Endoscopic submucosal injection of umbilical cord mesenchymal stem cells for radiation-induced late rectal injury

A case description Radiation-induced late rectal injury (RLRI) is a devastating complication of pelvic radiotherapy, characterized by ulcers, mucosal erythema, telangiectasia and fibrosis,[ 1​ ] yet there is currently no standardized treatment strategy for this condition. Mesenchymal stem cells (MSCs) have shown promising safety and efficacy in the local treatment of active intestinal lesions.[ 2​ ] [ ​3​ ] We report a case of RLRI treated with endoscopic submucosal injection of umbilical cord-derived mesenchymal stem cells (UC-MSCs; [ Video 1 ]). A 65-year-old female patient with cervical cancer presented with recurrent hematochezia and rectal pain 6 months after completing concurrent chemoradiotherapy. In December 2023, colonoscopy performed at an outside hospital led to a diagnosis of RLRI. Despite conventional treatments including oral and enema mesalazine, oral hemostatic agents and symptomatic analgesia, her symptoms progressively worsened. In June 2024, the patient was admitted to our hospital. Endoscopic examination revealed a large deep rectal ulcer measuring approximately 5×5 cm ([ Fig. 1 ]). The total dose of UC-MSCs for injection was 3×10⁷ cells, with a total volume of 6 mL. Under colonoscopy guidance, the cell suspension was injected submucosally at four points evenly distributed around the ulcer margin. Normal saline was first injected to elevate the submucosa to confirm the proper needle placement before each MSC injection, with 1.5 mL of cell suspension administered per site ([ Fig. 2 ]). No adverse events occurred during treatment and 1-year follow-up. The patient’s hematochezia and pain symptoms resolved completely. Endoscopic examination showed complete ulcer healing with scar formation at 1 year. The LENT–SOMA score decreased from 1.64 to 0.07, and Vienna Rectosigmoidoscopic Score (VRS) and Rectal Telangiectasia Density Score (RTD) also improved significantly ([ Fig. 3 ]). Imaging and histopathological findings confirmed a marked reduction of local inflammation and edema ( Figs. [ 4 ] and [ 5 ]). Endoscopic local injection of UC-MSCs is a safe and effective novel therapy for refractory RLRI, which can promote mucosal healing and prevent severe complications. Video 1 Demonstrates the endoscopic UC-MSC injection technique: submucosal saline elevation to confirm needle placement, followed by slow, evenly distributed four-point injection around the ulcer margin. Download Video Fig. 1 Endoscopic findings before and after treatment. ( a ) Before treatment: A large deep rectal ulcer with yellow exudate, surrounding mucosal erythema and scattered telangiectasias. ( b ) 2 months after treatment: Reduced ulcer size and thinner exudate. ( c ) Four months after treatment: Further reduction in ulcer size and improvement in surrounding telangiectasias. ( d ) One year after treatment: Complete ulcer healing with scar formation. Fig. 2 Endoscopic injection procedure. ( a ) The UC-MSC product vial containing 3×10⁷ viable cells in 6 mL. ( b and c ) Submucosal elevation with normal saline to confirm needle placement prior to MSC injection. Fig. 3 Disease severity scores. LENT–SOMA Score, which integrates both objective and subjective symptoms, decreased from 1.64 at baseline to 0.07 at 1 year. VRS and RTD scores, which reflect endoscopic severity, also showed significant improvement. Fig. 4 Pelvic MRI findings before and after treatment. ( a and b ) Sagittal T2-weighted images; ( c and d ) coronal fat-suppressed images; ( e and f ) axial images. All sequences show significant improvement in rectal and sigmoid wall edema after treatment. Fig. 5 Histopathological findings (HE staining,×200 magnification). ( a ) Biopsy from the margin of the deep ulcer before treatment showing dense inflammatory cell infiltration from the mucosal layer to the lamina propria. ( b ) Biopsy from the same site 1 year after treatment showing markedly reduced inflammatory cell infiltration. Endoscopy_UCTN_Code_TTT_1AQ_2AG Publication History Received: 24 April 2026 Accepted after revision: 25 May 2026 Article published online: 11 August 2026 © 2026. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/). Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany