Fetal adrenal capsular cells serve as progenitor cells for steroidogenic and stromal adrenocortical cell lineages in M. musculus.

The lineage relationships of fetal adrenal cells and adrenal capsular cells to the differentiated adrenal cortex are not fully understood. Existing data support a role for each cell type as a progenitor for cells of the adult cortex. This report reveals that subsets of capsular cells are descendants of fetal adrenocortical cells that once expressed Nr5a1. These fetal adrenocortical cell descendants within the adrenal capsule express Gli1, a known marker of progenitors of steroidogenic adrenal cells. The capsule is also populated by cells that express Tcf21, a known inhibitor of Nr5a1 gene expression. We demonstrate that Tcf21-expressing cells give rise to Nr5a1-expressing cells but only before capsular formation. After the capsule has formed, capsular Tcf21-expressing cells give rise only to non-steroidogenic stromal adrenocortical cells, which also express collagen 1a1, desmin and platelet-derived growth factor (alpha polypeptide) but not Nr5a1. These observations integrate prior observations that define two separate origins of adult adrenocortical steroidogenic cells (fetal adrenal cortex and/or the adrenal capsule). Thus, these observations predict a unique temporal and/or spatial role of adult cortical cells that arise directly from either fetal cortical cells or from fetal cortex-derived capsular cells. Last, the data uncover the mechanism by which two populations of fetal cells (fetal cortex derived Gli1-expressing cells and mesenchymal Tcf21-expressing mesenchymal cells) participate in the establishment of the homeostatic capsular progenitor cell niche of the adult cortex.

A Comparison of Skeletal Injuries Arising from Moped and Motorcycle Collisions.

Motorcycle and moped injuries remain a significant cause of motor-vehicle related morbidity and mortality. There is a paucity of literature describing the skeletal injuries of moped riders and how these compare to those of motorcyclists, however. This study seeks to examine the skeletal injuries sustained in such incidents and determine if there are significant differences. Hospitalized riders injured on powered two-wheeled vehicles (PTW) between 2004 and 2007 were entered into a registry along with their presentation and clinical course. This registry was sorted by PTW type. Riders with injuries of the appendicular skeleton, bony pelvis, and spine were extracted. Injuries were categorized by bone location. Demographic data, helmet use, head injury, facial fracture, Injury Severity Score (ISS), and mortality were extracted. Overall, 406/578 motorcyclists, 197/357 moped riders, and 62/92 dirt-bike riders sustained fractures of the appendicular skeleton, pelvis and/or spine. Motorcyclists had a significantly higher ISS upon presentation and had increased first-hospital day mortality in addition to more skeletal injuries, more fractures of the upper extremity, and more fractures of the spine, pelvis, and foot. Moped riders had a significantly lower rate of helmet use and higher rate of head injuries and facial fractures. In summary, while both moped and motorcycle riders share a risk for injuries of the lower extremity, their overall pattern of injury differs. Motorcyclists appear to be at increased risk for more severe injuries and injuries of the upper extremity, spine, and pelvis, while moped riders are at increased risk for significant head and facial injury.

Cutibacterium acnes (formerly Proprionibacterium acnes) and Shoulder Surgery.

Infection is a rare but serious complication of shoulder arthroplasty. The most prevalent cause of patient infections is Cutibacterium acnes (formerly Proprionibacterium acnes), a commensal skin bacterial species. Its presentation is often non-specific and can occur long after shoulder arthroplasty, leading to delay in diagnosis. This bacterium is difficult to culture, typically taking 14 to 17 days for a positive culture and often does not exhibit abnormal results on a standard laboratory workup for infection (eg, ESR, CRP, and synovial WBC count). Male patients are at particularly high-risk due to having a greater number of sebaceous follicles than females. While it is difficult to diagnose, early diagnosis can lead to decreased morbidity, appropriate treatment, and improved clinical outcomes. Current options for treatment include antibiotics, one stage implant exchange, or two stage implant exchange, although success rates of each are not currently well described. A better understanding of the prevention, diagnosis, and treatment of C. acnes infection could lead to better patient outcomes from shoulder arthroplasty.