Line height in multi-line cells

Thanks for reading this topic.

I'm using multi-line cells (with <br>'s) with a small font size because of too much information. However, the space between the lines in a multi-line cell seems to be fixed... For example, if I set font size to 6px and line-height to 8px, the font size works fine, but line-height don't (remains unchanged, I guess).

Any suggestion?

Thanks a lot.