This article may help members to decide whether or not there is any convincing evidence that prolotherapy is of any use.

Prolotherapy - Wikipedia

Note that prolotherapy does not involve stem cells. There are many kinds of stem cells. For example, some specific stem cells are responsible for making the various kinds of blood cells. In my view a "one size fits all" approach is not appropriate; the specific stem cells which make blood cells will be of no use in treating a disorder which does not involve blood cells.