What proteins/molecules in the biochemical composition of horse serum
that induces adipogenic differentiation of Multipotent Adult
Progenitor Cells (MAPC) but not mesenchymal stem cells
(MSC)?
Also, horse serum is far better at inducing the myogenic
differentiation of C2C12 myoblasts, why?

These sites may be of interest to you:
http://anatomy.med.unsw.edu.au/cbl/research/methods/cellsc2.htm

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10415081&dopt=Abstract

www.nd.edu/~ljordan/butterfly/genetics/western.ppt 

"Crystallographic studies of equine serum albumin reveal two binding
sites for 2,3,5-triiodobenzoic acid identical with those previously
reported for human serum albumin which are located within subdomains
in IIA and IIIA. Details and comparisons of the binding chemistry are
discussed."
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8344282&dopt=Abstract

http://www.macropore.com/pdf/myogenic.pdf

http://odelberglab.genetics.utah.edu/PDFs/Odelberg.pdf

regards, Crabcakes