Repair and regeneration of bone requires mesenchymal stem cells that by self-renewal,are able to generate a critical mass of cells with the ability to differentiate into osteoblasts that can produce bone protein matri...Repair and regeneration of bone requires mesenchymal stem cells that by self-renewal,are able to generate a critical mass of cells with the ability to differentiate into osteoblasts that can produce bone protein matrix(osteoid)and enable its mineralization.The number of human mesenchymal stem cells(hMSCs)diminishes with age and ex vivo replication of hMSCs has limited potential.While propagating hMSCs under hypoxic conditions may maintain their ability to self-renew,the strategy of using human telomerase reverse transcriptase(hTERT)to allow for hMSCs to prolong their replicative lifespan is an attractive means of ensuring a critical mass of cells with the potential to differentiate into various mesodermal structural tissues including bone.However,this strategy must be tempered by the oncogenic potential of TERT-transformed cells,or their ability to enhance already established cancers,the unknown differentiating potential of high population doubling hMSCs and the source of hMSCs(e.g.,bone marrow,adipose-derived,muscle-derived,umbilical cord blood,etc.)that may provide peculiarities to self-renewal,differentiation,and physiologic function that may differ from non-transformed native cells.Tissue engineering approaches to use hMSCs to repair bone defects utilize the growth of hMSCs on three-dimensional scaffolds that can either be a base on which hMSCs can attach and grow or as a means of sequestering growth factors to assist in the chemoattraction and differentiation of native hMSCs.The use of whole native extracellular matrix(ECM)produced by hMSCs,rather than individual ECM components,appear to be advantageous in not only being utilized as a three-dimensional attachment base but also in appropriate orientation of cells and their differentiation through the growth factors that native ECM harbor or in simulating growth factor motifs.The origin of native ECM,whether from hMSCs from young or old individuals is a critical factor in"rejuvenating"hMSCs from older individuals grown on ECM from younger individuals.展开更多
AIM: To investigate the effect of secreted frizzledrelated proteins(s FRPs) on CXC chemokine expression in human mesenchymal stem cells(h MSCs).METHODS: CXC chemokines such as CXCL5 and CXCL8 are induced in h MSCs dur...AIM: To investigate the effect of secreted frizzledrelated proteins(s FRPs) on CXC chemokine expression in human mesenchymal stem cells(h MSCs).METHODS: CXC chemokines such as CXCL5 and CXCL8 are induced in h MSCs during differentiation with osteogenic differentiation medium(OGM) and may be involved in angiogenic stimulation during bone repair. h MSCs were treated with conditioned medium(CM) from L-cells expressing non-canonical Wnt5 a protein, or with control CM from wild type L-cells, or directly with s FRPs for up to 10 d in culture. m RNA expression levels of both CXCL5 and CXCL8 were quantitated by real-time reverse transcriptase-polymerase chain reaction and secreted protein levels of these proteins determined by ELISA. Dose-(0-500 ng/m L) and time-response curves were generated for treatment with s FRP1. Signal transduction pathways were explored by western blot analysis with pan- or phosphorylation-specific antibodies, through use of specific pathway inhibitors, and through use of si RNAs targeting specific frizzled receptors(Fzd)-2 and 5 or thereceptor tyrosine kinase-like orphan receptor-2(Ro R2) prior to treatment with s FRPs. RESULTS: CM from L-cells expressing Wnt5 a, a noncanonical Wnt, stimulated an increase in CXCL5 m RNA expression and protein secretion in comparison to control L-cell CM. s FRP1, which should inhibit both canonical and non-canonical Wnt signaling, surprisingly enhanced the expression of CXCL5 at 7 and 10 d. Dickkopf1, an inhibitor of canonical Wnt signaling prevented the s FRPstimulated induction of CXCL5 and actually inhibited basal levels of CXCL5 expression at 7 but not at 10 d post treatment. In addition, all four s FRPs isoforms induced CXCL8 expression in a dose- and time-dependent manner with maximum expression at 7 d with treatment at 150 ng/m L. The largest increases in CXCL5 expression were seen from stimulation with s FRP1 or s FRP2. Analysis of mitogen-activated protein kinase signaling pathways in the presence of OGM showed s FRP1-induced phosphorylation of extracellular signal-regulated kinase(ERK)(p44/42) maximally at 5 min after s FRP1 addition, earlier than that found in OGM alone. Addition of a phospholipase C(PLC) inhibitor also prevented s FRPstimulated increases in CXCL8 m RNA. si RNA technology targeting the Fzd-2 and 5 and the non-canonical Fzd co-receptor Ro R2 also significantly decreased s FRP1/2-stimulated CXCL8 m RNA levels.CONCLUSION: CXC chemokine expression in h MSCs is controlled in part by s FRPs signaling through noncanonical Wnt involving Fzd2/5 and the ERK and PLC pathways.展开更多
