Developing an effective treatment for pulmonary emphysema will require a better understanding of the molecular changes responsible for distention and rupture of alveolar walls. A potentially useful approach to studying this process involves the concept of emergence in which interactions at different levels of scale induce a phase transition comprising a spontaneous reorganization of chemical and physical systems. Recent studies in our laboratory provide evidence of this phenomenon in pulmonary emphysema by relating the emergence of airspace enlargement to the release of elastin-specific desmosine and isodesmosine (DID) crosslinks from damaged elastic fibers. When the mean alveolar diameter exceeded 400 μm, the level of peptide-free DID in human lungs was greatly increased, reflecting rapid acceleration of elastin breakdown, alveolar wall rupture, and a phase transition to an active disease state that is less responsive to treatment. Based on this finding, it is hypothesized that free DID in urine and other body fluids may serve as a biomarker for early detection of airspace enlargement, thereby facilitating timely therapeutic intervention and reducing the risk of respiratory failure.

Preterm infants with oxygen supplementation are at high risk for bronchopulmonary dysplasia (BPD), a neonatal chronic lung disease. Inflammation with macrophage activation is central to the pathogenesis of BPD. CXCL10, a chemotactic and pro-inflammatory chemokine, is elevated in the lungs of infants evolving BPD and in hyperoxia-based BPD in mice. Here, we tested if CXCL10 deficiency preserves lung growth after neonatal hyperoxia by preventing macrophage activation. To this end, we exposed Cxcl10 knockout (Cxcl10-/-) and wild-type mice to an experimental model of hyperoxia (85% O2)-induced neonatal lung injury and subsequent regeneration. In addition, cultured primary human macrophages and murine macrophages (J744A.1) were treated with CXCL10 and/or CXCR3 antagonist. Our transcriptomic analysis identified CXCL10 as a central hub in the inflammatory network of neonatal mouse lungs after hyperoxia. Quantitative histomorphometric analysis revealed that Cxcl10-/- mice are in part protected from reduced alveolar. These findings were related to the preserved spatial distribution of elastic fibers, reduced collagen deposition, and protection from macrophage recruitment/infiltration to the lungs in Cxcl10-/- mice during acute injury and regeneration. Complimentary, studies with cultured human and murine macrophages showed that hyperoxia induces Cxcl10 expression that in turn triggers M1-like activation and migration of macrophages through CXCR3. Finally, we demonstrated a temporal increase of macrophage-related CXCL10 in the lungs of infants with BPD. In conclusion, our data demonstrate macrophage-derived CXCL10 in experimental and clinical BPD that drives macrophage chemotaxis through CXCR3, causing pro-fibrotic lung remodeling and arrest of alveolarization. Thus, targeting the CXCL10-CXCR3 axis could offer a new therapeutic avenue for BPD.

BACKGROUND: Granuloma annulare (GA) has diverse clinical manifestations, multiple subtypes, and unknown etiology and pathogenesis. Existing studies regarding GA in children are scarce.
OBJECTIVE: To examine the correlation between clinical manifestation and histopathology of pediatric GA.
METHODS: A total of 39 patients under 18 years of age with both a clinical and pathological diagnosis of GA at Kunming Children\'s Hospital from 2017 to 2022 were retrieved. Their medical records were consulted, and clinical data of the children were recorded and summarized, including gender, age, disease site, etc. Existing wax blocks of skin lesion specimens of children and pathological films were retrieved for further study and relevant histology, including hematoxylin-eosin, Alcian blue, elastic fiber (Victoria blue-Lichon red method), and antacid staining. Finally, the children\'s clinical manifestations, histopathological results, and special staining characteristics were analyzed.
RESULTS: The clinical manifestations of granuloma annulare in children were diverse: 11 cases presented with a single lesion, 25 with multiple lesions, and 3 with generalized lesions. The pathological typing comprised histiocytic infiltration, palisading granuloma, epithelioid nodular, and mixed types in 4, 11, 9, and 15 cases, respectively. Thirty-nine cases were negative for antacid staining. The positive rate of Alcian blue staining was 92.3%, and that of elastic fiber staining was 100%. The degree of elastic fiber dissolution and granuloma annulare histopathological typing were positively correlated (r = 0.432, P < 0.05). No correlation was found between clinical presentation and histopathological typing of the granuloma annulare in children. In the pathological diagnosis of granuloma annulare, the positive elastic fiber staining rate was higher than that of Alcian blue staining. A correlation was found between elastic fiber dissolution degree and histopathological staging. However, the differences in pathological staging may have been related to the pathological manifestation of granuloma annulare at different periods.
CONCLUSIONS: Elastic fiber degradation may be a critical step in the pathogenesis of pediatric granuloma annulare. This is also one of the first studies focused on granuloma annulare in children.

