Mechanical compliance has been demonstrated to be a key determinant of cell behavior, directing processes such as spreading, migration, and differentiation. Durotaxis, directional migration from softer to more stiff regions of a substrate, has been observed for a variety of cell types. Recent stiffness mapping experiments have shown that local changes in tissue stiffness in disease are often accompanied by an altered ECM composition in vivo. However, the importance of ECM composition in durotaxis has not yet been explored. To address this question, we have developed and characterized a polyacrylamide hydrogel culture platform featuring highly tunable gradients in mechanical stiffness. This feature, together with the ability to control ECM composition, allows us to isolate the effects of mechanical and biological signals on cell migratory behavior. Using this system, we have tracked vascular smooth muscle cell migration in vitro and quantitatively analyzed differences in cell migration as a function of ECM composition. Our results show that vascular smooth muscle cells undergo durotaxis on mechanical gradients coated with fibronectin but not on those coated with laminin. These findings indicate that the composition of the adhesion ligand is a critical determinant of a cell's migratory response to mechanical gradients.durotaxis | cell migration | extracellular matrix | polyacrylamide C ell migration is essential to numerous biological processes, including development, angiogenesis, wound healing, and cancer metastasis (1-4). The movement of cells in these processes is determined by a complex assessment of environmental cues that include soluble factors, ECM composition, orientation, and stiffness. Numerous experiments have demonstrated that directional cell migration can result from gradients in these environmental cues: for example, chemotaxis (cell migration in response to gradients of soluble signals) and haptotaxis (cell migration in response to gradients of bound ligands) have been established in both in vitro and in vivo experimental systems (5-7). More recently, it has been demonstrated that cells are also capable of directed migration in response to gradients in substrate stiffness, a process termed durotaxis (8). Though there have been limited reports of specifically measured in vivo gradients (9), a number of recent stiffness mapping measurements imply the presence of stiffness gradients in both healthy and diseased tissues spanning a wide range of stiffnesses (10-13). In vitro experiments have demonstrated that directed migration in response to stiffness gradients can be observed in numerous cell types, using various materials as substrates, and across various stiffness levels (8,(14)(15)(16)(17)(18)(19). However, the role of ECM composition in mediating this behavior has not been thoroughly investigated.The interplay between mechanical stiffness and matrix composition in normal and pathological physiology is only now becoming appreciated. Recent studies in which tissue stiffness was mapped by atomic fo...
Extracellular matrix composition and stiffness are known to be critical determinants of cell behavior, modulating processes including differentiation, traction generation, and migration. Recent studies have demonstrated that the ECM composition can modulate how cells migrate in response to gradients in environmental stiffness, altering a cell’s ability to undergo durotaxis. These observations were limited to single varieties of extracellular matrix, and typically cells are exposed to environments containing complex mixtures of extracellular matrix proteins. Here, we investigate migration of NIH 3T3 fibroblasts on mechanical gradients coated with one or more type of extracellular matrix protein. Our results show that NIH 3T3 fibroblasts exhibit durotaxis on fibronectin-coated mechanical gradients but not on those coated with laminin, demonstrating that extracellular matrix type can act as a regulator of cell response to mechanical gradients. Interestingly, NIH 3T3 fibroblasts were also observed to migrate randomly on gradients coated with a mixture of both fibronectin and laminin, suggesting that there may be a complex interplay in the cellular response to mechanical gradients in the presence of multiple extracellular matrix signals. These findings indicate that specific composition of available adhesion ligands is a critical determinant of a cell’s migratory response to mechanical gradients.
Prolonged waiting time for a second transplant was associated with inferior patient and graft outcomes.
See Covering the Cover synopsis on page 379.BACKGROUND AND AIMS: Current guidelines recommend surveillance for patients with nondysplastic Barrett's esophagus (NDBE) but do not include a recommended age for discontinuing surveillance. This study aimed to determine the optimal age for last surveillance of NDBE patients stratified by sex and level of comorbidity. METHODS: We used 3 independently developed models to simulate patients diagnosed with NDBE, varying in age, sex, and comorbidity level (no, mild, moderate, and severe). All patients had received regular surveillance until their current age. We calculated incremental costs and quality-adjusted life-years (QALYs) gained from 1 additional endoscopic surveillance at the current age versus not performing surveillance at that age. We determined the optimal age to end surveillance as the age at which incremental costeffectiveness ratio of 1 more surveillance was just less than
We report the case of a patient with familial atypical haemolytic uraemic syndrome (aHUS) who underwent successful retransplantation 30 months following his failed first kidney allograft from recurrent aHUS. He achieved excellent graft function (creatinine 90 μmol/L), with no evidence of disease recurrence on standard maintenance immunosuppression 9 months after his second deceased donor kidney transplantation. Genetic mutation testing was not available prior to first transplant but screening prior to retransplant identified the patient as having a newly discovered mutation, c.T3566A, within exon 23 of the complement factor H (CFH) gene. Currently, public financing and subsidisation for eculizumab, a costly but effect complement (C5) inhibitor for the treatment of aHUS is not available in Australia. The decision for retransplantation must balance between the risk of disease recurrence and greater risk of death on dialysis. The absence of a more severe CFH genotype assisted in the decision for retransplantation and suggests the importance of genetic mutation screening in order to stratify the risk of disease recurrence and graft loss versus the benefit of transplantation.
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