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The small intestine has a robust regenerative capacity, and various cell types serve as “cells-of-origin” in the epithelial regeneration process after injury. However, how much each population contributes to regeneration remains unclear. Using lineage tracing, we found that Lgr5-expressing cell derivatives contained radioresistant intestinal stem cells (ISCs) crucial for epithelial regeneration in the damaged intestine after irradiation. Single-cell qRT-PCR analysis showed that surviving Lgr5-expressing cell derivatives in the damaged intestine are remarkably heterogeneous, and that the expression levels of a YAP-target gene Sca1 were inversely correlated with their “stemness”, suggesting that the YAP/Wnt signal balance in surviving crypt epithelial cells determines the cellular contribution to epithelial regeneration. Single-cell RNA sequencing of Sca1–Lgr5-derivatives revealed that expression of a tetraspanin family member CD81 correlated well with the expression of ISC- and proliferation-related genes. Consistent with these findings, organoid-forming ability was confined to the CD81hiSca1– fraction within the damaged crypt epithelial cells. Characterization of radioresistant epithelial stem cell heterogeneity in the damaged intestine may contribute to therapeutic strategies for gastrointestinal diseases.

Small cell carcinoma in the oral and maxillofacial region is an extremely rare, high-grade malignancy. We report a case of small cell carcinoma in the palatal mucosa. An 80-year-old man was referred to our clinic with swelling in the right maxilla. An 80-mm lymph node was seen in the right neck. The clinical diagnosis was malignant tumor of the palatal mucosa and biopsy was performed. The histopathological diagnosis was small cell carcinoma. Systemic examination diagnosed cervical lymph node metastasis, liver metastasis and multiple bone metastases. Considering the clinical stage and performance status, best supportive care was selected. The patient died of multiple-organ failure 3 months after the first visit.

We report a very rare case of systemic amyloidosis occurring in bilateral mandibular condyles and showing condylar bone destruction and lesions in the buccal mucosa bilaterally. The patient was a 61-year-old man complaining of malocclusion in which the lower teeth extended abnormally over the upper teeth. He first noticed this about 1 year earlier. Medical history included renal cancer, rheumatic myalgia in multiple joints, osteoporosis, hypothyroidism, chronic hepatitis, malignant lymphoma and hemodialysis for renal failure. Panoramic radiography and computed tomography showed bone destruction in bilateral mandibular condyles and a soft tissue mass lesion around the condyle. Slightly raised mass lesions with areas of whitish and purplish coloration were also observed on the buccal mucosa bilaterally. Histopathological examination revealed amyloid deposition in these lesions, and AA and/or Aβ2M amyloidosis was diagnosed. However, we were informed that the patient died within 3 months from when he had a last check-up at our clinic due to systemic problems.

We report a case of oral ulceration during the treatment of type-2 diabetes mellitus with a dipeptidyl peptidase (DPP)-4 inhibitor, sitagliptin. The patient was a 77-year-old woman with oral ulceration of the left lower labial mucosa. The ulcer showed a flat, clean surface with no bleeding. Ulcer margins were slightly raised and showed no induration. Topical steroid proved ineffective and the ulcer was surgically resected, but soon recurred. After cessation of sitagliptin, the lesion epithelialized within 3 weeks. This report is the first report of oral ulceration induced by DPP-4 inhibitor.