Microvascular smooth muscle cells exhibit divergent phenotypic switching responses to platelet-derived growth factor and insulin-like growth factor 1.

OBJECTIVE: Vascular smooth muscle cell (VSMC) phenotypic switching is critical for normal vessel formation, vascular stability, and healthy brain aging. Phenotypic switching is regulated by mediators including platelet derived growth factor (PDGF)-BB, insulin-like growth factor (IGF-1), as well as transforming growth factor-ß (TGF-ß) and endothelin-1 (ET-1), but much about the role of these factors in microvascular VSMCs remains unclear. METHODS: We used primary rat microvascular VSMCs to explore PDGF-BB- and IGF-1-induced phenotypic switching. RESULTS: PDGF-BB induced an early proliferative response, followed by formation of polarized leader cells and rapid, directionally coordinated migration. In contrast, IGF-1 induced cell hypertrophy, and only a small degree of migration by unpolarized cells. TGF-ß and ET-1 selectively inhibit PDGF-BB-induced VSMC migration primarily by repressing migratory polarization and formation of leader cells. Contractile genes were downregulated by both growth factors, while other genes were differentially regulated by PDGF-BB and IGF-1. CONCLUSIONS: These studies indicate that PDGF-BB and IGF-1 stimulate different types of microvascular VSMC phenotypic switching characterized by different modes of cell migration. Our studies are consistent with a chronic vasoprotective role for IGF-1 in VSMCs in the microvasculature while PDGF is more involved in VSMC proliferation and migration in response to acute activities such as neovascularization. Better understanding of the nuances of the phenotypic switching induced by these growth factors is important for our understanding of a variety of microvascular diseases.

Single-Cell RNA Sequencing of Childhood Ependymoma Reveals Neoplastic Cell Subpopulations That Impact Molecular Classification and Etiology.

Ependymoma (EPN) is a brain tumor commonly presenting in childhood that remains fatal in most children. Intra-tumoral cellular heterogeneity in bulk-tumor samples significantly confounds our understanding of EPN biology, impeding development of effective therapy. We, therefore, use single-cell RNA sequencing, histology, and deconvolution to catalog cellular heterogeneity of the major childhood EPN subgroups. Analysis of PFA subgroup EPN reveals evidence of an undifferentiated progenitor subpopulation that either differentiates into subpopulations with ependymal cell characteristics or transitions into a mesenchymal subpopulation. Histological analysis reveals that progenitor and mesenchymal subpopulations co-localize in peri-necrotic zones. In conflict with current classification paradigms, relative PFA subpopulation proportions are shown to determine bulk-tumor-assigned subgroups. We provide an interactive online resource that facilitates exploration of the EPN single-cell dataset. This atlas of EPN cellular heterogeneity increases understanding of EPN biology.

The effects of perchlorate on thyroidal gene expression are different from the effects of iodide deficiency.

Perchlorate (ClO4⁻), which is a ubiquitous and persistent ion, competitively interferes with iodide (I) accumulation in the thyroid, producing I deficiency (ID), which may result in reduced thyroid hormone synthesis and secretion. Human studies suggest that ClO4⁻ presents little risk in healthy individuals; however, the precautionary principle demands that the sensitive populations of ID adults and mothers require extra consideration. In an attempt to determine whether the effects on gene expression were similar, the thyroidal effects of ClO4⁻ (10 mg/kg) treatment for 14 d in drinking water were compared with those produced by 8 wk of ID in rats. The thyroids were collected (n = 3 each group) and total mRNA was analyzed using the Affymetrix Rat Genome 230 2.0 GeneChip. Changes in gene expression were compared with appropriate control groups. The twofold gene changes due to ID were compared with alterations due to ClO4⁻ treatment. One hundred and eighty-nine transcripts were changed by the ID diet and 722 transcripts were altered by the ClO4⁻ treatment. Thirty-four percent of the transcripts changed by the I-deficient diet were also altered by ClO4⁻ and generally in the same direction. Three specific transporter genes, AQP1, NIS, and SLC22A3, were changed by both treatments, indicating that the membrane-specific changes were similar. Iodide deficiency primarily produced alterations in retinol and calcium signaling pathways and ClO4⁻ primarily produced changes related to the accumulation of extracellular matrix proteins. This study provides evidence that ClO4⁻, at least at this dose level, changes more genes and alters different genes compared to ID.

Idiopathic persistent pulmonary hypertension in an infant with Smith-Lemli-Opitz syndrome.

Persistent pulmonary hypertension (PPHN) of the newborn remains a challenging condition to diagnose and treat. It has been reported in infants with Smith-Lemli-Opitz syndrome (SLOS), a rare defect in cholesterol synthesis. Typically, there is evidence of pulmonary hypoplasia. We report the first case of PPHN in the absence of pulmonary hypoplasia or other parenchymal diseases in an infant with SLOS. Perturbations in cholesterol metabolism interrupt key signaling pathways that participate in the normal maintenance of pulmonary vascular tone. We found that caveolae-dependent signaling may be involved in this process since our patient had altered expression of caveolin-1.