Intestinal brush border assembly driven by protocadherin-based intermicrovillar adhesion.

Transporting epithelial cells build apical microvilli to increase membrane surface area and enhance absorptive capacity. The intestinal brush border provides an elaborate example with tightly packed microvilli that function in nutrient absorption and host defense. Although the brush border is essential for physiological homeostasis, its assembly is poorly understood. We found that brush border assembly is driven by the formation of Ca(2+)-dependent adhesion links between adjacent microvilli. Intermicrovillar links are composed of protocadherin-24 and mucin-like protocadherin, which target to microvillar tips and interact to form a trans-heterophilic complex. The cytoplasmic domains of microvillar protocadherins interact with the scaffolding protein, harmonin, and myosin-7b, which promote localization to microvillar tips. Finally, a mouse model of Usher syndrome lacking harmonin exhibits microvillar protocadherin mislocalization and severe defects in brush border morphology. These data reveal an adhesion-based mechanism for brush border assembly and illuminate the basis of intestinal pathology in patients with Usher syndrome. PAPERFLICK:

An alternative N-terminal fold of the intestine-specific annexin A13a induces dimerization and regulates membrane-binding.

Annexin proteins function as Ca2+-dependent regulators of membrane trafficking and repair that may also modulate membrane curvature. Here, using high-resolution confocal imaging, we report that the intestine-specific annexin A13 (ANX A13) localizes to the tips of intestinal microvilli and determined the crystal structure of the ANX A13a isoform to 2.6 Å resolution. The structure revealed that the N terminus exhibits an alternative fold that converts the first two helices and the associated helix-loop-helix motif into a continuous α-helix, as stabilized by a domain-swapped dimer. We also found that the dimer is present in solution and partially occludes the membrane-binding surfaces of annexin, suggesting that dimerization may function as a means for regulating membrane binding. Accordingly, as revealed by in vitro binding and cellular localization assays, ANX A13a variants that favor a monomeric state exhibited increased membrane association relative to variants that favor the dimeric form. Together, our findings support a mechanism for how the association of the ANX A13a isoform with the membrane is regulated.

An Analysis of Independent Variables Affecting Surgical Outcomes in Patients Undergoing Repair of Maxillofacial Trauma: An American College of Surgeons National Surgical Quality Improvement Program Study.

INTRODUCTION: Facial fractures, from straightforward closed nasal reductions to complex pan facial fractures, are commonly encountered in the Plastic Surgical community. However, very little has been discussed in the literature regarding the outcomes of facial fractures relating to contributing factors. Our aim was to evaluate a battery of independent variables in order to identify, which, if any, factors correlate with suboptimal outcomes in patients who have undergone facial fracture surgery. METHODS: Under the data use agreement of the American College of Surgeons public use files of the NSQIP, patients involving repair of facial fractures, Current Procedural Terminology codes 21310 to 21470 inclusive, were queried. The outcomes examined included: wound dehiscence, superficial surgical site infection, deep surgical site infection, readmission, open wound/wound infection and return to the operating room. RESULTS: There were 2069 facial fracture patients in the National Surgical Quality Improvement Program datasets (2005-2013). Thirteen perioperative risk factors and patient comorbidities were evaluated for correlation with the 6 outcomes. Of the 6 outcomes evaluated, open wound/wound infection was the most prevalent outcome (6%). Factors statistically significant for presence of open wound/wound infection were American Society of Anesthesiology classification (P = 0.002), presence of bleeding disorder (P = 0.008), emergency patient (P = 0.001), chronic alcohol use (P = 0.002), and chronic steroid use (P = 0.034). DISCUSSION: Several factors correlated with presence of an open wound/wound infection; however, variables such as diabetes and active tobacco use, which are often thought to contribute to wound infections, were shown to be statistically nonsignificant. Although this study was limited by its observational nature, these data may indicate a change in perception of the factors correlated with wound infections.

Successful treatment of Parry-Romberg syndrome with autologous fat grafting: 14-year follow-up and review.

Parry first described the syndrome of progressive facial atrophy in 1825, followed by Romberg in 1846. The clinical hallmark of the syndrome is atrophy of the facial soft tissues, including fat and muscle as well as underlying bone. Clinicians have classically reserved treatment until the end of the disease process, after the "burn out" stage. Various treatment modalities have been attempted with differing results. In this study, we present a case of Parry-Romberg syndrome treated with autologous fat grafting. This case report reviews the history of the disease, examines the safety and clinical outcomes of fat grafting as a treatment modality, and challenges the classic timing of that treatment. Additionally, long-term follow-up with photos and histological analysis of specimens are included.

Squamous cell carcinoma of the scrotum in a radiation technologist and the use of sentinel lymph node biopsy in recurrent disease.

