I feel sorry about your horse, unfortunately there is no much sound experience around there, from us, or from other teams, indicating that there could be an interest in using stem cells for helping regenerating a damaged stomach.
There are some encouraging data in the lab from studies performed by several teams around the world, showing that stem cells help vascularization of the stomach and the repair of the stomach's wall. But this is too premature to translate such results to the horse.
I hope you will find the most suitable solution for your horse,
Stéphane from Vetbiobank Equine Team.