Henoch-Schönlein purpura in the setting of COVID-19 infection: Two pediatrics cases and review of the literature

Henoch-Schönlein purpura (HSP) is the most common systemic vasculitis in children, often following a viral infection. Various types of rashes attributed to COVID-19 infection have been described in the literature; however, HSP has rarely been reported. We report two children with HSP associated with acute COVID-19 infection with a review of the available literature. We highlight the clinical presentation, medical management, outcome and age-related difference of reported patients. A limitation of this article is the retrospective nature, limiting full patient history and associated conditions. The findings of this review show that HSP in the setting of COVID-19 is more common in children than adults, with a male predominance, involving various body systems creating a constellation of presentations. Given that HSP can have long-term morbidity from renal disease if untreated, this review may help guide the practitioner's approach to HSP and recognition in the setting of COVID-19 infection.

Small intestinal immunopathology and GI-associated antibody formation in hereditary alpha-tryptasemia

BACKGROUND

Hereditary alpha-tryptasemia (HαT) is characterized by elevated basal serum tryptase due to increased copies of the TPSAB1 gene. Individuals with HαT frequently present with multisystem complaints, including anaphylaxis and seemingly functional gastrointestinal (GI) symptoms.

OBJECTIVE

We sought to determine the prevalence of HαT in an irritable bowel syndrome cohort and associated immunologic characteristics that may distinguish patients with HαT from patients without HαT.

METHODS

Tryptase genotyping by droplet digital PCR, flow cytometry, cytometry by time-of-flight, immunohistochemistry, and other molecular biology techniques was used.

RESULTS

HαT prevalence in a large irritable bowel syndrome cohort was 5% (N = 8/158). Immunophenotyping of HαT PBMCs (N ≥ 27) revealed increased total and class-switched memory B cells. In the small bowel, expansion of tissue mast cells with expression of CD203c, HLA-DR, and FcεRI, higher intestinal epithelial cell pyroptosis, and increased class-switched memory B cells were observed. IgG profiles in sera from individuals with HαT (N = 21) significantly differed from those in individuals with quiescent Crohn disease (N = 20) and non-HαT controls (N = 19), with increased antibodies directed against GI-associated proteins identified in individuals with HαT.

CONCLUSIONS

Increased mast cell number and intestinal epithelial cell pyroptosis in the small intestine, and class-switched memory B cells in both the gut and peripheral blood associated with IgG reactive to GI-related proteins, distinguish HαT from functional GI disease. These innate and adaptive immunologic findings identified in association with HαT are suggestive of subclinical intestinal inflammation in symptomatic individuals.

RETRACTED: Btbd7 is essential for region-specific epithelial cell dynamics and branching morphogenesis in vivo

Branching morphogenesis of developing organs requires coordinated but poorly understood changes in epithelial cell-cell adhesion and cell motility. We report that Btbd7 is a crucial regulator of branching morphogenesis in vivo. Btbd7 levels are elevated in peripheral cells of branching epithelial end buds, where it enhances cell motility and cell-cell adhesion dynamics. Genetic ablation of Btbd7 in mice disrupts branching morphogenesis of salivary gland, lung and kidney. Btbd7 knockout results in more tightly packed outer bud cells, which display stronger E-cadherin localization, reduced cell motility and decreased dynamics of transient cell separations associated with cleft formation; inner bud cells remain unaffected. Mechanistic analyses using in vitro MDCK cells to mimic outer bud cell behavior establish that Btbd7 promotes loss of E-cadherin from cell-cell adhesions with enhanced migration and transient cell separation. Btbd7 can enhance E-cadherin ubiquitination, internalization, and degradation in MDCK and peripheral bud cells for regulating cell dynamics. These studies show how a specific regulatory molecule, Btbd7, can function at a local region of developing organs to regulate dynamics of cell adhesion and motility during epithelial branching morphogenesis.

Patterned cell and matrix dynamics in branching morphogenesis

Wang et al. discuss the intricate processes required during embryogenesis for the formation of the branched architecture of organs such as the lung, kidney, and blood vessels.

