Search

We previously reported that corneal fibroblasts within 3D fibrin matrices secrete, bind, and organize fibronectin into tracks that facilitate cell spreading and migration. Other cells use these fibronectin tracks as conduits, which leads to the development of an interconnected cell/fibronectin network. In this study, we investigate how cell-induced reorganization of fibrin correlates with fibronectin track formation in response to two growth factors present during wound healing: PDGF BB, which stimulates cell spreading and migration; and TGFβ 1, which stimulates cellular contraction and myofibroblast transformation. Both PDGF BB and TGFβ 1 stimulated global fibrin matrix contraction (p < 0.005); however, the cell and matrix patterning were different. We found that, during PDGF BB-induced cell spreading, fibronectin was organized simultaneously with the generation of tractional forces at the leading edge of pseudopodia. Over time this led to the formation of an interconnected network consisting of cells, fibronectin and compacted fibrin tracks. Following culture in TGFβ 1, cells were less motile, produced significant local fibrin reorganization, and formed fewer cellular connections as compared to PDGF BB (p < 0.005). Although bands of compacted fibrin tracks developed in between neighboring cells, fibronectin labeling was not generally present along these tracks, and the correlation between fibrin and fibronectin labeling was significantly less than that observed in PDGF BB (p < 0.001). Taken together, our results show that cell-induced extracellular matrix (ECM) reorganization can occur independently from fibronectin patterning. Nonetheless, both events seem to be coordinated, as corneal fibroblasts in PDGF BB secrete and organize fibronectin as they preferentially spread along compacted fibrin tracks between cells, producing an interconnected network in which cells, fibronectin and compacted fibrin tracks are highly correlated. This mechanism of patterning could contribute to the formation of organized cellular networks that have been observed following corneal injury and refractive surgery. [ABSTRACT FROM AUTHOR]

Abstract: The objective of the present study was to synthesize and characterize chitosans with different degrees of deacetylation (DDA%), prepare chitosan microspheres with controlled chemistry and geometry, and fabricate three-dimensional (3-D) chitosan matrices based on microspheres with appropriate pore size, porosity and mechanical properties suitable for bone tissue engineering applications. Chitosans with three DDA% of 69%, 79% and 97% were obtained using a thermomechanochemical technique by varying the applied pressure and NaOH solution concentration. The prepared chitosans were comprehensively characterized by proton nuclear magnetic resonance, elemental analysis, viscosity measurements, thermal analyses and X-ray diffraction. In addition, chitosan microspheres were prepared using an ionotropic gelation method. Three-dimensional chitosan matrices were fabricated via a sintered microsphere technique. Scanning electron microscopy revealed rough surfaces of the prepared chitosan microspheres. Mercury intrusion porosimetry revealed a porosity of 19.2% and a median pore diameter of 199.62μm of the fabricated 3-D matrix. The compressive modulus of the sintered microsphere matrix (662.26±54.53MPa) was in the range of human cancellous bone (10–2000MPa), making it suitable for bone tissue engineering applications. [Copyright &y& Elsevier]