Squamous cell carcinoma (SCC) of the scrotum is an uncommon neoplasm. It has been described in many different occupations and is associated with a myriad of carcinogens, yet the etiology still remains a mystery. This is the first report of its occurrence in a radiation technologist. Additionally, the use of sentinel lymph node biopsy in SCC has been advocated as a safe method of limiting the morbidity associated with bilateral ilioinguinal dissections. This is the first report of its use in recurrent metastatic SCC of the scrotum.

Aesthetic Female-to-Male Chest Transformation: Power of Combining Modified Mastectomy with a Pectoral Implant.

Gender reassignment surgery has gained in popularity with increased media exposure and society's recognition of gender dysphoria. Female-to-male gender reassignment often begins with the "top" or chest surgery. Mastectomy with free nipple grafting is the most frequently described technique in the literature. This technique is reliable yet lacks the ability to provide a true male chest shape. We discuss our technique for female-to-male "top" surgery combining traditional mastectomy techniques with a lower pole pedicle vascularized areola and a pectoral implant. A 32-year-old African American female with bilateral C cup breast with grade 2/3 ptosis presented for "top" surgery. Intraoperatively, the nipple areola complex was maintained on a lower pole pedicle at a thickness of 1.5 cm to maintain neurovascularity. A superior mastectomy flap was raised at the level of the breast capsule and remaining breast tissue excised. A lateral subpectoral pocket was created for insertion of a silicone pectoral implant. The new nipple position matured in the infero-lateral quadrant of greatest projecting portion of the chest. Lower pole pedicle provided vascularity to the areola, which avoids the need for a free nipple graft and potential hypopigmentation. Pectoral silicone implant provided upper pole fullness to mimic the male chest muscular distribution. Modification of mastectomy-based female-to-male gender reassignment surgery with a lower pole pedicle-based areola and pectoral implant provides an aesthetic improvement over the classic mastectomy with free nipple graft technique.

ANKS4B Is Essential for Intermicrovillar Adhesion Complex Formation.

Transporting and sensory epithelial cells shape apical specializations using protocadherin-based adhesion. In the enterocyte brush border, protocadherin function requires a complex of cytoplasmic binding partners, although the composition of this complex and logic governing its assembly remain poorly understood. We found that ankyrin repeat and sterile α motif domain containing 4B (ANKS4B) localizes to the tips of adherent brush border microvilli and is essential for intermicrovillar adhesion. ANKS4B interacts with USH1C and MYO7B, which link protocadherins to the actin cytoskeleton. ANKS4B and USH1C also bind to the MYO7B cargo-binding tail at distinct sites. However, a tripartite complex only forms if ANKS4B and MYO7B are first activated by USH1C. This study uncovers an essential role for ANKS4B in brush border assembly, reveals a hierarchy in the molecular interactions that drive intermicrovillar adhesion, and informs our understanding of diseases caused by mutations in USH1C and ankyrin repeat proteins, such as Usher syndrome.

Dynamics of brush border remodeling induced by enteropathogenic E. coli.

Enteropathogenic Escherichia coli (EPEC) induces dramatic remodeling of enterocyte brush borders, a process that includes microvillar effacement and actin pedestal formation. Although the Arp2/3 complex is involved in formation of a branched actin network within pedestals, the fate of parallel actin bundles in microvilli during infection remains unclear. Here, we find that in polarized intestinal epithelial cells, EPEC stimulates long-range microvillar dynamics, pulling protrusions toward sites of bacterial attachment in a process mediated by the adhesion molecule protocadherin-24. Additionally, retraction of the EPEC bundle forming pilus stimulates directed elongation of nearby microvilli. These processes lead to coalescence of microvilli and incorporation of the underlying parallel actin bundles into pedestals. Furthermore, stabilization of microvillar actin bundles delays pedestal formation. Together, these results suggest a model where EPEC takes advantage of pre-existing actin filaments in microvillar core bundles to facilitate pedestal formation.

Breast implant-associated anaplastic large-cell lymphoma: long-term follow-up of 60 patients.

PURPOSE: Breast implant-associated anaplastic large-cell lymphoma (ALCL) is a recently described clinicopathologic entity that usually presents as an effusion-associated fibrous capsule surrounding an implant. Less frequently, it presents as a mass. The natural history of this disease and long-term outcomes are unknown. PATIENTS AND METHODS: We reviewed the literature for all published cases of breast implant-associated ALCL from 1997 to December 2012 and contacted corresponding authors to update clinical follow-up. RESULTS: The median overall survival (OS) for 60 patients was 12 years (median follow-up, 2 years; range, 0-14 years). Capsulectomy and implant removal was performed on 56 of 60 patients (93%). Therapeutic data were available for 55 patients: 39 patients (78%) received systemic chemotherapy, and of the 16 patients (28%) who did not receive chemotherapy, 12 patients opted for watchful waiting and four patients received radiation therapy alone. Thirty-nine (93%) of 42 patients with disease confined by the fibrous capsule achieved complete remission, compared with complete remission in 13 (72%) of 18 patients with a tumor mass. Patients with a breast mass had worse OS and progression-free survival (PFS; P = .052 and P = .03, respectively). The OS or PFS were similar between patients who received and did not receive chemotherapy (P = .44 and P = .28, respectively). CONCLUSION: Most patients with breast implant-associated ALCL who had disease confined within the fibrous capsule achieved complete remission. Proper management for these patients may be limited to capsulectomy and implant removal. Patients who present with a mass have a more aggressive clinical course that may be fatal, justifying cytotoxic chemotherapy in addition to removal of implants.

