[stormhill]

An injection that gives middle-aged men the hairline of their youth could be available in just five years, scientists predicted

In the '80s scientists announced a scheme of multiplying healthy folicles in a test tube and injecting or trasplanting them into the scalp. That would also be 'ready in five years'

[HiTech RedNeck]

This might be more promising, since bald spots don’t usually reflect a lack of follicles (adding more wouldn’t help if they are all obeying the same hormonal signal) but a dormancy of the follicles present.