Adipose-derived stem cells (ASCs) are a widely investigated type of mesenchymal stem cell with great potential for musculoskeletal regeneration. However, use of ASCs is complicated by their cellular heterogeneity, which exists at both the population and single-cell levels. This study demonstrates a live-cell assay to investigate gene expression in ASCs undergoing osteogenesis using fluorescently tagged DNA hybridization probes called molecular beacons. Three molecular beacons were designed to target mRNA sequences for alkaline phosphatase, type I collagen, and osteocalcin (ALPL, COL1A1, and BGLAP), genes characteristically expressed during osteogenesis. The percentage of cells expressing these genes in a population was monitored daily to quantify the uniformity of the differentiation process. Differentiating ASC populations were repeatedly measured in a nondestructive fashion over a 21-day period to obtain temporal gene expression data. Results showed consistent expression patterns for the investigated osteogenic genes in response to induction medium. Peak expression was observed at days 3-4 for ALPL, day 14 for COL1A1, and day 21 for BGLAP. Additionally, the differentiation response of sample populations became more uniform after 2 weeks in osteogenic induction medium, suggesting a syncing of ASCs occurs over time. These findings are consistent with previous studies of osteogenic differentiation and suggest that molecular beacons are a viable means to monitor the spatiotemporal gene expression of live, differentiating ASCs.

Adipose-derived stem cells (ASCs) are a widely investigated type of mesenchymal stem cells with great potential for musculoskeletal regeneration. However, the use of ASCs is complicated by their cellular heterogeneity, which exists at both the population and single-cell levels. This study demonstrates a live-cell assay to investigate gene expression in ASCs undergoing osteogenesis using fluorescently tagged DNA hybridization probes called molecular beacons. A molecular beacon was designed to target the mRNA sequence for alkaline phosphatase (ALPL), a gene characteristically expressed during early osteogenesis. The percentage of cells expressing this gene in a population was monitored daily to quantify the uniformity of the differentiation process. Differentiating ASC populations were repeatedly measured in a nondestructive fashion over a 10-day period to obtain temporal gene expression data. Results showed consistent expression patterns for the investigated osteogenic genes in response to induction medium. Peak signal level, indicating when the most cells expressed ALPL at once, was observed on days 3-5. The differentiation response of sample populations was generally uniform when assessed on a well-by-well basis over time. The expression of alkaline phosphatase is consistent with previous studies of osteogenic differentiation, suggesting that molecular beacons are a viable means of monitoring the spatiotemporal gene expression of live, differentiating ASCs.

Radioembolization (RE) is a selective internal radiation therapy (SIRT) delivering targeted, high-dose, intra-arterial radiation directly to the vascular supply of liver tumors. Complications can occur due to aberrant deposition or migration of radiation microspheres into nontarget locations, including normal hepatic parenchyma, lungs, pancreas, and upper gastrointestinal (UGI) tract. We report a case of gastric ulcers due to yttrium-90 (90Y) seed migration to the stomach to alert clinicians to this rare cause of gastric injury. A 57-year-old woman with stage IV breast cancer with liver and lung metastases presented to the hospital with 2 months of worsening nausea and vomiting. Two months prior, she had received SIRT with 90Y microspheres without complications. Upper GI endoscopy showed diffuse gastritis and extensive antral ulceration. Biopsies revealed black, spherical foreign bodies, consistent with 90Y microspheres, documenting radiation injury. Radiation-induced UGI ulceration is caused by direct radiation injury from beta-radiation. Delay in diagnosis may be due to the nonspecificity of symptoms and temporal delay of symptom onset from SIRT, which was 2 months in our patient. Also, complaints may be attributed erroneously to adjuvant chemotherapy or widespread metastatic disease. Clinicians must consider radiation-associated toxicity in any SIRT-treated patient developing abdominal symptoms.