Detection of the Ki-67 proliferation associated nuclear epitope in normal canine tissues using the monoclonal antibody MIB-1

Evaluation of Ki-67, goblet cell and MUC2 mucin RNA expression in dogs with lymphoplasmacytic and granulomatous colitis

Intestinal mucus barrier disruption may occur with chronic inflammatory enteropathies. The lack of studies evaluating mucus health in dogs with chronic colitis arises from inherent challenges with assessment of the intestinal mucus layer. It is therefore unknown if reduced goblet cell (GBC) numbers and/or mucin 2 (MUC2) expression, which are responsible for mucus production and secretion, correlate with inflammation severity in dogs with granulomatous colitis (GC) or lymphocytic-plasmacytic colitis (LPC). It is undetermined if Ki-67 immunoreactivity, which has been evaluated in dogs with small intestinal inflammation, similarly correlates to histologic severity in GC and LPC. Study objectives included comparing Ki-67 immunoreactivity, GBC population and MUC2 expression in dogs with GC, LPC and non-inflamed colon; and exploring the use of ribonucleic acid (RNAscope®) in-situ hybridization (ISH) to evaluate MUC2 expression in canine colon. Formalin-fixed endoscopic colonic biopsies were obtained from 48 dogs over an eight-year period. A blinded pathologist reviewed all biopsies. Dogs were classified into the GC (n=19), LPC (n=19) or no colitis (NC) (n=10) group based on final histopathological diagnosis. Ki-67 immunohistochemistry, Alcian-Blue/PAS staining to highlight GBCs, and RNAscope® ISH using customized canine MUC2-targeted probes were performed. At least five microscopic fields per dog were selected to measure Ki-67 labelling index (KI67%), GBC staining percentage (GBC%) and MUC2 expression (MUC2%) using image analysis software. Spearman's correlation coefficients were used to determine associations between World Small Animal Veterinary Association histologic score (WHS) and measured variables. Linear regression models were used to compare relationships between WHS with KI67%, GBC%, and MUC2%; and between GBC% and MUC2%. Median WHS was highest in dogs with GC. Median KI67% normalised to WHS was highest in the NC group (6.69%; range, 1.70-23.60%). Median GBC% did not correlate with colonic inflammation overall. Median MUC2% normalised to WHS in the NC group (10.02%; range, 3.05-39.09%) was two- and three-fold higher than in the GC and LPC groups respectively. With increased colonic inflammation, despite minimal changes in GBC% overall, MUC2 expression markedly declined in the LPC group (-27.4%; 95%-CI, -49.8, 5.9%) and mildly declined in the GC and NC groups. Granulomatous colitis and LPC likely involve different pathways regulating MUC2 expression. Decreased MUC2 gene expression is observed in dogs with chronic colitis compared to dogs without colonic signs. Changes in MUC2 expression appear influenced by GBC activity rather than quantity in GC and LPC.

Investigation of Gastrointestinal Toxicities Associated with Concurrent Abdominal Radiation Therapy and the Tyrosine Kinase Inhibitor Sunitinib in a Mouse Model

Tyrosine kinase inhibitors (TKIs) may be combined with radiation therapy (RT) to enhance tumor control; however, increased incidences of gastrointestinal (GI) toxicity have been reported with this combination. We hypothesize that toxicity is due to compromised intestinal healing caused by inhibition of vascular repair and proliferation pathways. This study explores underlying tissue toxicity associated with abdominal RT and concurrent sunitinib in a mouse model. Four groups of CD-1 mice were treated with 12 Gy abdominal RT, oral sunitinib, abdominal RT + sunitinib, or sham treatment. Mice received oral sunitinib or the vehicle via gavage for 14 days. On day 7, mice were irradiated with 12 Gy abdominal RT or sham treated. Mice were euthanized on day 14 and intestinal tract was harvested for semiquantitative histopathologic evaluation and immunohistochemical quantification of proliferation (Ki67) and vascular density (CD31). Non-irradiated groups had stable weights while abdominal irradiation resulted in weight loss, with mice receiving RT + SUN having greater weight loss than mice receiving RT alone. Semiquantitative analysis showed significant increases in inflammation in irradiated groups. The difference in the density of CD31+ cells was significantly increased in RT alone compared to SUN alone. Ki67+ density was not significant. In summary, we identify a lack of angiogenic response in irradiated GI tissues when abdominal RT is combined with a TKI, which may correlate with clinical toxicities seen in canine and human patients receiving combined treatment.