基金Supported by Veterans Administration Merit Review Award 2 I01 BX000170-05
文摘Repair and regeneration of bone requires mesenchymal stem cells that by self-renewal,are able to generate a critical mass of cells with the ability to differentiate into osteoblasts that can produce bone protein matrix(osteoid)and enable its mineralization.The number of human mesenchymal stem cells(hMSCs)diminishes with age and ex vivo replication of hMSCs has limited potential.While propagating hMSCs under hypoxic conditions may maintain their ability to self-renew,the strategy of using human telomerase reverse transcriptase(hTERT)to allow for hMSCs to prolong their replicative lifespan is an attractive means of ensuring a critical mass of cells with the potential to differentiate into various mesodermal structural tissues including bone.However,this strategy must be tempered by the oncogenic potential of TERT-transformed cells,or their ability to enhance already established cancers,the unknown differentiating potential of high population doubling hMSCs and the source of hMSCs(e.g.,bone marrow,adipose-derived,muscle-derived,umbilical cord blood,etc.)that may provide peculiarities to self-renewal,differentiation,and physiologic function that may differ from non-transformed native cells.Tissue engineering approaches to use hMSCs to repair bone defects utilize the growth of hMSCs on three-dimensional scaffolds that can either be a base on which hMSCs can attach and grow or as a means of sequestering growth factors to assist in the chemoattraction and differentiation of native hMSCs.The use of whole native extracellular matrix(ECM)produced by hMSCs,rather than individual ECM components,appear to be advantageous in not only being utilized as a three-dimensional attachment base but also in appropriate orientation of cells and their differentiation through the growth factors that native ECM harbor or in simulating growth factor motifs.The origin of native ECM,whether from hMSCs from young or old individuals is a critical factor in"rejuvenating"hMSCs from older individuals grown on ECM from younger individuals.
基金Supported by Merit Review Award from the United States,Department of Veterans Affairs Biomedical Laboratory Research and Development Service of the VA Office of Research and Development,No.I01BX000170
文摘AIM: To investigate the effect of secreted frizzledrelated proteins(s FRPs) on CXC chemokine expression in human mesenchymal stem cells(h MSCs).METHODS: CXC chemokines such as CXCL5 and CXCL8 are induced in h MSCs during differentiation with osteogenic differentiation medium(OGM) and may be involved in angiogenic stimulation during bone repair. h MSCs were treated with conditioned medium(CM) from L-cells expressing non-canonical Wnt5 a protein, or with control CM from wild type L-cells, or directly with s FRPs for up to 10 d in culture. m RNA expression levels of both CXCL5 and CXCL8 were quantitated by real-time reverse transcriptase-polymerase chain reaction and secreted protein levels of these proteins determined by ELISA. Dose-(0-500 ng/m L) and time-response curves were generated for treatment with s FRP1. Signal transduction pathways were explored by western blot analysis with pan- or phosphorylation-specific antibodies, through use of specific pathway inhibitors, and through use of si RNAs targeting specific frizzled receptors(Fzd)-2 and 5 or thereceptor tyrosine kinase-like orphan receptor-2(Ro R2) prior to treatment with s FRPs. RESULTS: CM from L-cells expressing Wnt5 a, a noncanonical Wnt, stimulated an increase in CXCL5 m RNA expression and protein secretion in comparison to control L-cell CM. s FRP1, which should inhibit both canonical and non-canonical Wnt signaling, surprisingly enhanced the expression of CXCL5 at 7 and 10 d. Dickkopf1, an inhibitor of canonical Wnt signaling prevented the s FRPstimulated induction of CXCL5 and actually inhibited basal levels of CXCL5 expression at 7 but not at 10 d post treatment. In addition, all four s FRPs isoforms induced CXCL8 expression in a dose- and time-dependent manner with maximum expression at 7 d with treatment at 150 ng/m L. The largest increases in CXCL5 expression were seen from stimulation with s FRP1 or s FRP2. Analysis of mitogen-activated protein kinase signaling pathways in the presence of OGM showed s FRP1-induced phosphorylation of extracellular signal-regulated kinase(ERK)(p44/42) maximally at 5 min after s FRP1 addition, earlier than that found in OGM alone. Addition of a phospholipase C(PLC) inhibitor also prevented s FRPstimulated increases in CXCL8 m RNA. si RNA technology targeting the Fzd-2 and 5 and the non-canonical Fzd co-receptor Ro R2 also significantly decreased s FRP1/2-stimulated CXCL8 m RNA levels.CONCLUSION: CXC chemokine expression in h MSCs is controlled in part by s FRPs signaling through noncanonical Wnt involving Fzd2/5 and the ERK and PLC pathways.
