Am. J. Respir. Crit. Care Med., Vol 152, No. 5, 11 1995, 1659-1665.
Immunohistochemical identification and characterization of smooth muscle-like cells in idiopathic pulmonary fibrosis
K Ohta, RL Mortenson, RA Clark, N Hirose and TE King Jr
Department of Medicine, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206, USA.
The interstitium of the fibrotic lung possesses a contractile capability
that is unusual for nonmuscle tissue. An abundance of actin filament-laden
cells have been demonstrated in animal and human studies of fibrotic lung
tissue and have frequently been termed myofibroblasts. The origin and
significance of these cells remain unclear. Proliferation of cells with the
capability to contract and thereby generate force within the parenchyma is
potentially a significant contribution to the increased lung elastic recoil
of advanced pulmonary fibrosis. In the present study, we
immunohistochemically examined these intermediate phenotypes of
filament-laden cells with a focus on those expressing smooth
muscle-associated isoforms of actin. The monoclonal antibody HHF35 was used
to study the presence and distribution of cells expressing alpha and gamma
smooth muscle actin in idiopathic pulmonary fibrosis (IPF). Adjacent
sections of tissue from open lung biopsies of eight patients with IPF were
stained with a pentachrome stain and with multiple antibodies (HHF35,
polyclonal anti-actin, anti-vimentin, anti- keratin, anti-procollagen I,
and anti-von Willebrand Factor VIII) to identify specific cell types. In
addition, anti-laminin antibody was used to stain basement membrane. Many
tightly packed, HHF35-reactive cells were found to be architecturally
dissociated from airways and blood vessels in all eight patients with IPF.
Some HHF35-reactive bundles were composed of loosely associated cells, and
single smooth muscle cell types (SMC) were distributed in the fibrotic
interstitium. Interestingly, some of the SMC were distinctly negative for
anti- laminin and stained atypically with pentachrome. Moreover, some
single SMC were found to be anti-procollagen type I reactive with double
staining technique.(ABSTRACT TRUNCATED AT 250 WORDS)
