Influence of 1α, 25-dihydroxyvitamin D3 [1, 25(OH)2D3] on the expression of Sox 9 and the transient receptor potential vanilloid 5/6 ion channels in equine articular chondrocytes

Background Sox 9 is a major marker of chondrocyte differentiation. When chondrocytes are cultured in vitro they progressively de-differentiate and this is associated with a decline in Sox 9 expression. The active form of vitamin D, 1, 25 (OH)2D3 has been shown to be protective of cartilage in both humans and animals. In this study equine articular chondrocytes were grown in culture and the effects of 1, 25 (OH)2D3 upon Sox 9 expression examined. The expression of the transient receptor potential vanilloid (TRPV) ion channels 5 and 6 in equine chondrocytes in vitro, we have previously shown, is inversely correlated with de-differentiation. The expression of these channels in response to 1, 25 (OH)2D3 administration was therefore also examined. Results The active form of vitamin D (1, 25 (OH)2D3) when administered to cultured equine chondrocytes at two different concentrations significantly increased the expression of Sox 9 at both. In contrast 1, 25 (OH)2D3 had no significant effect upon the expression of either TRPV 5 or 6 at either the protein or the mRNA level. Conclusions The increased expression of Sox 9, in equine articular chondrocytes in vitro, in response to the active form of vitamin D suggests that this compound could be utilized to inhibit the progressive de-differentiation that is normally observed in these cells. It is also supportive of previous studies indicating that 1α, 25-dihydroxyvitamin D3 can have a protective effect upon cartilage in animals in vivo. The previously observed correlation between the degree of differentiation and the expression levels of TRPV 5/6 had suggested that these ion channels may have a direct involvement in, or be modulated by, the differentiation process in vitro. The data in the present study do not support this

Effect of osmotic stress on the expression of TRPV4 and BKCa channels and possible interaction with ERK1/2 and p38 in cultured equine chondrocytes.

The metabolic activity of articular chondrocytes is influenced by osmotic alterations that occur in articular cartilage secondary to mechanical load. The mechanisms that sense and transduce mechanical signals from cell swelling and initiate volume regulation are poorly understood. The purpose of this study was to investigate how the expression of two putative osmolyte channels [transient receptor potential vanilloid 4 (TRPV4) and large-conductance Ca(2+)-activated K(+) (BKCa)] in chondrocytes is modulated in different osmotic conditions and to examine a potential role for MAPKs in this process. Isolated equine articular chondrocytes were subjected to anisosmotic conditions, and TRPV4 and BKCa channel expression and ERK1/2 and p38 MAPK protein phosphorylation were investigated using Western blotting. Results indicate that the TRPV4 channel contributes to the early stages of hypo-osmotic stress, while the BKCa channel is involved in responding to elevated intracellular Ca(2+) and mediating regulatory volume decrease. ERK1/2 is phosphorylated by hypo-osmotic stress (P < 0.001), and p38 MAPK is phosphorylated by hyperosmotic stress (P < 0.001). In addition, this study demonstrates the importance of endogenous ERK1/2 phosphorylation in TRPV4 channel expression, where blocking ERK1/2 by a specific inhibitor (PD98059) prevented increased levels of the TRPV4 channel in cells exposed to hypo-osmotic stress and decreased TRPV4 channel expression to below control levels in iso-osmotic conditions (P < 0.001)

Expression of Transient Receptor Potential Vanilloid (TRPV) channels in different passages of articular chondrocytes.

Ion channels play important roles in chondrocyte mechanotransduction. The transient receptor potential vanilloid (TRPV) subfamily of ion channels consists of six members. TRPV1-4 are temperature sensitive calcium-permeable, relatively non-selective cation channels whereas TRPV5 and TRPV6 show high selectivity for calcium over other cations. In this study we investigated the effect of time in culture and passage number on the expression of TRPV4, TRPV5 and TRPV6 in articular chondrocytes isolated from equine metacarpophalangeal joints. Polyclonal antibodies raised against TRPV4, TRPV5 and TRPV6 were used to compare the expression of these channels in lysates from first expansion chondrocytes (P0) and cells from passages 1-3 (P1, P2 and P3) by western blotting. TRPV4, TRPV5 and TRPV6 were expressed in all passages examined. Immunohistochemistry and immunofluorescence confirmed the presence of these channels in sections of formalin fixed articular cartilage and monolayer cultures of methanol fixed P2 chondrocytes. TRPV5 and TRPV6 were upregulated with time and passage in culture suggesting that a shift in the phenotype of the cells in monolayer culture alters the expression of these channels. In conclusion, several TRPV channels are likely to be involved in calcium signaling and homeostasis in chondrocytes

