Assuming that those should be numeric vectors:
a{1} = [1 2 3 4 5];
a{2} = [2 2 4 5];
a{3} = [8 2];
a{4} = [8 2 9 9 2 1 3];
v = cellfun('size',a,2);
r = numel(a);
M = zeros(r,max(v));
for k = 1:r
M(k,1:v(k)) = a{k};
end
Giving:
>> M
M =
1 2 3 4 5 0 0
2 2 4 5 0 0 0
8 2 0 0 0 0 0
8 2 9 9 2 1 3
>>