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A 3D System for Culturing Human Articular Chondrocytes in Synovial Fluid
Published on: January 31, 2012
Calcium sensing in cultured chondrogenic RCJ3.1C5.18 cells.
1Endocrine Research Unit, Veterans Affairs Medical Center, University of California, San Francisco 94121, USA.
Endocrinology
|March 31, 1999
Summary
Extracellular calcium (Ca2+) levels regulate cartilage formation. Chondrocytes detect these changes via calcium-sensing receptors (CaRs), altering matrix protein gene expression.
Area of Science:
- Biochemistry
- Cell Biology
- Skeletal Biology
Background:
- Extracellular calcium (Ca2+) availability is crucial for regulating cartilage and bone formation.
- Chondrocytes, the cells responsible for cartilage maintenance and formation, are hypothesized to sense and respond to changes in extracellular calcium concentrations ([Ca2+]o).
Purpose of the Study:
- To investigate how chondrocytes detect and respond to alterations in extracellular calcium levels.
- To determine the impact of varying extracellular calcium on the expression of key cartilage matrix proteins and associated genes.
- To explore the potential role of calcium-sensing receptors (CaRs) in mediating these chondrocyte responses.
Main Methods:
- Quantification of matrix protein expression using alcian green staining of cartilage nodules.
- Assessment of cartilage-specific gene RNA levels in chondrogenic RCJ3.1C5.18 (C5.18) cells.
- Evaluation of calcium-sensing receptor (CaR) expression via protein staining, in situ hybridization, and immunoblotting.
- Investigation of CaR function using antisense oligonucleotides.
Main Results:
- Alcian green staining decreased in a dose-dependent and reversible manner with increasing [Ca2+]o.
- RNA levels for aggrecan and type II collagen significantly decreased as [Ca2+]o increased.
- Expression of type X collagen and alkaline phosphatase RNA also reduced under high [Ca2+]o conditions.
- Responses were rapid, with significant changes in aggrecan RNA levels observed within 4 hours of altering [Ca2+]o.
- C5.18 cells expressed CaR protein and RNA, with a detectable ~150-kDa CaR protein.
- CaR antisense oligonucleotides reduced CaR protein expression and increased aggrecan RNA levels.
Conclusions:
- Chondrocytes detect and respond to changes in extracellular calcium concentration ([Ca2+]o).
- Calcium-sensing receptors (CaRs) are expressed in chondrogenic cells and appear to play a role in regulating chondrogenic gene expression.
- These findings suggest CaRs are involved in modulating cartilage matrix production in response to extracellular calcium availability.
