Hi Manu,
I had this happen to a bellina of mine as well, and I'm sorry to say... Unfortunately, it died.
My understanding with cold damage and cell collapse is that you notice the damage after the plant is stressed by some factor, often months later, by heat or sun for example. This is what happened to mine, I believe.
I bought it from a vendor I no longer frequent, who put the bellina in a cold greenhouse (I'm not sure why, since they're warm growers.). I remember when I bought it that the leaves were lime green and actually cold to the touch. If I'd known more about bellinas (and the vendor) at the time, I wouldn't have purchased it.
The cell collapse didn't spread to the rest of my plants, though I think another of that vendor's plants died the same fate. If I remember correctly, it tried to grow new leaves, but as each leaf grew out it would show the same symptoms of collapse and die off. Eventually, I think the base of the plant turned creamy white and the whole thing died.
I hope you have a different experience. Good luck!