Matrix stiffening with downstream activation of mechanosensitive pathways is strongly implicated in progressive fibrosis; however, pathologic changes in extracellular matrix (ECM) that initiate mechano-homeostasis dysregulation are not defined in human disease. By integrated multiscale biomechanical and biological analyses of idiopathic pulmonary fibrosis lung tissue, we identify that increased tissue stiffness is a function of dysregulated post-translational collagen cross-linking rather than any collagen concentration increase whilst at the nanometre-scale collagen fibrils are structurally and functionally abnormal with increased stiffness, reduced swelling ratio, and reduced diameter. In ex vivo and animal models of lung fibrosis, dual inhibition of lysyl oxidase-like (LOXL) 2 and LOXL3 was sufficient to normalise collagen fibrillogenesis, reduce tissue stiffness, and improve lung function in vivo. Thus, in human fibrosis, altered collagen architecture is a key determinant of abnormal ECM structure-function, and inhibition of pyridinoline cross-linking can maintain mechano-homeostasis to limit the self-sustaining effects of ECM on progressive fibrosis.

neutrophilic airway inflammation. Our data indicate that the increase of a specific profile of DAMPs rather than that of HMGB1 alone, which has been implicated in COPD development [6], may be an important determinant of the susceptibility towards neutrophilic airway inflammation upon cigarette smoking.In future studies it will be of interest to confirm whether a similar DAMP release signature is present in COPD patients, whether this is related to the susceptibility of smoking individuals to develop COPD and whether this signature can be used for the early detection of susceptibility to or the presence of COPD. @ERSpublications A specific profile of DAMPs identifies susceptibility towards smoke induced neutrophilic airway inflammation in mice

Superresolution (SR) optical microscopy has allowed the investigation of many biological structures below the diffraction limit; however, most of the techniques are hampered by the need for fluorescent labels. Nonlinear label-free techniques such as second-harmonic generation (SHG) provide structurally specific contrast without the addition of exogenous labels, allowing observation of unperturbed biological systems. We use the photonic nanojet (PNJ) phenomena to achieve SR-SHG. A resolution of with respect to the fundamental wavelength, that is, a -fold improvement over conventional or diffraction-limited SHG under the same imaging conditions is achieved. Crucially we find that the polarization properties of excitation are maintained in a PNJ. This is observed in experiment and simulations. This may have widespread implications to increase sensitivity by detection of polarization-resolved SHG by observing anisotropy in signals. These new, to the best of our knowledge, findings allowed us to visualize biological SHG-active structures such as collagen at an unprecedented and previously unresolvable spatial scale. Moreover, we demonstrate that the use of an array of self-assembled high-index spheres overcomes the issue of a limited field of view for such a method, allowing PNJ-assisted SR-SHG to be used over a large area. Dysregulation of collagen at the nanoscale occurs in many diseases and is an underlying cause in diseases such as lung fibrosis. Here we demonstrate that pSR-SHG allows unprecedented observation of changes at the nanoscale that are invisible by conventional diffraction-limited SHG imaging. The ability to nondestructively image SHG-active biological structures without labels at the nanoscale with a relatively simple optical method heralds the promise of a new tool to understand biological phenomena and drive drug discovery.

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Super-resolution (SR) optical microscopy has allowed the investigation of many biological structures below the diffraction limit, however, most of the techniques are hampered by the need for fluorescent labels. Non-linear label-free techniques such as Second Harmonic Generation (SHG) provide structurally specific contrast without the addition of exogenous labels, allowing observation of unperturbed biological systems. Here we achieve super-resolution SHG (SR-SHG) for the first time. We use the photonic nanojet (PNJ) phenomena to achieve a resolution of ~λ/6 with respect to the fundamental wavelength, a ~2.7-fold improvement over diffraction-limited SHG under the same imaging conditions. Crucially we find that the polarisation properties of excitation are maintained in a PNJ allowing the resolution to be further enhanced by detection of polarisation-resolved SHG (p-SHG) by observing anisotropy in signals. These new findings allowed us to visualise biological SHG-active structures such as collagen at an unprecedented and previously unresolvable spatial scale. Moreover, we demonstrate that the use of an array of self-assembled high-index spheres overcomes the issue of a limited field of view for such a method, allowing PNJ-assisted SR-SHG to be used over a large area. Dysregulation of collagen at the nanoscale occurs in many diseases and is an underlying cause in diseases such as lung fibrosis. Here we are able to demonstrate that pSR-SHG allows unprecedented observation of changes at the nanoscale that are invisible by conventional diffraction-limited SHG imaging. The ability to non-destructively image SHG-active biological structures without labels at the nanoscale with a relatively simple optical method heralds the promise of a new tool to understand biological phenomena and drive drug discovery. List of abbreviationsSecond Harmonic Generation (SHG), Super-resolution (SR), Barium Titanate Glass (BTG), Photonic Nanojet (PNJ), Point Spread Function (PSF) Calculation of Polarisation anisotropyPolarisation anisotropy images were created using a home written Fiji macro in which the key steps are as follows: A difference image was generated by (Ipar -Iperp), this was divided by a total intensity image (Ipar + 2Iperp). The total intensity image was used to select the region of the image containing signal and for display all pixels outside of this region were set to 0. Only the regions containing signal were used for further anisotropy analysis. Collagen fibre analysisCollagen fibre analysis was performed using CT-FIRE V1.3. SHG intensity images were converted to 8bit format before being batch processed using default parameters. Four parameters were measured to describe fibre morphology, width, length, straightness and angle.

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