Major Structural Protein Research Articles

Targeted modulation of pennycress lipid droplet proteins impacts droplet morphology and seed oil content.

Lipid droplets (LDs) are unusual organelles that have a phospholipid monolayer surface and a hydrophobic matrix. In oilseeds, this matrix is nearly always composed of triacylglycerols (TGs) for efficient storage of carbon and energy. Various proteins play a role in their assembly, stability and turnover, and even though the major structural oleosin proteins in seed LDs have been known for decades, the factors influencing LD formation and dynamics are still being uncovered mostly in the "model oilseed" Arabidopsis. Here we identified several key LD biogenesis proteins in the seeds of pennycress, a potential biofuel crop, that were correlated previously with seed oil content and characterized here for their participation in LD formation in transient expression assays and stable transgenics. One pennycress protein, the lipid droplet associated protein-interacting protein (LDIP), was able to functionally complement the Arabidopsis ldip mutant, emphasizing the close conservation of lipid storage among these two Brassicas. Moreover, loss-of-function ldip mutants in pennycress exhibited increased seed oil content without compromising plant growth, raising the possibility that LDIP or other LD biogenesis factors may be suitable targets for improving yields in oilseed crops more broadly.

Exploring You-gui Pill for the Treatment of Diabetic Erectile Dysfunction: Data Mining Analysis, Network Pharmacology and Experiments In Vitro.

The You-gui pill (YGP) is a classical compound used for treating antidiabetic erectile dysfunction (DMED). However, the specific active ingredients responsible for its effects on DMED and their mechanisms remain unclear. In this paper, we used data mining techniques to analyze high-frequency herbs and herb combinations used in Chinese medicine for the treatment of DMED based on existing literature. Using network pharmacology to study the active components and mechanism of action of YGP against DMED, molecular docking was used to analyze the interactions of the active components with major structural proteins, nonstructural proteins, and mutants. Also, the therapeutic effect of YGP on hyperglycemic modelling and its underlying mechanisms were experimentally validated in CCEC cells by analyzing the expression of its relevant target mRNAs. Network pharmacological analysis identified the three core components of YGP as quercetin, kaempferol, and β-sitosterol, and constructed a PPI network map of common targets of YGP and DMED, which included HIF-1α, ALB, Bcl-2, INS, IL-1β, IL-6, TNF-α, CASP3, and TP53. Combined with molecular docking results, these targets had a strong binding affinity between them and the active ingredient compounds, with the highest affinity for HIF-1α and TNF-α. During the in vitro cellular assay validation, the HIF-1α, ALB, Bcl-2, TNF-α, and IL-6 mRNA in CCECs cells showed positive regulation after YGP intervention. The combination of "data mining - network pharmacology - molecular docking - experimental validation" provides a powerful methodological basis for the study of the main active components and mechanism of action of YGP against DMED, as well as the development and application of the drug.

Impact of Cold Atmospheric Plasma Treatment on Native and Glycated Collagen

ABSTRACTCollagen is a major structural protein in the body, providing critical stability to the skin. Recent advancements have highlighted cold atmospheric plasma (CAP) as a versatile tool for various applications, including biomolecule modification, sterilization, food preservation, and wound healing. This study investigates the effects of CAP on both native and glycated collagen, analyzing the resulting changes. SEM and AFM analyses reveal that CAP induces protein self‐assembly in both glycated and non‐glycated collagen. Thioflavin assays further demonstrate that CAP‐treated glycated collagen exhibits greater fluorescence intensity compared to untreated glycated samples, indicating an increase in β‐sheet content and suggesting enhanced self‐assembly. These findings provide insights into the potential applications of CAP in modulating protein structures and understanding various biological processes and diseases.

Machine learning tools used for mapping some immunogenic epitopes within the major structural proteins of the bovine coronavirus (BCoV) and for the in silico design of the multiepitope-based vaccines.

