7B). Figure 7. Ultrastructure of fibroblasts immobilized in a matrigel plug after one week of subcutaneous implantation by transmission electron microscopy. (A) The implanted fibroblasts produced collagen in the matrigel (black arrowhead indicates … selleck inhibitor Discussion Understanding how to promote angiogenesis in a damaged tissue by using cells embedded in an injectable biomaterial continues to be a challenge in tissue regeneration. The need for proper vascularization, which involves the assembly of a microvascular network and its anastomosis with the host vasculature, remains one of the major hurdles for clinical success of complex tri-dimensional tissue engineered structures.22 In order to address if neonatal human dermal fibroblasts could influence the formation of early microvascular structures the matrigel plug model was used.
The matrigel plug assay has been described as a good model to study angiogenesis because it protects growth factors from degradation and dispersion23,24 and additionally provides the embedded cells with a suitable environment to proliferate and differentiate without scattering.25,26 The present in vivo study supports the hypothesis that implanted fibroblasts were able to recruit endothelial cells to vascularize an implanted artificial extracellular matrix with functional vessels after one week. As observed, the same matrix implanted without fibroblasts did not become vascularized, as confirmed by hemoglobin levels. Regarding the time-frame of one week, the cell infiltration and the observation of angiogenesis events in this period seems to be in agreement with the literature.
26,27 Soluble factors produced by fibroblasts, such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), probably influenced the interactions with endothelial cells and their recruitment. VEGF is required for survival, differentiation, and network formation of endothelial cells.28 bFGF promotes both endothelial cell scattering, that is required during the first step of the angiogenesis process, and the formation of the cell-cell interactions required for vessel maturation.23,24,29,30 Presta et al. presented evidence suggesting the possibility that bFGF indirectly induces neovascularization by activation of the VEGF/VEGFR system.
29 Angiogenesis and inflammation are intimately related since immune cells produce cytokines and growth factors that target endothelial cells and stimulate angiogenesis and, in turn, the new vessels formed transport oxygen and nutrients, as well as immune cells.31 In tissue regeneration it seems important to modulate inflammation to an adequate level.32 AV-951 Thus, it was evaluated if fibroblasts transplanted with matrigel changed the inflammatory profile by measuring inflammatory markers, namely NO and NAG. NAG is a lysosomal enzyme which shows increased activity in monocytes and macrophages activated during inflammatory diseases.