TASK DEFINITION: In this task, you are given a passage which has a question and the context. You have to generate an answer to the question based on the information present in the context.
PROBLEM: Context: Cord blood (CB) hematopoietic stem cell transplantation has often been limited by the scarcity of stem cells. Therefore, the number of CB hematopoietic stem/progenitor cells (HSPCs) should be increased while maintaining the stem cell characteristics.', 'We designed an ex vivo culture system using endothelial progenitor cells (EPCs) as stroma to determine the capacity of expanding CB-HSPCs in a defined medium, the effect on engraftment of the expanded cells in a mouse model and the underlying mechanism.', "After 7 days of culture, compared with those cultured with cytokines alone (3.25 ± 0.59), CD34+ cells under contact and non-contact co-culture with EPCs were expanded by 5.38 ± 0.61 (P = 0.003) and 4.06 ± 0.43 (P = 0.025)-fold, respectively. Direct cell-to-cell contact co-culture with EPCs resulted in more primitive CD34+ CD38- cells than stroma-free culture (156.17 ± 21.32 versus 79.12 ± 19.77-fold; P = 0.010). Comparable engraftment of day 7 co-cultured HSPCs with respect to HSPCs at day 0 in nonobese diabetic-severe combined immunodeficiency disease (NOD/SCID) mice was measured as a percentage of chimerism (13.3% ± 11.0% versus 16.0% ± 14.3%; P = 0.750). EPCs highly expressed interleukin 6 (IL6) and angiopoietin 1 (ANGPT1), the hematopoietic- related cytokines. A higher transcriptional level of WNT5A genes in EPCs and co-cultured HSPCs suggests that the activation of Wnt signaling pathway may play a role in HSPCs' expansion ex vivo.\Question: Do endothelial progenitor cells promote efficient ex vivo expansion of cord blood-derived hematopoietic stem/progenitor cells?

SOLUTION: These data demonstrated that EPCs improve the CD34+ population but do not compromise the repopulating efficacy of the amplified HSPCs, possibly via cytokine secretion and Wnt signaling pathway activation.

PROBLEM: Context: To assess how different imputation methods used to account for missing variance data in primary studies influence tests of heterogeneity and pooled results from a meta-analysis with continuous outcomes.', 'Point and variance estimates for changes in serum creatinine, glomerular filtration rate, systolic blood pressure, and diastolic blood pressure were variably reported among 48 primary longitudinal studies of living kidney donors (71%-78% of point estimates were reported, 8%-13% of variance data were reported). We compared the results of meta-analysis, which either were restricted to available data or used four methods to impute missing variance data. These methods used reported P-values, reported nonparametric summaries, results from other similar studies using multiple imputation, or results from estimated correlation coefficients.', 'Significant heterogeneity was present in all four outcomes regardless of the imputation methods applied. The random effects point estimates and 95% confidence intervals varied little across imputation methods, and the differences were not clinically significant.\Question: Do imputing variance estimates alter the conclusions of a meta-analysis with continuous outcomes : a case study of changes in renal function after living kidney donation?

SOLUTION: Different methods to impute the variance data in the primary studies did not alter the conclusions from this meta-analysis of continuous outcomes. Such reproducibility increases confidence in the results. However, as with most meta-analyses, there was no gold standard of truth, and results must be interpreted judiciously. The generalization of these findings to other meta-analyses, which differ in outcomes, missing data, or between-study heterogeneity, requires further consideration.

PROBLEM: Context: Congenital cystic adenomatoid malformation (CCAM) of the lung may result from a localized aberrant epithelial-mesenchymal interaction during lung development. We used laser microdissection (LMD) to isolate the epithelium and mesenchyme of CCAM, and studied candidate gene expression in these pure cell populations.', 'Congenital cystic adenomatoid malformation tissue was obtained from fetal (n = 5) and postnatal (n = 5) surgical specimens. Normal fetal lung (n = 10) was obtained from abortus material, and normal postnatal lung (n = 5) was identified from surgical specimens. Whole tissue was analyzed using immunohistochemistry and reverse transcriptase polymerase chain reaction (RT-PCR). Using LMD, columnar bronchiolar type epithelium and underlying mesenchyme were isolated. Multiplex nested RT-PCR was then used to detect message levels of candidate genes.', 'Reverse transcriptase polymerase chain reaction performed on LMD-isolated tissue, but not whole tissue homogenate, revealed differences between CCAM and normal lung. In this report, we focus on the fibroblast growth factor (FGF) family. By RT-PCR, there was 4-fold more epithelial expression of FGF9 in fetal CCAM vs normal fetal lung (P < .07). This was qualitatively confirmed by immunohistochemistry. We also detected decreased FGF7 expression in CCAM mesenchyme (P < .05) but no significant differences in FGF10 or FGFR2.\Question: Does laser microdissection allow detection of abnormal gene expression in cystic adenomatoid malformation of the lung?

SOLUTION:
LMD may be used to overcome the limitations of tissue heterogeneity in the study of CCAM. Abnormal growth factor expression may play a role in the etiology of this lesion.