Angiogenesis potential of human limbal stromal niche cells.
ABSTRACT The perivascular localization of stem cell (SC) niches suggests the presence of a vascular niche. We aimed to determine the angiogenesis potential of limbal niche cells (NCs).
Human limbal NCs were isolated and serially passaged on plastic or coated Matrigel in embryonic SC medium containing BFGF and leukemia inhibitory factor before being reseeded in 3D Matrigel. Expression of angiogenesis markers was assessed by RT-qPCR and immunofluorescence staining. Their angiogenesis potential was measured by differentiation into vascular endothelial cells and by supporting vascular tube network formed by human umbilical vein endothelial cells (HUVEC) on Matrigel. Their support of limbal epithelial progenitor cells (LEPC) was examined in sphere growth formed by reunion in 3D Matrigel.
On plastic, limbal NC could be cultured only up to four passages before turning into myofibroblasts. In contrast, on coated Matrigel, they could be expanded for up to 12 passages with upregulation of markers suggestive of angiogenesis progenitors when reseeded in 3D Matrigel because they could differentiate into vascular endothelial cells and pericytes stabilizing the tube network formed by HUVEC. Although both expanded limbal NCs and HUVEC rejoined with LEPC to form spheres to upregulate expression of ΔNp63α, CK15, and CEBPδ, the former but not the latter abolished expression of CK12 keratin.
Human limbal NCs continuously expanded on the basement membrane differentiate into angiogenesis progenitors that prevent differentiation of LEPC/SCs. They may partake in formation of the vascular niche and contribute to angiogenesis during wound healing.
Article: The impact of the expansion of urban vegetable farming on malaria transmission in major cities of Benin.[show abstract] [hide abstract]
ABSTRACT: Urban agricultural practices are expanding in several cities of the Republic of Benin. This study aims to assess the impact of such practices on transmission of the malaria parasite in major cities of Benin. A cross sectional entomological study was carried out from January to December 2009 in two vegetable farming sites in southern Benin (Houeyiho and Acron) and one in the northern area (Azèrèkè). The study was based on sampling of mosquitoes by Human Landing Catches (HLC) in households close to the vegetable farms and in others located far from the farms. During the year of study, 71,678 female mosquitoes were caught by HLC of which 25% (17,920/71,678) were Anopheles species. In the areas surveyed, the main malaria parasite, Plasmodium falciparum was transmitted in the south by Anopheles gambiae s.s. Transmission was high during the two rainy seasons (April to July and October to November) but declined in the two dry seasons (December to March and August to September). In the north, transmission occurred from June to October during the rainy season and was vehicled by two members of the An. gambiae complex: Anopheles gambiae s.s. (98%) and Anopheles arabiensis (2%).At Houeyiho, Acron and Azèrèkè, the Entomological Inoculation Rates (EIRs) and the Human Biting Rates (HBRs) were significantly higher during the dry season in Households Close to Vegetable Farms (HCVF) than in those located far from the vegetable areas (HFVF) (p < 0.05.). However, there were no significant differences in HBRs or EIRs between HCFV and HFVF during the rainy seasons at these sites (p > 0.05).The knock-down resistance (kdr) mutation was the main resistance mechanism detected at high frequency (0.86 to 0.91) in An. gambiae s.l. at all sites. The ace-1R mutation was also found but at a very low frequency (< 0.1). These findings showed that communities living close to vegetable farms are permanently exposed to malaria throughout the year, whereas the risk in those living far from such agricultural practices is limited and only critical during the rainy seasons. Measures must be taken by African governments to create awareness among farmers and ultimately decentralize farming activities from urban to rural areas where human-vector contact is limited.Parasites & Vectors 01/2010; 3:118. · 2.94 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: The basement membrane zone of the limbal epithelium adjacent to the cornea was examined by ultrastructural and immunohistochemical techniques to determine whether differences exist between this region and central cornea. In human limbus, the percentage of basal cell membrane occupied by hemidesmosomes was significantly less (14.9 +/- 3.5) than that in central cornea 27.9 +/- 9.2), whereas the area of basement membrane/100 microns of cell membrane did not differ significantly. In rabbits, both percentage of membrane occupied by hemidesmosomes and area of basement membrane were less in the limbal region. Comparison of laminin and type VII collagen (anchoring fibril collagen) localisation in limbus and in central cornea demonstrated that both matrix proteins had a more convoluted pattern of localisation in the limbus. In addition, short segments of basement membrane with associated anchoring fibrils were present in the zone between the basal cells' basement membrane and blood vessels. These areas of duplicated basement membrane with anchoring fibrils were separated from the epithelium by layers of extracellular matrix that included collagen fibrils. Scanning electron microscopy of the surface topography of human limbal and central corneal basement membrane, prepared by removal of the epithelium with EDTA, demonstrated that in the limbal zone between the Palisades of Vogt and cornea, a very rough undulating surface was present with papillae or 'pegs' of stroma extending upward, and that central cornea lacked such papillae. Rabbit limbal basement membrane surface showed no such papillae, only occasional indentations into the stroma.(ABSTRACT TRUNCATED AT 250 WORDS)Eye 02/1989; 3 ( Pt 2):132-40. · 1.85 Impact Factor