Transforming Growth Factor Beta Signaling Is Essential for the Autonomous Formation of Cartilage-Like Tissue by Expanded Chondrocytes

Cartilage is a tissue with limited self-healing potential. Hence, cartilage defects require surgical attention to prevent or postpone the development of osteoarthritis. For cell-based cartilage repair strategies, in particular autologous chondrocyte implantation, articular chondrocytes are isolated from cartilage and expanded in vitro to increase the number of cells required for therapy. During expansion, the cells lose the competence to autonomously form a cartilage-like tissue, that is in the absence of exogenously added chondrogenic growth factors, such as TGF-βs. We hypothesized that signaling elicited by autocrine and/or paracrine TGF-β is essential for the formation of cartilage-like tissue and that alterations within the TGF-β signaling pathway during expansion interfere with this process. Primary bovine articular chondrocytes were harvested and expanded in monolayer culture up to passage six and the formation of cartilage tissue was investigated in high density pellet cultures grown for three weeks. Chondrocytes expanded for up to three passages maintained the potential for autonomous cartilage-like tissue formation. After three passages, however, exogenous TGF-β1 was required to induce the formation of cartilage-like tissue. When TGF-β signaling was blocked by inhibiting the TGF-β receptor 1 kinase, the autonomous formation of cartilage-like tissue was abrogated. At the initiation of pellet culture, chondrocytes from passage three and later showed levels of transcripts coding for TGF-β receptors 1 and 2 and TGF-β2 to be three-, five- and five-fold decreased, respectively, as compared to primary chondrocytes. In conclusion, the autonomous formation of cartilage-like tissue by expanded chondrocytes is dependent on signaling induced by autocrine and/or paracrine TGF-β. We propose that a decrease in the expression of the chondrogenic growth factor TGF-β2 and of the TGF-β receptors in expanded chondrocytes accounts for a decrease in the activity of the TGF-β signaling pathway and hence for the loss of the potential for autonomous cartilage-like tissue formation

Maternal and neonatal outcomes after caesarean delivery in the African Surgical Outcomes Study: a 7-day prospective observational cohort study.

BACKGROUND: Maternal and neonatal mortality is high in Africa, but few large, prospective studies have been done to investigate the risk factors associated with these poor maternal and neonatal outcomes. METHODS: A 7-day, international, prospective, observational cohort study was done in patients having caesarean delivery in 183 hospitals across 22 countries in Africa. The inclusion criteria were all consecutive patients (aged ≥18 years) admitted to participating centres having elective and non-elective caesarean delivery during the 7-day study cohort period. To ensure a representative sample, each hospital had to provide data for 90% of the eligible patients during the recruitment week. The primary outcome was in-hospital maternal mortality and complications, which were assessed by local investigators. The study was registered on the South African National Health Research Database, number KZ_2015RP7_22, and on ClinicalTrials.gov, number NCT03044899. FINDINGS: Between February, 2016, and May, 2016, 3792 patients were recruited from hospitals across Africa. 3685 were included in the postoperative complications analysis (107 missing data) and 3684 were included in the maternal mortality analysis (108 missing data). These hospitals had a combined number of specialist surgeons, obstetricians, and anaesthetists totalling 0·7 per 100 000 population (IQR 0·2-2·0). Maternal mortality was 20 (0·5%) of 3684 patients (95% CI 0·3-0·8). Complications occurred in 633 (17·4%) of 3636 mothers (16·2-18·6), which were predominantly severe intraoperative and postoperative bleeding (136 [3·8%] of 3612 mothers). Maternal mortality was independently associated with a preoperative presentation of placenta praevia, placental abruption, ruptured uterus, antepartum haemorrhage (odds ratio 4·47 [95% CI 1·46-13·65]), and perioperative severe obstetric haemorrhage (5·87 [1·99-17·34]) or anaesthesia complications (11·47 (1·20-109·20]). Neonatal mortality was 153 (4·4%) of 3506 infants (95% CI 3·7-5·0). INTERPRETATION: Maternal mortality after caesarean delivery in Africa is 50 times higher than that of high-income countries and is driven by peripartum haemorrhage and anaesthesia complications. Neonatal mortality is double the global average. Early identification and appropriate management of mothers at risk of peripartum haemorrhage might improve maternal and neonatal outcomes in Africa. FUNDING: Medical Research Council of South Africa.Medical Research Council of South Africa