Types Of Pericytes Research Articles

Laminin differentially regulates the stemness of type I and type II pericytes

BackgroundLaminin, a major basement membrane component that has direct contact with pericytes under physiological conditions, actively regulates the proliferation and differentiation/fate determination of pericytes. Recently, two types of pericytes (type I and type II) with different molecular markers and functions have been identified in skeletal muscles. Whether laminin differentially regulates the proliferation and differentiation of these two subpopulations remains unclear.MethodsWild-type and pericytic laminin-deficient mice under Nestin-GFP background were used to determine if laminin differentially regulates the proliferation and differentiation of type I and type II pericytes. Specifically, type I and type II pericytes were isolated from these mice, and their proliferation and differentiation were examined in vitro. Moreover, in vivo studies were also performed.ResultsWe demonstrate that, although laminin inhibits the proliferation of both type I and type II pericytes in vitro, loss of laminin predominantly induces proliferation of type II pericytes in vivo. In addition, laminin negatively regulates the adipogenic differentiation of type I pericytes and positively regulates the myogenic differentiation of type II pericytes in vitro.ConclusionsLaminin differentially regulates the proliferation and differentiation of type I and type II pericytes.

The distinct abilities of tube-formation and migration between brain and spinal cord microvascular pericytes in rats

Pericytes are contractile cells that wrap around the endothelial cells of capillaries throughout the body. They play an important role in regulating the blood brain barrier (BBB) and blood spinal cord barrier (BSCB). The differences between brain and spinal cord microvascular endothelial cells have been investigated. However, no report has elucidated the similarities and differences between brain microvascular pericytes (BMPs) and spinal cord microvascular pericytes (SCMPs) in vitro. The similarities were found between the two types of pericytes not only in the proliferation ability but also in the expression of toll like receptor 4. On the other hand, BMPs showed more than 2 fold in tubular length formation compared with SCMPs. The number of migratory SCMPs was larger than that of migratory BMPs. The expressions of connexin 43 and vascular endothelial growth factor (VEGF) in BMPs were increased compared with those in SCMPs, while SCMPs expressed more desmin and N-cadherin than BMPs. The abilities of tube-formation and migration between BMPs and SCMPs were markedly different, which might be mediated by VEGF, connexin 43, N-cadherin and desmin. These distinguishing features may reflect the more widespread differences between the BBB and BSCB which directly impact pathophysiological processes in various major diseases.

Role of Pericytes in Skeletal Muscle Regeneration and Fat Accumulation

Stem cells ensure tissue regeneration, while overgrowth of adipogenic cells may compromise organ recovery and impair function. In myopathies and muscle atrophy associated with aging, fat accumulation increases dysfunction, and after chronic injury, the process of fatty degeneration, in which muscle is replaced by white adipocytes, further compromises tissue function and environment. Some studies suggest that pericytes may contribute to muscle regeneration as well as fat formation. This work reports the presence of two pericyte subpopulations in the skeletal muscle and characterizes their specific roles. Skeletal muscle from Nestin-GFP/NG2-DsRed mice show two types of pericytes, Nestin-GFP-/NG2-DsRed+ (type-1) and Nestin-GFP+/NG2-DsRed+ (type-2), in close proximity to endothelial cells. We also found that both Nestin-GFP-/NG2-DsRed+ and Nestin-GFP+/NG2-DsRed+ cells colocalize with staining of two pericyte markers, PDGFRβ and CD146, but only type-1 pericyte express the adipogenic progenitor marker PDGFRα. Type-2 pericytes participate in muscle regeneration, while type-1 contribute to fat accumulation. Transplantation studies indicate that type-1 pericytes do not form muscle in vivo, but contribute to fat deposition in the skeletal muscle, while type-2 pericytes contribute only to the new muscle formation after injury, but not to the fat accumulation. Our results suggest that type-1 and type-2 pericytes contribute to successful muscle regeneration which results from a balance of myogenic and nonmyogenic cells activation.

Three-dimensional architecture of pericytes with special reference to their topographical relationship to microvascular beds.

Microvascular beds and pericytes in the submandibular gland, thyroid gland and heart were studied by combined scanning electron microscopy and chemical digestion. The submandibular gland had a relatively loose network of blood capillaries, the thyroid gland possessed a close-meshed network of capillaries, and those in the myocardium ran parallel to the long axis of myocardial cells. The thyroid gland exhibited the largest numbers of pericytes. Three types of pericytes could be distinguished by their shape and localization. Type I pericytes, which were confined to true capillaries, had a fusiform or polygonal cell body, a few long, slender longitudinal processes (primary ones) and short, fine circumferential processes (secondary ones). Type II pericytes, which were found in the arterial side of myocardial capillaries, were characterized by large, circumferential band-like processes completely encircling the vessel. Type III pericytes, which were seen on the venous side of thyroid and myocardial capillaries, had a flattened cell body and short, irregular processes. Type II and III pericytes appear to show an intermediate or transitional form between smooth muscle cells and typical pericytes (Type I). Judging from the configuration of pericytes suggests that these are related to functions such as contraction as well as mechanical support.

Hemangiopericytoma of the breast.

The clinical and pathologic features of three hemangiopericytomas of the breast in women are described. The three tumors presented as painless, nontender nodules. The morphologic variation typical of hemangiopericytomas was present in each tumor. One case was studied by electron microscopy and was found to be composed of two types of pericytes. Both cell types were closely associated with vessels, partially or completely surrounded by basal lamina, and contained pinocytotic vesicles. There were only minor differences between the two forms of pericytes. Smooth muscle cells, fibroblasts, or transitional cell forms were not observed. The two patients on whom follow-up information was available have remained free of tumor 2.8 and 4 years after their surgery, indicating that not all vascular tumors of the breast are highly aggressive neoplasms.

ULTRASTRUCTURAL STUDY OF HEMANGIOMAS

A case of benign hemangioendothelioma which occurred in the hard palate was observed and its electron microscopic findings were described. The endothelial cells contained an abundance of cytoplasmic filaments, but they contained a small number of Weibel‐Palade bodies. Two types of endothelial cells, light and dark, were found in our specimen. The former had a cytoplasm with an abundance of ribosomes, rough endoplasmic reticulum and scant filaments. The latter had a cytoplasm with numerous cytoplasmic filaments and a well‐developed Golgi apparatus. Tight junctions were seen between the endothelial cells. The majority of the pericytes were accompanied with the vessels in the tumor. Three types of pericytes were recognized: endothelial cell‐like, fibroblast‐like, and smooth muscle cell‐like pericytes.

Surface view of pericytes on the retinal capillary in rabbits revealed by scanning electron microscopy.

Retinal capillaries of the rabbit were treated with HCl and collagenase to visualize the pericytes attached to the stromal surface of the capillary walls under the scanning electron microscope. Two types of pericytes were distinguishable on the basis of shape and localization. One type (Type I) had a slightly bulged, fusiform cell body with a few, long, branching cytoplasmic processes, and these cells were scattered mainly in the region of the true capillary. The other type (Type II) possessed a rather flattened and polymorphic cell body from which radiated short irregular cytoplasmic processes, and these cells, which tended to overlap more or less, were present predominantly in the region of the pre- or postcapillary vessels in the capillary bed. The latter type cells were assumed to be precursors of the smooth muscle cells.