I think the CEO's action prompted some people to short this stock, but looks like it is very dangerous to do that as the company has received significant amount of money from government and unveiled the prototype of stemdisc450, a promising product.
If you go through the executive compensation section, you will find that the company owes some 124 grand to a company owned by CEO and chairman. My guess is the CEO has sold shares to recoup that money. Further, company's recent filing shows that number of shares held by CEO increased. Remember, the company is paying the CEO company stocks for compensation. I guess this is his full-time job, so he cashed some stocks. None of other insiders is selling shares. It is very risky to short this stock as the company has so many short term catalysts that it could skyrocket within a very short period of time. JMHO