Effect of adenosine monophosphate deaminase-1 C34T allele on the requirement for donor inotropic support and on the incidence of early graft dysfunction after cardiac transplantation.

The C34T T allele of the adenosine monophosphate deaminase-1 (AMPD1) gene has been associated with improved outcome in patients with cardiac dysfunction. We hypothesized that possession of this allele by donor hearts plays a role in the outcome of cardiac transplantation; 262 cardiac donors and 190 of their recipients were studied. AMPD1 C34T genotype was determined using 5' exonuclease chemistry. Requirement for inotropic agents before organ donation, 1-year post-transplantation survival, cause of death, and factors known to affect survival after transplantation were also studied. Multiple regression models for factors affecting survival were constructed. A significant yearly increase in frequency of the T allele in donors was noted (0.06 to 0.18 from 1994 to 1999). Donors with the CT or TT genotype required less inotropic support than those with the CC genotype (mean number of inotropes per donor with CT or TT genotype 0.27 compared with 0.47 per donor with CC genotype, n = 206, p = 0.03). Recipients of T-allele-carrying organs showed worse 1-year survival after transplantation (59% vs 79%, p <0.001). Excess deaths in these patients was due to early graft dysfunction (odds ratio for early graft dysfunction 6.6, 95% confidence interval 2 to 21.6, p = 0.0001). Multivariate analysis showed donor AMPD1 genotype, recipient age, and pretransplantation anemia to independently affect 1-year post-transplantation survival (adjusted hazard ratios 3.7, 1.06, and 2.6, respectively). In conclusion, possession of the AMPD1 T allele is associated with decreased inotropic requirements before heart donation. The incidence of early graft dysfunction, however, was significantly higher in recipients who received AMPD1 T-allele-possessing organs resulting in worse 1-year survival.

Collagen synthesis by mesenchymal stem cells and aortic valve interstitial cells in response to mechanical stretch.

OBJECTIVE: The synthesis of appropriate extracellular matrix by cells in tissue engineered heart valve constructs will be important for the maintenance of valve cusp integrity and function. We have examined and compared the capacity of mesenchymal stem cells to synthesise collagen in response to stretch in comparison with native aortic valve interstitial cells. METHODS: Cells were stretched on a Flexercell FX4000 apparatus and total collagen synthesis was measured by the incorporation of [3H]-proline. The effect of stretch on gene expression of different collagen types was assessed by RT-PCR. RESULTS: There was a significant (p<0.01) increase in [3H]-proline incorporation into stretched valve cells at 10%, 14% and 20% stretch. The response of mesenchymal stem cells at 14% stretch was similar to that seen in the valve cells. Incorporation of [3H]-proline into soluble proteins in the cell media was significantly higher (p<0.01) only at 14% and 20% stretch in valve interstitial cells. These effects were shared with mesenchymal stem cells at 14% stretch. RT-PCR experiments demonstrated that 14% stretch up-regulated levels of mRNA for COL3A1 gene (type III collagen) but did not increase the expression of COL1A1 gene (type I collagen) in valve interstitial cells. However, both collagen genes could be detected in non-stretched and stretched mesenchymal stem cells. There was no evidence that the mesenchymal stem cells had started to adopt an osteoblastic cell phenotype in response to stretch. CONCLUSIONS: Collagen synthesis by valve interstitial cells is dependent upon the degree and duration of stretch. This response can be mimicked closely by exposure of mesenchymal stem cells to the same stretching profile. These properties could have important implications for the choice of cells and programme of conditioning with which to tissue engineer heart valves.

C34T AMP deaminase 1 gene mutation protects cardiac function in donors.

Dysfunction of the donor heart is an important clinical problem that could be affected by genetic factors. We tested the hypothesis that possession of the C34T nonsense mutation in AMPD1 gene, which is known to improve survival in chronic heart failure, protects against cardiac dysfunction in donors. Genetic analysis for C34T mutation was performed by single-stranded conformational polymorphism (SSCP) in 22 donor hearts used for transplantation, 10 unused donor hearts with acute heart failure (HF), 37 patients with chronic HF, and 207 healthy controls. We found a significantly higher frequency of the mutation among donors with healthy hearts used for transplantation (31.8%) as compared to control population (13.5%, P < 0.001) and a lower frequency in dysfunctional donor hearts (5.0% P = 0.025); the frequency of the C34T mutation in patients with chronic heart failure (14.8%) was not different from that of a control population. The presence of the C34T mutation in AMPD1 gene appears to be protective against acute heart failure in cardiac donors.

Decreased cardiac activity of AMP deaminase in subjects with the AMPD1 mutation--a potential mechanism of protection in heart failure.

OBJECTIVES: Possession of the C34T (Glu12Stop) nonsense mutation in the AMP-deaminase 1 (AMPD1) gene has been shown to be associated with improved prognosis in heart failure and ischemic heart disease. The most likely event leading to these clinical effects is a reduced capacity of the AMP deamination pathway and increased production of cardio-protective adenosine. However, since AMPD1 is predominantly expressed in skeletal muscle, the protective effects could be related not only to local cardiac changes, but also to a systemic mechanism. In the present study we evaluated the effect of the C34T mutation on cardiac AMP-deaminase activity and on the systemic changes in adenosine production. METHODS: The presence of the C34T mutation was assayed by single-stranded conformational polymorphism (SSCP). Analysis of the AMPD1 genotype and measurement of enzyme activities was performed on 27 patients with heart failure (HF). In addition, blood adenosine concentration was measured by liquid chromatography/mass spectrometry (LC/MS) in 21 healthy subjects with established AMPD1 genotype at rest and following exhaustive exercise. RESULTS: Cardiac AMP-deaminase activity in heterozygotes (C/T) was 0.59+/-0.02 nmol/min/g wet wt-about half of the activity found in normal wild-type (C/C) individuals (1.06+/-0.09 nmol/min/g wet wt, P=0.003). There were no significant differences in the activities of any other enzymes between subjects with the C/T or C/C genotype. Resting venous blood adenosine concentration was similar in subjects with C/C, C/T and homozygous for the mutated allele (T/T) genotype. Following exercise, a significant increase in adenosine was observed in T/T subjects (by 0.013+/-0.009 micromol/l, P=0.035) but not in C/C (0.003+/-0.009 micromol/l) or C/T (-0.002+/-0.011 micromol/l). CONCLUSIONS: Our findings indicate that the C34T mutation of AMPD1 leads to a decrease in cardiac enzyme activity of AMP-deaminase without changes in any other adenosine-regulating enzymes, highlighting the importance of local cardiac metabolic changes. Systemic (blood) changes in adenosine concentration were apparent only in homozygous subjects and therefore may play a relatively small part in cardio-protection.