BCoV is one of the significant causes of enteritis in young calves; it may also be responsible for many respiratory outbreaks in young calves. BCoV participates in the development of bovine respiratory disease complex in association with other bacterial pathogens. Our study aimed (1) to map the immunogenic epitopes (B and T cells) within the major BCoV structural proteins. These epitopes are believed to induce a robust immune response through the interaction with major histocompatibility complex (MHC class II) molecules (2) to design some novel BCoV multiepitope-based vaccines. The goal is achieved through several integrated in silico prediction computational tools to map these epitopes within the major BCoV structural proteins. The final vaccine was constructed in conjugation with the Choleratoxin B toxin as an adjuvant. The tertiary structure of each vaccine construct was modeled through the AlphaFold2 tools. The constructed vaccine was linked to some immunostimulants such as Toll-like receptors (TLR2 and TLR4). We also predicted the affinity binding of these vaccines with this targeted protein using molecular docking. The stability and purity of each vaccine construct were assessed using the Ramachandran plot and the Z-score values. We created the in silico cloning vaccine constructs using various expression vectors through vector builder and Snap gene. The average range of major BCoV structural proteins was detected within the range of 0.4 to 0.5, which confirmed their antigen and allergic properties. The binding energy values were detected between -7.9 and -9.4 eV and also confirmed their best interaction between our vaccine construct and Toll-like receptors. Our in silico cloning method expedited the creation of vaccine constructs and established a strong basis for upcoming clinical trials and experimental validations. Our designed multiepitope vaccine candidates per each BCoV structural protein showed high antigenicity, immunogenicity, non-allergic, non-toxic, and high-water solubility. Further studies are highly encouraged to validate the efficacy of these novel BCoV vaccines in the natural host.

Long Amplicon Nanopore Sequencing for Dual-Typing RdRp and VP1 Genes of Norovirus Genogroups I and II in Wastewater

Noroviruses (NoVs) are the leading cause of non-bacterial gastroenteritis with societal costs of US$60.3 billion per annum. Development of a long amplicon nanopore-based method for dual-typing the RNA-dependent RNA polymerase (RdRp) and major structural protein (VP1) regions from a single RNA fragment could improve existing norovirus typing methods. Application to wastewater-based epidemiology (WBE) and environmental testing could enable the discovery of novel types and improve outbreak tracking and source apportionment. Here, we have developed such a method with a consensus-based bioinformatics pipeline and optimised reverse transcription (RT) and PCR procedures. Inhibitor removal and LunaScript® RT gave robust amplification of the ≈ 1000 bp RdRP + VP1 amplicon for both the GI and GII PCR assays. Platinum™ Taq polymerase showed good sensitivity and reduced levels non-specific amplification (NSA) when compared to other polymerases. Optimised PCR annealing temperatures significantly reduced NSA (51.3 and 42.4% for GI and GII), increased yield (86.5% for GII) and increased taxa richness (57.7%) for GII. Analysis of three NoV positive faecal samples showed 100% nucleotide similarity with Sanger sequencing. Eight GI genotypes, 11 polymerase types (p-types) and 13 combinations were detected in wastewater along with 4 GII genotypes, 4 p-types and 8 combinations; highlighting the diversity of norovirus taxa present in wastewater in England. The most common genotypes detected in clinical samples were all detected in wastewater while we also frequently detected several GI genotypes not reported in the clinical data. Application of this method into a WBE scheme, therefore, may allow for more accurate measurement of norovirus diversity within the population.

The silent protector: Nucleoporin93's role in vascular health.

Nuclear envelope proteins have recently gained traction as novel regulators of endothelial and vascular function. Nuclear pore complexes (NPCs) stand as one of the largest protein complexes found at the nuclear envelope yet the role of component NPC proteins (i.e., nucleoporins) in vascular health remains unclear. In the issue of Aging Cell, Nguyen et al. (2024) identify Nucleoporin93, a major structural protein of the NPC, as an indispensable player in endothelial protection. This discovery raises the possibility that endothelial NPCs are susceptible to risk factors for consequent vascular disease.

The Role of NEU1 in Coronavirus Infection and Pathogenesis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the coronavirus disease 2019 (COVID-19) pandemic, resulting in millions of infections and deaths worldwide. Although vaccines are available, they appear to be less efficacious against newly emerging variants of the virus. Thus, therapeutic modalities are urgently needed. The coronavirus genome encodes four major structural proteins: the spike (S) protein, nucleocapsid (N) protein, membrane (M) protein, and envelope (E) protein, all of which are required to produce a structurally complete viral particle. N protein is one of the most abundant structural proteins, participates in the regulation of viral replication and virion assembly, and is a major immunogen in coronavirus infection-induced disease. Sialylation is the addition of sialic acids to the terminal glycans of glycoproteins and glycolipids, which act as key components for biological functions of glycoproteins or glycolipids. Sialidases (or neuraminidases) are glycosidases that remove sialic acid residues (desialylation) from glycan portions of glycoproteins or glycolipids. Through desialylation, sialidases modulate the functionality of sialic acid-containing molecules and are involved in both physiological and pathological pathways. This review aims to explore the current understanding of NEU1's involvement in coronavirus infection and pathogenesis, synthesizing available research and identifying areas for future investigation.

