An update on cutaneous melanocytic lesions

Significant advances in our understanding of melanocytic neoplasms at the genomic level have occurred in the last decade. This includes identifying initiating genomic events which correlate highly to morphology for benign intermediate and malignant melanocytic neoplasms. Among spitzoid melanocytic neoplasms, mRNA sequencing has revealed specific genomic fusions correlating to morphologic features. Additionally a number of biomarkers for intermediate and malignant grade lesions have been identified. This includes molecular studies looking for copy number aberrations or specific mutations in spitzoid neoplasms, deep penetrating nevi, and blue nevi. mRNA expression profiling has become an important test for prognostication of melanoma. In this review, we provide an overview of the molecular landscape and summarize the histomorphology of a subset of melanocytic neoplasms, including blue nevi, deep penetrating nevi, pigmented epithelioid melanocytomas, Spitz nevi, and BAPomas. We further discuss novel biomarkers for prognostication and the recent updates to melanoma staging.     

Phenotypic plasticity of mesenchymal stem cells is crucial for mesangial repair in a model of immunoglobulin light chain-associated mesangial damage

Mesangiopathies produced by glomerulopathic monoclonal immunoglobulin light chains (GLCs) acting on the glomerular mesangium produce two characteristic lesions: AL-amyloidosis (AL-Am) and light chain deposition disease (LCDD). In both cases, the pathology is centered in the mesangium, where initial and progressive damage occurs. In AL-Am the mesangial matrix is destroyed and replaced by amyloid fibrils and in LCDD, the mesangial matrix is increased and remodeled. The collagen IV rich matrix is replaced by tenascin. In both conditions, mesangial cells (MCs) become apoptotic as a direct effect of the GLCs.

MCs were incubated in-vitro with GLCs and animal kidneys were perfused ex-vivo via the renal artery with GLCs, producing expected lesions, and then mesenchymal stem cells (MSCs) were added to both platforms. Each of the two platforms provided unique information that when put together created a comprehensive evaluation of the processes involved. A “cocktail” with growth and differentiating factors was used to study its effect on mesangial repair.

MSCs displayed remarkable phenotypic plasticity during the repair process. The first role of the MSCs after migrating to the affected areas was to dispose of the amyloid fibrils (in AL-Am), the altered mesangial matrix (in LCDD) and apoptotic MCs/debris. To accomplish this task, MSCs transformed into facultative macrophages acquiring an abundance of lysosomes and endocytotic capabilities required to engage in phagocytic functions. Once the mesangial cleaning was completed, MSCs transformed into functional MCs restoring the mesangium to normal. “Cocktail” made the repair process more efficient.     

Role of metabolic changes of mucosal layer in the intestinal barrier dysfunction following trauma/hemorrhagic shock

Background

The mucosal layer plays an important role in regulating the intestinal barrier function. However, the underlying mechanisms of intestinal barrier dysfunction caused by trauma-hemorrhagic shock (THS) are still unknown.

Determination of Intimate Composition of Theranostic Polyplexes Based on (Co)Polymers of Poly(vinyl benzyl trimethylammonium chloride)

Novel hybrid nanoparticulate systems that exhibit potential to combine therapeutic, diagnostic, and sensing modalities in a single nanoparticle are investigated. They are composed of a homopolymer of poly(vinyl benzyl trimethylammonium chloride) (or its copolymer with poly[oligo(ethylene glycol) methacrylate]), DNA, and gold nanoparticles (AuNPs). Using the approach of classic dynamic and static light scattering, parameters such as molar mass, particle size, geometry and density, and intimate composition are determined, trying to establish what the theranostic polyplexes really carry. According to the analysis, the polyplex particles are composed of up to 154 DNA molecules and 1612 (co)polymer molecules at amino‐to‐phosphate groups ratio (N/P) of 0.5 and 1 DNA and up to 252 (co)polymer molecules at higher N/P ratios. The particle morphology is consistent with “hairy surface on a compact sphere” with density that is lower than the density of the familiar copolymer micelles. The introduction of AuNPs does not influence the density and structure of the carriers, which could be related to the low number fraction of polyplex particles carrying AuNPs. Additional data from transmission electron microscopy, electrophoretic light scattering, and analytical ultracentrifugation validate the morphology, structure, and molar mass of the theranostic nanoassemblies and confirm the conclusions derived from light scattering.     

