Celiac disease (CD) is an autoimmune inflammatory disorder caused by the consumption of gluten, a dietary protein, in genetically susceptible individuals. Some of the digestion products are resistant to further degradation and induce a cascade of inflammatory responses including recruitment and activation of intraepithelial lymphocytes, antigen presenting cells and a release of cytokines. These inflammatory responses cause tissue damage and subsequent villous atrophy [1, 2].
The prevalence of CD in the United States is estimated to be nearly 1%, though many cases are thought to be undiagnosed [3]. The clinical manifestations are broad, including diarrhea, constipation, weight loss, vomiting, osteoporosis, dermatitis herpetiformis, infertility, and neuropsychiatric issues [4]. CD has also been linked to a 2 to 4-fold increased risk of lymphoma, oral, esophageal, small intestinal, and hepatocellular carcinoma, and a 1.4-fold increase in overall mortality [5, 6]. Treatment requires commitment to a life-long gluten-free diet (GFD).
The diagnosis of CD is multidisciplinary, and is established by a characteristic duodenal biopsy, usually in a patient with positive serologic markers, and improvement of clinical symptoms after initiation of a GFD [7]. Genetic testing is useful in borderline presentations. The characteristic histologic findings in active celiac disease are intraepithelial lymphocytosis (IEL), crypt hyperplasia, and villous atrophy [8]. Upon initiation of a GFD, symptoms typically improve within weeks and serologic markers can normalize within months [4], however villous height has been shown to take a median of 3.8 years to recover [9]. In some patients, villous height recovers, but intraepithelial lymphocytosis persists, the implications of which are unclear [10]. In other patients, symptoms and villous height do not recover despite adherence to a GFD. This is termed refractory celiac disease (RCD) and is further sub-classified into RCD type I with a normal IEL phenotype, and RCD type II, with an abnormal, clonal IEL phenotype, although the diagnosis is complicated by clinically insignificant subclones [11, 12].
The mechanism of villous atrophy is thought to be a disruption in the balance between epithelial cell proliferation and death [13]. Intestinal epithelial cells normally proliferate in crypts and migrate towards the lumen where they function for a period of time and subsequently undergo apoptosis and are shed. The normal number of crypt apoptotic bodies in small intestinal mucosa is controversial, though for the purposes of graft-versus-host-disease diagnosis, the National Institutes of Health consensus statements suggests 1 per biopsy fragment [14]. This value is highly sensitive, though not specific for graft-versus-host disease [15, 16].
Despite this confusion about the threshold, excessive crypt apoptosis is abnormal and is associated with certain disease states, such as graft-versus-host disease, acute cellular rejection in small bowel allografts, and medication injury, such as in patients with toxicity due to mycophenolate mofetil [16, 17]. Apoptosis in intestinal crypts has been demonstrated in biopsies of active celiac disease by a variety of methods, including nick-end labelling assays [15, 17] and immunohistochemistry for epithelial apoptosis markers [18,19,20]. Studies have shown an increase in the degradation end products of apoptosis (i.e. M30, H2AX, cleaved caspase 3), down regulation of apoptotic inhibitor Bcl2, and upregulation of Ki-67 proliferation index in celiac disease [19]. This evidence is also corroborated by studies showing in vitro induction of enterocyte apoptosis via exposure to wheat gliadin [21].
Although crypt apoptosis has been observed in CD with ancillary techniques, a histologic assessment of crypt apoptotic body count (ABC) in celiac disease has not been reported. Histologic assessment of ABC is the mainstay of diagnosis for the aforementioned conditions associated with increased apoptosis, and ancillary techniques have not become part of clinical practice. The intent of this study is to assess and quantify crypt apoptosis as seen on routine hematoxylin and eosin stained sections of biopsies in active celiac disease, and to correlate ABC with the degree of villous blunting and atrophy.