Biological features of fowl adenovirus serotype-4.

Fowl adenovirus serotype 4 (FAdV-4) is highly pathogenic to broilers aged 3 to 5 weeks and has caused considerable economic loss in the poultry industry worldwide. FAdV-4 is the causative agent of hydropericardium-hepatitis syndrome (HHS) or hydropericardium syndrome (HPS). The virus targets mainly the liver, and HPS symptoms are observed in infected chickens. This disease was first reported in Pakistan but has now spread worldwide, and over time, various deletions in the FAdV genome and mutations in its major structural proteins have been detected. This review provides detailed information about FAdV-4 genome organization, physiological features, epidemiology, coinfection with other viruses, and host immune suppression. Moreover, we investigated the role and functions of important structural proteins in FAdV-4 pathogenesis. Finally, the potential regulatory effects of FAdV-4 infection on ncRNAs are also discussed.

An obesogenic diet alters muscle function in mdx mice

Duchenne muscular dystrophy (DMD) is a progressive muscle degenerative disease that occurs in 1 in 5000 boys born worldwide. DMD is caused by the absence of a functional dystrophin protein, a major structural protein within muscle. Boys with DMD commonly develop obesity and insulin resistance (IR) compounded by limited mobility and extended treatment with glucocorticoids; however, the extent to which obesity and/or IR affect dystrophic pathology are unknown. We hypothesized that a high fat/high sucrose diet (HF/HSD) would further antagonize disease-related losses in muscle function and that these losses would be partially offset by prednisolone (Pred). To test this hypothesis, male C57 and mdx mice were fed a control diet (CD) or HF/HSD for 19 weeks, with or without Pred supplementation, followed by in vitro muscle function tests. Insulin resistance was confirmed via glucose and insulin tolerance tests. The absolute and relative weight of gastrocnemius, soleus, extensor digitorum longus (EDL), and tibialis anterior muscles were increased in mdx groups compared to C57 (p<0.01) but decreased in mdx groups treated with Pred compared to untreated mdx groups (p<0.01). Muscle mass was similar between dietary treatment groups in C57 and mdx mice. Specific tension in the diaphragm was decreased by disease (p<0.01) but was not altered by diet or Pred treatment. Diaphragms from mdx mice were less fatigue resistant than from C57 mice (p<0.01). Within mdx diaphragms, the addition of Pred and/or HF/HSD decreased fatigue resistance compared to mice maintained on CD. The C57 CD/Pred group was less fatigable than other C57 groups (p<0.01). In the soleus, tetanic force was increased in mdx compared to C57 mice (p<0.01) but was decreased by the HF/HSD in mdx groups (p=0.05). Soleus specific tension was similar between C57 and mdx groups but was decreased in mdx HF/HSD groups compared to CD (p<0.01). In the soleus, mdx groups were less resistant to fatigue than C57 groups (p<0.01); however, the HF/HSD and/or Pred treatment did not further promote fatigue in C57 or mdx mice. In EDL, tetanic force was increased in mdx groups compared to C57 groups (p<0.01), and in both C57 and mdx mice, Pred-treated groups had decreased force compared to untreated groups (p<0.01), but force was not impacted by diet. Specific tension was decreased in mdx groups compared to C57 (p<0.01). Within mdx groups, specific tension of Pred-treated groups was increased compared to untreated groups (p<0.01). The EDL was more resistant to contraction-induced injury in C57 compared to mdx mice. Within mdx mice, the HF/HSD and Pred-treated groups were more resistant to eccentric injury than mdx CD/no Pred mice (p<0.01). These data suggest that a HF/HSD and/or Pred can alter parameters of muscle function. This work is supported by Muscular Dystrophy Association grant #962344. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Multi-Gene Recombinant Baculovirus Expression Systems: From Inception to Contemporary Applications.

