[R-meta] rma.mv meta-regression

Dear all,
as usual, apologies for a potentially silly question.

I am doing multi-variate meta-analysis of studies looking a different
inflammatory markers (called cytokines, in short cyto).
Each study measured multiple cytokines for the same sample.

The code is running like so:

rma.mv(yi=yi,V=vi, mods=~cyto-1, random = ~cyto|studycode, struct="UN", method='REML', data = mydata, control=list(optimizer="hjk"))

I was wondering if it is possible to perform meta-regression using the
same technique, such as on average study participant age (a variable
called age), on all studies at the same time, but grouped by cyto, and
what the code would look like.

Many thanks for your help.

Emanuele