OBJECTIVE: To define the localization and configuration of the elastic fibers of the cricoarytenoid ligament (CAL) and their relationship with the cricoarytenoid joint (CAJ) capsule.
METHODS: Twenty-four CAJs from twelve cadavers were analyzed using Verhoeff-Van Gieson staining, and immunohistochemistry methods. This is a prospective study.
RESULTS: The CAL was classified into two parts: an extra-capsular anterior-CAL and an intra-capsular posterior-CAL. The both parts contained rich elastic fibers. The elastic fibers of the anterior-CAL were orientated in both anterior-posterior and superior-inferior directions and under a relaxation status, whereas the elastic fibers of the posterior-CAL were arranged in a lateral-medial direction and under a taut status.
CONCLUSIONS: This study defined the fine configuration of the CAL, particularly its elastic fibers, which may help us to better understand the biomechanics of the CAJ motions, and differential diagnosis of CAJ disorders. The results of the study re-confirm that the P-CAL is the key posterior-lateral passive force to limit the mobility of the muscular process of the arytenoid cartilage and stabilize the CAJ, whereas the A-CAL may protect the CAJ from an over superior-lateral-posterior motion.
METHODS: H/A.

UNASSIGNED: Laennec\'s capsule is a fibrous membrane attached to the surface of the liver, which is independent of the hepatic veins. However, the presence of Laennec\'s capsule surrounding the peripheral hepatic veins is controversial. This study aims to describe the characteristic of Laennec\'s capsule around the hepatic veins at all levels.
UNASSIGNED: Seventy-one hepatic surgical specimens were collected along the cross and longitudinal sections of the hepatic vein. Tissue sections of 3-4 mm were cut and stained with hematoxylin and eosin (H&E), resorcinol-fuchsin (R&F), and Victoria blue (V&B). Elastic fibers were observed around the hepatic veins. They were measured using K-Viewer software.
UNASSIGNED: Morphologically, we observed a thin, dense fibrous layer (so-called Laennec\'s capsule) around the hepatic veins at all levels, which was different from the thick elastic fibers of the hepatic vein wall. Therefore, there was a potential gap between Laennec\'s capsule and the hepatic veins. Laennec\'s capsule was visualized significantly better with R&F and V&B staining compared to H&E staining. The thickness of Laennec\'s capsule around the main, first, and secondary branches of the hepatic vein were 79.86 ± 24.20 μm, 48.41 ± 18.25 μm, and 23.56 ± 10.03 μm in the R&F staining, and 80.15 ± 21.85 μm, 49.46 ± 17.52 μm, and 25.05 ± 11.03 μm in the V&B staining, respectively. They were significantly different from each other (P < .001).
UNASSIGNED: The hepatic veins were surrounded by Laennec\'s capsule at all levels, including the peripheral hepatic veins. However, it is thinner along the vein branches. The gap between the Laennec\'s capsule and hepatic veins shows potential supplemental value for liver surgery.

