Biomedical Engineering Reference
In-Depth Information
hypertensive sheeps have demonstrated regional variability in the expression
of proET-1 gene in pulmonary arteries (28). To what extent regional varia-
tions may explain the lack of expression of ET-1 in arteries evaluated in
COPD patients is uncertain.
C.
Smooth Muscle Cells
The majority of cells proliferating in hyperplasic intimas of pulmonary mus-
cular arteries in patients with mild-to-moderate COPD are smooth muscle
cells (SMCs), as shown by positive immunoreaction to
a
-smooth muscle
actin (18) (Fig. 2). Interestingly, comparative analyses of serial sections
showed that some of the SMCs in the intima did not express desmin fila-
ments, whereas all cells expressed vimentin filaments (18) (Fig. 2). The pat-
tern of expression of both intermediate filaments may discriminate between
a synthetic phenotype of SMCs and the contractile phenotype observed in
mature cells (29,30). Accordingly, vimentin-positive, desmin-negative SMCs
represent a subpopulation of less differentiated SMCs that may possess syn-
thetic capacity and take part in an ongoing process of vascular remodeling
(31). These findings are consistent with previous observations in patients
with advanced COPD showing muscle deposition in pulmonary muscular
arteries and formation of a definite muscle layer in small arterioles
(11,12). Newly formed smooth muscle bounds adopt a longitudinal disposi-
tion that differs from the circumferential disposition of normal smooth
muscle.
The origin of SMCs proliferating in the intima of muscular arteries
and in small arterioles, which in normal conditions lack of muscular cells,
is uncertain. One possibility is that after endothelial injury, SMCs migrate
Figure 2
Photomicrographs of a pulmonary muscular artery from a patient with
mild COPD with prominent intimal hyperplasia. Serial sections were immunostained
for (A)
a
-smooth muscle actin and (B) desmin, a contractile filament. Note that a
number of smooth muscle cells proliferating in the intima did not express desmin fila-
ments, indicating a less differentiated phenotype. (Original magnification
400.)
