We have investigated the potential of human pluripotent cells to restore function in rats paralyzed with a virus-induced motor neuronopathy. Cells derived from embryonic germ cells, termed embryoid body-derived (EBD) cells, introduced into the CSF were distributed extensively over the rostrocaudal length of the spinal cord and migrated into the spinal cord parenchyma in paralyzed, but not uninjured, animals. Some of the transplanted human cells expressed the neuroglial progenitor marker nestin, whereas others expressed immunohistochemical markers characteristic of astrocytes or mature neurons. Rare transplanted cells developed immunoreactivity to choline acetyltransferase (ChAT) and sent axons into the sciatic nerve as detected by retrograde labeling. Paralyzed animals transplanted with EBD cells partially recovered motor function 12 and 24 weeks after transplantation, whereas control animals remained paralyzed. Semi-quantitative analysis revealed that the efficiency of neuronal differentiation and extension of neurites could not account for the functional recovery. Rather, transplanted EBD cells protected host neurons from death and facilitated reafferentation of motor neuron cell bodies. In vitro, EBD cells secrete transforming growth factor-alpha (TGF-alpha) and brain-derived neurotrophic factor (BDNF). Neutralizing antibodies to TGF-alpha and to BDNF abrogated the ability of EBD-conditioned media to sustain motor neuron survival in culture, whereas neutralizing antibodies to BDNF eliminated the axonal outgrowth from spinal organotypics observed with direct coculture of EBD cells. We conclude that cells derived from human pluripotent stem cells have the capacity to restore neurologic function in animals with diffuse motor neuron disease via enhancement of host neuron survival and function.

Pathological evidence suggests that alterations of the blood-brain barrier (BBB) may occur in association with human immunodeficiency virus (HIV) dementia (HIVD). Increased BBB permeability could contribute to the development of dementia by facilitating the entry of activated and infected monocytes, as well as potentially toxic serum proteins, into the central nervous system. One mechanism by which BBB permeability may be altered is through increased activity of select matrix metalloproteinases (MMPs). In the present study, we examined the possibility that MMPs that target critical BBB proteins, including laminin, entactin, and collagen type IV, are elevated in the cerebrospinal fluid (CSF) of patients with HIVD. We also examined the possibility that such MMPs could be produced by brain-derived cells, and that MMP production by these cells might be increased by tumor necrosis factor-␣, an inflammatory cytokine that is produced by HIV-infected monocytes/microglia and is elevated in HIVD. By using western blot and enzyme-linked immunosorbent assay, we observed that CSF levels of pro-MMP-2 and pro-MMP-7 were increased in association with HIVD. In addition, through the use of gelatin substrate zymography, a sensitive functional assay for MMP-2 and MMP-9, we observed that MMP-2 or pro-MMP-9 activity was more frequently detectable in the CSF of individuals with HIV dementia (9/16) than in the CSF from either nondemented seropositive (2/11) or seronegative (0/11) controls. Although the presence of MMPs in the serum could contribute to elevated levels in the CSF, we also show that brain-derived cells release MMP-2, 7, and 9, and that such release is increased after their stimulation with tumor necrosis factor-␣. Together, these results suggest that elevated CSF levels of select MMPs may reflect immune activation within the central nervous system. They also suggest that further studies may be warranted to determine whether these proteins may play a role in the development of symptomatic neurological disease.

Immune reconstitution inflammatory syndrome should be suspected in patients who show clinical or radiologic deterioration following initiation of antiretroviral therapy accompanied with improvement in CD4 cell count and viral load. Some patients may respond to a brief course of treatment with corticosteroids.