Pten regulates neural crest proliferation and differentiation during mouse craniofacial development

Background: The phosphatase and tensin homolog deleted on chromosome TEN (Pten) is implicated in a broad range of developmental events and diseases. However, its role in neural crest and craniofacial development has not been well illustrated. Results: Using genetically engineered mouse models, we showed that inactivating Pten specifically in neural crest cells causes malformation of craniofacial structures. Pten conditional knockout mice exhibit perinatal lethality with overgrowth of craniofacial structures. At the cellular level, Pten deficiency increases cell proliferation rate and enhances osteoblast differentiation. Our data further revealed that inactivating Pten elevates PI3K/Akt signaling activity in neural crest derivatives, and confirmed that attenuation of PI3K/Akt activity led to decreased neural crest cell proliferation and differentiation both in vitro and in vivo. Conclusions: Our study revealed that Pten is essential for craniofacial morphogenesis in mice. Inactivating Pten in neural crest cells increases proliferation rate and promotes their differentiation toward osteoblasts. Our data further indicate that Pten acts via modulating PI3K/Akt activity during these processes. Developmental Dynamics 247:304–314, 2018. © 2017 Wiley Periodicals, Inc.     

Immunoglobulin free light chains in saliva: a potential marker for disease activity in multiple sclerosis

A new procedure was developed and applied to study immunoglobulin free light chains (FLC) in saliva of healthy subjects and patients with multiple sclerosis (MS). The procedure was based on a Western blot analysis for detection and semiquantitative evaluation of monomeric and dimeric FLCs. The FLC indices accounting for the total FLC levels and for the monomer/dimer ratios of κ and λ FLC were calculated, and the cut‐off values of the FLC indices were determined to distinguish healthy state from MS disease. The obtained FLC index values were statistically different in the saliva of three groups: active MS patients, MS patients in remission and healthy subjects groups. Our FLC monomer–dimer analysis allowed differentiation between healthy state and active MS with specificity of 100% and a sensitivity of 88·5%. The developed technique may serve as a new non‐invasive complementary tool to evaluate the disease state by differentiating active MS from remission with sensitivity of 89% and specificity of 80%.     

Variations in internal structure,composition and protein distribution between intra‐ and extra‐articular knee ligaments and tendons

Tendons and ligaments play key roles in the musculoskeletal system in both man and animals. Both tissues can undergo traumatic injury, age‐related degeneration and chronic disease, causing discomfort, pain and increased susceptibility to wider degenerative joint disease. To date, tendon and ligament ultrastructural biology is relatively under‐studied in healthy, non‐diseased tissues. This information is essential to understand the pathology of these tissues with regard to function‐related injury and to assist with the future development of tissue‐engineered tendon and ligament structures. This study investigated the morphological, compositional and extracellular matrix protein distribution differences between tendons and ligaments around the non‐diseased canine stifle joint. The morphological, structural characteristics of different regions of the periarticular tendons and ligaments (the intra‐articular anterior cruciate ligament, the extra‐articular medial collateral ligament, the positional long digital extensor tendon and energy‐storing superficial digital flexor tendons) were identified using a novel semi‐objective histological scoring analysis and by determining their biochemical composition. Protein distribution of extracellular matrix collagens, proteoglycans and elastic fibre proteins in anterior cruciate ligament and long digital extensor tendon were also determined using immunostaining techniques. The anterior cruciate ligament was found to have significant morphological differences in comparison with the other three tissues, including less compact collagen architecture, differences in cell nuclei phenotype and increased glycosaminoglycan and elastin content. Intra‐ and interobserver differences of histology scoring resulted in an average score 0.7, indicative of good agreement between observers. Statistically significant differences were also found in the extracellular matrix composition in terms of glycosaminoglycan and elastin content, being more prominent in the anterior cruciate ligament than in the other three tissues. A different distribution of several extracellular matrix proteins was also found between long digital extensor tendon and anterior cruciate ligament, with a significantly increased immunostaining of aggrecan and versican in the anterior cruciate ligament. These findings directly relate to the different functions of tendon and ligament and indicate that the intra‐articular anterior cruciate ligament is subjected to more compressive forces, reflecting an adaptive response to normal or increased loads and resulting in different extracellular matrix composition and arrangement to protect the tissue from damage.     

