Robust coupling of angiogenesis and osteogenesis by VEGF-decorated matrices for bone regeneration.

Rapid vascularization of clinical-size bone grafts is an unsolved challenge in regenerative medicine. Vascular endothelial growth factor-A (VEGF) is the master regulator of angiogenesis. Its over-expression by genetically modified human osteoprogenitors has been previously evaluated to drive vascularization in osteogenic grafts, but has been observed to cause paradoxical bone loss through excessive osteoclast recruitment. However, during bone development angiogenesis and osteogenesis are physiologically coupled by VEGF expression. Here we investigated whether the mode of VEGF delivery may be a key to recapitulate its physiological function. VEGF activity requires binding to the extracellular matrix, and heterogeneous levels of expression lead to localized microenvironments of excessive dose. Therefore we hypothesized that a homogeneous distribution of matrix-associated factor in the microenvironment may enable efficient coupling of angiogenesis and bone formation. This was achieved by decorating fibrin matrices with a cross-linkable engineered version of VEGF (TG-VEGF) that is released only by enzymatic cleavage by invading cells. In ectopic grafts, both TG-VEGF and VEGF-expressing progenitors similarly improved vascularization within the first week, but efficient bone formation was possible only in the factor-decorated matrices, whereas heterogenous, cell-based VEGF expression caused significant bone loss. In critical-size orthotopic calvaria defects, TG-VEGF effectively improved early vascular invasion, osteoprogenitor survival and differentiation, as well as bone repair compared to both controls and VEGF-expressing progenitors. In conclusion, homogenous distribution of matrix-associated VEGF protein preserves the physiological coupling of angiogenesis and osteogenesis, providing an attractive and clinically applicable strategy to engineer vascularized bone. STATEMENT OF SIGNIFICANCE: The therapeutic regeneration of vascularized bone is an unsolved challenge in regenerative medicine. Stimulation of blood vessel growth by over-expression of VEGF has been associated with paradoxical bone loss, whereas angiogenesis and osteogenesis are physiologically coupled by VEGF during development. Here we found that controlling the distribution of VEGF dose in an osteogenic graft is key to recapitulate its physiological function. In fact, homogeneous decoration of fibrin matrices with engineered VEGF could improve both vascularization and bone formation in orthotopic critical-size defects, dispensing with the need for combined osteogenic factor delivery. VEGF-decorated fibrin matrices provide a readily translatable platform for engineering a controlled microenvironment for bone regeneration.

Particulate air pollution and respiratory disease in Anchorage, Alaska.

This paper examines the associations between average daily particulate matter less than 10 microns in diameter (PM10) and temperature with daily outpatient visits for respiratory disease including asthma, bronchitis, and upper respiratory illness in Anchorage, Alaska, where there are few industrial sources of air pollution. In Anchorage, PM10 is composed primarily of earth crustal material and volcanic ash. Carbon monoxide is measured only during the winter months. The number of outpatients visits for respiratory diagnoses during the period 1 May 1992 to 1 March 1994 were derived from medical insurance claims for state and municipal employees and their dependents covered by Aetna insurance. The data were filtered to reduce seasonal trends and serial autocorrelation and adjusted for day of the week. The results show that an increase of 10 micrograms/m3 in PM10 resulted in a 3-6% increase in visits for asthma and a 1-3% increase in visits for upper respiratory diseases. Winter CO concentrations were significantly associated with bronchitis and upper respiratory illness, but not with asthma. Winter CO was highly correlated with automobile exhaust emissions. These findings are consistent with the results of previous studies of particulate pollution in other urban areas and provide evidence that the coarse fraction of PM10 may affect the health of working people.

Use of biomarkers in an indoor air study: lack of correlation between aromatic VOCs with respective urinary biomarkers.

The benzene and toluene levels inside of eight homes with attached garages were measured during July 1998 in Fairbanks, Alaska. A thermal desorption tube method and charcoal tube method were used to collect and analyze samples (thermal desorption tube method %RDS = 1.9 for n = 6; charcoal tube method %RDS = 6.5 for n = 4). Results for both methods were compared and showed indoor benzene levels ranging between 1.2 and 72 ppbv. The charcoal tube method usually gave lower results than the thermal desorption method. Nevertheless, the difference observed in benzene levels from each method was not significant as determined by application of the Wilcoxon t-test to these data. Using the thermal desorption method, the range of toluene found in homes was 0.1-111 ppbv. A correlation between toluene and benzene levels suggested the same point source. The benzene and toluene content of the indoor air and the number of small engines stored in the attached garage was also correlated. There was no correlation found between the urinary biomarker concentrations and the level of benzene or toluene measured inside the homes in the summer.

Associations between respiratory illness and PM10 air pollution.

