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Abstract

The E-11 and 1-B8 monoclonal antibodies raised to the smooth muscle (SM)-specific SM22 protein from pig stomach were used to study the in vivo and in vitro phenotypic characteristics of myofibroblasts (MF) and SM cells (SMC) from the bladder detrusor muscle and serosal thickening of male rabbit. The 22-kDa SM22 band found in the SM extract appeared to be composed of distinct isoforms when examined in non-equilibrium two-dimensional gel electrophoresis (2D-EF): alpha (the most basic), beta, gamma, and delta (the most acidic) in the ratio of 34(alpha):23(beta):36(gamma):8(delta). Western blots of 2D-electrophoresed bladder extracts treated with E-11 and 1-B8 showed that alpha, beta, and delta, but not gamma isoforms were labeled with E-11, whereas alpha, beta, and gamma isoforms were stained with 1-B8. This differential immunoreactivity was not influenced by phosphorylation. The tissue distribution of SM22 immunostaining was heterogeneous in the bladder SM and serosal thickening developed as a consequence of partial outflow obstruction of the urinary bladder. At the cellular level, the 1-B8 and E-11 antibodies stained the SMC in a "diffuse" (the whole cytoplasm) and "honeycomb" (the peripheral cytoplasm) manner, whereas MF immunostaining was quite homogeneous. The two antibodies also reacted with cultured primary bladder SMC and MF grown in low serum conditions showing a heterogeneous SM22 cell distribution but an identical subcellular localization, i.e., the actin-containing filamentous network, distinguishable in part from that found in vivo. The immunocytochemical, Western blotting and 2D-EF patterns of MF from thickened serosa indicated that the gamma isoform alone is expressed in this tissue. This SM22 variant appeared before the completion of the cellular transition from MF to fully differentiated SMC. This pattern is reminiscent of bladder ontogenesis where SM22 expression in the developing bladder wall precedes that of SM myosin. Taken together these data suggest that: (i) SM22 isoforms are differently assorted in MF vs. SMC; (ii) SM22 is a SMC-lineage marker inasmuch as its expression occurs in an experimental condition characterized by a time-related cell phenotypic transition from MF to SMC, and (iii) cell conversion ability of serosal cells in the adult might take place via the reactivation of a specific "foetal" gene programme.

Altered fibroblast proteoglycan production in COPD

“…Furthermore, central and distal fibroblasts showed immunoreactivity for the fibroblast markers prolyl 4-hydroxylase and vimentin (Figure 2B, C, F and 2G). The contractile protein Sm22 has been found to be expressed by smooth muscle cells and myofibroblasts but not by fibroblasts [16]. The isolated fibroblasts were negative for sm22.…”

Gene expression of muscarinic, tachykinin, and purinergic receptors in porcine bladder: comparison with cultured cells

“…This may indicate that different cell types, which were differentiated in the native tissue, may undergo myogenic conversion after 2 weeks in the culture. Several studies have reported the conversion of fibroblasts, myofibroblasts and muscle cells depending on the experimental conditions (Darby et al, 1990; Salvatori et al, 1995; Chiavegato et al, 1999; Darby and Hewitson, 2007). …”

Evaluation of gel spun silk-based biomaterials in a murine model of bladder augmentation

“…In comparison to silk matrices, the smooth muscle compartment reconstituted by the PGA augments displayed smooth muscle bundles expressing α-actin, however SM22α and calponin expression was localized to submucosal cell populations surrounding fibrotic tissue indicative of the presence of myofibroblasts at the defect site [48,49]. The reduced width of the regenerated tissue may also reflect the immature state of repair supported by the PGA implants in comparison to the silk matrices.…”