Development and maturation of the fibrous components of the arterial roots in the mouse heart

The arterial roots are important transitional regions of the heart, connecting the intrapericardial components of the aortic and pulmonary trunks with their ventricular outlets. They house the arterial (semilunar) valves and, in the case of the aorta, are the points of coronary arterial attachment. Moreover, because of the semilunar attachments of the valve leaflets, the arterial roots span the anatomic ventriculo‐arterial junction. By virtue of this arrangement, the interleaflet triangles, despite being fibrous, are found on the ventricular aspect of the root and located within the left ventricular cavity. Malformations and diseases of the aortic root are common and serious. Despite the mouse being the animal model of choice for studying cardiac development, few studies have examined the structure of their arterial roots. As a consequence, our understanding of their formation and maturation is incomplete. We set out to clarify the anatomical and histological features of the mouse arterial roots, particularly focusing on their walls and the points of attachment of the valve leaflets. We then sought to determine the embryonic lineage relationships between these tissues, as a forerunner to understanding how they form and mature over time. Using histological stains and immunohistochemistry, we show that the walls of the mouse arterial roots show a gradual transition, with smooth muscle cells (SMC) forming the bulk of wall at the most distal points of attachments of the valve leaflets, while being entirely fibrous at their base. Although the interleaflet triangles lie within the ventricular chambers, we show that they are histologically indistinguishable from the arterial sinus walls until the end of gestation. Differences become apparent after birth, and are only completed by postnatal day 21. Using Cre‐lox‐based lineage tracing technology to label progenitor populations, we show that the SMC and fibrous tissue within the walls of the mature arterial roots share a common origin from the second heart field (SHF) and exclude trans‐differentiation of myocardium as a source for the interleaflet triangle fibrous tissues. Moreover, we show that the attachment points of the leaflets to the walls, like the leaflets themselves, are derived from the outflow cushions, having contributions from both SHF‐derived endothelial cells and neural crest cells. Our data thus show that the arterial roots in the mouse heart are similar to the features described in the human heart. They provide a framework for understanding complex lesions and diseases affecting the aortic root.     

