No abstract

No abstract

Reactive astrogliosis, defined by abnormal morphology and excessive cell proliferation, is a characteristic response of astrocytes to CNS injuries, including intracerebral hemorrhage. Thrombin, a major blood-derived serine protease, leaks into the brain parenchyma upon blood-brain barrier disruption and can induce brain injury and astrogliosis. Transient receptor potential canonical (TRPC) channels, Ca 2ϩ -permeable, nonselective cation channels, are expressed in astrocytes and involved in Ca 2ϩ influx after receptor stimulation; however, their pathophysiological functions in reactive astrocytes remain unknown. We investigated the pathophysiological roles of TRPC in thrombin-activated cortical astrocytes. Application of thrombin (1 U/ml, 20 h) upregulated TRPC3 protein, which was associated with increased Ca 2ϩ influx after thapsigargin treatment. Pharmacological manipulations revealed that the TRPC3 upregulation was mediated by protease-activated receptor 1 (PAR-1), extracellular signal-regulated protein kinase, c-Jun NH 2 -terminal kinase, and nuclear factor-B signaling and required de novo protein synthesis. The Ca 2ϩ signaling blockers BAPTA-AM, cyclopiazonic acid, and 2-aminoethoxydiphenyl borate and a selective TRPC3 inhibitor, pyrazole-3, attenuated TRPC3 upregulation, suggesting that Ca 2ϩ signaling through TRPC3 contributes to its increased expression. Thrombin-induced morphological changes at 3 h upregulated S100B, a marker of reactive astrocytes, at 20 h and increased astrocytic proliferation by 72 h, all of which were inhibited by Ca 2ϩ -signaling blockers and specific knockdown of TRPC3 using small interfering RNA. Intracortical injection of SFLLR-NH 2 , a PAR-1 agonist peptide, induced proliferation of astrocytes, most of which were TRPC3 immunopositive. These results suggest that thrombin dynamically upregulates TRPC3 and that TRPC3 contributes to the pathological activation of astrocytes in part through a feedforward upregulation of its own expression.

These cells may play a role in the regenerative response during arthritic diseases and are promising candidates for developing novel cell-based therapeutic approaches for postnatal skeletal tissue repair.

Recent studies revealed C-type natriuretic peptide (CNP) and its receptor, guanylyl cyclase-B (GC-B) are potent stimulators of endochondral bone growth. As they exist ubiquitously in body, we investigated the physiological role of the local CNP/GC-B in the growth plate on bone growth using cartilage-specific knockout mice. Bones were severely shorter in cartilage-specific CNP or GC-B knockout mice and the extent was almost the same as that in respective systemic knockout mice. Cartilage-specific GC-B knockout mice were shorter than cartilage-specific CNP knockout mice. Hypertrophic chondrocyte layer of the growth plate was drastically reduced and proliferative chondrocyte layer, along with the proliferation of chondrocytes there, was moderately reduced in either cartilage-specific knockout mice. The survival rate of cartilage-specific CNP knockout mice was comparable to that of systemic CNP knockout mice. The local CNP/GC-B system in growth plate is responsible for physiological endochondral bone growth and might further affect mortality via unknown mechanisms.

No abstract

No abstract

These results suggest the possibility of the effective clinical use of human BMP-2 gene therapy using transcutaneous sonoporation, and should facilitate clinical applications of BMP-2 gene therapy.