Rac Inhibition Reverses the Phenotype of Fibrotic Fibroblasts

Background

Fibrosis, the excessive deposition of scar tissue by fibroblasts, is one of the largest groups of diseases for which there is no therapy. Fibroblasts from lesional areas of scleroderma patients possess elevated abilities to contract matrix and produce α−smooth muscle actin (α-SMA), type I collagen and CCN2 (connective tissue growth factor, CTGF). The basis for this phenomenon is poorly understood, and is a necessary prerequisite for developing novel, rational anti-fibrotic strategies.

Methods and Findings

Compared to healthy skin fibroblasts, dermal fibroblasts cultured from lesional areas of scleroderma (SSc) patients possess elevated Rac activity. NSC23766, a Rac inhibitor, suppressed the persistent fibrotic phenotype of lesional SSc fibroblasts. NSC23766 caused a decrease in migration on and contraction of matrix, and α−SMA, type I collagen and CCN2 mRNA and protein expression. SSc fibroblasts possessed elevated Akt phosphorylation, which was also blocked by NSC23766. Overexpression of rac1 in normal fibroblasts induced matrix contraction and α−SMA, type I collagen and CCN2 mRNA and protein expression. Rac1 activity was blocked by PI3kinase/Akt inhibition. Basal fibroblast activity was not affected by NSC23766.

Conclusion

Rac inhibition may be considered as a novel treatment for the fibrosis observed in SSc.     

Paternal deprivation induces dendritic and synaptic changes and hemispheric asymmetry of pyramidal neurons in the somatosensory cortex

Similar to maternal care, paternal care is a source of neonatal sensory stimulation, which in primates and rodents has been shown to be essential for developing structure and function of sensory cortices. The aim of our study in the biparental rodent Octodon degus was to assess the impact of paternal deprivation on dendritic and synaptic development in the somatosensory cortex. We (i) quantified the amount of paternal care in relation to total parental investment and (ii) compared dendritic and synaptic development of pyramidal neurons in the somatosensory cortex of animals raised by a single mother or by both parents. On the behavioral level we show that paternal care comprises 37% of total parent‐offspring interactions, and that the somatosensory stimulation provided by the fathers primarily consists of huddling, licking/grooming, and playing. On the morphological level we found that, compared with offspring raised by both parents (mother and father), the father‐deprived animals displayed significantly reduced spine numbers on the basal dendrites of pyramidal neurons. Furthermore, paternal deprivation induces hemispheric asymmetry of the dendritic morphology of somatosensory pyramidal neurons. Father‐deprived animals show shorter and less complex basal dendrites in the left somatosensory cortex compared with the right hemisphere. These findings indicate that paternal deprivation results in delayed or retarded dendritic and synaptic development of somatosensory circuits. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009     

Divergent S Phase Checkpoint Activation Arising from Prereplicative Complex Deficiency Controls Cell Survival

The DNA replication machinery plays additional roles in S phase checkpoint control, although the identities of the replication proteins involved in checkpoint activation remain elusive. Here, we report that depletion of the prereplicative complex (pre-RC) protein Cdc6 causes human nontransformed diploid cells to arrest nonlethally in G1-G1/S and S phase, whereas multiple cancer cell lines undergo G1-G1/S arrest and cell death. These divergent phenotypes are dependent on the activation, or lack thereof, of an ataxia telangiectasia and Rad3-related (ATR)-dependent S phase checkpoint that inhibits replication fork progression. Although pre-RC deficiency induces chromatin structural alterations in both nontransformed and cancer cells that normally lead to ATR checkpoint activation, the sensor mechanisms in cancer cells seem to be compromised such that higher levels of DNA replication stress/damage are required to trigger checkpoint response. Our results suggest that therapy-induced disruption of pre-RC function might exert selective cytotoxic effects on tumor cells in human patients.     

Donor-Derived Brain Tumor Following Neural Stem Cell Transplantation in an Ataxia Telangiectasia Patient

Background

Neural stem cells are currently being investigated as potential therapies for neurodegenerative diseases, stroke, and trauma. However, concerns have been raised over the safety of this experimental therapeutic approach, including, for example, whether there is the potential for tumors to develop from transplanted stem cells.

Methods and Findings

A boy with ataxia telangiectasia (AT) was treated with intracerebellar and intrathecal injection of human fetal neural stem cells. Four years after the first treatment he was diagnosed with a multifocal brain tumor. The biopsied tumor was diagnosed as a glioneuronal neoplasm. We compared the tumor cells and the patient''s peripheral blood cells by fluorescent in situ hybridization using X and Y chromosome probes, by PCR for the amelogenin gene X- and Y-specific alleles, by MassArray for the ATM patient specific mutation and for several SNPs, by PCR for polymorphic microsatellites, and by human leukocyte antigen (HLA) typing. Molecular and cytogenetic studies showed that the tumor was of nonhost origin suggesting it was derived from the transplanted neural stem cells. Microsatellite and HLA analysis demonstrated that the tumor is derived from at least two donors.

Conclusions

This is the first report of a human brain tumor complicating neural stem cell therapy. The findings here suggest that neuronal stem/progenitor cells may be involved in gliomagenesis and provide the first example of a donor-derived brain tumor. Further work is urgently needed to assess the safety of these therapies.     

Chemosystematic evaluation of Aloe section Pictae (Asphodelaceae)

The chemosystematic value of UV-absorbing leaf constituents was considered in previously uncharacterised representatives of Aloe section Pictae, the problematic maculate species complex. Comparative data indicate that the anthrone C-glycoside, 6′-malonylnataloin (7-hydroxychrysaloin 6′-O-malonate) is typical of maculate species in East Africa, but is unconvincing as a synapomorphy for section Pictae. A naphthalene derivative found widely in Aloe, plicataloside, was detected in Aloe greatheadii. Biogeographical trends were observed in the occurrence of the flavonoids isoorientin (luteolin-6-C-glucoside) and isovitexin (apigenin 6-C-glucoside). Isoorientin is a common constituent of tropical and sub-tropical species of Aloe, whereas isovitexin is restricted to a few southern African species. Isoorientin and isovitexin co-occur in the southern African maculate species Aloe parvibracteata, and the disjunct West African maculate species, Aloe macrocarpa. This is the first report of isoorientin and isovitexin in maculate species of Aloe; the presence of flavonoids in section Pictae is of taxonomic interest.