually impossible 1,2. VML patients must deal with permanent functional impairments, chronic inflammation, and chronic pain 1. Current clinical strategies for VML treatment include muscle flap autografts and free tissue transfer that, while salvaging the injured limb, are often no better than amputation in terms of functional improvement and patient quality of life 3,4. Much research in the field has been focused on overcoming the challenges and deficits associated with this clinical gold-standard. Biomaterial strategies using decellularized extracellular matrix (ECM) derived from skeletal muscle, porcine small intestinal submucosa (SIS), and urinary bladder matrix (UBM) have been extensively studied, with multiple FDA-approved products available for clinical use 5–7. However, these studies continue to show that minimal levels of physiologically-relevant muscle fibers are regenerated in both human and animal trials of acellular matrices. Instead, regenerated tissue has been overwhelmingly composed of non-functional and non-contractile fibrotic and adipose tissue 6. Common between both the clinical gold standards and the acellular matrix strategies being studied is the over-looking of the inhospitable microenvironment caused by persistent inflammation that serves to activate fibrotic pathways of regeneration 1,7. Thus, the need for an alternative strategy that targets this pathological inflammation and results in better long-term functional outcomes for patients after severe extremity trauma is clear.

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Towards a Real-time Seizure Detection Algorithm for Closed-loop Optogenetic Modulation of an Animal Model of Epilepsy

2015-01-28 , Rahsepar, Bahar

Epilepsy is a highly prevalent disease affecting 50 million people worldwide, and 3 million domestically in United States of America. About one-third of the epileptic population does not respond to pharmacological treatment and are classified as medically refractory. Surgical intervention is the alternative solution for this population, however it is not effective in the whole population and leaves 10-15% of the patients deprived of relief from seizures. Deep Brain Stimulation is a novel treatment that is being investigated for this disease. In order to fully understand this treatment, one needs to be informed about the neural circuitry and downstream effects of the stimulation. A powerful investigation needs to be done in closed-loop fashion to tie the stimulation with onset of the seizure, without otherwise affecting the brain. This study evaluates the proper metrics for a real-time algorithm with high detection sensitivity and low latency for a closed-loop setup to be used in the experimental setups of epilepsy research. The study first investigates the previous features used for seizure detection, and implements Line-Length (LLN), Mean Power Spectral Density (MPSD) in 12-25 Hz and Maximum Cross Correlation in its algorithm. Offline performance evaluation of candidates identified LLN and MPSD as powerful features with high sensitivity and low detection latency, which could be implemented in future online algorithms for closed-loop experimental setup.

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Investigation of immunomodulation on myofibroblast activation: Implications for fibrotic development in wound healing

2017-05-03 , Lawler, Matthew S.

Endogenous mechanisms of wound healing and remodeling are a particularly attractive avenue for targeting traumatic injury and incomplete growth. Macrophages are highly involved in this process, and generally exhibit either an inflammatory (M1) phenotype, promoting cell debris clearance, or an anti-inflammatory (M2) phenotype, promoting tissue regeneration and remodeling, although fluidity exists in these phenotypes for injury repair in vivo. Type I collagen is also crucial to the repair process through development of extracellular matrix (ECM), which provides scaffolding for cellular and vascular growth as well as controlling cell differentiation later in the process. Myofibroblasts are the source of Type I collagen deposition, and differentiate from fibroblasts in the presence of transforming growth factor-beta (TGF-β), among other pathways. However, persistent myofibroblast activity can perpetuate fibrosis, leading to incomplete repair and scarring. While it is clear that macrophages and myofibroblasts are involved in the wound healing process, the interplay between these two populations has not been thoroughly investigated. Two in vitro experiments of M1, M2a, and M2c macrophage phenotypes with 10T1/2 fibroblasts were conducted. The first experiment involved fibroblasts interacting with cytokines produced by each macrophage phenotype at three different initial seeding densities: 500,000, 750,000, and 1 million cells per well. The second experiment involved fibroblasts and macrophages in a co-culture. Expression of alpha-smooth muscle actin (α-SMA), an indicator of myofibroblast activation, was probed via immunofluorescence after 72-hour incubation for both experiments. Through confocal microscopy and image analysis, it was determined that fibroblast interaction with M1 soluble factors lead to significantly higher levels of normalized α-SMA expression within fibroblasts compared to the M2a and M2c at a seeding density of 750,000. However, the co-culture model, with macrophages of different phenotypes interacting with fibroblasts in a contact dependent manner, saw no significant difference between these groups or the control. M2a and M2c may play an important role in promoting tissue regeneration over excessive fibrotic activity, whereas pro-inflammatory signaling from M1 may promote more collagen production. However, the lack of significant results from contact dependency may suggest different macrophage behavior. More investigation is necessary to comprehensively understand macrophage-fibroblast/myofibroblast interplay in wound healing.

