How autobiographical memories can support episodic recall: transfer and maintenance effect of memory training with old-old low-autonomy adults.

BACKGROUND AND AIMS: A large body of research has demonstrated that, although specific memory activities can enhance the memory performance of healthy older adults, the extent of the increment is negatively associated with age. Conversely, few studies have examined the case of healthy elderly people not living alone. This study has two mains goals: to understand whether older adults with limited autonomy can benefit from activities devoted to increasing their episodic memory performance, and to test the efficacy of a memory training program based on autobiographical memories, in terms of transfer and maintenance effect. We postulated that being able to rely on stable autobiographical memories (intrinsically associated with emotions) would be a valuable memory aid. METHODS: Memory training was given to healthy older adults (aged 75-85) living in a retirement home. Two programs were compared: in the first, participants were primed to recall autobiographical memories around certain themes, and then to complete a set of episodic memory tasks (experimental group); in the second, participants were only given the episodic tasks (control group). RESULTS: Both groups improved their performance from pre- to post-test. However, the experimental group reported a greater feeling of well-being after the training, and maintained the training gains relating to episodic performance after three months. CONCLUSIONS: Our findings suggest that specific memory activities are beneficial to elderly people living in a retirement home context. In addition, training based on reactivation of autobiographical memories is shown to produce a long-lasting effect on memory performance.

Transcriptional enhancers induce insertional gene deregulation independently from the vector type and design.

The integration characteristics of retroviral (RV) vectors increase the probability of interfering with the regulation of cellular genes, and account for a tangible risk of insertional mutagenesis in treated patients. To assess the potential genotoxic risk of conventional or self-inactivating (SIN) gamma-RV and lentiviral (LV) vectors independently from the biological consequences of the insertion event, we developed a quantitative assay based on real-time reverse transcriptase--PCR on low-density arrays to evaluate alterations of gene expression in individual primary T-cell clones. We show that the Moloney leukemia virus long terminal repeat (LTR) enhancer has the strongest activity in both a gamma-RV and a LV vector context, while an internal cellular promoter induces deregulation of gene expression less frequently, at a shorter range and to a lower extent in both vector types. Downregulation of gene expression was observed only in the context of LV vectors. This study indicates that insertional gene activation is determined by the characteristics of the transcriptional regulatory elements carried by the vector, and is largely independent from the vector type or design.

PPARdelta is a ligand-dependent negative regulator of vitamin D3-induced monocyte differentiation.

A number of reports indicate that peroxisome proliferator-activated receptor (PPAR) delta is involved in the molecular control of monocyte-macrophage differentiation. In this regard, the recent demonstration that PPARdelta is a primary response gene of 1alpha,25-dihydroxyvitamin D3 (VD), i.e. a powerful inducer of such process, allowed us to hypothesize the existence of a cross talk between PPARdelta and VD receptor pathways. To address this issue, we analyzed the effects promoted by stimulation with PPARdelta ligands and by overexpression of this nuclear receptor in monoblastic cell lines undergoing exposure to VD. The results obtained evidenced that, although promoting a weak differentiation effect by themselves, PPARdelta ligands efficiently co-operated with VD treatment. In spite of this, PPARdelta overexpression exerted a remarkable inhibitory effect on monocyte-macrophage differentiation induced by VD that was, at least partly, reverted by stimulation with a highly specific PPARdelta ligand. These data indicate that, although acting through a ligand-dependent modality, PPARdelta is a negative regulator of VD-mediated monocyte differentiation, allowing us to hypothesize a role of the investigated nuclear receptor in the differentiation block of M5 type (monoblastic) acute myeloid leukemias (AMLs). Bioinformatic analysis of a microarray database, containing the expression profiles of 285 AML cases, further supported this hypothesis demonstrating the existence of a subset of M5 type (monoblastic) AMLs that overexpress PPARdelta gene.

Hot spots of retroviral integration in human CD34+ hematopoietic cells.

Insertional oncogenesis is a possible consequence of the integration of gamma-retroviral (RV) or lentiviral (LV) vectors into the human genome. RV common insertion sites (CISs) have been identified in hematopoietic malignancies and in the nonmalignant progeny of transduced hematopoietic stem/progenitor cells (HSCs), possibly as a consequence of clonal selection in vivo. We have mapped a large number of RV and LV integrations in human CD34(+) HSCs, transduced in vitro and analyzed without selection. Recurrent insertion sites (hot spots) account for more than 21% of the RV integration events, while they are significantly less frequent in the case of LV vectors. RV but not LV hot spots are highly enriched in proto-oncogenes, cancer-associated CISs, and growth-controlling genes, indicating that at least part of the biases observed in the HSC progeny in vivo are characteristics of RV integration, already present in nontransplanted cells. Genes involved in hematopoietic and immune system development are targeted at high frequency and enriched in hot spots, suggesting that the CD34(+) gene expression program is instrumental in directing RV integration. The lower propensity of LV vectors for integrating in potentially dangerous regions of the human genome may be a factor determining a better safety profile for gene therapy applications.

Competitive engraftment of hematopoietic stem cells genetically modified with a truncated erythropoietin receptor.

Transplantation of genetically modified hematopoietic stem cells (HSCs) has therapeutic potential for a variety of blood genetic disorders. Engraftment of HSCs, however, requires toxic myeloablative treatments, which render this approach questionable for non-life-threatening disorders. A potential alternative is the use of transgenes, which allows positive selection of HSCs in vivo. We used retroviral vectors to express a truncated derivative of the erythropoietin receptor (tEpoR) in murine and human hematopoietic cells. Murine HSCs expressing tEpoR at different levels (1500 to 13,000 receptors/cell) acquire a competitive repopulation capacity in vivo upon transplantation into fully or partially myeloablated co-isogenic mouse recipients. Long-term analysis of transplanted mice showed that expression of tEpoR at paraphysiological levels (approximately 1500 receptors/cell) has no effect on steady-state hematopoiesis and induces no further expansion of transduced cells after the engraftment period. Human cord blood-derived CD34+ stem/progenitor cells transduced with a lentiviral vector expressing tEpoR expand their clonogenic capacity in vitro, and significantly increase their marrow repopulation capacity upon xenotransplantation into sublethally irradiated NOD-SCID mice, with no alteration in their phenotype, survival, and differentiation properties. These data indicate that expression of tEpoR is an effective strategy to promote selective engraftment of genetically modified HSCs upon transplantation in both myeloablative and nonmyeloablative conditions, without the use of toxic drugs for selection.