Nivalenol has a greater impact than deoxynivalenol on pig jejunum mucosa in vitro on explants and in vivo on intestinal loops

The mycotoxins deoxynivalenol (DON) and nivalenol (NIV), worldwide cereal contaminants, raise concerns for animal and human gut health, following contaminated food or feed ingestion. The impact of DON and NIV on intestinal mucosa was investigated after acute exposure, in vitro and in vivo. The histological changes induced by DON and NIV were analyzed after four-hour exposure on pig jejunum explants and loops, two alternative models. On explants, dose-dependent increases in the histological changes were induced by DON and NIV, with a two-fold increase in lesion severity at 10 µM NIV. On loops, NIV had a greater impact on the mucosa than DON. The overall proliferative cells showed 30% and 13% decrease after NIV and DON exposure, respectively, and NIV increased the proliferative index of crypt enterocytes. NIV also increased apoptosis at the top of villi and reduced by almost half the proliferative/apoptotic cell ratio. Lamina propria cells (mainly immune cells) were more sensitive than enterocytes (epithelial cells) to apoptosis induced by NIV. Our results demonstrate a greater impact of NIV than DON on the intestinal mucosa, both in vitro and in vivo, and highlight the need of a specific hazard characterization for NIV risk assessment.

Proliferation patterns in the canine endometrium during the estrous cycle

The proliferative activity in the endometrium of 58 bitches in different stages of the estrous cycle was assessed by immunohistochemical detection of the Ki-67 proliferation associated nuclear antigen and by counting mitotic figures. The Ki-67 labelling index and the mitotic index were determined in the surface epithelium, the stroma, the crypts and the basal glands by calculating the percentage of Ki-67 positive cells and mitotic figures, respectively, on a total of 500 cells of each category. Endometrial vascular proliferation was also verified by counting the number of Ki-67 positive cells on a total of 100 endothelial cells. The present study showed two proliferation peaks involving different cell groups. In the surface epithelium, the stroma, the blood vessels and the crypts, the highest labelling and mitotic indexes were noticed during proestrus, whereas for the basal glands these indexes significantly increased (P < 0.05) during estrus compared to late metestrus and anestrus. Furthermore, a slightly positive correlation (P < 0.05) was found between the labelling index in the basal glands and the serum progesterone levels, whereas the labelling indexes in the other cell groups were positively correlated with the estradiol-17 beta levels, although not always significantly. These findings suggest that regulation of the proliferation in the surface epithelium, the stroma, the blood vessels and the crypts is different from the proliferation in the basal glands.

Cell proliferation during the early stages of human eye development

The distribution as well as the ultrastructural and biochemical characteristics of proliferating cells in the human eye were investigated in five conceptuses of 5-9 postovulatory weeks, using morphological techniques and Ki-67 immunostaining. The Ki-67 nuclear protein was used as a proliferation marker because of its expression in all phases of the cell cycle except the resting phase (G0). The labelling indices of Ki-67-positive cells were analysed by means of the Kruskal-Wallis ANOVA test and the Wilcoxon matched-pairs test. In the 5th week, mitotic cells were the most numerous between the two layers of the optic cup, the optic cup and stalk, and between the lens pit and the surface ectoderm. During the 6th week, cells were observed in the lens epithelium covering the whole cavity of the lens vesicle as well as in the neuroblast zone and the pigmented epithelium of the retina. At later stages (7th-9th weeks), Ki-67-positive cells were restricted to the anterior lens epithelium, the outer neuroblast zone, and the pigmented retina. Throughout all stages examined, mitotic figures were found lying exclusively adjacent to the intraretinal space. Early in the lens pit, they were confined to the free epithelial surface, and later were facing the cavity of the lens vesicle. The proliferative activity was the most intensive in the 6th week, whereas it decreased significantly in the later stages. Additionally, when proliferative activities were compared, the peripheral retina appeared to be less mature than the central before the 9th week. In the earliest analysed stage, cell proliferation might be associated with the sculpturing of the optic cup and stalk, the cornea, and the lens. In the 6th week, the most intensive proliferation seems to be involved not only in the further morphogenesis of the optic cup and the lens vesicle but also in the retinal neurogenesis. At later stages, the decreased proliferation might participate in the neurogenesis of the outer neuroblast zone and the secondary lens fibre formation.

