An Exploratory, Randomized, Crossover MRI Study of Microbicide Delivery with the SILCS Diaphragm Compared to a Vaginal Applicator

Background—Microbicide gels studied for HIV prevention often are delivered via a single-use vaginal applicator. Using a contraceptive diaphragm such as the SILCS diaphragm for gel delivery could have advantages, including lower cost and additional pregnancy prevention. Study Design—We performed an exploratory, nonblinded, randomized, crossover study among healthy, sexually active, nonpregnant women. Using BufferGel®, we evaluated three microbicide delivery methods for gel distribution and retention: SILCS single-sided gel delivery, SILCS double-sided gel delivery and a vaginal applicator (without SILCS). Magnetic resonance images were taken at baseline, after gel insertion, and immediately and 6 h after simulated intercourse. Three women completed all gel delivery methods described in this article. Results—Magnetic resonance imaging analysis indicated similar gel spread in the vagina among all three methods. SILCS single-sided gel application resulted in the most consistent longitudinal coverage; SILCS double-sided gel application was the most consistent in the transverse dimension. Conclusions—Gel coverage was similar with all three methods. These results suggest that the SILCS microbicide delivery system is comparable to vaginal applicators for delivery of gel products intravaginally

Inhibiting expression of specific genes in mammalian cells with 5′ end-mutated U1 small nuclear RNAs targeted to terminal exons of pre-mRNA

Reducing or eliminating expression of a given gene is likely to require multiple methods to ensure coverage of all of the genes in a given mammalian cell. We and others [Furth, P. A., Choe, W. T., Rex, J. H., Byrne, J. C., and Baker, C. C. (1994) Mol. Cell. Biol. 14, 5278–5289] have previously shown that U1 small nuclear (sn) RNA, both natural or with 5′ end mutations, can specifically inhibit reporter gene expression in mammalian cells. This inhibition occurs when the U1 snRNA 5′ end base pairs near the polyadenylation signal of the reporter gene's pre-mRNA. This base pairing inhibits poly(A) tail addition, a key, nearly universal step in mRNA biosynthesis, resulting in degradation of the mRNA. Here we demonstrate that expression of endogenous mammalian genes can be efficiently inhibited by transiently or stably expressed 5′ end-mutated U1 snRNA. Also, we determine the inhibitory mechanism and establish a set of rules to use this technique and to improve the efficiency of inhibition. Two U1 snRNAs base paired to a single pre-mRNA act synergistically, resulting in up to 700-fold inhibition of the expression of specific reporter genes and 25-fold inhibition of endogenous genes. Surprisingly, distance from the U1 snRNA binding site to the poly(A) signal is not critical for inhibition, instead the U1 snRNA must be targeted to the terminal exon of the pre-mRNA. This could reflect a disruption by the 5′ end-mutated U1 snRNA of the definition of the terminal exon as described by the exon definition model

Inhibiting expression of specific genes in mammalian cells with 5' end-mutated U1 small nuclear RNAs targeted to terminal exons of pre-mRNA

Reducing or eliminating expression of a given gene is likely to require multiple methods to ensure coverage of all of the genes in a given mammalian cell. We and others [Furth, P. A., Choe, W. T., Rex, J. H., Byrne, J. C., and Baker, C. C. (1994) Mol. Cell. Biol. 14, 5278-5289] have previously shown that U1 small nuclear (sn) RNA, both natural or with 5' end mutations, can specifically inhibit reporter gene expression in mammalian cells. This inhibition occurs when the U1 snRNA 5' end base pairs near the polyadenylation signal of the reporter gene's pre-mRNA. This base pairing inhibits poly(A) tail addition, a key, nearly universal step in mRNA biosynthesis, resulting in degradation of the mRNA. Here we demonstrate that expression of endogenous mammalian genes can be efficiently inhibited by transiently or stably expressed 5' end-mutated U1 snRNA. Also, we determine the inhibitory mechanism and establish a set of rules to use this technique and to improve the efficiency of inhibition. Two U1 snRNAs base paired to a single pre-mRNA act synergistically, resulting in up to 700-fold inhibition of the expression of specific reporter genes and 25-fold inhibition of endogenous genes. Surprisingly, distance from the U1 snRNA binding site to the poly(A) signal is not critical for inhibition, instead the U1 snRNA must be targeted to the terminal exon of the pre-mRNA. This could reflect a disruption by the 5' end-mutated U1 snRNA of the definition of the terminal exon as described by the exon definition model