Recent comments from the administration in Transnistria regarding a desire to join Russia in a formal union raised eyebrows in Chisinau, with the Prime Minister of Moldova publicly commenting as to Moldova's concerns regarding a Russian territorial ambitions. Moldova's armed forces are miniscule, however so are those in Transnistria (even with the Russian contingent already in place).
The force Ukraine can bring to bear, however, is something entirely different, especially given the geographical nature of Transnistria.
The head of intelligence of the Ukrainian Ministry of Defence stated Ukraine will assist Moldova if they need to remove Russian soldiers. This raises the stakes dramatically for the Transnistrian authorities as Russia will not be able to supply them with military assistance (having to pass through either Moldova or Ukraine to do so).
Whilst no-one is expecting Transnistria to act given the implications, it does raise the issue of the how long client bodies that rely on Russian largesse can continue without having to commit troops.