Many embryonic organs undergo branching morphogenesis to maximize their functional epithelial surface area. Branching morphogenesis requires the coordinated interplay of multiple types of cells with the extracellular matrix (ECM). During branching morphogenesis, new branches form by “budding” or “clefting.” Cell migration, proliferation, rearrangement, deformation, and ECM dynamics have varied roles in driving budding versus clefting in different organs. Elongation of the newly formed branch and final maturation of the tip involve cellular mechanisms that include cell elongation, intercalation, convergent extension, proliferation, and differentiation. New methodologies such as high-resolution live imaging, tension sensors, and force-mapping techniques are providing exciting new opportunities for future research into branching morphogenesis.

ECM-modulated cellular dynamics as a driving force for tissue morphogenesis

The extracellular matrix (ECM) plays diverse regulatory roles throughout development. Coordinate interactions between cells within a tissue and the ECM result in the dynamic remodeling of ECM structure. Both chemical signals and physical forces that result from such microenvironmental remodeling regulate cell behavior that sculpts tissue structure. Here, we review recent discoveries illustrating different ways in which ECM remodeling promotes dynamic cell behavior during tissue morphogenesis. We focus first on new insights that identify localized ECM signaling as a regulator of cell migration, shape, and adhesion during branching morphogenesis. We also review mechanisms by which the ECM and basement membrane can both sculpt and stabilize epithelial tissue structure, using as examples Drosophila egg chamber development and cleft formation in epithelial organs. Finally, we end with an overview of the dynamic mechanisms by which the ECM can regulate stem cell differentiation to contribute to proper tissue morphogenesis.

A focal adhesion protein-based mechanochemical checkpoint regulates cleft progression during branching morphogenesis

Cleft formation is the initial step of branching morphogenesis in many organs. We previously demonstrated that ROCK 1 regulates a nonmuscle myosin II-dependent mechanochemical checkpoint to transition initiated clefts to progressing clefts in developing submandibular salivary glands. Here, we report that ROCK-mediated integrin activation and subsequent formation of focal adhesion complexes comprise this mechanochemical checkpoint. Inhibition of ROCK1 and nonmuscle myosin II activity decreased integrin β1 activation in the cleft region and interfered with localization and activation of focal adhesion complex proteins, such as focal adhesion kinase (FAK). Inhibition of FAK activity also prevented cleft progression, by disrupting recruitment of the focal adhesion proteins talin and vinculin and subsequent fibronectin assembly in the cleft region while decreasing ERK1/2 activation. These results demonstrate that inside-out integrin signaling leading to a localized recruitment of active FAK-containing focal adhesion protein complexes generates a mechanochemical checkpoint that facilitates progression of branching morphogenesis.

Multiscale feature analysis of salivary gland branching morphogenesis

Pattern formation in developing tissues involves dynamic spatio-temporal changes in cellular organization and subsequent evolution of functional adult structures. Branching morphogenesis is a developmental mechanism by which patterns are generated in many developing organs, which is controlled by underlying molecular pathways. Understanding the relationship between molecular signaling, cellular behavior and resulting morphological change requires quantification and categorization of the cellular behavior. In this study, tissue-level and cellular changes in developing salivary gland in response to disruption of ROCK-mediated signaling by are modeled by building cell-graphs to compute mathematical features capturing structural properties at multiple scales. These features were used to generate multiscale cell-graph signatures of untreated and ROCK signaling disrupted salivary gland organ explants. From confocal images of mouse submandibular salivary gland organ explants in which epithelial and mesenchymal nuclei were marked, a multiscale feature set capturing global structural properties, local structural properties, spectral, and morphological properties of the tissues was derived. Six feature selection algorithms and multiway modeling of the data was performed to identify distinct subsets of cell graph features that can uniquely classify and differentiate between different cell populations. Multiscale cell-graph analysis was most effective in classification of the tissue state. Cellular and tissue organization, as defined by a multiscale subset of cell-graph features, are both quantitatively distinct in epithelial and mesenchymal cell types both in the presence and absence of ROCK inhibitors. Whereas tensor analysis demonstrate that epithelial tissue was affected the most by inhibition of ROCK signaling, significant multiscale changes in mesenchymal tissue organization were identified with this analysis that were not identified in previous biological studies. We here show how to define and calculate a multiscale feature set as an effective computational approach to identify and quantify changes at multiple biological scales and to distinguish between different states in developing tissues.

