Stimulation of Superficial Zone Protein/Lubricin/PRG4 by Transforming Growth Factor-β in Superficial Zone Articular Chondrocytes and Modulation by Glycosaminoglycans

Abstract

Superficial zone protein (SZP), also known as lubricin and proteoglycan 4 (PRG4), plays an important role in the boundary lubrication of articular cartilage and is regulated by transforming growth factor (TGF)-b. Here, we evaluate the role of cell surface glycosaminoglycans (GAGs) during TGF-b1 stimulation of SZP/lubricin/PRG4 in superficial zone articular chondrocytes. We utilized primary monolayer superficial zone articular chondrocyte cultures and treated them with various concentrations of TGF-b1, in the presence or absence of heparan sulfate (HS), heparin, and chondroitin sulfate (CS). The cell surface GAGs were removed by pretreatment with either heparinase I or chondroitinase-ABC before TGF-b1 stimulation. Accumulation of SZP/lubricin/PRG4 in the culture medium in response to stimulation with TGF-b1 and various exogenous GAGs was demonstrated by immunoblotting and quantitated by enzyme-linked immunosorbent assay. We show that TGF-b1 and exogenous HS enhanced SZP accumulation of superficial zone chondrocytes in the presence of surface GAGs. At the dose of 1 ng/mL of TGF-b1, the presence of exogenous heparin inhibited SZP accumulation whereas the presence of exogenous CS stimulated SZP accumulation in the culture medium. Enzymatic depletion of GAGs on the surface of superficial zone chondrocytes enhanced the ability of TGF-b1 to stimulate SZP accumulation in the presence of both exogenous heparin and CS. Collectively, these results suggest that GAGs at the surface of superficial zone articular chondrocytes influence the response to TGF-b1 and exogenous GAGs to stimulate SZP accumulation. Cell surface GAGs modulate superficial zone chondrocytes' response to TGF-b1 and exogenous HS.

Kappa opioid receptor signaling protects cartilage tissue against posttraumatic degeneration

“…Lubricin, also known as proteoglycan 4 (Prg4) or superficial zone protein (SZP), is secreted by articular chondrocytes and synovial cells and is believed to play a role in modulating inflammatory responses in synovial joints (24,25). Therefore, we investigated the expression of lubricin in mice 1 week after injury.…”

Inhibitors of DNA methylation support TGF-β1-induced IL11 expression in gingival fibroblasts

“…The 2 TGF receptor types, TGF-β receptor type I (TGF-βRI) and TGF-β receptor type II (TGF-βRII) dimerize in response to ligand binding and signal via the corresponding intracellular receptor kinase [5], ultimately causing the expression of their target genes, including interleukin-11 (IL11) [6], proteoglycan 4 (PRG4) [7], and NADPH oxidase 4 (NOX4) [8]. Oral fibroblasts from the gingiva and other mesenchymal cells change IL11, PRG4, and NOX4 expression upon activation of TGF-β signaling [9].…”

Comparative effect of physicomechanical and biomolecular cues on zone-specific chondrogenic differentiation of mesenchymal stem cells

“…Conversely, TGF-β1 did not increase SZP expression in stiff Calcified gel (Figure 2a). Although the beneficial effect of TGF-β1 on SZP expression is previously reported [34], the data in Table 2 show the dominating effect of matrix compliance on chondrogenic differentiation of encapsulated hMSCs to the superficial zone phenotype. In the presence of TGF-β1, optimum matrix modulus (80 kPa) increased SZP mRNA and protein expressions of the encapsulated hMSCs by 51% and 26%, respectively (Table 2).…”