Extracellular vesicles: communication, coercion, and conditioning.

Cells communicate with neighboring cells and condition their local environment by secreting soluble factors into the extracellular space. These well-studied facets of cell biology are essential for the establishment and maintenance of physiological homeostasis. However, accumulating evidence has revealed that specific ligands, enzymes, and macromolecules are distributed into the extracellular space by virtue of their association with small vesicles, which are released by a variety of cell types. Although the biological significance of such vesicles was initially debated, purification and subsequent functional studies have shown that these extracellular vesicles are bioactive organelles carrying a wide range of protein and nucleic acid cargoes. In many cases these vesicles are laden with molecules that are involved in cell signaling, although other diverse functions are being revealed at a rapid pace. In this Perspective, we discuss recent developments in the understanding of the major pathways of extracellular vesicle biogenesis and how these vesicles contribute to the maintenance of physiological homeostasis.

Ready aim fire into the lumen: a new role for enterocyte microvilli in gut host defense.

Recent studies from our laboratory revealed that enterocyte brush border microvilli release small vesicles laden with host defense machinery into the intestinal lumen. In this addendum, we introduce a multi-faceted model for the function of these lumenal vesicles in the gut; we also consider some of the important unanswered questions that must be addressed in order to develop our understanding of this novel aspect of innate intestinal immunity.

Enterocyte microvillus-derived vesicles detoxify bacterial products and regulate epithelial-microbial interactions.

The continuous monolayer of intestinal epithelial cells (IECs) lining the gut lumen functions as the site of nutrient absorption and as a physical barrier to prevent the translocation of microbes and associated toxic compounds into the peripheral vasculature. IECs also express host defense proteins such as intestinal alkaline phosphatase (IAP), which detoxify bacterial products and prevent intestinal inflammation. Our laboratory recently showed that IAP is enriched on vesicles that are released from the tips of IEC microvilli and accumulate in the intestinal lumen. Here, we show that these native "lumenal vesicles" (LVs) (1) contain catalytically active IAP that can dephosphorylate lipopolysaccharide (LPS), (2) cluster on the surface of native lumenal bacteria, (3) prevent the adherence of enteropathogenic E. coli (EPEC) to epithelial monolayers, and (4) limit bacterial population growth. We also find that IECs upregulate LV production in response to EPEC and other Gram-negative pathogens. Together, these results suggest that microvillar vesicle shedding represents a novel mechanism for distributing host defense machinery into the intestinal lumen and that microvillus-derived LVs modulate epithelial-microbial interactions.

The enterocyte microvillus is a vesicle-generating organelle.

For decades, enterocyte brush border microvilli have been viewed as passive cytoskeletal scaffolds that serve to increase apical membrane surface area. However, recent studies revealed that in the in vitro context of isolated brush borders, myosin-1a (myo1a) powers the sliding of microvillar membrane along core actin bundles. This activity also leads to the shedding of small vesicles from microvillar tips, suggesting that microvilli may function as vesicle-generating organelles in vivo. In this study, we present data in support of this hypothesis, showing that enterocyte microvilli release unilamellar vesicles into the intestinal lumen; these vesicles retain the right side out orientation of microvillar membrane, contain catalytically active brush border enzymes, and are specifically enriched in intestinal alkaline phosphatase. Moreover, myo1a knockout mice demonstrate striking perturbations in vesicle production, clearly implicating this motor in the in vivo regulation of this novel activity. In combination, these data show that microvilli function as vesicle-generating organelles, which enable enterocytes to deploy catalytic activities into the intestinal lumen.

Sternal salvage with rigid fixation in the setting of a massive mediastinal aortic pseudoaneurysm: a case report and review of the literature.

Reconstruction of sternal nonunion following surgical resection can be difficult. Presented here is a case of sternal salvage with rigid fixation in the face of a massive aortic pseudoaneurysm. Plating is a safe and efficient technique that provides bone approximation and results in long term rigid sternal fixation. This case report highlights the history and biomechanical theory and examines the safety and clinical outcomes of sternal reconstruction with plating fixation.