[Progress in research on forest tree comparative genomics].

Comparative genomics is one of the important research fields in genomics. By comparative genomic studies it was possible to establish a giant genetic system beyond one species which might be significant to tree. Comparative genomics in Salicaceae, Pinaceae, Rosaceae, Fagaceae and Hamamelidaceae had shown that the organization of genomes remained highly conserved over long evolutionary periods and extensive synteny or collinarity or microcollinarity existed in tree genomes. A total of 13,019 pairs of orthologs were identified between genes in Populus and Arabidopsis using the best bidirectional Basic Local Alignment Search Tool (BLAST) hits, with an average mutual coverage of these alignments equal to 93%; 11,654 pairs of orthologs had greater than 90% alignment of gene lengths. The progress of comparative genomics in tree species was reviewed and the prospect of this field was discussed, which might be useful to tree genomics in China.

Biological characteristics of human placental mesenchymal stem cells and their proliferative response to various cytokines.

The placenta is an attractive new source of mesenchymal stem cells (MSCs), but the biological characteristics of placenta-derived MSCs (P-MSCs) have not yet been characterized. We successfully isolated, cultured and expanded P-MSCs using routine methods. Under appropriate induction conditions, these cells can differentiate into bone, cartilage, fat and hepatocyte-like cells. In addition, the proliferative response of P-MSCs to different cytokines was monitored using the MTT assay. The results show that low concentrations of proinflammatory cytokines, e.g. RANTES, interleukin (IL)-1, IL-6 and IL-8 can stimulate the proliferation of P-MSCs in a dose-dependent manner, peaking at concentrations of 40 ng/ml of RANTES, 10 ng/ml of IL-1 and IL-6, and 150 ng/ml of IL-8 (p < 0.01). The level of proliferation decreased when the concentration of these four cytokines increased beyond these values. On the other hand, anti-inflammatory cytokines hepatocyte growth factor and IL-4 had an inhibitory effect on P-MSCs. In conclusion, the placenta contains MSCs that are consistent with the characteristics of bone marrow MSCs. Low concentrations of proinflammatory chemokines stimulated the proliferation of P-MSCs while anti-inflammatory cytokines inhibited the growth of P-MSCs in a dose-dependent manner.