Many protein expression systems are primarily utilised to produce a single, specific recombinant protein. In contrast, most biological processes such as virus assembly rely upon a complex of several interacting proteins rather than the activity of a sole protein. The high complexity of the baculovirus genome, coupled with a multiphase replication cycle incorporating distinct transcriptional steps, made it the ideal system to manipulate for high-level expression of a single, or co-expression of multiple, foreign proteins within a single cell. We have developed and utilised a series of recombinant baculovirus systems to unravel the sequential assembly process of a complex non-enveloped model virus, bluetongue virus (BTV). The high protein yields expressed by the baculovirus system not only facilitated structure-function analysis of each viral protein but were also advantageous to crystallography studies and supported the first atomic-level resolution of a recombinant viral protein, the major BTV capsid protein. Further, the formation of recombinant double-shelled virus-like particles (VLPs) provided insights into the structure-function relationships among the four major structural proteins of the BTV whilst also representing a potential candidate for a viral vaccine. The baculovirus multi-gene expression system facilitated the study of structurally complex viruses (both non-enveloped and enveloped viruses) and heralded a new generation of viral vaccines.

Morphological Changes of 3T3 Cells under Simulated Microgravity.

Cells are sensitive to changes in gravity, especially the cytoskeletal structures that determine cell morphology. The aim of this study was to assess the effects of simulated microgravity (SMG) on 3T3 cell morphology, as demonstrated by a characterization of the morphology of cells and nuclei, alterations of microfilaments and microtubules, and changes in cycle progression. 3T3 cells underwent induced SMG for 72 h with Gravite®, while the control group was under 1G. Fluorescent staining was applied to estimate the morphology of cells and nuclei and the cytoskeleton distribution of 3T3 cells. Cell cycle progression was assessed by using the cell cycle app of the Cytell microscope, and Western blot was conducted to determine the expression of the major structural proteins and main cell cycle regulators. The results show that SMG led to decreased nuclear intensity, nuclear area, and nuclear shape and increased cell diameter in 3T3 cells. The 3T3 cells in the SMG group appeared to have a flat form and diminished microvillus formation, while cells in the control group displayed an apical shape and abundant microvilli. The 3T3 cells under SMG exhibited microtubule distribution surrounding the nucleus, compared to the perinuclear accumulation in control cells. Irregular forms of the contractile ring and polar spindle were observed in 3T3 cells under SMG. The changes in cytoskeleton structure were caused by alterations in the expression of major cytoskeletal proteins, including β-actin and α-tubulin 3. Moreover, SMG induced 3T3 cells into the arrest phase by reducing main cell cycle related genes, which also affected the formation of cytoskeleton structures such as microfilaments and microtubules. These results reveal that SMG generated morphological changes in 3T3 cells by remodeling the cytoskeleton structure and downregulating major structural proteins and cell cycle regulators.

Major structural protein in locust mandible capable of forming extraordinarily stiff materials via hierarchical self-assembly

Major structural protein in locust mandible capable of forming extraordinarily stiff materials via hierarchical self-assembly

Isolation, characterization and antibiofilm efficacy of a novel Klebsiella pneumoniae phage

The multidrug-resistant (MDR) Klebsiella pneumoniae is an important pathogen that threatens public health directly with life-threatening infections. The need for the development of new effective and well tolerated alternative treatments for these infections is crucial. Therefore, the interest in phage therapy as a promising alternative is increasing. Here, a novel phage named ΦAYH was isolated from the Tigris River water, Baghdad, IRAQ near sewage of Baghdad Medical City with its specific host from the same site. Phage ΦAYH belongs to Podoviridae family in the order Caudovirales. The ΦAYH maintained stability at different temperatures (−10 to 60°C) and pH values (5–11). The phage was able to lyse 8 from 32 clinical K. pneumoniae isolates in vitro with no lytic activity against other tested species. For one-step growth, latent period was 10 min with burst size ∼64 virions/cell at multiplicity of infection (MOI) 10. The SDS-PAGE test revealed one major structural protein and different structural proteins ranging from 28 to 89 kDa in size. The phage host and 32 clinical K. pneumoniae isolates were tested for phenotypic identification and antibiotics profile by VITEK-2 system and genotypically using rpob gene. All clinical K. pneumoniae isolates showed resistance to the most antibiotics tested while phage host was resistant only to amoxicillin. Biofilm production by all clinical isolates including the host isolate was tested. These isolates showed different ability as following: 72.72% as weak, 6.06% as moderate, and 21.21% as strong biofilm producer. Together these results demonstrate that ΦAYH is a promising alternative against MDR K. pneumoniae.

