Objective. Caspases, cysteine proteases traditionally associated with apoptosis and inflammation, have recently been identified as important regulators of autophagy and reported within the growth plate, a cartilaginous part of the developing bone. The aim of this research was to identify novel autophagy-related molecules affected by inhibition of pro-apoptotic caspases in chondrocytes. Design. Chondrocyte micromasses derived from mouse limb buds were treated with pharmacological inhibitors of caspases. Autophagy-related gene expression was examined and possible novel molecules were confirmed by real-time polymerase chain reaction and immunocytofluorescence. Individual caspases inhibitors were used to identify the effect of specific caspases. Results. Chondrogenesis accompanied by caspase activation and autophagy progression was confirmed in micromass cultures. Expression of several autophagy-associated genes was significantly altered in the caspases inhibitors treated groups with the most prominent decrease for Pik3cg and increase of Tnfsf10. The results showed the specific pro-apoptotic caspases that play a role in these effects. Importantly, use of caspase inhibitors mimicked changes triggered by an autophagy stimulator, rapamycin, linking loss of caspase activity to an increase in autophagy. Conclusion. Caspase inhibition significantly affects regulation of autophagy-related genes in chondrocytes cultures. Detected markers are of importance in diagnostics and thus the data presented here open new perspectives in the field of cartilage development and degradation.

• Keywords
• autophagy, caspase, gene expression, inhibition, limb,
• MeSH
• Autophagy MeSH
• Chondrocytes * metabolism   MeSH
• Chondrogenesis MeSH
• Caspase Inhibitors metabolism   pharmacology   MeSH
• Caspases * metabolism   pharmacology   MeSH
• Mice MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Caspase Inhibitors MeSH
• Caspases * MeSH

Caspases are proteases traditionally associated with inflammation and cell death. Recently, they have also been shown to modulate cell proliferation and differentiation. The aim of the current research was to search for osteogenic molecules affected by caspase inhibition and to specify the individual caspases critical for these effects with a focus on proapoptotic caspases: caspase-2, -3, -6, -7, -8 and -9. Along with osteocalcin (Ocn), general caspase inhibition significantly decreased the expression of the Phex gene in differentiated MC3T3-E1 cells. The inhibition of individual caspases indicated that caspase-8 is a major contributor to the modification of Ocn and Phex expression. Caspase-2 and-6 had effects on Ocn and caspase-6 had an effect on Phex. These data confirm and expand the current knowledge about the nonapoptotic roles of caspases and the effect of their pharmacological inhibition on the osteogenic potential of osteoblastic cells.

• MeSH
• Cell Line MeSH
• Caspase Inhibitors pharmacology   MeSH
• Caspases metabolism   MeSH
• Mice MeSH
• PHEX Phosphate Regulating Neutral Endopeptidase metabolism   MeSH
• Osteoblasts cytology   metabolism   MeSH
• Osteogenesis drug effects   MeSH
• Osteocalcin metabolism   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Caspase Inhibitors MeSH
• Caspases MeSH
• PHEX Phosphate Regulating Neutral Endopeptidase MeSH
• Osteocalcin MeSH
• Phex protein, mouse MeSH Browser

Caspases have functions particularly in apoptosis and inflammation. Increasing evidence indicates novel roles of these proteases in cell differentiation, including those involved in osteogenesis. This investigation provides a complex screening of osteogenic markers affected by pan caspase inhibition in micromass cultures derived from mouse forelimbs. PCR Array analysis showed significant alterations in expression of 49 osteogenic genes after 7 days of inhibition. The largest change was a decrease in CD36 expression, which was confirmed at organ level by caspase inhibition in cultured mouse ulnae followed by CD36 immunohistochemical analysis. So far, available data point to osteogenic potential of pro-apoptotic caspases. Therefore, the expression of pro-apoptotic caspases (-3, -6, -7, -8, -9) within the growth plate of mouse forelimbs at the stage where the individual zones are clearly apparent was studied. Caspase-9 was reported in the growth plate for the first time as well as caspase-6 and -7 in the resting zone, caspase-7 in the proliferation, and caspase-6 and -8 in the ossification zone. For all caspases, there was a gradient increase in activation toward the ossification zone. The distribution of staining varied significantly from that of apoptotic cells, and thus, the results further support non-apoptotic participation of caspases in osteogenesis.

• Keywords
• PCR Array analysis, caspases, endochondral ossification, growth plate, immunohistochemistry, micromass cultures,
• MeSH
• CD36 Antigens analysis   genetics   MeSH
• Immunohistochemistry MeSH
• Caspase Inhibitors pharmacology   MeSH
• Caspases metabolism   MeSH
• Cells, Cultured MeSH
• Mice MeSH
• Organ Culture Techniques MeSH
• Osteogenesis * drug effects   MeSH
• Forelimb growth & development   metabolism   MeSH
• Gene Expression Regulation, Developmental drug effects   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• CD36 Antigens MeSH
• Caspase Inhibitors MeSH
• Caspases MeSH

Caspases, well-known players in apoptosis or inflammation, appear to have roles also in other processes such as cell differentiation. Caspase-3, in particular, was recently demonstrated to have non-apoptotic functions in osteogenesis. However, the molecular pathways involved are not yet known. Therefore, we used osteogenic PCR arrays to provide a comprehensive screening of possible interactions of caspases in general and specifically of caspase-3 in osteogenic networks. Embryonic micromass cultures derived from mouse forelimbs were established and pharmacological fluoromethylketone (FMK) inhibitors applied. Alterations were observed in expression of several genes after caspase inhibition (Bmp1, Bmp5, Bmp6, Col10a1, Col2a1, Comp, Egf, Fgfr2, Gli1, Igf1, Nog, Phex, Sox9, Spp1). The list suggests molecular interactions of caspases and osteogenic molecules and creates a background for further temporospatial and functional studies.

• Keywords
• Caspase-3, Caspases, Chondrogenesis, Gene expression, Osteogenesis,
• MeSH
• Apoptosis drug effects   MeSH
• Cell Differentiation drug effects   MeSH
• Chondrogenesis drug effects   MeSH
• Caspase Inhibitors administration & dosage   MeSH
• Caspase 3 genetics   metabolism   MeSH
• Mesenchymal Stem Cells drug effects   MeSH
• Mice MeSH
• Osteogenesis drug effects   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Caspase Inhibitors MeSH
• Caspase 3 MeSH