The success of tissue engineering applications can potentially be dramatically improved with the addition of adjuncts that increase the proliferation and differentiation of progenitor or stem cells. Platelet-rich plasma (PRP) has recently emerged as a potential biologic tool to treat acute and chronic tendon disorders. The regenerative potential of PRP is based on the release of growth factors that occurs with platelet rupture. Its autologous nature gives it a significant advantage in tissue engineering applications. To test whether PRP may be useful specifically for cartilage regeneration, a cell culture experiment was devised in which mesenchymal stem cells (MSCs) were grown in control media or media enhanced with inactivated, buffered PRP. Proliferation 7 days after PRP treatment was increased: 1.041 versus 0.199 for the control media cells ( p < 0.001). The messenger RNA (mRNA) level of the osteogenic marker RUNX2 was 52.84 versus 26.88 for the control group ( p < 0.005). Likewise the mRNA level of the chondrogenic markers Sox-9 and aggrecan was 29.74 versus 2.29 for the control group ( p < 0.001) and 21.04 versus 1.93 ( p < 0.001), respectively. These results confirm that PRP enhances MSC proliferation and suggest that PRP causes chondrogenic differentiation of MSC in vitro.

Background: This multicenter international cross-sectional observational study characterized vascular and valvular calcification burden and correlations with pulse pressure, diabetes, hypertension, and cardiovascular diseases in prevalent hemodialysis patients. Methods: We enrolled 275 consecutive adults with end-stage renal disease on maintenance hemodialysis for ⩾3 months. Coprimary endpoints were prevalences of: (1) echocardiographic calcification in mitral valve, aortic valve or mitral annulus; (2) aortoiliac tree vascular calcifications by plain lateral lumbar X-ray. Correlations among calcification sites and with demographics and comorbidities were determined. Pulse pressures were determined. Results: Subjects' mean ± standard deviation (SD) age was 56 ± 15.9 years; mean (SD) dialysis duration was 4.5 ± 4.3 years. Overall, 100% of echocardiographically imaged patients (n = 243) had calcification in aortic valve, mitral valve, or mitral annulus; 77.8% of X-rayed patients (n = 248) had abdominal aortic calcification. Radiographic abdominal aortic calcification score correlated significantly with calcification of aortic valve (p < 0.0001) and mitral annulus (p = 0.0001) but not mitral valve. Aortic valve, mitral valve, and mitral annulus calcification correlated significantly among themselves (p < 0.0001). Moderate/severe aortic valve calcification was significantly more prevalent in patients aged ⩾65 years than <65 years, men than women, and Whites than African Americans. Pulse pressure correlated significantly with vascular calcification score (p = 0.0049) but not with valvular calcification at any site. Conclusions: Vascular and valvular calcification are highly prevalent in the hemodialysis population. Peripheral vascular calcification correlates significantly with elevated pulse pressure and can be assessed easily using lateral lumbar X-ray. Further studies investigating the interaction between pulse pressure and development or progression of vascular calcification are of interest.

Background: Predicting or diagnosing underlying kidney disease by analyzing whole urine remains the mainstay of nephrology practice. However, whole urine is a poor compartment to assess many structural changes in the kidney because whole urine contains only a few proteins derived from the kidney itself. Urinary exosomes, on the other hand, which are derived from the kidney, contain proteins secreted by the kidney. We experimentally tested the hypothesis that ‘urinary exosomes more faithfully represent changes in the kidney tissue than whole urine'. A direct comparison between whole urine and urine exosomal levels of two chosen kidney disease markers, gelatinase and ceruloplasmin, was carried out on diabetic kidney disease patients. Methods: Urinary exosomes were separated from whole urine by sequential centrifugation including ultra-centrifugation. Gelatinase activity was measured using fluorosceinated gelatin as the substrate, and ceruloplasmin was measured by sandwich ELISA. A few kidney specimens from patients biopsied for atypical features were histochemically stained for validation of the biochemical results. Results: We found that changes in both, gelatinase (decreased activity) and ceruloplasmin (increased levels), in the urinary exosomes of diabetic kidney patients were in agreement with the alterations of these two proteins in the kidney tissue. In contrast, the levels of these two proteins in whole urine were highly variable and did not correlate with levels in the diabetic kidney tissue. Conclusion: In conclusion, these results confirmed our hypothesis that protein markers in urinary exosomes better reflected the underlying protein changes in the kidney than in whole urine samples.

AIM:To investigate the mechanism of liver regeneration induced by fusing the omentum to a small traumatic injury created in the liver. We studied three groups of rats. In one group the rats were omentectomized; in another group the omentum was left in situ and was not activated, and in the third group the omentum was activated by polydextran particles. METHODS:We pre-activated the omentum by injecting polydextran particles and then made a small wedge wound in the rat liver to allow the omentum to fuse to the wound. We monitored the regeneration of the liver by determining the ratio of liver weight/body weight, by histological evaluation (including immune staining for cytokeratin-19, an oval cell marker), and by testing for developmental gene activation using reverse transcription polymerase chain reaction (RT-PCR). RESULTS:There was no liver regeneration in the omentectomized rats, nor was there significant regeneration when the omentum was not activated, even though in this instance the omentum had fused with the liver. In contrast, the liver in the rats with the activated omentum expanded to a size 50% greater than the original, and there was histologically an interlying tissue between the wounded liver and the activated omentum in which bile ducts, containing cytokeratin-19 positive oval cells, extended from the wound edge. In this interlying tissue, oval cells were abundant and appeared to proliferate to form new liver tissue. In rats pre-treated with drugs that inhibited hepatocyte growth, liver proliferation was ongoing, indicating that regeneration of the liver was the result of oval cell expansion. CONCLUSION:Activated omentum facilitates liver regeneration following injury by a mechanism that depends largely on oval cell proliferation.