I am working with ~50 ml urine after prostatic massage, and I use a RNA stabilizator, but I would like to study transcripts from prostate cells in urine.Do I need to lyse the cells?
It depends on how you plan to extract the RNA. The kits I have experience with all have as one of their first steps the immersion of your tissue sample in a lysis buffer and the cell walls simply dissolve from the chaotropic salts. Qiagen Allprep DNA/RNA kit has the RLT buffer and there are well-tested protocols for study of RNA from urine samples. MirVana also have a decent protocol - see
Curated MicroRNAs in Urine and Blood Fail to Validate as Predictive Biomarkers for High-Risk Prostate Cancer, PLoS ONE 9(4): e91729.
for an example (alter the protocol according to your needs).