WP_Query don't return posts when call from a classA to classB

I have two classes class A {} and class B {} . And i has WP_Query loop within class A {} as below

class A {
    static function YPE_lastposts($divide_to, $col) {
	$my_query = 'showposts = '.$divide_to;
	$my_query = new WP_Query($my_query);
	while ($my_query->have_posts()) : $my_query->the_post();
		$item_output .= '<div class="col-sm-'.$col.'">';
		$item_output .= get_the_title();
		$item_output .= '</div>';
	endwhile;
	wp_reset_postdata();
    }
}

And i have class B {} as below and called above method within it but don’t return any post from WP_Query loop

class B extend C {
    public function start_el() {
        if (!empty($item->divideto_4)) {
	    $col = 3;
	    $divide_to = 12 / $col;
	    YPE_Bootstrap_Navbar_Content::YPE_lastposts($divide_to, $col);
        }
    }
}

When put WP_Query loop directly within start_el() method work and return posts.
But when call WP_Query loop from other class not work Why?