EDIT

function render_registration($registration){

  $markup = '';

  if(isset($registration->identifier) && $registration->status == 'PUBLISHED'){

    $office_class_attribute = '';

    if(isset($registration->institution->titleCache)){

      $office_class_attribute = 'registration-' . strtolower(preg_replace('/[^a-zA-Z0-9]/', '-', $registration->institution->titleCache));

    }

    $markup = "<span class=\"registration $office_class_attribute\">" . l($registration->identifier, $registration->identifier) . ', '

      .  preg_replace('/^([^T]*)(.*)$/', '${1}', $registration->registrationDate)

    . '</span>';

  }

  return $markup;

}