Investigation of salmon calcitonin in regulating fibrosis-related molecule production and cell-substrate adhesion in frozen shoulder synovial/capsular fibroblasts

The purpose of this study was to evaluate the effect of salmon calcitonin (sCT) on improving fibrosis-related indicators in frozen shoulder synovial/capsular fibroblasts (SCFs) and detect the potential downstream pathway. Quantitative real-time polymerase chain reaction and cell-substrate adhesion assays were used to measure alterations in fibrosis-related molecule expression and the cell adhesion ability of frozen shoulder SCFs after treatment with range concentrations of sCT. The presence of calcitonin receptors (CTRs) in shoulder joint synovial/capsular tissue samples was detected by immunohistochemistry (IHC). The downstream pathways of sCT in SCFs were further explored by utilizing three classical pathway inhibitors. With the addition of sCT to the culture medium of frozen shoulder SCFs, the messenger RNA (mRNA) expression of collagen type I (COL1A1), COL3A1, fibronectin 1, laminin 1, transforming growth factor-β1 (TGF-β1), and interleukin-1α (IL-1α) showed a descending trend as the sCT concentration increased. Treatment with sCT increased the expression of vascular endothelial growth factor and IL-6 in a dose-dependent manner. The enhanced adhesion ability of frozen shoulder SCFs gradually diminished with increasing concentrations of sCT. By using IHC, the CTR was detected extensively in the frozen shoulder joint synovium and capsule. Blocking the protein kinase C (PKC) pathway reversed the sCT-mediated suppression of COL1A1 production. Blocking the PKC or protein kinase A (PKA) pathway eliminated the sCT-induced inhibition of TGF-β1 production. This study demonstrated that sCT effectively improved the mRNA expression of fibrosis-related molecules and decreased the enhanced cell-substrate adhesion ability of frozen shoulder SCFs. sCT might achieve these effects by interacting with the CTR that is expressed on the SCF surface and by activating the downstream PKC or PKA pathway.

Cytokine receptor-like factor 1 is highly expressed in damaged human knee osteoarthritic cartilage and involved in osteoarthritis downstream of TGF-beta

Osteoarthritis (OA) is the most prevalent joint disease and is characterized by pain and functional loss of the joint. However, the pathogenic mechanism of OA remains unclear, and no drug therapy for preventing its progress has been established. To identify genes related to the progress of OA, the gene expression profiles of paired intact and damaged cartilage obtained from OA patients undergoing joint substitution were compared using oligo microarrays. Using functional categorization combined with gene ontology and a statistical analysis, five genes were found to be highly expressed in damaged cartilage (HBEGF, ASUS, CRLF1, LOX, CDA), whereas three genes were highly expressed in intact tissues (CHST2, PTPRD, CPAN6). Among these genes, the upregulated expression of CRLF1 was reconfirmed using real-time PCR, and the in vivo expression of CRLF1 was detected in clusters of chondrocytes and fibrocartilage-like cells in damaged OA cartilages using in situ hybridization. In vitro, the transcriptional level of CRLF1 was positively regulated by TGF-beta1 in the mouse chondrogenic cell line ATDC5. Additionally, the CRLF1/CLC complex promoted the proliferation of ATDC5 cells and suppressed the expression level of aggrecan and type II collagen. Our data suggest that the CRLF1/CLC complex disrupts cartilage homeostasis and promotes the progress of OA by enhancing the proliferation of chondrocytes and suppressing the production of cartilage matrix. A component of the complex, CRLF1, may be useful as a biomarker of OA; and the corresponding receptor is a potential new drug target for OA.

Calcitonin induces connective tissue growth factor through ERK1/2 signaling in renal tubular cells

Calcitonin (CT), a polypeptide hormone, plays important roles in a variety of physiological processes. CT has been used clinically to treat osteoporosis and humoral hypercalcemia of malignancy. In order to clarify the pharmacological effects of CT in the kidney, we identified potential downstream genes induced by CT in the renal cells. Using a cDNA subtraction hybridization method, we identified connective tissue growth factor (CTGF) as a CT-induced gene in the porcine renal cell line, LLC-PK1. Furthermore, we found that CT-mediated induction of the gene was not inhibited by cycloheximide, which suggests that CTGF gene was not induced by an increased synthesis of regulating proteins. Therefore, CTGF is an immediate early gene. We further demonstrated that the regulation of CTGF gene expression by CT involved the ERK1/2 pathway, because PD98059, a MEK1 inhibitor, partially inhibited the mRNA expression of CTGF induced by CT. CT-induced CTGF protein expression was also observed in vivo. Our present findings suggest that CT induces the transcription of CTGF through ERK1/2 phosphorylation. We also identified twelve other genes induced by CT that, like CTGF, were related to wound healing. These results suggest that CT may have an effect on renal differentiation and wound healing in the kidney.

