Leiomyoma is a benign
smooth muscle tumor of the uterus that affects many women in active reproductive life. It is composed by bundles of smooth muscle cells surrounded by extracellular matrix. We have recently shown that the glycosylation of extracellular matrix
proteoglycans is modified in
leiomyoma: increased amounts of galactosaminoglycans with structural modifications are present. The data here presented show that
decorin is present in both normal myometrium and
leiomyoma but tumoral
decorin is glycosylated with longer
galactosaminoglycan side chains. Furthermore, these chains contain a higher ratio D-
glucuronate/L-
iduronate, as compared to normal tissue. To determine if these changes in
proteoglycan glycosylation correlates with modifications in the extracellular matrix organization, we compared the general structural architecture of
leiomyoma to normal myometrium. By histochemical and immunofluorescence methods, we found a reorganization of muscle fibers and extracellular matrix, with changes in the distribution of
glycoproteins,
proteoglycans, and
collagen. Thin
reticular fibers, possibly composed by types I and III
collagen, were replaced by thick fibers, possibly richer in
type I collagen.
Type I collagen colocalized with
decorin both in
leiomyoma and normal myometrium, in contrast to
type IV collagen that did not. The relative amount of
decorin was increased and the distribution of
decorin and
collagen was totally modified in the
tumor, as compared to the normal myometrium. These findings reveal that not only
decorin structure is modified in
leiomyoma but also the tissue architecture changed, especially concerning extracellular matrix.