Demetri J. Merianos

Platelets regulate lymphatic vascular development through CLEC-2–SLP-76 signaling

Although platelets appear by embryonic day 10.5 in the developing mouse, an embryonic role for these cells has not been identified. The SYK-SLP-76 signaling pathway is required in blood cells to regulate embryonic blood-lymphatic vascular separation, but the cell type and molecular mechanism underlying this regulatory pathway are not known. In the present study we demonstrate that platelets regulate lymphatic vascular development by directly interacting with lymphatic endothelial cells through C-type lectin-like receptor 2 (CLEC-2) receptors. PODOPLANIN (PDPN), a transmembrane protein expressed on the surface of lymphatic endothelial cells, is required in nonhematopoietic cells for blood-lymphatic separation. Genetic loss of the PDPN receptor CLEC-2 ablates PDPN binding by platelets and confers embryonic lymphatic vascular defects like those seen in animals lacking PDPN or SLP-76. Platelet factor 4-Cre-mediated deletion of Slp-76 is sufficient to confer lymphatic vascular defects, identifying platelets as the cell type in which SLP-76 signaling is required to regulate lymphatic vascular development. Consistent with these genetic findings, we observe SLP-76-dependent platelet aggregate formation on the surface of lymphatic endothelial cells in vivo and ex vivo. These studies identify a nonhemostatic pathway in which platelet CLEC-2 receptors bind lymphatic endothelial PDPN and activate SLP-76 signaling to regulate embryonic vascular development.

Maternal alloantibodies induce a postnatal immune response that limits engraftment following in utero hematopoietic cell transplantation in mice

The lack of fetal immune responses to foreign antigens, i.e., fetal immunologic tolerance, is the most compelling rationale for prenatal stem cell and gene therapy. However, the frequency of engraftment following in utero hematopoietic cell transplantation (IUHCT) in the murine model is reduced in allogeneic, compared with congenic, recipients. This observation supports the existence of an immune barrier to fetal transplantation and challenges the classic assumptions of fetal tolerance. Here, we present evidence that supports the presence of an adaptive immune response in murine recipients of IUHCT that failed to maintain engraftment. However, when IUHCT recipients were fostered by surrogate mothers, they all maintained long-term chimerism. Furthermore, we have demonstrated that the cells responsible for rejection of the graft were recipient in origin. Our observations suggest a mechanism by which IUHCT-dependent sensitization of the maternal immune system and the subsequent transmission of maternal alloantibodies to pups through breast milk induces a postnatal adaptive immune response in the recipient, which, in turn, results in the ablation of engraftment after IUHCT. Finally, we showed that non-fostered pups that maintained their chimerism had higher levels of Tregs as well as a more suppressive Treg phenotype than their non-chimeric, non-fostered siblings. This study resolves the apparent contradiction of induction of an adaptive immune response in the pre-immune fetus and confirms the potential of actively acquired tolerance to facilitate prenatal therapeutic applications.

In Utero Hematopoietic Stem Cell Transplantation: Progress toward Clinical Application

In utero hematopoietic stem cell transplantation (IUHCT) is a potential therapeutic alternative to postnatal hematopoietic stem cell transplantation (HSCT) for congenital hematologic disorders that can be diagnosed early in gestation and can be cured by HSCT. The rationale is to take advantage of normal events during hematopoietic and immunologic ontogeny to facilitate allogeneic hematopoietic engraftment. Although the rationale remains compelling, IUHCT has not yet achieved its clinical potential. Achieving therapeutic levels of engraftment by IUHCT alone remains challenging. However, considerable experimental progress has been made toward the clinical strategy of using IUHCT to induce donor-specific tolerance to facilitate a relatively nontoxic postnatal HSCT. Because donor specific tolerance induction requires relatively minimal engraftment, this strategy may hold the key to broad clinical application of IUHCT in the near future.

Smartphones, trainees, and mobile education: implications for graduate medical education.

Smartphones are one of the fastest-growing sectors in the technology industry, and they continue to evolve to combine faster processors, better memory, and more efficient operating systems into a compact handheld device. Smartphones also offer a dynamic tool for use in personal and professional environments.1 The role of smartphones in medicine continues to expand as additional uses and applications emerge. An estimated 80% of physicians, trainees, and medical students use smartphones, and this percentage is expected to increase.2–,4 Smartphones provide a multifaceted platform for mobile health care, allowing users to access a vast amount of information and interact with resources conveniently and quickly.5 Applications range from patient monitoring to use as a tool for diagnosis, to communication and medical education. Recent advances in smartphone technology have led many educators to extend their teaching methods into the mobile learning environment, providing an “anytime, anywhere” approach to learning. Mobile learning has been shown to have efficacy within the traditional classroom environment, and brief communications via short message service (SMS) supplement interactive classroom sessions, resulting in enhanced interest in and attention to classroom activity.6 Given the nature of graduate medical education (GME), where trainees are expected to assimilate a vast amount of information that is constantly evolving, and often are away from traditional classroom settings, the benefits of mobile learning with its uninterrupted access to educational resources can be particularly advantageous. In this perspective, we characterize the current and potential uses of smartphone technology in GME and provide recommendations for future studies on incorporating smartphone technology as an educational platform.

Developmental stage determines efficiency of gene transfer to muscle satellite cells by in utero delivery of adeno-associated virus vector serotype 2/9

Efficient gene transfer to muscle stem cells (satellite cells) has not been achieved despite broad transduction of skeletal muscle by systemically administered adeno-associated virus serotype 2/9 (AAV-9) in mice. We hypothesized that cellular migration during fetal development would make satellite cells accessible for gene transfer following in utero intravascular injection. We injected AAV-9 encoding green fluorescent protein (GFP) marker gene into the vascular space of mice ranging in ages from post-coital day 12 (E12) to postnatal day 1 (P1). Satellite cell transduction was examined using: immunohistochemistry and confocal microscopy, satellite cell migration assay, myofiber isolation and FACS analysis. GFP positive myofibers were detected in all mature skeletal muscle groups and up to 100% of the myofibers were transduced. We saw gestational variation in cardiac and skeletal muscle expression. E16 injection resulted in 27.7 ± 10.0% expression in satellite cells, which coincides with the timing of satellite cell migration, and poor satellite cell expression before and after satellite cell migration (E12 and P1). Our results demonstrate that efficient gene expression is achieved in differentiated myofibers and satellite cells after injection of AAV-9 in utero. These findings support the potential of prenatal gene transfer for muscle based treatment strategies.

MALT Lymphoma of the Gastric Remnant After Roux-en-Y Gastric Bypass

Surgery for morbid obesity is becoming increasingly popular in the industrial world [1]. It has created a subgroup of individuals in which gastric malignancies may be overlooked. Initial symptoms of this patient may be attributed to the surgery, leading to the advance presentations despite prolonged history of symptoms. Tumors growing in the excluded gastric remnant provide further challenges to clinician in diagnosis and follow up. We present one such case of an extranodal marginal zone B-cell lymphoma (MALToma) growing in the gastric remnant.

A case of congenital pyloric atresia with dystrophic epidermolysis bullosa

Pyloric atresia with epidermolysis bullosa (EB) dystrophica is a rare entity that may not be immediately recognized. We describe the fourth confirmed case of pyloric atresia associated with the dystrophic subtype of EB diagnosed by standard pathologic measures, and discuss the clinical disease features and recent advances in the pathophysiology.