Pediatric Health Care Provider Perspectives on Injury Prevention Counseling in Acute and Primary Care Settings.

The objective of this study was to characterize how pediatric primary care and emergency medicine health care providers and trainees engage in injury prevention counseling and assess perceptions toward injury prevention resources. We surveyed physicians, advanced practice providers, and trainees in the Emergency Department, Primary Care Network, and Pediatric Residency Program at Children's Hospital of Philadelphia from September to November 2019. Of the 578 eligible participants, 208 (36.0%) completed the survey. When asked to rank the suitability of alternative personnel for providing counseling, 63.0% of the participants selected an injury prevention specialist as best suited. Seventy-six percent of the providers considered a tablet or mobile device used before a patient encounter to be a helpful resource. Variability existed in provider comfort, knowledge, and frequency of counseling by injury topic. Free-text responses cited time as a barrier to counseling. Opportunities exist to improve the provision of injury education through the utilization of novel resources and personnel.

Inheritance of Histones H3 and H4 during DNA Replication In Vitro.

Nucleosomes are believed to carry epigenetic information through the cell cycle, including through DNA replication. It has been known for decades that parental histones are reassembled on newly replicated chromatin, but the mechanisms underlying histone inheritance and dispersal during DNA replication are not fully understood. We monitored the fate of histones H3 or H4 from a single nucleosome through DNA replication in two in vitro systems. In the SV40 system, histones assembled on a single nucleosome positioning sequence can be inherited by their own daughter DNA but are dispersed from their original location. In Xenopus laevis extracts, histones are dynamic, and nucleosomes are repositioned independent of and prior to DNA replication. Nevertheless, a high fraction of histones H3 and H4 that are inherited through DNA replication remains near its starting location. Thus, inheritance of histone proteins and their dispersal can be mechanistically uncoupled.

Smad4 regulates growth plate matrix production and chondrocyte polarity.

Smad4 is an intracellular effector of the TGFß family that has been implicated in Myhre syndrome, a skeletal dysplasia characterized by short stature, brachydactyly and stiff joints. The TGFß pathway also plays a critical role in the development, organization and proliferation of the growth plate, although the exact mechanisms remain unclear. Skeletal phenotypes in Myhre syndrome overlap with processes regulated by the TGFß pathway, including organization and proliferation of the growth plate and polarity of the chondrocyte. We used in vitro and in vivo models of Smad4 deficiency in chondrocytes to test the hypothesis that deregulated TGFß signaling leads to aberrant extracellular matrix production and loss of chondrocyte polarity. Specifically, we evaluated growth plate chondrocyte polarity in tibiae of Col2-Cre+/-;Smad4fl/fl mice and in chondrocyte pellet cultures. In vitro and in vivo, Smad4 deficiency decreased aggrecan expression and increased MMP13 expression. Smad4 deficiency disrupted the balance of cartilage matrix synthesis and degradation, even though the sequential expression of growth plate chondrocyte markers was intact. Chondrocytes in Smad4-deficient growth plates also showed evidence of polarity defects, with impaired proliferation and ability to undergo the characteristic changes in shape, size and orientation as they differentiated from resting to hypertrophic chondrocytes. Therefore, we show that Smad4 controls chondrocyte proliferation, orientation, and hypertrophy and is important in regulating the extracellular matrix composition of the growth plate.

Smad3 binds Scleraxis and Mohawk and regulates tendon matrix organization.

TGFß plays a critical role in tendon formation and healing. While its downstream effector Smad3 has been implicated in the healing process, little is known about the role of Smad3 in normal tendon development or tenocyte gene expression. Using mice deficient in Smad3 (Smad3(-/-) ), we show that Smad3 ablation disrupts tendon architecture and has a dramatic impact on normal gene and protein expression during development as well as in mature tendon. In developing and adult tendon, loss of Smad3 results in reduced protein expression of the matrix components Collagen 1 and Tenascin-C. Additionally, when compared to wild type, tendon from adult Smad3(-/-) mice shows a down regulation of key tendon marker genes. Finally, we have established that Smad3 has the ability to physically interact with the critical transcriptional regulators Scleraxis and Mohawk. Together these results indicate a central role for Smad3 in normal tendon formation and in the maintenance of mature tendon.