Ventricular Zone Disruption in Human Neonates With Intraventricular Hemorrhage.

To determine if ventricular zone (VZ) and subventricular zone (SVZ) alterations are associated with intraventricular hemorrhage (IVH) and posthemorrhagic hydrocephalus, we compared postmortem frontal and subcortical brain samples from 12 infants with IVH and 3 nonneurological disease controls without hemorrhages or ventriculomegaly. Birth and expiration estimated gestational ages were 23.0-39.1 and 23.7-44.1 weeks, respectively; survival ranges were 0-42 days (median, 2.0 days). Routine histology and immunohistochemistry for neural stem cells (NSCs), neural progenitors (NPs), multiciliated ependymal cells (ECs), astrocytes (AS), and cell adhesion molecules were performed. Controls exhibited monociliated NSCs and multiciliated ECs lining the ventricles, abundant NPs in the SVZ, and medial vs. lateral wall differences with a complex mosaic organization in the latter. In IVH cases, normal VZ/SVZ areas were mixed with foci of NSC and EC loss, eruption of cells into the ventricle, cytoplasmic transposition of N-cadherin, subependymal rosettes, and periventricular heterotopia. Mature AS populated areas believed to be sites of VZ disruption. The cytopathology and extension of the VZ disruption correlated with developmental age but not with brain hemorrhage grade or location. These results corroborate similar findings in congenital hydrocephalus in animals and humans and indicate that VZ disruption occurs consistently in premature neonates with IVH.

Cell Junction Pathology of Neural Stem Cells Is Associated With Ventricular Zone Disruption, Hydrocephalus, and Abnormal Neurogenesis.

Fetal-onset hydrocephalus affects 1 to 3 per 1,000 live births. It is not only a disorder of cerebrospinal fluid dynamics but also a brain disorder that corrective surgery does not ameliorate. We hypothesized that cell junction abnormalities of neural stem cells (NSCs) lead to the inseparable phenomena of fetal-onset hydrocephalus and abnormal neurogenesis. We used bromodeoxyuridine labeling, immunocytochemistry, electron microscopy, and cell culture to study the telencephalon of hydrocephalic HTx rats and correlated our findings with those in human hydrocephalic and nonhydrocephalic human fetal brains (n = 12 each). Our results suggest that abnormal expression of the intercellular junction proteins N-cadherin and connexin-43 in NSC leads to 1) disruption of the ventricular and subventricular zones, loss of NSCs and neural progenitor cells; and 2) abnormalities in neurogenesis such as periventricular heterotopias and abnormal neuroblast migration. In HTx rats, the disrupted NSC and progenitor cells are shed into the cerebrospinal fluid and can be grown into neurospheres that display intercellular junction abnormalities similar to those of NSC of the disrupted ventricular zone; nevertheless, they maintain their potential for differentiating into neurons and glia. These NSCs can be used to investigate cellular and molecular mechanisms underlying this condition, thereby opening the avenue for stem cell therapy.

Expression of tuberalin II, alpha-subunit of glycoprotein hormones and beta-thyrotropin hormone in the pars tuberalis of the rat: immunocytochemical evidence for pars tuberalis-specific cell types.

Increasing evidence suggests that the hypophyseal pars tuberalis (PT) plays a key role in the transduction of light/dark (melatonin) information to the endocrine system. It has been shown that PT-specific cells express melatonin receptors and thyrotropin hormone (TSH) subunits. However, these cells do not resemble thyrotrophs or any other of the pars distalis (PD) cells. There is evidence that PT-specific cells secrete a glycoprotein hormone designated as 'tuberalin'. We have identified a putative tuberalin of 21 kDa (tuberalin II) and have raised antibodies against it. To further investigate whether tuberalin II is a distinct secretory compound of the PT, absorption studies of antituberalin II with TSH or with an extract of the rat PD containing beta-TSH, beta-luteinizing hormone (LH) and the common alpha-subunit of glycoprotein hormones (GSU), were performed. Neither of the absorption tests abolished the immunoreactivity of the PT to antituberalin II, suggesting that tuberalin II is different from TSH or the other PD glycoprotein hormones. Double immunofluorescence analyses using antibodies against tuberalin II, beta-TSH and GSU revealed that in the developing and adult PT there are 3 populations of PT-specific cells expressing tuberalin II and GSU (type 1), beta-TSH and GSU (type 2) and tuberalin II, beta-TSH and GSU (type 3). This further indicates that tuberalin II and beta-TSH correspond to different compounds and that they may be expressed either by different cells types or coexpressed in a 3rd cell type. The distribution and temporal expression of tuberalin II, beta-TSH, beta-LH and GSU were investigated in the developing pituitary gland. At E14.5, tuberalin II and GSU were expressed by cells of the PT primordium but not by the PD and pars intermedia primordia. The onset of expression of beta-TSH, beta-LH and GSU in cells of the PD occurred about 1 day later, further indicating the distinct nature of tuberalin II and supporting the earlier view that the secretion of polypeptides from the fetal rat pituitary gland begins in PT-specific cells.