Apolipoprotein A-I inhibited group II innate lymphoid cell response mediated by microRNA-155 in allergic rhinitis

BackgroundGroup 2 innate lymphoid cells (ILC2s) have been found to take part in type 2 inflammation by secreting Th2 cytokines. Apolipoprotein A-I (Apo-AI), a major structural and functional protein of high-density lipoproteins, plays anti-inflammatory effects on neutrophils, monocytes, macrophages and eosinophils. However, its effects on ILC2 are not well characterized. ObjectiveIn this study, we aimed to investigate to the effect of Apo-AI on the proliferation and function of ILC2 as well as possible mechanism. MethodsThe protein expression of Apo-AI and the percentage of ILC2 in peripheral blood between 20 AR and 20 controls were detected using enzyme-linked immunosorbnent assay (ELISA) and flow cytometry. The effect of Apo-AI and miR-155 on ILC2 proliferation and function were detected by tritiated thymidine incorporation and ELISA. Anima models were adopted to verify the effect of Apo-AI in vivo. ResultsElevated expression of Apo-AI was observed in AR patients. The Apo-AI promotes ABCA1 expression by ILC2, which can be inhibited by anti-Apo-AI. The Apo-AI decreased ILC2 proliferation and the mRNA levels of GATA3 and RORα from ILC2. The miR-155 over-expression promoted the up-regulation of GATA-3 and type II cytokines from ILC2, while the addition of Apo-AI or miR-155 inhibitor inhibited the expression of GATA-3 and type II cytokines by ILC2 significantly. Apo-AI-/- mice showed as enhanced allergen-induced airway inflammation. The miR-155 inhibitor can reverse the enhanced allergen-induced airway inflammation in Apo-AI-/- mice, while miR-155 mimics can reverse the decreased allergen-induced airway inflammation in Apo-AI treated mice. ConclusionApo-AI suppressed the proliferation and function of ILC2 through miR-155 in AR. Our data provided new insights into the mechanism of allergen-induced airway inflammation.

Undercover lung damage in pediatrics -a hot spot in morbidity caused by collagenoses.

Connective tissue represents the support matrix and the connection between tissues and organs. In its composition, collagen, the major structural protein, is the main component of the skin, bones, tendons and ligaments. Especially at the pediatric age, its damage in the context of pathologies such as systemic lupus erythematosus, scleroderma or dermatomyositis can have a significant negative impact on the development and optimal functioning of the body. The consequences can extend to various structures (e.g., joints, skin, eyes, lungs, heart, kidneys). Of these, we retain and reveal later in our manuscript, mainly the respiratory involvement. Manifested in various forms that can damage the chest wall, pleura, interstitium or vascularization, lung damage in pediatric systemic inflammatory diseases is underdeveloped in the literature compared to that described in adults. Under the threat of severe evolution, sometimes rapidly progressive and leading to death, it is necessary to increase the popularization of information aimed at physiopathological triggering and maintenance mechanisms, diagnostic means, and therapeutic directions among medical specialists. In addition, we emphasize the need for interdisciplinary collaboration, especially between pediatricians, rheumatologists, infectious disease specialists, pulmonologists, and immunologists. Through our narrative review we aimed to bring up to date, in a concise and easy to assimilate, general principles regarding the pulmonary impact of collagenoses using the most recent articles published in international libraries, duplicated by previous articles, of reference for the targeted pathologies.

Identification of the p34 Protein of African Swine Fever Virus as a Novel Viral Antigen with Protection Potential.

African swine fever (ASF) is a highly contagious disease caused by African swine fever virus (ASFV), affecting domestic and wild boars. The polyprotein pp220 of ASFV is responsible for producing the major structural proteins p150, p37, p14, p34, and p5 via proteolytic processing. The p34 protein is the main component of the ASFV core shell. However, the immunologic properties of the p34 protein in vitro and in vivo remain unclear. The results showed that the recombinant p34 protein expressed in prokaryotes and eukaryotes could react with convalescent swine sera to ASFV, suggesting that p34 is an immunogenic protein. Significantly, anti-p34 antibodies were found to inhibit the replication of ASFV in target cells. Furthermore, rabbits immunized with the recombinant C-strain of classical swine fever virus containing p34 produced both anti-p34 humoral and cellular immune responses. In addition, the p34 protein could induce a cell-mediated immune response, and a T-cell epitope on the p34 protein was identified using immunoinformatics and enzyme-linked immunospot (ELIspot) assay. Our study demonstrates that the p34 protein is a novel antigen of ASFV with protective potential.

