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    Biomechanics

    Low-Intensity Pulsed Ultrasound Increases FGF-2 Secretion in Human Endothelial Cells

    (C-117) Low-Intensity Pulsed Ultrasound Increases FGF-2 Secretion in Human Endothelial Cells

    Friday, October 13, 2023
    3:30 PM – 4:30 PM PDT
    Location: Exhibit Hall - Row C - Poster # 117

      Presenting Author(s)

    • Maneesha D. Mahanama

      Undergraduate Student Researcher
      Bucknell University
      Bowie, Maryland, United States

      • Primary Investigator(s)

    • OB

      Olivia Boerman

      Assistant Professor
      Bucknell University
      Lewisburg, Pennsylvania, United States

    Introduction::


    Low-intensity pulsed ultrasound therapy (LIPUS) is a developing noninvasive method that is being tested for its efficacy in promoting wound healing. A previous study found LIPUS to increase cell proliferation and accelerate chronic wound closure.    1 However, the biological mechanisms of how ultrasound promotes wound healing are not yet understood. 
    Angiogenesis is a biological process that involves the formation of new blood vessels from pre-existing ones, making it a vital component of wound healing. This process occurs through a series of steps including endothelial cell activation, migration, and proliferation. Basic fibroblast growth factor (FGF-2) is a key angiogenic factor that stimulates endothelial cell proliferation and migration by activating the Ras-MAPK and PI3K-Akt pathway.    2 Quantifying the amount of FGF-2 released by endothelial cells can serve as an indirect measure of angiogenic activity. The purpose of this study is to compare levels of FGF-2 secretion between LIPUS-treated and control groups to assess whether LIPUS has the potential to enhance angiogenesis. Further investigation into the effects of LIPUS on angiogenesis can provide a framework for the development of novel therapies in wound healing and tissue regeneration. 



    Materials and Methods::

    Human umbilical vein endothelial cells (HUVEC) were cultured and seeded with a  control group and three varying ultrasound intensities, 50 mW/cm2, 100 mW/cm2, and 150 mW/cm2 (n=3). The ultrasound parameters were set as follows: frequency of 36 kHz, pulse repetition frequency of 25 Hz, 50% duty cycle, and 15-minute exposure time. 24 hours after ultrasound exposure, conditioned media was collected for FGF-2 protein quantification via enzyme-linked immunosorbent assay (ELISA). The results were then analyzed for statistical significance using a single factor ANOVA and post hoc Tukey test. A p-value of less than 0.05 was considered to be significant.



    Results, Conclusions, and Discussions:: All groups were found to have an FGF-2 concentration in the range of 2,000 to 3,000 μg/mL (Fig. 1A). FGF-2 secretion between groups was found to be statistically significant with a p-value of 0.00675. (Fig. 1B). The observed trend indicates increasing ultrasound intensity corresponds to higher FGF-2 secretion in endothelial cells. The average values for each group was calculated and graphed on a histogram to display this trend (Fig. 1C). FGF-2 secretion was statistically significant between the control and 100 mW/cm2 groups and the control and 150 mW/cm2. (Fig. 1D)


    These results may indicate that LIPUS promotes angiogenesis. The observed increase of FGF-2 concentration in HUVECs treated with LIPUS suggests that the treatment may have angiogenic-inducing capabilities. Impaired angiogenesis is a common feature in various pathological conditions such as chronic wounds and diabetic ulcers. LIPUS therapy holds promise as a non-invasive targeted approach for conditions that require enhanced blood flow and oxygen supply. Its pro-angiogenic effects can also be used for developments in tissue regeneration, accelerated wound healing, and tissue engineering. 


    Furthermore, the findings from this study provide insight into the underlying mechanisms by which ultrasound promotes angiogenesis. The lack of a statistically significant difference in FGF-2 concentration between the control and 50 mW/cm2 intensity group suggests a threshold intensity may be necessary to elicit a measurable effect. It was observed that higher LIPUS intensities resulted in more FGF-2 secretion, which is a critical indicator of angiogenesis. The significant difference observed in FGF-2 concentration between the control group and the 100 mW/cm2 and 150 mW/cm2 intensity groups indicates that 100 mW/cm2 may be the minimum therapeutic threshold. Further investigation is needed to determine the precise ultrasound parameters for optimal FGF-2 stimulation and angiogenesis promotion.





    Acknowledgements (Optional): :

    References (Optional): :

    [1]


    Samuels, J. A., Weingarten, M. S., Margolis, D. J., Zubkov, L., Sunny, Y., Bawiec, C. R., Conover, D., & Lewin, P. A. (2013, August). Low-frequency (< 100 kHz), low-intensity (< 100 mW/cm2) ultrasound to treat venous ulcers: A human study and in vitro experiments. The Journal of the Acoustical Society of America, 134(2), 1541-1547. https://doi.org/10.1121/1.4812875


     




    [2] 


    Mossahebi-Mohammadi, Majid et al. “FGF Signaling Pathway: A Key Regulator of Stem Cell Pluripotency.” Frontiers in cell and developmental biology vol. 8 79. 18 Feb. 2020, doi:10.3389/fcell.2020.00079