The chronic overexpression of matrix metalloproteases leading to consequent degradation and loss of the elastic matrix with the reduction in tissue elasticity is central to the pathophysiology of proteolytic disorders, such as abdominal aortic aneurysms (AAAs), which are localized rupture-prone aortic expansions. Effecting tissue repair to alleviate this condition is contingent on restoring elastic matrix homeostasis in the aortic wall. This is naturally irreversible due to the poor elastogenicity of adult and diseased vascular cells, and the impaired ability to assemble mature elastic fibers, more so in the context of phenotypic changes to medial smooth muscle cells (SMCs) owing to the loss of nitric oxide (NO) signaling in the AAA wall tissue. In this study, we report the benefits of the exposure of primary human aneurysmal SMCs (aHASMCs) to NO donor drug, sodium nitroprusside (SNP), in improving extracellular matrix homeostasis, particularly aspects of elastic fiber assembly, and inhibition of proteolytic degradation. SNP treatment (100 nM) upregulated elastic matrix regeneration at both gene (p < 0.05) and protein levels (p < 0.01) without affecting cell proliferation, improved gene, and protein expression of crosslinking enzyme, lysyl oxidase (p < 0.05), inhibited the expression of MMP2 (matrix metalloprotease 2) significantly (p < 0.05) and promoted contractile SMC phenotypes in aHASMC culture. In addition, SNP also attenuated the expression of mitogen-activated protein kinases, a significant player in AAA formation and progression. Our results indicate the promise of SNP for therapeutic augmentation of elastic matrix regeneration, with prospects for wall repair in AAAs. Impact Statement Chronic and naturally irreversible enzymatic degradation and loss of elastic fibers are centric to proteolytic disorders such as abdominal aortic aneurysms (AAAs). This is linked to poor elastogenicity of adult and diseased vascular cells, compromising their ability to assemble mature elastic fibers. Toward addressing this, we demonstrate the phenotype-modulatory properties of a nitric oxide donor drug, sodium nitroprusside on aneurysmal smooth muscle cells, and its dose-specific proelastogenic and antiproteolytic properties for restoring elastic matrix homeostasis. Combined with the development of vehicles for site-localized, controlled drug delivery, this can potentially lead to a new nonsurgical approach for AAA wall repair in the future.

Mummified and corified bodies are particularly complex scenarios to investigate, starting from identifying the post-mortem interval (PMI), even more so in indoor environments. In these bodies, the skin has the peculiar feature to resist for a long time. Among its components, there are elastic fibers, which are characterized by intrinsic resistance to post-mortem degenerative phenomena. Starting from these considerations, we investigated microscopically the persistence, detectability, and changes of elastic fibers in the skin of mummified and corified bodies with different known PMI. The aim was to evaluate whether they could provide an additional tool to aid in PMI estimation in these cases. Therefore, we collected skin samples from mummified or corified bodies found in a domestic environment with different known PMI, as well as from corified bodies that had been exhumed after 11 years of burial. Histochemical staining specific for elastic fibers, namely, Weigert\'s resorcin fuchsin, showed their prolonged persistence and a progressive and different degradation between mummified and corified skin as a function of PMI. Moreover, on the whole, we observed greater preservation of elastic fibers in mummified skin than in corified one at the same PMI. Therefore, histological analysis of elastic fibers in mummified and corified skin may help to provide valuable aid in estimating PMI, especially in those particular cases where more reliable alternatives are lacking.

Late-onset focal dermal elastosis is a rare cutaneous condition classified as an increased dermal elastic tissue disorder. It is distinguished clinically by multiple papules with a preference for the neck and other flexures, as well as histologically by focally increased elastic fibers in the reticular dermis. Several elastic tissue disorders in the skin have a similar clinical presentation. The distinction between late-onset focal dermal elastosis and other pseudoxanthoma elasticum mimickers is critical because they are not associated with systemic lesions. We present a case of late-onset focal dermal elastosis and conduct a literature review on this unusual condition.

Despite extensive efforts over the past 40 years, there is still a significant gap in knowledge of the characteristics of elastic fibers in the intervertebral disc (IVD). More studies are required to clarify the potential contribution of elastic fibers to the IVD (healthy and diseased) function and recommend critical areas for future investigations. On the other hand, current IVD in-vitro models are not true reflections of the complex biological IVD tissue and the role of elastic fibers has often been ignored in developing relevant tissue-engineered scaffolds and realistic computational models. This has affected the progress of IVD studies (tissue engineering solutions, biomechanics, fundamental biology) and translation into clinical practice. Motivated by the current gap, the current review paper presents a comprehensive study (from the early 1980s to 2022) that explores the current understanding of structural (multi-scale hierarchy), biological (development and aging, elastin content, and cell-fiber interaction), and biomechanical properties of the IVD elastic fibers, and provides new insights into future investigations in this domain.

Papular elastorrhexis (PE) is a rare disorder of dermal elastic fibers, which presents as firm, hypopigmented papules, commonly distributed on the trunk and extremities. The facial area is rarely involved. We report the case of a 47-year-old woman with multiple asymptomatic, soft, skin-colored facial papules whose histopathological features are compatible with PE. Facial PE may be a variant of PE, and special staining in showing changes in both elastic and collagen fibers may be of great value in diagnosis.