Vascular Smooth Muscle Cells in the Branching of Renal Arteries

Histological, morphometric, cytophotometry and statistical methods studied isolated smooth muscle cells at sites of the renal arteries with different hemodynamic conditions in newborns. It is shown that the population of smooth muscle cells on the straight sections of the renal arteries represented subpopulations of small, medium and large mononuclear cells. In the area of the arteries blood fl ow dividers, characterized by turbulence, twists, recycling and complex distribution of shear stress on the vascular wall, there is a pronounced polymorphism in the structure of the arteries of the population. Smooth muscle cells in these hemodynamic conditions, undergo hypertrophy and hyperplasia polyploidization. Phenotypic modulation myocytes occurring in arteries with high branching, anastomosing, many turns may initiate the development of hypertension, heart failure, ischemia, diabetes and obesity. Research Article


Introduction
Areas of vascular branching attracted the attention of researchers since the mid 50-ies of the last century [1,2]. Dividers blood fl ow correspond to areas of increased permeability of the endothelial lining and are prone to the formation of atheroma [3,4]. As the analysis of the literature [5], the least studied structural component of the vascular wall in hemodynamic stress zone are smooth myocytes (SM). It is known that SM can acquire branched form, and their contact with the basement membrane of endothelial cells alone [6].
Hemodynamic conditions may be a factor infl uencing the properties of the SM of the vascular wall [7].

The purpose of work
Morphometric and cytophotometry analysis isolated smooth muscle cells in arteries areas with different hemodynamic conditions.

Material and Methods
We studied the right and left renal arteries in the branch at the gates of the body 26 newborn infants who died of cerebrovascular accidents in case of damage of the skull bones.
For comparison, the study area is the same vascular blood fl ow dividers. Specimens were fi xed in 10% neutral formalin, 0.1 M phosphate buffer at pH 7.0. Isolated smooth muscle cells (SM) was prepared by alkaline cell dissociation and stained with hematoxylin and eosin Feulgen (hydrolysis of a 5 N HCl at 37 0 C 12 minutes). We counted the relative abundance of twonuclear elements, screw ocular micrometer measured linear parameters of the nucleus and cytoplasm of single-core and dual-core SM, as well as calculate their area and volume. The level of DNA in the nuclei of single-and dual-core assayed for SM cytophotometry "MIF-K" (Moscow State University) at a wavelength of 580 nm. Quantitative data were processed by the method of variation statistics.

Results of the Study
Population structure of smooth muscle cells of the renal arteries of newborn children on the straight sections of the vessel and presented heterogeneous, mostly single-core elements ( Figure 1). The morphometric analysis helps identify a subpopulation of small (up to 1000 mcm 3 to 24.8% -( Figure   2)), medium (1000 -3000 mcm 3 to 53.4% - (Figure 3)) and larger GM (more than 3000 mcm 3 21.8 % - (Figure 4)). It was also found a small amount (0.2%) dual-core forms of SM ( Figure 5). Cytophotometry analysis shows that SM population comprises mononuclear preferably diploid elements ( Figure 6).        SM dual-characterized, compared to single-core, large size ( Figure 15). Thus, their average length is increased to 1.8 (P <0.01), and the cross section -in a 1, 7 (P <0,01) times. Area and volume dual-core cell above, respectively, 4.5 (P <0.01) and 10,4 (P <0,01) fold. This same pattern was observed in the measurement of myocyte nuclei: their length exceeds a       fold.
Dual сore myocytes also differ in their nuclei topography.
There SM with nuclei lying one behind the other (Figure 10) or in parallel ( Figure 17).
Cytophotometry redistribution study shows ploidy classes in the population of smooth muscle cells in the zone of the branching renal arteries (Figure 20), Table 1).

Discussion of the Data
Unlike straight segments laminar character movement, and fi eld bends fl ow dividers are special sections with turbulence, swirling, recirculation, and complex shear stress distribution on the nature of the arterial wall [5,8]. It is important to bear in mind that the pressure (stress / strain) and fl ow (shear) can regulate the function of blood [9], differentiation, proliferation and migration of vascular myocytes [9,10].
The morphological laboratories Yaroslavl Medical University found that areas dividers fetal blood and adult arterial fl ow distinguished by the presence of additional regulatory smooth complexes in the inner membrane of vessels [11,12].
SM artery walls respond to hemodynamic stress cytoskeleton reorganization and migration [13]. Development in the tunica intima of the SM and the musculo-elastic sphincter is a consequence of the penetration of SM medium choroid into the interior through the Fenestra in the elastic membrane [14].
The role of migration in SM endothelin and platelet-derived growth factor [14,15].
It was established that in the arterial wall area of blood fl ow dividers marked a pronounced polymorphism of smooth muscle cells, their hypertrophy and polyploidy. In the analysis of mechanisms polyploidy smooth muscle tissue was shown that growth of tangential stress and increased pressure in the vessels associated with activation of DNA synthesis in the nucleus of muscle cells [12,16]. In this work in areas of     [17], it is considered as a variant of polyploidy [18].
In our laboratory we show that the regeneration conditions morphogenesis rat aortic population becomes more reactive SM tunica: labeled nuclei index compared to control them in 53-fold increases in [19].  [21]. The authors believe that a group of small SM is young, actively synthesizing protein cells having proliferative activity; SM's average form the basis of population and retain proliferative potential; SM is a large terminal elements lose their ability to proliferate.
Thus, these data confi rm the information [10,21] about the heterogeneity of the SM populations. Isolated phenotype small phase (fast) SM, capable of passing through hypertrophic growth and tonic (slow) vascular SM undergoing hyperplasia [9]. Load changes can cause phenotypic modulation of myocyte proliferation and SM [9,10]. Thus, hemodynamic conditions can be a factor affecting the properties SM vascular wall.
Phenotypic modulation myocytes, which occur in the arteries that are highly branched, anastomosing, many turns, are discussed to initiate the development of hypertension, heart failure, ischemia, obesity and diabetes [22].