ROCK1-directed basement membrane positioning coordinates epithelial tissue polarity

The basement membrane is crucial for epithelial tissue organization and function. However, the mechanisms by which basement membrane is restricted to the basal periphery of epithelial tissues and the basement membrane-mediated signals that regulate coordinated tissue organization are not well defined. Here, we report that Rho kinase (ROCK) controls coordinated tissue organization by restricting basement membrane to the epithelial basal periphery in developing mouse submandibular salivary glands, and that ROCK inhibition results in accumulation of ectopic basement membrane throughout the epithelial compartment. ROCK-regulated restriction of PAR-1b (MARK2) localization in the outer basal epithelial cell layer is required for basement membrane positioning at the tissue periphery. PAR-1b is specifically required for basement membrane deposition, as inhibition of PAR-1b kinase activity prevents basement membrane deposition and disrupts overall tissue organization, and suppression of PAR-1b together with ROCK inhibition prevents interior accumulations of basement membrane. Conversely, ectopic overexpression of wild-type PAR-1b results in ectopic interior basement membrane deposition. Significantly, culture of salivary epithelial cells on exogenous basement membrane rescues epithelial organization in the presence of ROCK1 or PAR-1b inhibition, and this basement membrane-mediated rescue requires functional integrin β1 to maintain epithelial cell-cell adhesions. Taken together, these studies indicate that ROCK1/PAR-1b-dependent regulation of basement membrane placement is required for the coordination of tissue polarity and the elaboration of tissue structure in the developing submandibular salivary gland.

Nasopharyngeal dendritic cell sarcoma, not otherwise specified, in a 34-year-old man

Dendritic cell sarcoma, not otherwise specified (NOS), is an entity that is poorly defined because of its rarity and poorly understood pathogenesis. It is characterized by positive immunohistochemical staining for S-100 and CD1a, along with an absence of cytoplasmic Birbeck granules on electron microscopy. We report the case of a surgically inaccessible nasopharyngeal dendritic cell sarcoma, NOS, in a 34-year-old man. Treatment with chemotherapy along with adjuvant radiation therapy was successful in decreasing the size of the nasopharyngeal mass, and the patient remained free of any evidence of recurrence nearly 5 years after treatment.

Syndecan-1 regulates cell migration and fibronectin fibril assembly

Corneal scarring is a major cause of blindness worldwide and can result from the deposition of abnormal amounts of collagen fibers lacking the correct size and spacing required to produce a clear cornea. Collagen fiber formation requires a preformed fibronectin (FN) matrix. We demonstrate that the loss of syndecan1 (sdc1) in corneal stromal cells (CSC) impacts cell migration rates, the sizes and composition of focal and fibrillar adhesions, the activation of integrins, and the assembly of fibronectin into fibrils. Integrin and fibronectin expression are not altered on sdc1-null CSCs. Cell adhesion, spreading, and migration studies using low compared to high concentrations of FN and collagen I (CNI) or vitronectin (VN) with and without activation of integrins by manganese chloride show that the impact of sdc1 depletion on integrin activation varies depending on the integrin-mediated activity evaluated. Differences in FN fibrillogenesis and migration in sdc1-null CSCs are reversed by addition of manganese chloride but cell spreading differences remain. To determine if our findings on sdc1 were specific to the cornea, we compared the phenotypes of sdc1-null dermal fibroblasts with those of CSCs. We found that without sdc1, both cell types migrate faster; however, cell-type-specific differences in FN expression and its assembly into fibrils exist between these two cell types. Together, our data demonstrate that sdc1 functions to regulate integrin activity in multiple cell types. Loss of sdc1-mediated integrin function results in cell-type specific differences in matrix assembly. A better understanding of how different cell types regulate FN fibril formation via syndecans and integrins will lead to better treatments for scarring and fibrosis.