Classification of sapoviruses based on comparison of phylogenetic trees for structural and non-structural proteins

Sapoviruses (SaVs) compose the Sapovirus genus in the Caliciviridae family. In the genome of SaVs, the junction of coding regions for the non-structural proteins (NSs) and the major structural protein (viral protein 1: VP1) is known as the recombination hotspot. SaVs have been divided into genogroups GI–GXIX based on the phylogenetic relationship of amino acid sequences for VP1. Here, phylogenetic analyses were conducted for NSs and VP1 of 326 SaV strains retrieved from the International Nucleotide Sequence Database. Shared clusters were identified between the phylogenetic trees, and genogroups of SaVs were classified into 10 shared cluster groups, which may represent the monophyletic recombining groups of SaVs. All of human GI, GII, GIV, and GV strains were classified into the same shared cluster group. Continuous surveillance may be warranted for monitoring emergence of intra-genogroup and inter-genogroup recombinants in human SaVs.

Molecular Insights into the Inhibitory Role of α-Crystallin against γD-Crystallin Aggregation.

Cataracts, a major cause of global blindness, contribute significantly to the overall prevalence of blindness. The opacification of the lens, resulting in cataract formation, primarily occurs due to the aggregation of crystallin proteins within the eye lens. Despite the high concentration of these crystallins, they remarkably maintain the lens transparency and refractive index. α-Crystallins (α-crys), acting as chaperones, play a crucial role in preventing crystallin aggregation, although the exact molecular mechanism remains uncertain. In this study, we employed a combination of molecular docking, all-atom molecular dynamics simulations, and advanced free energy calculations to investigate the interaction between γD-crystallin (γD-crys), a major structural protein of the eye lens, and α-crystallin proteins. Our findings demonstrate that α-crys exhibits an enhanced affinity for the NTD2 and CTD4 regions of γD-crys. The NTD2 and CTD4 regions form the interface between the N-terminal domain (NTD) and the C-terminal domain (CTD) of the γD-crys protein. By binding to the interface region between the NTD and CTD of the protein, α-crys effectively inhibits the formation of domain-swapped aggregates and mitigates protein aggregation. Analysis of the Markov state models using molecular dynamics trajectories confirms that minimum free energy conformations correspond to the binding of the α-crystallin domain (ACD) of α-crys to NTD2 and CTD4 that form the interdomain interface.

Pre-existing SARS-2-specific T cells are predicted to cross-recognize BA.2.86

Effective monitoring of evolving SARS-CoV-2 variants requires understanding the potential effect of mutations on immune evasion. Here, we predicted the impact of BA.2.86-associated mutations on SARS-CoV-2-specific Tcell responses. First, evaluating the effect on known experimentally defined Tcell epitopes, we found that 72% and 89% of the total SARS-CoV-2 CD4 and CD8 responses were 100% conserved, with lower rates (56% and 72%) for just spike, a major structural protein. Among the mutated spike epitopes, however, 96% and 62% still bound the same reported HLA-restricting alleles. Additional prediction analyses comparing the ancestral and BA.2 sequences with BA.2.86 mutations identified several potentially novel BA.2.86 epitopes. By simulating exposure with BA.2, the large number of epitopes conserved with BA.2.86 suggests that variant-specific epitopes induced following breakthrough infection or bivalent vaccination can bridge the gap between ancestral immunization and upcoming circulating variants, allowing for a more stable Tcell response across viral evolution.

Age-related changes in dermal collagen physical properties in human skin.

Collagen is the major structural protein in the skin. Fragmentation and disorganization of the collagen fibrils are the hallmarks of the aged human skin dermis. These age-related alterations of collagen fibrils impair skin structural integrity and make the tissue microenvironment more prone to skin disorders. As the biological function of collagen lies predominantly in its physical properties, we applied atomic force microscopy (AFM) and nanoindentation to evaluate the physical properties (surface roughness, stiffness, and hardness) of dermal collagen in young (25±5 years, N = 6) and aged (75±6 years, N = 6) healthy sun-protected hip skin. We observed that in the aged dermis, the surface of collagen fibrils was rougher, and fiber bundles were stiffer and harder, compared to young dermal collagen. Mechanistically, the age-related elevation of matrix metalloproteinase-1 (MMP-1) and advanced glycation end products (AGEs) are responsible for rougher and stiffer/harder dermal collagen, respectively. Analyzing the physical properties of dermal collagen as a function of age revealed that alterations of the physical properties of collagen fibrils changed with age (22-89 years, N = 18). We also observed that the reticular dermis is rougher and mechanically stiffer and harder compared to the papillary dermis in human skin. These data extend the current understanding of collagen beyond biological entities to include biophysical properties.