Stereological analysis of the normal red nucleus, and the effect of delayed treatment with adult-sourced adipose-derived mesenchymal stem cells on neonatal hypoxic-ischemic brain injury and motor skills, in the rat

Abstract

The red nucleus (RN) was investigated first to provide important data for the transfer of information through the RN and to learn key stereological methods that were then applied to the stem cell study. Six male rats, and a set of serial 40µm glycolmethacrylate sections for each rat, were used to quantify the absolute number, N, within the RN. A systematic sample of sections was obtained to estimate the total volume of the RN. The sampled sections were used to estimate the numerical density Nv using the optical disector method. It was found that the RN consisted, on average, of 8,400 parvicellular neurons and 7,000 magnocellular neurons.

Exposure to hypoxia and ischemia (or hypoxia-ischemia, HI) in the brain neonatally can lead to cerebral palsy. Due to difficulties regarding the early diagnosis and treatment of HI injury, there is an increasing need to find effective therapies. This research investigates the long- and short-term effects of delayed treatment with stem cells, derived from adult fatty tissue, on neuronal restoration in the brain, and motor skills. On postnatal day (PN) 7, male Sprague-Dawley rat pups were weight-matched, exposed to either HI brain injury or no HI injury, and assigned to groups (n = 8/group for long-term study, and 4/group for the short-term study) - untreated (HI+Dil), normal controls (Normal+Dil), single- and double stem cell-treated (HI+MSCs×1, HI+MSCs×2). On PN14 and 16, all groups were treated with either diluent or stem cells. For the long-term study, all animals were then tested repeatedly on the cylinder and staircase tests for their motor skill ability and perfused on PN107-109. However for the short-term study, the animals were perfused on PN21. Serial 5µm frozen sections were cut and stained for striatal dopamine- and cAMP-regulated phosphoprotein-(DARPP)-32-positive spiny projection neurons. The N of these neurons was estimated using the Cavalieri’s, physical disector and Abercrombie/unfolding methods for the long-term study, and Cavalieri’s and Abercrombie/unfolding methods for the short-term study. For the long-term study, the HI groups were impaired on left- versus right-sided motor skills on the staircase test, but the control animals were not. However, this promising outcome was not observed on the cylinder test which revealed no significant difference for L% - R% use among all groups (p>.05). A one-way ANOVA revealed no significant difference (p>.05) across all groups. The N of DARPP-32-positive neurons was also not significantly greater (Mann-Whitney test, p > 0.05) in the Normal+Dil compared to all HI groups. For the short-term study, there was a significant difference in the N of DARPP-32-positive neurons when all groups were compared (p<.033). Post-hoc comparisons revealed a significant increase in the N of striatal DARPP-32 neurons in the HI+MSCs×2 and Normal+Dil compared to the HI+Dil (p<.042; p<.043, respectively). There was an increase in the N of striatal DARPP-32 neurons in the HI+MSCs×1, but this was not significant (p>.05). These results suggest that double treatment with adipose-derived MSCs has therapeutic potential for rescuing striatal neurons after neonatal HI.