Identification of a mechanochemical checkpoint and negative feedback loop regulating branching morphogenesis

Cleft formation is the initial step in submandibular salivary gland (SMG) branching morphogenesis, and may result from localized actomyosin-mediated cellular contraction. Since ROCK regulates cytoskeletal contraction, we investigated the effects of ROCK inhibition on mouse SMG ex vivo organ cultures. Pharmacological inhibitors of ROCK, isoform-specific ROCK I but not ROCK II siRNAs, as well as inhibitors of myosin II activity stalled clefts at initiation. This finding implies the existence of a mechanochemical checkpoint regulating the transition of initiated clefts into progression-competent clefts. Downstream of the checkpoint, clefts are rendered competent through localized assembly of fibronectin promoted by ROCK I/myosin II. Cleft progression is primarily mediated by ROCK I/myosin II-stimulated cell proliferation with a contribution from cellular contraction. Furthermore, we demonstrate that FN assembly itself promotes epithelial proliferation and cleft progression in a ROCK-dependent manner. ROCK also stimulates a proliferation-independent negative feedback loop to prevent further cleft initiations. These results reveal that cleft initiation and progression are two physically and biochemically distinct processes.

Massive low-grade fibromyxoid sarcoma presenting as acute respiratory distress in a 12-year-old girl

Low-grade fibromyxoid sarcoma (LGFMS) is a rare soft-tissue sarcoma that usually presents in young adults as a painless, slow-growing mass. Evans first described LGFMS in 1987 as a spindle-cell sarcoma with bland histological features and paradoxically aggressive behavior. Although young adults are most frequently affected, recent reports describe pediatric cases being increasingly more common. Males and females are affected approximately equally and common locations include the deep soft tissue of the lower extremity, particularly the thigh and trunk. Primary occurrence within the chest cavity is exceedingly rare. Local recurrence and metastasis are not uncommon and present the clinician and radiologist with challenges regarding follow-up recommendations. Review of the literature reveals many cases of slowly progressive symptoms related to a mass effect. We present a healthy 12-year-old African-American girl who interestingly developed acute symptoms of shortness of breath and chest pain while playing with her brother.

Extracellular matrix dynamics in development and regenerative medicine

The extracellular matrix (ECM) regulates cell behavior by influencing cell proliferation, survival, shape, migration and differentiation. Far from being a static structure, the ECM is constantly undergoing remodeling--i.e. assembly and degradation--particularly during the normal processes of development, differentiation and wound repair. When misregulated, this can contribute to disease. ECM assembly is regulated by the 3D environment and the cellular tension that is transmitted through integrins. Degradation is controlled by complex proteolytic cascades, and misregulation of these results in ECM damage that is a common component of many diseases. Tissue engineering strives to replace damaged tissues with stem cells seeded on synthetic structures designed to mimic the ECM and thus restore the normal control of cell function. Stem cell self-renewal and differentiation is influenced by the 3D environment within the stem cell niche. For tissue-engineering strategies to be successful, the intimate dynamic relationship between cells and the ECM must be understood to ensure appropriate cell behavior.

Domestic abuse of the European rave drug prolintane

Prolintane is a sympathomimetic amine with pharmacologic properties similar to d-amphetamine. Side effects include insomnia, nervousness, and irritability. Overdoses of prolintane may cause hallucinations, psychosis, and death. The drug is commonly prescribed in Africa, Australia, and Europe but is not available in the United States. This manuscript reports the first medically documented cases of prolintane abuse in the United States. In the first, a 34-year-old male presented to the emergency department confused, agitated, and unable to follow commands. Initial drug and alcohol screens were negative, but analysis by gas chromatography-mass spectrometry (GC-MS) indicated the presence of amitriptyline, nortriptyline, nicotine, and prolintane. The second patient, a healthy 26-year-old female, presented to the emergency department after intrauterine fetal death and spontaneous delivery. GC-MS revealed the presence of multiple drugs, including cannabinoids, cocaine, nicotine, hydrocodone, and prolintane. The medical and scientific communities should be aware of the potential for prolintane abuse because it may cause symptoms similar to those of the amphetamines but is not likely to be detected by a routine urine drug screen.