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Leg, vertical, and joint stiffness levels in rear-foot and fore-foot strike landings

2014-05-02 , Gainer, Allison Nichol

Bouncing gait, specifically hopping, running, and jumping, involves a complex combination of legs, joints, muscles, and nerves coordinated to perform simple biomechanical tasks. The findings associated with spring-mass modeling of bouncing gait suggest that hopping and running humans maintain center of mass (CoM) motions by adjusting vertical leg stiffness. Overall, lower extremity stiffness increases with the demands of the activity such as increased hopping frequency, hopping or jumping height, and running speed, which are all associated with increased stiffness. The increase in leg, vertical, and joint stiffness occurs because as more physical demands are imparted on the body, greater resistance to movement is needed to produce controlled movements. Studies comparing fore-foot strike (FFS) and rear-foot strike (RFS) patterns in running and hopping have shown converse results regarding the contribution of knee and ankle joint stiffness levels in preserving total leg stiffness. It is known that fore-foot strike runners generate smaller collision forces than rear-foot strike runners. However, an understanding of how joint stiffness levels differ when in a fore-foot strike pattern compared to a rear-foot strike patterns is unknown. Moreover, it is unclear how leg, vertical, and joint stiffness are affected when humans run at increasing speeds with both a fore-foot and rear-foot strike pattern. Investigations that assess the relationship between strike patterns and changes in velocity are needed in order to clarify joint contributions to changes in performance tasks. We completed a study on vertical hopping, fore-foot strike running, and rear-foot strike running to determine how ankle and knee joint stiffness values vary across different performance tasks. Throughout the study, leg stiffness remained constant (P>0.05) and vertical stiffness increased as the step frequency increased (P<0.05). During the fore-foot strike running trials, there were greater increases in ankle joint stiffness in comparison to knee joint stiffness. This suggests that the knee joint was stiffer than the ankle joint throughout the fore-foot strike running performance. In contrast, there was a greater increase in knee joint stiffness than ankle joint stiffness throughout the rear-foot strike performance, which implies that the ankle joint was stiffer than the knee joint. The changes in joint stiffness levels across the two strike patterns could be attributed to the small decrease in knee excursion and increase in ankle excursion in the fore-foot strike pattern compared to the rear-foot strike pattern. Understanding how these joint-level responses to differentiating in tasks influence the stability of leg stiffness may aid robotic, lower limb prosthetic, and even running shoe design.

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Mechanical Stiffness in 3D Embryonic Stem Cell Aggregates Undergoing Osteochondral Differentiation

2015-01-28 , Baker, Christopher

This study aimed to investigate the effect of osteochondral differentiation on mechanical stiffness of 3D mouse embryonic stem cell (ESC) aggregates. Both soluble osteoinductive cues and mineral coated microparticles were used to induce osteochondral differentiation. Uniform 3D ESC aggregates were formed by forced aggregation of mouse D3 ESCs in AggreWell™. MPs were incorporated into ESC aggregates by mixing with ESCs prior to aggregate formation at either 1:3 or 1:1 MP to cell ratio. ESC aggregates were cultured in either basal media (BM) or differentiation media (DM) which contained β-glycerophosphate and ascorbic acid to induce osteochondral differentiation. The mechanical stiffness of aggregates was determined from the creep tests performed via the MicroSquisher. The DM groups were significantly stiffer (P<0.05) than the BM groups, but there was no significant difference between the concentrations of mineral particles within the treatment groups. The gene expression of osteogenic and chondrogenic markers was evaluated at D14 using RT-PCR. Osteogenic and chondrogenic markers expression in DM groups was significantly higher than in BM groups at D14 (P<0.05). MP incorporation also increased the expression of chondrogenic markers in BM and osteogenic marker expressions in DM compared to No MP groups (P<0.05). Alizarin Red and Safranin O/Fast Green stains were performed to assess the change of ECM composition of ESC aggregates on D14. In addition to the different glycosaminoglycan staining patterns between soluble treatments and MP incorporation, significant increase in mineralization was observed in DM culture in comparison to BM groups, which was further increased in the presence of MPs. It was evident that osteochondral differentiation occurred in the DM groups and increased stiffness. Together, these results suggested that osteoconductive cues alone or in combination with MPs can effectively promote osteochondral differentiation and enhance mineralization, which may contribute to the increase in stiffness of ESC aggregates.

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