factor over complex numbers?

Is there any option I can set to get factor(expr1) -> (-%i + x)^5  (%i + 
x)^5
instead of getting (1 + x^2)^5 ?

(%i1) display2d:false$

(%i2) expr1 : expand( (1+x^2)^5 );

(%o2) x^10 + 5*x^8 + 10*x^6 + 10*x^4 + 5*x^2 +
1
(%i3) solve(expr1,x);

(%o3) [x = -%i,x = %i]

(%i4) multiplicities;

(%o4) [5,5]

(%i5) factor( expr1 );

(%o5) (x^2+1)^5

I am thinking of something analogous to the Mathematica Factor option 
GaussianIntegers -> True

TIA
Ted Woollett