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.

[EX Q]: 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?
[EX A]: 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.

[EX Q]: Context: Old compared with young adults walk with reduced ankle and increased hip mechanical output. We examined the idea that age, leg strength, or both are related to the age-related changes in mechanical output during gait.', 'Healthy young (n = 32, age 21.5 years) and old adults (n = 32, age 76.8 years) participated in biomechanical gait analyses at 1.5 m/s and were also measured for maximal leg strength.', 'Analysis 1 confirmed previous data as old compared with young adults walked with 50 % more hip positive work and 18 % less ankle positive work. Analysis 2 showed that leg strength did not affect gait kinetics in groups of subjects with similar ages. In a weak young and a strong old group, Analysis 3 showed that old adults still walked with 23 % greater hip positive work. The group by joint interaction in Analysis 4 was suggestive of an even greater reliance on hip and less reliance on ankle work in weak compared with strong old adults.\Question: Do age and muscle strength mediate the age-related biomechanical plasticity of gait?
[EX A]: Age and leg strength both contribute to the age-related changes in mechanical output during gait. Exercise prescription, normally targeting the knee extensors, should also involve ankle and hip muscles.

[EX Q]: Context: Results from GOG 178 showed a prolongation of progression-free survival (PFS) with the immediate use of chemotherapy (CT) following a complete clinical response (CR) in patients with stage III-IV ovarian cancer. We wanted to evaluate our strategy of reserving second line (2nd line) chemotherapy to the time of clinical recurrence by determining PFS intervals following first, second, and third line agents and to compare these finding to results of GOG 178.', 'We conducted a retrospective parallel study to GOG 178 using identical criteria for PFS definitions. Patients (pts) with stage III-IV cancer achieving a CR following surgery and five to eight cycles of platinum-based CT were identified. Patients not obtaining a CR and those with a CR who underwent second look surgery were excluded. Rather than immediately beginning consolidation CT after CR, second line agents were started at recurrence and were followed by a third line when pts progressed. Clinical-pathologic characteristics were abstracted, and time intervals including time to recurrence, time to use of second line CT, time to use of third line (3rd line) CT, and survival were recorded. Time intervals were studied by Kaplan-Meier method.', 'Of 217 reviewed pts (1991-2001), 59 eligible pts were identified. Forty-nine patients had stage III disease and ten had stage IV. At completion of surgery, 44 were optimally debulked. With a median follow-up of 51 months, the median PFS (from CR) of all patients was 20 months. At 5 years, 36% of pts remain disease-free, and 66% of pts are alive. Twenty-three pts have not received second line agents, and thirty-six have received them. For all pts, the median time from CR to start of second line chemotherapy was 21 months, and the median time to start of third line agents was 43 months. Recurrences occurred after 6 months from completion of first line (1st line) therapy in 87% of cases and after 12 months in 50%.\Question: Is timing n't everything : an analysis of when to start salvage chemotherapy in ovarian cancer?
[EX A]:
Nearly 70% of pts achieving a CR after primary therapy eventually recurred. Most recurrences occurred greater than 6 months from completion of primary chemotherapy, and the use of second line agents at the time of recurrence was effective. In this study, the median time from CR to start of third line agent at 43 months compares favorably with the median PFS of 28 months following 12 months of Taxol reported in GOG 178 and challenges the concept of consolidation chemotherapy in ovarian cancer. A randomized trial to evaluate when to institute second line agents should be performed.