Franziska Paul

In multicellular organisms, biological function emerges when heterogeneous cell types form complex organs. Nevertheless, dissection of tissues into mixtures of cellular subpopulations is currently challenging. We introduce an automated massively parallel single-cell RNA sequencing (RNA-seq) approach for analyzing in vivo transcriptional states in thousands of single cells. Combined with unsupervised classification algorithms, this facilitates ab initio cell-type characterization of splenic tissues. Modeling single-cell transcriptional states in dendritic cells and additional hematopoietic cell types uncovers rich cell-type heterogeneity and gene-modules activity in steady state and after pathogen activation. Cellular diversity is thereby approached through inference of variable and dynamic pathway activity rather than a fixed preprogrammed cell-type hierarchy. These data demonstrate single-cell RNA-seq as an effective tool for comprehensive cellular decomposition of complex tissues.

Summary Background A previous randomised study suggested that the progestagen, levonorgestrel, given alone in two separate doses each of 0·75 mg caused nausea and vomiting in fewer women and might be more effective than the Yuzpe regimen of combined oral contraceptives for emergency contraception, although the difference was not significant. We compared these two regimens when started within 72 h of unprotected coitus. Methods We enrolled in the double-blind, randomised trial 1998 women at 21 centres worldwide. Women with regular menses, not using hormonal contraception, and requesting emergency contraception after one unprotected coitus, received levonorgestrel (0·75 mg, repeated 12 h later) or the Yuzpe regimen (ethinyloestradiol 100 g plus levonorgestrel 0·5 mg, repeated 12 h later). Findings Outcome was unknown for 43 women (25 assigned levonorgestrel, 18 assigned Yuzpe regimen). Among the remaining 1955 women, the crude pregnancy rate was 1·1% (11/976) in the levonorgestrel group compared with 3·2% (31/979) in the Yuzpe regimen group. The crude relative risk of pregnancy for levonorgestrel compared with the Yuzpe regimen was 0·36 (95% CI 0·18–0·70). The proportion of pregnancies prevented (compared with the expected number without treatment) was 85% (74–93) with the levonorgestrel regimen and 57% (39–71) with the Yuzpe regimen. Nausea (23·1 vs 50·5%) and vomiting (5·6 vs 18·8%) were significantly less frequent with the levonorgestrel regimen than with the Yuzpe regimen (p<0·01). The efficacy of both treatments declined with increasing time since unprotected coitus (p=0·01). Interpretation The levonorgestrel regimen was better tolerated and more effective than the current standard in hormonal emergency contraception. With either regimen, the earlier the treatment is given, the more effective it seems to be.