As a result of over five decades of investigation, mesenchymal stromal/stem cells (MSCs) have emerged as a versatile and frequently utilized cell source in the fields of regenerative medicine and tissue engineering. In this review, we summarize the history of MSC research from the initial discovery of their multipotency to the more recent recognition of their perivascular identity in vivo and their extraordinary capacity for immunomodulation and angiogenic signaling. As well, we discuss long-standing questions regarding their developmental origins and their capacity for differentiation toward a range of cell lineages. We also highlight important considerations and potential risks involved with their isolation, ex vivo expansion, and clinical use. Overall, this review aims to serve as an overview of the breadth of research that has demonstrated the utility of MSCs in a wide range of clinical contexts and continues to unravel the mechanisms by which these cells exert their therapeutic effects.

This article has an accompanying continuing medical education activity, also eligible for MOC credit, on page e119. Learning Objective-Upon completion of this activity, successful learners will be able to recognize the colonoscopy quality metrics and outcomes that are associated with performance of higher annual procedural volume. BACKGROUND & AIMS:In addition to monitoring adverse events (AEs) and post-colonoscopy colorectal cancers (PCCRC), indicators for assessing colonoscopy quality include adenoma detection rate (ADR) and cecal intubation rate (CIR). It is unclear whether there is an association between annual colonoscopy volume and ADR, CIR, AEs, or PCCRC. METHODS:We searched publication databases through March 2019 for studies assessing the relationship between annual colonoscopy volume and outcomes, including ADR, CIR, AEs, or PCCRC. Pooled odds ratios (ORs) were calculated using DerSimonian and Laird random effects models. Sensitivity analyses were performed to assess for potential methodological or clinical factors associated with outcomes. RESULTS:We performed a systematic review of 9235 initial citations, generating 27 retained studies comprising 11,276,244 colonoscopies. There was no association between procedural volume and ADR (OR, 1.00; 95% CI, 0.98-1.02 per additional 100 annual procedures). CIR improved with each additional 100 annual procedures (OR, 1.17; 95% CI, 1.08-1.28). There was a nonsignificant trend toward decreased overall AEs per additional 100 annual procedures (OR, 0.95; 95% CI, 0.90-1.00). There was considerable heterogeneity among most analyses. CONCLUSIONS:In a systematic review and meta-analysis, we found higher annual colonoscopy volumes to correlate with higher CIR, but not with ADR or PCCRC. Trends toward fewer AEs were associated with higher annual colonoscopy volumes. There are few data available from endoscopists who perform fewer than 100 annual colonoscopies. Studies are needed on extremes in performance volumes to more clearly elucidate associations between colonoscopy volumes and outcomes.

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