Three-Dimensional, Quantitative Analysis of Desmin and Smooth Muscle Alpha Actin Expression During Angiogenesis

Abstract

Angiogenic therapies have been designed for many pathological conditions, but when used as a single therapy, the clinical results have fallen short of expectations. In addition, strategies for vascularizing engineered tissues have been unsuccessful in promoting the formation of an extensive, stable vasculature. Recent evidence suggests that mural cells play a critical role in the success of these approaches, but our current understanding of the function of mural cells in the microvasculature is incomplete. We studied the three-dimensional spatial and temporal kinetics of the mural cell markers desmin and smooth muscle alpha actin during angiogenesis in an in vivo fibrin gel model. The results led to the following conclusions: (1) desmin and smooth muscle alpha actin positive cells are present during the initial development of vessel sprouts; (2) the presence of these cells in the microvasculature is not always an indicator of vessel stability; and (3) the mural cell markers desmin and smooth muscle alpha actin exhibit differential staining patterns during vessel formation. These findings shed new light on the complexity of the relationship between mural cells and the formation of a mature, stable microcirculation.

Biomaterials to Prevascularize Engineered Tissues

“…Adding a low concentration of growth factor such as VEGF or fibroblast growth factor-1 leads to a persistent and normal vascular response [77][78][79]. Co-culturing endothelial cells with mural cells (pericytes, smooth muscle cells) significantly accelerates the prevascularization process in fibrin gels (16 vessels per unit area for co-culture compared to nine to 12 vessels for individual culture), and it can also stabilize the capillary once formed [76,80]. Moreover, an in vitro prevascularized fibrin gel using EPC-ECs and fibroblasts implanted subcutaneously into an immune-compromised mouse will anastomose with the host within 27 h after implantation with an average of 150 vessels/mm 2 [16].…”

Multiple tissue response modifiers to promote angiogenesis and prevent the foreign body reaction around subcutaneous implants

“…For applications that investigated small tissue areas, such as in the studies reported here, histological evaluation is the most common method of assessment of angiogenesis. In the current studies, angiogenesis was monitored via immune-staining against sma, which is present on the surface of mature blood vessels (vessels with connected venous and arterial branches) [45][46][47]. Since the delivery system presented here was developed for implantable biosensors, the area nearest to the composite (200 μm from the composite surface) was utilized in counting blood capillaries.…”

Endothelial Cell–Matrix Interactions in Neovascularization

“…Vessel stability is likely a function of both the relative levels and composition of BM assembled combined with additional EC interactions with support cells, or pericytes. 29,35 Proteins in the BM may also play an active role in initiating neovascularization. Type IV collagen in the BM contains a matricryptic angiogenic site that is exposed after proteolysis.…”