Steroid effects on glial cells: detrimental or protective for spinal cord function?

Repair of damage and recovery of function are fundamental endeavors for recuperation of patients and experimental animals with spinal cord injury. Steroid hormones, such as progesterone (PROG), show regenerative and myelinating properties following injury of the peripheral and central nervous system. In this work, we studied PROG effects on glial cells of the normal and transected (TRX) spinal cord, to complement previous studies in motoneurons. Both neurons and glial cells expressed the classical PROG receptor (PR), suggesting that genomic mechanisms participated in PROG action. In TRX rats, PROG treatment stimulated the number of NADPH-diaphorase (nitric oxide synthase) active astrocytes, whereas the number of astrocytes expressing the glial fibrillary acidic protein (GFAP) was stimulated in control but not in TRX rats. PROG also stimulated the immunocytochemical staining for myelin-basic protein (MBP) and the number of oligodendrocyte precursor cells expressing the chondroitin sulfate proteoglycan NG2 in TRX rats. In terms of beneficial or detrimental consequences, these PROG effects may be supportive of neuronal recuperation, as shown for several neuronal functional parameters that were normalized by PROG treatment of spinal cord injured animals. Thus, PROG effects on glial cells go in parallel with morphological and biochemical evidence of survival of damaged motoneurons.