the G-shot uses hyaluronic acid gel which is the content of many of the fillers we use in the face (Juvederm, Restylane, Emervel etc) I haven't heard of injecting stem cells but a very popular treatment is the o-shot (trademarked by Dr. Charles Runels) which is the injection of Platelet Rich Plasma (PRP) which does contain growth factors and stem cells. this injection is inherently safer as it is your own blood and it is difficult to cause bad side effects. But, check with someone who is knowledgeable and trained in the techniques.
G spot amplification is done with fillers
G spot amplification with fillers is a specific technique known as the G-Shot and creates a fullness in the region of the G-spot that lasts 3-6 months. The O-shot is done with platelet rich plasma (PRP) which has stem cells and is slightly different in how the injections are placed. There is no way to tell in advance if either procedure will work for you and marketing materials don't help. Just try one out if you're interested. There is certainly no downside to these temporary treatments.
I would recommend you visit a surgeon that completes Vaginal Rejuvenation Surgery and Cosmetic Vaginal Surgery on a regular basis. Typically these type of surgeons have advanced training in Vaginal Reconstructive Surgery and therefore offer many options for sexual function enhancement, with the knowledge and training to recommend safe and effective options. The traditional Gshot is completed with filler agents (hyaluronic acid similar to Juvaderm). This has been very effective to bulk the Gspot up and make it more sensitive and typically lasts in the range of 4-6 months. Stem Cells (or PRP is what it actually is, ie platelet rich plasma) has been used more recently as well for injection into the Gspot and the Peri-Clitoral region. This has also shown some promising early results as well. Best idea is to talk to an expert in Vaginal Rejuvenation and see what would be best option for your particular case.
Dr Robert Moore