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During peripheral nerve injury, the myelin surrounding the neuronal axons is damaged, initiating an inflammatory response to remove myelin debris. Once myelin debris is cleared, Schwann cells acquire a proliferating phenotype which allows them to grow and divide so that remyelination can occur. The neuron stimulates Schwann cell division by secreting growth factors, like heregulin, and an unknown growth factor that activates the cAMP pathway. Although the role of cAMP in axonal regeneration is well-known, not much has been explored about its function in Schwann cells during nerve injury and inflammation. To simulate an inflammatory environment, the S16 Schwann cell line (SC-2941) was activated with lipopolysaccharide (LPS), a cell-wall immunostimulatory component of Gram-negative bacteria. It was hypothesized that Schwann cells stimulated with LPS and growth factors will have higher proliferation in comparison to LPS treatment only. Schwann cells were treated for 1, 3, 12 or 24 hours with no growth factors (control media, N2), 12.5 ng/mL heregulin (H), 2mM forskolin (F) or H+F and various doses of LPS at 5, 50 or 500 ng/mL. Using the MTT proliferation assay, preliminary studies in 24-hour cultures reveal that cell proliferation, as measured by optical density, was significantly higher in cells treated with 5 ng/mL of LPS+F (0.846 ± 0.054), and H+F (1.023 ± 0.189) in comparison to cells grown with H (0.699 ± 0.057) or N2 only (0.765 ± 0.016). In contrast, cells treated for 1, 3 and 12 hours, with various concentrations of LPS revealed an overall decrease in proliferation when compared to 24-hour cultures. However, cultures treated with LPS and F or H+F, for all time points, showed an increase in cell growth when compared to N2 and H. In summary, it appears as though a combination of LPS and forskolin, with or without heregulin, may promote more Schwann cell proliferation than LPS alone. These findings also suggest that, when LPS-activated cells are treated with heregulin or forskolin, alone, they may activate two very distinct pathways to initiate opposite responses, with heregulin hindering cell division and forskolin promoting cell division. However, when heregulin and forskolin are combined, the forskolin-activated cAMP pathway appears to promote higher proliferation to offset the decrease in proliferation initiated by the heregulin pathway. Considering these results, it appears that the cAMP pathway in Schwann cells may play a major role in the inflammatory environment during nerve injury.
Schwann cells, inflammation, heregulin, forskolin, lipopolysaccharide, nerve injury, proliferation, dose-response, cAMP
Biochemistry | Cell Biology | Molecular and Cellular Neuroscience | Nervous System Diseases
Henry, Caitlyn; Kimmel, Peyton; and Asirvatham, Angela, "Simulation of an Inflammatory Model Using Schwann Cells" (2022). Student Research Poster Presentations 2022. 9.