"Homing to Niche," a new criterion for hematopoietic stem cells?

By combining cell surface staining with fluorochrome-conjugated monoclonal antibodies and Hoechst 33342 dye supravital staining, Matsuzaki et al. have succeeded in enriching hematopoietic stem cells (HSCs) essentially to homogeneity. When single-cell transplantation analysis was performed using the isolated cells, over 95% of the recipient mice showed long-term multilineage engraftment. The work demonstrates unexpectedly high marrow seeding efficiency of HSCs and proposes high marrow homing capacity as a new criterion for HSCs.     

Expression of mRNAs related to connective tissue metabolism in rat hepatic stellate cells and myofibroblasts

Hepatic stellate cells (HSC) and liver myofibroblasts (MFB) are two cell populations most likely responsible for the synthesis of most connective tissue components in fibrotic liver. They differ in their origin and location, and possibly in patterns of gene expression. Normal and carbon tetrachloride-cirrhotic livers from rats were used to isolate HSC. Liver was perfused with pronase and collagenase solutions, followed by centrifugation of the cell suspension on a density gradient. HSC were quiescent 2 days after plating on plastic but they became activated after another 5 days in culture. When the culture was passaged 5 times, its character changed profoundly as HSC were replaced by MFB. Microarray analysis was used to determine gene expression in quiescent HSC, activated HSC and MFB. The expression of 49 genes coding for connective tissue proteins, proteoglycans, metalloproteinases and their inhibitors, growth factors and cellular markers was determined. The pattern of gene expression changed during HSC activation and there were distinct differences between HSC and MFB. Little difference between normal cells and cells isolated from cirrhotic liver was found.     

The effect of androgen on the retention of extinction memory after conditioned taste aversion in mice

Conditioned taste aversion (CTA) induced by the application of a novel taste such as sodium saccharin (Sac) as the conditioned stimulus (CS) and a malaise-inducing agent as the unconditioned stimulus (US), results in acquisition of CTA memory to Sac. In contrast, CTA is extinguished by repeated presentations of the CS without the US, resulting in acquisition of the extinction memory. We examined the effects of androgenic hormones on acquisition and retention of extinction memory in mice. We gonadectomized sexually immature mice and continuously administered androgens to these animals. After sexual maturation, the mice underwent a conditioning period followed by an extinction period. Retrieval tests revealed that the androgen-treated group showed significantly greater retention of extinction memory than the non-treated group 5 weeks later, whereas such significant difference was not observed in acquisition of extinction memory. These results demonstrate the enhancing effect of androgens on retention of extinction memory.     

Visualization of endothelial cell cycle dynamics in mouse using the Flt-1/eGFP-anillin system

Endothelial cell proliferation is a key process during vascular growth but its kinetics could only be assessed in vitro or ex vivo so far. To enable the monitoring and quantification of cell cycle kinetics in vivo, we have generated transgenic mice expressing an eGFP-anillin construct under control of the endothelial-specific Flt-1 promoter. This construct labels the nuclei of endothelial cells in late G1, S and G2 phase and changes its localization during the different stages of M phase, thereby enabling the monitoring of EC proliferation and cytokinesis. In Flt-1/eGFP-anillin mice, we found eGFP⁺ signals specifically in Ki67⁺/PECAM⁺ endothelial cells during vascular development. Quantification using this cell cycle reporter in embryos revealed a decline in endothelial cell proliferation between E9.5 to E12.5. By time-lapse microscopy, we determined the length of different cell cycle phases in embryonic endothelial cells in vivo and found a M phase duration of about 80 min with 2/3 covering karyokinesis and 1/3 cytokinesis. Thus, we have generated a versatile transgenic system for the accurate assessment of endothelial cell cycle dynamics in vitro and in vivo.     

Reaching Latinas with Our Bodies,Ourselves and the Guía de Capacitación para Promotoras de Salud: Health Education for Social Change

As the cultural and linguistic diversity of the United States continues to grow and population shifts transform the communities where we live and work, health care providers continue to face challenges to deliver health services in demographically redefined terrains. This report describes the development of a Spanish‐language training guide for community health workers (Guía de Capacitación para Promotoras de Salud) based on the book Nuestros Cuerpos, Nuestras Vidas (NCNV), the Spanish‐language translation and cultural adaptation of the classic women's health book Our Bodies, Ourselves. The guide aims to 1) provide a tool for addressing the health education needs of immigrant Latinas and 2) facilitate the use of the book NCNV as a health education tool in Latino communities. Thirty telephone interviews with individuals working in agencies and organizations serving Latinos and 2 focus groups with Latinas were conducted to select the topics included in the training guide, all of which were drawn directly from NCNV. The guide contains 11 modules organized into 6 workshops. The modules address 11 topics related to women's health, ranging from sexuality and pregnancy to domestic violence and mental health. An ecological framework is used to deliver the health information. The materials acknowledge the roles of history, environment, culture, economic conditions, migration history, and politics as key determinants of health and illness. The workshops are designed to train community health workers on the women's health topics contained in the guide and to equip them for the delivery of health education among immigrant Latinas.     

