Physical exercise enhances adult cortical plasticity in a neonatal rat model of hypoxic-ischemic injury: Evidence from BOLD-fMRI and electrophysiological recordings.

Neuroplasticity is considered essential for recovery from brain injury in developing brains. Recent studies indicate that it is especially effective during early postnatal development and during the critical period. The current study used functional magnetic resonance imaging (fMRI) and local field potential (LFP) electrophysiological recordings in rats that experienced neonatal hypoxic-ischemic (HI) injury during the critical period to demonstrate that physical exercise (PE) can improve cortical plasticity even when performed during adulthood, after the critical period. We investigated to what extent the blood oxygen level-dependent (BOLD)-fMRI responses were increased in the contralesional spared cortex, and how these increases were related to the LFP electrophysiological measurements and the functional outcome. The balance of excitation and inhibition was assessed by measuring excitatory and inhibitory postsynaptic currents in stellate cells in the primary somatosensory (S1) cortex, which was compared with the BOLD-fMRI responses in the contralesional S1 cortex. The ratio of inhibitory postsynaptic current (IPSC) to excitatory postsynaptic current (EPSC) at the thalamocortical (TC) input to the spared S1 cortex was significantly increased by PE, which is consistent with the increased BOLD-fMRI responses and improved functional outcome. Our data clearly demonstrate in an experimental rat model of HI injury during the critical period that PE in adulthood enhances neuroplasticity and suggest that enhanced feed-forward inhibition at the TC input to the S1 cortex might underlie the PE-induced amelioration of the somatosensory deficits caused by the HI injury. In summary, the results of the current study indicate that PE, even if performed beyond the critical period or during adulthood, can be an effective therapy to treat neonatal brain injuries, providing a potential mechanism for the development of a potent rehabilitation strategy to alleviate HI-induced neurological impairments.

Age Dependent Integration of Cortical Progenitors Transplanted at the Adult CSF-Brain Interface.

There has been renewed interest in neural transplantation of cells and tissues for brain repair. Recent studies have demonstrated the ability of transplanted neural precursor cells and in vitro grown organoids to mature and locally integrate into host brain neural circuitry. Much effort has focused on how the transplant behaves and functions after the procedure, but the extent to which the host brain can properly innervate the transplant, particularly in the context of aging, is largely unexplored. Here we report that transplantation of rat embryonic cortical precursor cells into the cerebrospinal fluid-subventricular zone (CSF-SVZ) of adult rat brains generates a brain-like tissue (BLT) at an ectopic site. This model allows for the assessment of long-range connectivity and cellular interactions between the transplant and the host brain as a function of host age. The transplanted precursor cells initially proliferate, then differentiate, and develop into mature BLTs, which receive supportive cellular components from the host including blood vessels, microglia, astrocytes, and oligodendrocytes. There was integration of the BLT into the host brain which occurred at all ages studied, suggesting that host age does not affect the maturation and integration of the transplant-derived BLT. Long-range axonal projections from the BLT into the host brain were robust throughout the different aged recipients. However, long-distance innervation originating from the host brain into the BLT significantly declined with age. This work demonstrates the feasibility and utility of integrating new neural tissue structures at ectopic sites into adult brain circuits to study host-transplant interactions.

Stem cell restores thalamocortical plasticity to rescue cognitive deficit in neonatal intraventricular hemorrhage.

Severe neonatal intraventricular hemorrhage (IVH) patients incur long-term neurologic deficits such as cognitive disabilities. Recently, the intraventricular transplantation of allogeneic human umbilical cord blood-derived mesenchymal stem cells (MSCs) has drawn attention as a therapeutic potential to treat severe IVH. However, its pathological synaptic mechanism is still elusive. We here demonstrated that the integration of the somatosensory input was significantly distorted by suppressing feed-forward inhibition (FFI) at the thalamocortical (TC) inputs in the barrel cortices of neonatal rats with IVH by using BOLD-fMRI signal and brain slice patch-clamp technique. This is induced by the suppression of Hebbian plasticity via an increase in tumor necrosis factor-α expression during the critical period, which can be effectively reversed by the transplantation of MSCs. Furthermore, we showed that MSC transplantation successfully rescued IVH-induced learning deficits in the sensory-guided decision-making in correlation with TC FFI in the layer 4 barrel cortex.