Effects of progesterone on oligodendrocyte progenitors, oligodendrocyte transcription factors, and myelin proteins following spinal cord injury

Abstract

Progesterone is emerging as a myelinizing factor for central nervous system injury. Successful remyelination requires proliferation and differentiation of oligodendrocyte precursor cells (OPC) into myelinating oligodendrocytes, but this process is incomplete following injury. To study progesterone actions on remyelination, we administered progesterone (16 mg/kg/day) to rats with complete spinal cord injury. Rats were euthanized 3 or 21 days after steroid treatment. Short progesterone treatment (a) increased the number of OPC without effect on the injury-induced reduction of mature oligodendrocytes, (b) increased mRNA and protein expression for the myelin basic protein (MBP) without effects on proteolipid protein (PLP) or myelin oligodendrocyte glycoprotein (MOG), and (c) increased the mRNA for Olig2 and Nkx2.2 transcription factors involved in specification and differentiation of the oligodendrocyte lineage. Furthermore, long progesterone treatment (a) reduced OPC with a concomitant increase of oligodendrocytes; (b) promoted differentiation of cells that incorporated bromodeoxyuridine, early after injury, into mature oligodendrocytes; (c) increased mRNA and protein expression of PLP without effects on MBP or MOG; and (d) increased mRNA for the Olig1 transcription factor involved in myelin repair. These results suggest that early progesterone treatment enhanced the density of OPC and induced their differentiation into mature oligodendrocytes by increasing the expression of Olig2 and Nkx2.2. Twenty-one days after injury, progesterone favors remyelination by increasing Olig1 (involved in repair of demyelinated lesions), PLP expression, and enhancing oligodendrocytes maturation. Thus, progesterone effects on oligodendrogenesis and myelin proteins may constitute fundamental steps for repairing traumatic injury inflicted to the spinal cord.

Progesterone Reduces Secondary Damage, Preserves White Matter, and Improves Locomotor Outcome after Spinal Cord Contusion

“…[9][10][11][12][63][64][65][66][67] We have demonstrated in previous works that chronic PROG administration increases the expression of transcription factors that define oligodendrocyte linage, such as Olig2 and Nkx2.2 after spinal cord transection. 21,29 In the present work, we report that PROG treatment reduced the loss of oligodendrocyte numbers and MBP immunoreactivity produced by SCI. This effect could be because of preservation of the myelinproducing cells, but also to an increase in oligodendrocyte numbers by differentiation of oligodendrocyte precursors into mature myelinating oligodendrocytes, promoting the remyelination process.…”

“…PROG was given to awake animals 1 h after injury. This dose of PROG has been shown to prevent edema and neuronal loss and to improve cognitive responses after brain-contusion injury, 28 to induce oligodendrogenesis and remyelination after spinal cord injury, 21,29 and to decrease reactive gliosis. 22 Sham-operated rats (n = 8, CTL) received a laminectomy but not SCI.…”

“…Immunostaining was performed as described previously 21 using primary antibodies against myelin basic protein (MBP 1:100, Abcam, Cambridge, UK), neurofilament H (NF-H 1:1000, Abcam, Cambridge, UK), or adenomatus polyposis coli (APC) clone (clone CC1 1:100, Calbiochem, Darmstadt, Germany), and secondary biotinylated anti-rabbit immunoglobulin G (IgG) (1/200 Vector Laboratories, Burlingame, CA) or biotinylated anti-mouse IgG (1/ 200 Vector Laboratories). After the incubation with secondary antibodies, sections were incubated with avidin-biotin complex (ABC) for 30 min (ABC kit, Vector Laboratories) and finally revealed with diaminobenzidine tetrachloride (0.50 mg/mL, Sigma, St. Louis, MO) in the presence of 0.01% H 2 O 2 for 7 min in the dark.…”

“…21 Briefly, inmmunostaining intensity was determined in areas (50,000 lm 2 ) covering three white matter regions: dorsal funiculus, lateral funiculus, and ventral funiculus, anatomically delimited by the method described in Labombarda and associates. 21 Computer-assisted image analysis (Bioscan Optimas II) was used to transform differences in color intensity of immunopositive areas into gray differences, and results were expressed as the meanstandard error of the mean inverse logarithm of gray intensity per unit area (mm 2 ) (ILIGV/area = LIGV). 20 Sections were processed simultaneously under identical light beam, wavelength, and grayscale threshold throughout the experiment and quantification analysis.…”

“…[13][14][15] This has permitted the development of two Phase II clinical trials that have recently shown significant improvements in patients with traumatic brain injury receiving PROG. [16][17][18] In our previous studies, we demonstrated beneficial effects of PROG after complete section of spinal cord: it restores the expression levels of several molecular markers, subsides chromatolysis in motoneurons, 19,20 enhances the differentiation of oligodendrocyte precursor cells by increasing the expression of pro-oligodendrogenic factors such as Olig2 and Nkx2.2, 21 and decreases the activation and proliferation of astrocytes and microglial cells. 22 In this study, we have assessed histological and functional effect of PROG with multiple approaches, including magnetic resonance imaging (MRI), stereological cell counting, open field based BassoBresnahan-Beattie (BBB) scale for locomotion, CatWalk gait analysis, Hargreaves plantar test, and dynamic Von Frey.…”