Universidad de Murcia. Departamento de Biología Celular e Histología
Abstract
Progenitor cell differentiation into fibroblastlike synoviocytes (FLSs) and their ensuing phenotypic
changes are incompletely explored. Synovial lining is
composed of intimal macrophages and FLSs. FLSs have
epithelioid morphology and directionally secrete
components of synovial fluid, including lubricin. We
stained human tissues and tumors using two anti-lubricin
antibodies. Lubricin was found in FLSs in synovium and
in tenosynovial giant cell tumors (TSGCTs) and not in
the associated monocyte/macrophage cells, which were
identified by double immunostaining for CD163. In
TSGCTs, giant cells, known to form by fusion of
mononuclear cells, were negative for both lubricin and
CD163. Occasional mononuclear cells with the same
phenotype were also seen, suggesting that the precursors
of the giant cells are derived from the minor CD163-
negative monocyte subset. Lubricin was also detected in
intramuscular myxomas, in early myxoid changes of
ganglion cysts, and in one of five low-grade
myxofibrosarcomas, but not in other fibroconnective
tissues, epithelial tissues, or other tumors tested. This
suggests that lubricin expression may typify adaptive
and neoplastic changes along a pathway toward FLSs.
Further support for this concept comes from ganglion
cysts and juxta-articular myxoma tumors, which show a
spectrum of myxoid, cystic and synovial differentiation,
and in which moderate lubricin staining of myxoid
stroma was seen