Assessment of Proliferative Potentials of Canine Osteosarcomas and Chondrosarcomas by MIB-1 Immunohistochemistry and Bromodeoxyuridine Incorporation

The proliferative potential of 17 canine osteosarcomas (OSs) (13 osteoblastic, two anaplastic, one fibroblastic and one chondroblastic), 18 chondrosarcomas (CSs) (13 mesenchymal and five ordinary), three osteomas, and one chondroma was evaluated immunohistochemically by labelling Ki-67 antigen with MIB-1 antibody, and incorporated bromodeoxyuridine (BrdU) with anti-BrdU antibody. The location of BrdU-positive cells in OSs and CSs was similar to that of MIB-1 positive cells, and the mean value of the BrdU labelling index (BrdU LI) and the MIB-1 positive index (MIB-1 PI) in each case were significantly correlated (rs = 0.942, P < 0.05 with Spearman rank correlation coefficient; r = 0.779 P < 0.05 with linear regression analysis). The mean MIB-1 PI of OSs was 29.5%, which was approximately 2.5 times that of CSs, and the highest MIB-1 PI was 34.8% +/- 1.8 S.E.M. in areas without osteoid. In CS cases, the survival rate after 24 months was significantly higher than in OS cases. The high MIB-1 PI therefore supports the view that OSs are clinically more aggressive than CSs in dogs. On the other hand, the highest MIB-1 PI values of mesenchymal CS components occurred in transitional areas, which were composed of poorly differentiated cells embedded in a myxomatous matrix between the chondroidal and mesenchymal regions. The MIB-1 PI was 21.3% +/- 3.0 S.E.M. P < 0.001 in transitional areas. Proliferative markers may be useful in diagnosis and prognosis.

Lymphocyte proliferation in lymphoid organs of the dromedary camel using the monoclonal antibody MIB-5 against the proliferation-associated nuclear epitope Ki-67

Detection of proliferating lymphocytes is useful for studying immune reactions and for the prognosis of tumours of lymphocyte origin. Markers detecting proliferating cells are lacking in the dromedary camel. This study deals with the immunohistochemical detection of the Ki-67 proliferation-associated nuclear epitope using MIB-5 in frozen sections from spleens, different lymph nodes and haemal nodes of eight camels (0.5-12 years old). Frozen sections from rat spleens were labelled in parallel with camel tissue as a positive control. Large numbers of cells expressing the Ki-67 epitope were localized in germinal centres of all lymphoid organs tested. A few cells were found in the periarterial lymphoid sheath and the red pulp of the spleen, also in the lymphatic cords of the lymph nodes and the haemal nodes. There were no obvious differences in respect to the age of the animals. The Ki-67 epitope is well expressed by proliferating cells in camel lymphoid organs. MIB-5 can be applied to identify this epitope and will be a useful marker for cell production in immune reactions.

MIB-1 immunoreactivity correlates with biologic behaviour in canine cutaneous melanoma

The growth fraction of 68 canine cutaneous melanomas was determined by immunostaining with MIB-1, a monoclonal antibody to a Ki-67 epitope that recognizes all proliferating cells. Fifty tumours were classified histologically as benign and 18 as malignant. The Ki-67 proliferative index (percentage of positive cells over 500 neoplastic cells) was low (< 15%) in 55 cases and high (> or = 15%) in 13 cases. High Ki-67 proliferative index and histological malignancy were both associated with significantly poorer 2-year survival (P < 0.0001). However, the predictive value of the Ki-67 proliferative index (97%) was higher than the predictive value of classical histology (91%). The evaluation of the growth fraction by the Ki-67 proliferative index is highly predictive of the biological behaviour of canine cutaneous melanoma.