Early induction of osteoactivin expression in rat renal tubular epithelial cells after unilateral ureteral obstruction

In this study, we examined the expression of osteoactivin in the rat kidney after unilateral ureteral obstruction. Male Wistar rats were sacrificed at 6h, and on days 1, 2, 3 and 7 after the obstruction. The renal tubular lumens gradually dilated, and marked interstitial fibrosis was confirmed histologically on day 3 after the obstruction. The expressions of osteoactivin and collagen type III were examined by quantitative real-time RT-PCR. An 8-fold increase in osteoactivin mRNA expression as compared with that in the sham-operated group was observed at 6h after the obstruction, whereas no elevation of collagen type III mRNA expression was observed at this early stage. Furthermore, semi-quantitative RT-PCR was performed to identify upregulation of expression of matrix metalloproteinase-13 mRNA relative to that in the sham-operated control, and normalized to the expression level of beta-actin. Intense osteoactivin expression localized in the dilated tubular epithelium and interstitial fibroblasts in the obstructive kidney was detected by immunohistochemistry and by in situ hybridization. These results suggested that the early-phase upregulation of osteoactivin expression in the tubular epithelium in response to renal injury might play a role in triggering renal interstitial fibrosis via activation of matrix metalloproteinase expression and collagen remodeling in rats.

Molecular pathological evaluation of clusterin in a rat model of unilateral ureteral obstruction as a possible biomarker of nephrotoxicity

In the present study, to determine the validity of considering clusterin as a possible biomarker of nephrotoxicity, the expression and distribution of clusterin in the rat UUO kidney were investigated. Real-time RT-PCR revealed an immediate increase in the clusterin mRNA level in the kidney, within 6 hours after UUO, and also maintenance of the mRNA expression level from day-1 to day-3 was 60-fold higher in the UUO kidney than in the sham kidney. ISH analysis revealed clusterin mRNA signals in the UUO renal tubular epithelium, whereas no signal was observed in the sham kidney. Detection of clusterin-alpha and -beta was conducted using the subtype-specific antibodies, by both of western blotting and immunohistochemistry. Although clusterin-alpha was predominant in the UUO urine, only faint signals were noted at the brush border of the tubular epithelium or intraductal. On the other hand, strong signals of clusterin-beta were detected in the UUO kidney homogenate, and the molecule was localized in the renal tubular epithelium. These results suggest that clusterin was translated in the renal tubular epithelium after de novo expression induced by renal injury. Thus, detection of clusterin mRNA and clusterin-beta in the kidney or clusterin-alpha in the urine may be useful for predicting nephrotoxicity.

Expression and significance of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-1 in an animal model of renal interstitial fibrosis induced by unilateral ureteral obstruction

To evaluate the pathological roles of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-1 in rat renal interstitial fibrosis, we examined the expression, localization and effect on growth of ADAMTS-1 in a normal rat kidney cell line (NRK-49F). Increased ADAMTS-1 mRNA expression was observed in the kidney by in situ hybridization after induction of unilateral ureteral obstruction (UUO) in male Wistar rats, the mRNA was localized in the renal tubular epithelial cells in the outer stripe of the outer medulla in the UUO kidney. On the other hand, no positive signals were observed in the sham-operated-kidney. Western-blot analysis of stable human embryonic kidney 293 (HEK293) transformant cells expressing rat ADAMTS-1 containing the V5 tag using anti-V5 tag monoclonal antibody revealed the presence of two post-translationally processed bands in the cells: an 87-kDa band with a metalloproteinase motif and 65-kDa band with a thrombospondin motifs. On the other hand, secretion of the 65-kDa protein into the culture supernatants from the transformant cells was confirmed. Treatment with the culture supernatant of the transformant cells potently reduced the uptake of 3H-thymidine in the NRK-49F cells, no such inhibitory effect was observed with the culture medium of the HEK293 cells. These results suggest that the UUO-induced expression of ADAMTS-1 in the rat renal tubular epithelial cells may actively contribute to the inhibition of DNA synthesis in the renal interstitial fibroblasts via the 65-kDa moiety with thrombospondin motifs.

Expression of calcitonin receptor in rat mammary gland during lactation

Calcitonin (CT) and calcitonin receptor (CTR) have been reported to play an important role in mammary tissue during pregnancy, lactation, and involution. In the present study, the expression and distribution of CTR mRNA in rat mammary tissue during pregnancy and lactation were investigated. As measured by real-time RT-PCR, CTR mRNA levels were increased only slightly during pregnancy, but increased markedly immediately postpartum and remained elevated through lactation, with the highest levels observed 14 days postpartum. In situ hybridization analysis showed that intense CTR mRNA signals were detected in the whole mammary gland. We performed immunohistochemistry to determine distribution of CTR in the mammary epithelium. CTR has been reported to act as an amylin receptor when heterodimerized with receptor activity modifying protein-1 (RAMP1) or RAMP3. mRNA expression of RAMP1 and RAMP3 in mammary tissue decreased during pregnancy and lactation, and amylin mRNA was undetectable, suggesting that up-regulated CTR in lactating mammary tissues binds CT rather than amylin. In primary cultures of mammary cells isolated from rat dams 14 days postpartum, CT produced a statistically significant decrease in thymidine incorporation. These results suggest that up-regulation of CTR during lactation may contribute to inhibition of mammary epithelial cell proliferation.