Why hasn't Professor X used Wolverine's DNA to heal his spine, or whatever injury caused him to be unable to use his legs. If Stryker can put DNA (with powers) into anyone, why doesn't Professor X, who is a much more intelligent person with an unlimited budget, do the experiment? He is friends with Wolverine, after all.
I haven't followed the X-men or New Mutants (or any related groups) for quite a few years, but I remember that near the beginning of the New Mutants, Professor X was irritated at his inability to walk, as his body was fine; it was nothing more than psychosomatic pain that kept him from walking. As possibly the most powerful telepath on earth, that was rather frustrating and confusing to him.
He was later able to walk; how long it lasted is unknown to me, as I stopped reading around then.
Xavier and the X-Men typically shy away from genetic experiments on Mutants. Historically, such experiments end badly or are so morally questionable that it's a line they just don't want to cross.
He has, however, had his legs cured by the results (or more specifically the side effects) of genetic experimentation (the Legacy Virus) and by the powers of another mutant (Xorn).