Cellular Changes in Injured Rat Spinal Cord Following Electrical Brainstem Stimulation

Abstract

Spinal cord injury (SCI) is a major cause of disability and pain, but little progress has been made in its clinical management. Low-frequency electrical stimulation (LFS) of various anti-nociceptive targets improves outcomes after SCI, including motor recovery and mechanical allodynia. However, the mechanisms of these beneficial effects are incompletely delineated and probably multiple. Our aim was to explore near-term effects of LFS in the hindbrain’s nucleus raphe magnus (NRM) on cellular proliferation in a rat SCI model. Starting 24 h after incomplete contusional SCI at C5, intermittent LFS at 8 Hz was delivered wirelessly to NRM. Controls were given inactive stimulators. At 48 h, 5-bromodeoxyuridine (BrdU) was administered and, at 72 h, spinal cords were extracted and immunostained for various immune and neuroglial progenitor markers and BrdU at the level of the lesion and proximally and distally. LFS altered cell marker counts predominantly at the dorsal injury site. BrdU cell counts were decreased. Individually and in combination with BrdU, there were reductions in CD68 (monocytes) and Sox2 (immature neural precursors) and increases in Blbp (radial glia) expression. CD68-positive cells showed increased co-staining with iNOS. No differences in the expression of GFAP (glia) and NG2 (oligodendrocytes) or in GFAP cell morphology were found. In conclusion, our work shows that LFS of NRM in subacute SCI influences the proliferation of cell types implicated in inflammation and repair, thus providing mechanistic insight into deep brain stimulation as a neuromodulatory treatment for this devastating pathology.

Brainstem-Evoked Transcription of Defensive Genes After Spinal Cord Injury

“…To better understand the proximate causes of improved recovery with NRM stimulation, this and some other studies have focused on more acute, post-injury endpoints and shorter stimulation periods. An immunostaining study of 3-day C5 injury after 2 days of NRM stimulation showed changes in numbers of inflammatory cell types and a transition from neural precursors to radial glia that facilitate differentiation (Jermakowicz et al, 2019). In rats with 3-day T8 contusions, 2 h of NRM stimulation, as in the present protocol, restored normal levels of injury-depleted cAMP, phosphorylated cAMP response binding element (pCREB), and pPKA (Carballosa-Gonzalez et al, 2014).…”

Surgery for Spine Disease and Intractable Pain

“…Spinal cord injury is an important cause of disability due to paralysis and loss of function as well as frequently associated neuropathic pain. Jermakowicz et al evaluated the mechanisms underlying low-frequency electrical stimulation and the ability of stimulation to improve motor recovery and lessen allodynia related to spinal cord injury [5]. In the experiments performed, rats received a spinal cord injury at the cervical spinal level.…”