Opponent melanopsin and S-cone signals in the human pupillary light response

In the human, cone photoreceptors (L, M, and S) and the melanopsin-containing, intrinsically photosensitive retinal ganglion cells (ipRGCs) are active at daytime light intensities. Signals from cones are combined both additively and in opposition to create the perception of overall light and color. Similar mechanisms seem to be at work in the control of the pupil’s response to light. Uncharacterized however, is the relative contribution of melanopsin and S cones, with their overlapping, short-wavelength spectral sensitivities. We measured the response of the human pupil to the separate stimulation of the cones and melanopsin at a range of temporal frequencies under photopic conditions. The S-cone and melanopsin photoreceptor channels were found to be low-pass, in contrast to a band-pass response of the pupil to L- and M-cone signals. An examination of the phase relationships of the evoked responses revealed that melanopsin signals add with signals from L and M cones but are opposed by signals from S cones in control of the pupil. The opposition of the S cones is revealed in a seemingly paradoxical dilation of the pupil to greater S-cone photon capture. This surprising result is explained by the neurophysiological properties of ipRGCs found in animal studies.Under daylight conditions, human visual perception originates with signals generated by three classes of cone photoreceptors (the L, M, and S cones; Fig. 1A, Left) with peak sensitivities at long, middle, and short wavelengths of visible light (Fig. 1A, Center).Open in a separate windowFig. 1.Experimental design. (A, Left) L, M, and S cones and melanopsin-containing ipRGCs mediate vision at daytime light levels. (Center) Photoreceptor spectral sensitivities. (Right) Physiological measurements of ipRGCs find excitatory L and M cone inputs and inhibitory S-cone inputs (12). (B) A digital spectral integrator produces sinusoidal photoreceptor-directed modulations that pass through an artificial pupil into the pharmacologically dilated left eye. The consensual pupil response of the right eye is recorded. (C) Photoreceptor-directed modulations. Balanced changes in the spectrum of light around a background spectrum nominally isolate targeted photoreceptors.Distinct neural pathways process signals originating in cone photoreceptors for visual perception. Luminance pathways combine signals from separate classes of cones synergistically, providing a spectrally broadband indication of the overall light intensity at each location in the retinal image. Red–green and blue–yellow chromatic channels combine signals from separate classes of cones in an opponent (subtractive) fashion, providing sensitivity to the relative spectral content of light and supporting the perception of color independent of luminance (1).A parallel set of pathways contributes to the response of the pupil of the eye to light. Most familiar is a synergistic cone effect that causes the pupil to constrict in response to increased luminance. Illustrating a commonality of principles that characterize neural mechanisms for perception and pupil response, rectified signals from red–green and blue–yellow opponent channels also contribute to the pupil’s light response (2–7).Recently, it has been discovered that mammalian retinas contain an additional photoreceptor class that also operates under daylight conditions. Intrinsically photosensitive retinal ganglion cells (ipRGCs) express the photopigment melanopsin, which has a peak spectral sensitivity (480 nm) between that of S and M cones (8, 9). Among other, “non-image-forming” functions of the eye, melanopsin-containing ipRGCs contribute to a delayed and sustained constriction of the pupil (10). Studies in patients with loss of photoreceptor function (11) suggest that melanopsin may also contribute to conscious visual perception.The discovery of an additional photoreceptor class raises the fundamental question of how melanopsin signals are combined with those from the cones. Do melanopsin signals add to cones to measure overall light intensity, or do they interact in an opponent fashion, enhancing the ability to detect changes in the relative spectrum of incident light?Single-unit studies of the primate retina find that L- and M-cone signals add with those of melanopsin to produce the responses of ipRGCs but suggest that signals from S cones are inhibitory (12) (Fig. 1A, Right). Prior studies of short-wavelength light upon the human pupil response preceded the discovery of melanopsin and have offered complicated results. A transient constriction of the pupil was found to follow the offset of a short-wavelength stimulus on a long-wavelength background (2), and the results were interpreted in terms of an S-cone opponent input to the control of the pupil. However, alternation between short- and long-wavelength tritanopic metamers that yielded equivalent excitation of L and M cones was found to modulate the pupil in a manner suggesting in-phase S and L/M cone contributions to the pupillary light response (13). Critically, the interpretation of these earlier results—and particularly the relative contribution of the S cones and melanopsin to the pupil response—must be revisited given the overlapping spectral sensitivities of these two photoreceptor classes and the unknown role of melanopsin in mediating the earlier results.Here we study how melanopsin and the three classes of cones contribute to the human pupillary light response (PLR). Despite the intuition that pupil size should be responsive to the overall intensity of the incident light, our results reveal that a spectrally opponent system involving melanopsin contributes to pupil control at photopic light levels. The nature of this response reflects, qualitatively, the spectral opponency seen in ipRGCs: Signals from melanopsin combine additively with those from L and M cones and are opposed by signals from S cones.