Expansion of hematopoietic stem cells in the developing liver of a mouse embryo

The activity of hematopoietic stem cells in the developing liver of a C57BL/6 mouse embryo was quantified by a competitive repopulation assay. Different doses of fetal liver cells at days 11 to 18 of gestation were transplanted into irradiated mice together with 2 x 10(5) adult bone marrow cells. A long-term repopulation in myeloid-, B-cell, and T-cell lineage by fetal liver cells was evaluated at 20 weeks after transplantation. At day 12 of gestation multilineage repopulating activity was first detected in the liver as 50 repopulating units (RU) per liver. The number of RU per liver increased 10-fold and 33-fold by day 14 and day 16 of gestation, and decreased thereafter, suggesting a single wave of stem cell development in the fetal liver. A limiting dilution analysis revealed that the frequency of competitive repopulating units (CRU) in fetal liver cells at day 12 of gestation was similar to that at day 16 of gestation. Because of an increase of total fetal liver cell number, the absolute number of CRU per liver from days 12 to 16 of gestation increased 38-fold. Hence, the mean activity of stem cells (MAS) that is given by RU per CRU remained constant from days 12 to 16 of gestation. From these data we conclude that hematopoietic stem cells expand in the fetal liver maintaining their level of repopulating potential.     

Exposure to environmental tobacco smoke and urinary 1-hydroxypyrene levels in preschool children

Environmental tobacco smoke (ETS) contains relatively high concentrations of polycyclic aromatic hydrocarbons (PAHs). Urinary 1-hydroxypyrene (1-OHP), a metabolite of pyrene, is a good indicator of PAH exposure in occupational studies. In this study, we investigated the relationship between urinary 1-OHP concentration and ETS exposure in preschool children. Forty preschool children, aged 24-76 months, were studied during November and December, 1999. Two spot-urine specimens (one in the morning immediately after the subject woke up and the other at night before the subject went to bed) were collected 1 day after completion of a questionnaire, in order to determine 1-OHP concentrations by fluorescent spectrophotometry. Overall, urinary 1-OHP concentrations were relatively low but detectable (morning: median, 0.021 microg/g creatinine; range, 0.002-1.019 microg/g creatinine; night: median, 0.015 microg/g creatinine; range, 0.002-1.328 microg/g creatinine). Multiple linear regression analyses revealed that the total number of cigarettes smoked by the children's fathers during the 3 days prior to collection of the urine specimens was significantly associated with their urinary 1-OHP concentrations, after adjusting for other confounders. Each cigarette smoked by a child's father resulted in an average 9.6% increase in 1-OHP concentration in the morning urine specimen (95% confidence interval = 1.8-18.1%; p = 0.02). We did not find a significant increase in the 1-OHP concentration in night urine specimens (p = 0.19). Although the sample size was small, these findings indicate that urinary 1-OHP may be a suitable biomarker of ETS carcinogen exposure in children.     

Deformable registration of preoperative MR,pre-resection ultrasound,and post-resection ultrasound images of neurosurgery

Purpose

Sites that use ultrasound (US) in image-guided neurosurgery (IGNS) of brain tumors generally have three sets of imaging data: preoperative magnetic resonance (MR) image, pre-resection US, and post-resection US. The MR image is usually acquired days before the surgery, the pre-resection US is obtained after the craniotomy but before the resection, and finally, the post-resection US scan is performed after the resection of the tumor. The craniotomy and tumor resection both cause brain deformation, which significantly reduces the accuracy of the MR–US alignment.

Method

Three unknown transformations exist between the three sets of imaging data: MR to pre-resection US, pre- to post-resection US, and MR to post-resection US. We use two algorithms that we have recently developed to perform the first two registrations (i.e., MR to pre-resection US and pre- to post-resection US). Regarding the third registration (MR to post-resection US), we evaluate three strategies. The first method performs a registration between the MR and pre-resection US, and another registration between the pre- and post-resection US. It then composes the two transformations to register MR and post-resection US; we call this method compositional registration. The second method ignores the pre-resection US and directly registers the MR and post-resection US; we refer to this method as direct registration. The third method is a combination of the first and second: it uses the solution of the compositional registration as an initial solution for the direct registration method. We call this method group-wise registration.

Results

We use data from 13 patients provided in the MNI BITE database for all of our analysis. Registration of MR and pre-resection US reduces the average of the mean target registration error (mTRE) from 4.1 to 2.4 mm. Registration of pre- and post-resection US reduces the average mTRE from 3.7 to 1.5 mm. Regarding the registration of MR and post-resection US, all three strategies reduce the mTRE. The initial average mTRE is 5.9 mm, which reduces to 3.3 mm with the compositional method, 2.9 mm with the direct technique, and 2.8 mm with the group-wise method.

Conclusion

Deformable registration of MR and pre- and post-resection US images significantly improves their alignment. Among the three methods proposed for registering the MR to post-resection US, the group-wise method gives the lowest TRE values. Since the running time of all registration algorithms is less than 2 min on one core of a CPU, they can be integrated into IGNS systems for interactive use during surgery.

     

Two anatomically distinct niches regulate stem cell activity

The niche microenvironment controls stem cell number, fate, and behavior. The bone marrow, intestine, and skin are organs with highly regenerative potential, and all produce a large number of mature cells daily. Here, focusing on adult stem cells in these organs, we compare the structures and cellular components of their niches and the factors they produce. We then define the niche as a functional unit for stem cell regulation. For example, the niche possibly maintains quiescence and regulates fate in stem cells. Moreover, we discuss our hypothesis that many stem cell types are regulated by both specialized and nonspecialized niches, although hematopoietic stem cells, as an exception, are regulated by a nonspecialized niche only. The specialized niche is composed of 1 or a few types of cells lying on the basement membrane in the epithelium. The nonspecialized niche is composed of various types of cells widely distributed in mesenchymal tissues. We propose that the specialized niche plays a role in local regulation of stem cells, whereas the nonspecialized niche plays a role in relatively broad regional or systemic regulation. Further work will verify this dual-niche model to understand mechanisms underlying stem cell regulation.