Background: The underlying risk factor of non-communicable diseases is
inflammation. The pathophysiology of asthma and/or allergic asthma is also, no
surprisingly, also linked to chronic inflammation. The prevalence and incidence of
asthma is on the increase, despite of a variety of treatment modalities. Asthma
therefore is a growing burden on healthcare system and on society.
Asthma pathophysiology is not only linked to inflammation, but also with
activation of coagulation and reduced fibrinolysis due to plasma and locally derived
factors in the airways. Alterations to these factors may thus influence the biophysical
and mechanical properties of the coagulation, fibrin deposition followed by asthma
Methodology: The objective of this study was to evaluate changes of blood
components in asthma patients (n=30) compared to controls (n=30) using routine
haematology screening using a haematology analyser; structural changes and axial
ratio analysis using light microscopy (erythrocytes), elasticity using atomic force
microscopy (erythrocytes); ultrastructural changes using scanning electron
microscopy (erythrocytes, platelets and fibrin), transmission electron microscopy
(platelets) and confocal microscopy (platelets) as well as the viscoelastic properties
of the fibrin clot using thromboelastography; and mRNA levels of FXIII-A in whole
blood by quantitative PCR.
Results: The haematology findings of controls and asthma patients were within
normal clinical ranges. There was, however, a significantly higher level of circulating
monocytes (p=0.0066), erythrocytes (p=0.0004), haemoglobin (p=0.0057) and
The analysis of eosin stained erythrocytes by light microscopy showed more
echinocytes, acanthocytes and ovalocytes compared to controls and the axial ratio
was also significantly higher (controls: 1.2�0.22nm vs. asthma: 1.165�0.16nm,
p<0.0001). Atomic force microscopy findings showed significantly reduced
erythrocyte membrane elasticity (p=0.001). Morphological changes of erythrocytes
were also noted from scanning electron microscopy. Platelet morphology and ultrastructure were qualitatively assessed using scanning
electron microscopy, transmission electron microscopy and confocal microscopy and
showed morphological changes indicative of platelet activation in asthma samples.
In addition, the assessment of clot kinetics by thromboelastography also
showed alteration with a tendency to produce stronger fibrin clots in asthma
samples. The reaction time was higher (p<0.0001), alpha-angle was lower
(p<0.0001), maximum rate of clot formation was higher (p<0.0001) � all indicative of
a longer time for clotting to occur but the maximal amplitude which is indicative of
clot strength and stability was significantly higher in asthma samples (p=0.0478). As
the aggregation and cross-linking of fibrin fibres depends on factor XIII (FXIII), its
excessive production may lead to alterations in fibrin polymerisation and crosslinking
resulting in stronger fibrin clot formation and resistance to fibrinolysis. Densitometry
analysis of scanning electron microscopy images of fibrin fibres showed a
significantly lower variance in asthma samples (p<0.0001) indicative of more matt
like structures compared to normal fibrin fibres in controls.
The analysis of gene expression by qPCR revealed a significant 17.34-fold
higher FXIII-A mRNA level in whole blood of asthma patients compared to controls
indicating greater potential for de novo production of FXIII-A compared to the control
group. These results would facilitate further research possibilities for identifying
potential biomarkers in allergic asthma.
These findings support the hypothesis of this study: enhanced coagulation
may be attributed to the altered morphology and activation of platelets, erythrocyte
and fibrin networks in asthma.
Conclusion: In conclusion, altered erythrocyte and platelet morphology, excess
production of FXIII-A, altered fibrin architecture and clot properties affects the
coagulation profile in asthma, systemically. Further research is needed to extrapolate
exact mechanism by which increased systemic coagulation contributes to the
pathophysiology of the disease locally.