This 2022 human study investigated tissue-specific epigenetic clock measurements:

“We used DNA methylation data representing 11 human tissues (adipose, blood, bone marrow, heart, kidney, liver, lung, lymph node, muscle, spleen, and pituitary gland) to quantify the extent to which epigenetic age acceleration (EAA) in one tissue correlates with EAA in another tissue.

Epigenetic age was moderately correlated across tissues:

• Blood had the greatest number and degree of correlation, most notably with spleen and bone marrow. Blood did not correlate with epigenetic age of liver.
• EAA in liver was weakly correlated with EAA in kidney, adipose, lung, and bone marrow.
• Hypertension was associated with EAA in several tissues, consistent with multiorgan impacts of this illness.
• HIV infection was associated with positive age acceleration in kidney and spleen.
• Men were found to exhibit higher EAA than women across all tissues when analyzed together. Significant results were also observed in individual tissues (muscle, spleen, and lymph nodes).

Blood alone will often fail to detect EAA in other tissues. It will be advisable to profile several sources of DNA (including blood, buccal cells, adipose, and skin) to get a comprehensive picture of the epigenetic aging state of an individual.”

https://link.springer.com/article/10.1007/s11357-022-00560-0 “HIV, pathology and epigenetic age acceleration in different human tissues”