One aspect of the invention generally relates to use of tissue enriched miRNAs as biomarker to estimate tissue damage in a fluid sample. In a second aspect, methods are provided for monitoring a subject who is exposed or might have been exposed to an agent that has a risk of causing tissue injury. In a third aspect, methods are provided for identifying an agent as having a risk of causing tissue injury to a vertebrate subject. In a fourth aspect, kits are provided for practicing the methods of above-listed aspects. The contents of this ABSTRACT are not intended to in anyway limit the scope of the inventions claimed herein.