In this study, the association between daily morbidity and respirable particulate pollution (i.e., particles with a mass median aerodynamic diameter of < or = 10 microns [PM10]) was evaluated in the general population of Anchorage, Alaska. Using insurance claims data for state employees and their dependents who lived in Anchorage, Alaska, the authors determined the number of medical visits for asthma, bronchitis, and upper respiratory infections. The number of visits were related to the level of particulate pollution in ambient air measured at air-monitoring sites. This study was conducted during a 3-y period, which included several weeks of higher-level particulate pollution that resulted from a volcanic eruption (i.e., August 1992). The particulate pollution was measured by the Anderson head sampler (24-h accumulation). The medical visits of the population at risk were also tallied daily. To help confirm whether PM10 exposure was a risk factor in the exacerbation of asthma, we used a regression analysis to regress daily asthma visits on PM10 pollution levels, controlling for seasonal variability. A significant positive association between morbidity and PM10 pollution was observed. The strongest association was with concurrent-day PM10 levels. The relative risk of morbidity was higher with respect to PM10 pollution during warmer days.

Benzene in Alaska.

Alaska Department of Environmental Conservation took indoor and ambient air samples during the winter of 1992-93 in Fairbanks. The samples showed a significant increase in the level of benzene in the air between December and February. The highest levels occurred in indoor air and exceeded workplace standards in garages. These findings were corroborated by NIOSH and OSHA personal monitoring studies done at the same time in Fairbanks and by blood samples taken by Centers for Disease Control and Prevention from workers exposed to gasoline in December and February. The blood samples showed a 300 percent increase in the amount of benzene in worker's blood after MTBE was taken out of gasoline. The most likely cause of this air pollution is gasoline evaporation and exhaust emissions. The benzene content of Alaska gasoline is 5 percent which is the highest in the nation. In view of these findings the Environmental Protection Agency is funding a new study of indoor air organic compounds including benzene in Anchorage, Alaska.

Expanding use of thrombolytic therapy in the treatment of acute myocardial infarction in rural Alaskan hospitals.

This paper focuses on clinical quality improvement comparing the results of two studies done approximately one year apart on treatment of acute myocardial infarction in four rural hospitals. The purpose of both studies was to determine how often eligible, elderly Medicare patients with acute myocardial infarction received thrombolytic treatment and aspirin. The studies were done by abstracting medical records for the calendar year 1993 and again in the year between October 1, 1994 and September 30, 1995. The results show that the use of thrombolytic therapy in these hospitals for the Medicare population increased by 40% between 1993 and 1995, a statistically significant increase (95% confidence intervals (CI) 20.1% to 60.0%). The rate of thrombolytic therapy among eligible Medicare patients went from 25.5% in 1993 to 65.7% in 1995. The use of aspirin also increased by 12.5% which was borderline significant (95% CI, 0.0% to 34%). The results were not as dramatic because the baseline for aspirin use with acute myocardial infarction was already 67.5% in 1993. These results indicate that the treatment of acute myocardial infarction is evolving closely in line with the American Heart Association/American College of Cardiology 1996 guidelines. Studies of clinical quality improvement such as this are now requirements for hospital certification.

Antithrombotic therapy for stroke prevention among Medicare beneficiaries hospitalized in Alaska with atrial fibrillation.

Although warfarin therapy reduces the risk of stroke among patients with atrial fibrillation (AF), the risk of hemorrhagic complications and other concerns may make clinicians reluctant to prescribe this treatment for elderly patients. Aspirin is a lower-risk alternative to warfarin but is also less effective. This study examines the use of antithrombotic therapy with warfarin or aspirin at hospital discharge among 182 Medicare beneficiaries 65 or older with chronic AF who were admitted to nine Alaska hospitals during 1996. Sixty-five percent of patients without contraindications were discharged on warfarin, and an additional 16% received aspirin. The rate of anticoagulation with warfarin was much higher among patients aged 65-74 (95%) than among those 75 or older (45%). The relatively low rate of warfarin use for very elderly patients may represent an opportunity to improve care. Although these patients have the highest risk of hemorrhagic complications, they also have the greatest potential to benefit from anticoagulation.

Health effects of methyl tertiary butyl ether (MTBE) in gasoline in Alaska.

OBJECTIVES: This ecologic study assessed whether there was a change in health status in Alaska in the winter of 1992-93 after the introduction of MTBE in gasoline. Methyl tertiary butyl ether(MTBE) is used as a fuel oxygenate in the United States and in Europe. In the winter of 1992-93 MTBE was added to gasoline in the cities of Fairbanks and Anchorage, Alaska. The program was discontinued in Fairbanks in December, 1992, but continued in Anchorage until February 28, 1993. METHODS: Outpatient visits for state employees and dependents (n = approximately 28,000) living in Alaska were compared over three winters by analyzing health insurance claims. RESULTS: Odds ratios were calculated. The odds ratios indicated that the winter of 92-93 was not statistically different from previous winters in numbers of claims for upper respiratory illness, bronchitis, headache, or asthma in either Anchorage or Fairbanks. CONCLUSION: There was no increase in claims for respiratory illness in either city after introduction of MTBE.