Raman microspectroscopy as a diagnostic tool for the non-invasive analysis of fibrillin-1 deficiency in the skin and in the in vitro skin models

Raman microspectroscopy and Raman imaging reveal biomarkers specific for thoracic aortic aneurysms

Aortic rupture and dissection are life-threatening complications of ascending thoracic aortic aneurysms (aTAAs), and risk assessment has been largely based on the monitoring of lumen size enlargement. Temporal changes in the extracellular matrix (ECM), which has a critical impact on aortic remodeling, are not routinely evaluated, and cardiovascular biomarkers do not exist to predict aTAA formation. Here, Raman microspectroscopy and Raman imaging are used to identify spectral biomarkers specific for aTAAs in mice and humans by multivariate data analysis (MVA). Multivariate curve resolution-alternating least-squares (MCR-ALS) combined with Lasso regression reveals elastic fiber-derived (Ce1) and collagen fiber-derived (Cc6) components that are significantly increased in aTAA lesions of murine and human aortic tissues. In particular, Cc6 detects changes in amino acid residues, including phenylalanine, tyrosine, tryptophan, cysteine, aspartate, and glutamate. Ce1 and Cc6 may serve as diagnostic Raman biomarkers that detect alterations of amino acids derived from aneurysm lesions.

Label-free Raman imaging of human/murine ascending thoracic aortic aneurysm (aTAA)

Multivariate analysis of Raman spectra allows detection of aTAA molecular features

Identification of spectral biomarkers for aTAA in elastic and collagen fibers

Alterations in amino acid spectra correlate with aTAA formation

An in vitro 3D diabetic human skin model from diabetic primary cells

Diabetes mellitus, a complex metabolic disorder, leads to many health complications like kidney failure, diabetic heart disease, stroke, and foot ulcers. Treatment approaches of diabetes and identification of the mechanisms underlying diabetic complications of the skin have gained importance due to continued rapid increase in the diabetes incidence. A thick and pre-vascularized in vitro 3D type 2 diabetic human skin model (DHSM) was developed in this study. The methacrylated gelatin (GelMA) hydrogel was produced by photocrosslinking and its pore size (54.85 ± 8.58 μm), compressive modulus (4.53 ± 0.67 kPa) and swelling ratio (17.5 ± 2.2%) were found to be suitable for skin tissue engineering. 8% GelMA hydrogel effectively supported the viability, spreading and proliferation of human dermal fibroblasts. By isolating dermal fibroblasts, human umbilical vein endothelial cells and keratinocytes from type 2 diabetic patients, an in vitro 3D type 2 DHSM, 12 mm in width and 1.86 mm thick, was constructed. The skin model consisted of a continuous basal epidermal layer and a dermal layer with blood capillary-like structures, ideal for evaluating the effects of anti-diabetic drugs and wound healing materials and factors. The functionality of the DHSM was showed by applying a therapeutic hydrogel into its central wound; especially fibroblast migration to the wound site was evident in 9 d. We have demonstrated that DHSM is a biologically relevant model with sensitivity and predictability in evaluating the diabetic wound healing potential of a therapeutic material.

The fibrillin microfibril/elastic fibre network: A critical extracellular supramolecular scaffold to balance skin homoeostasis

Supramolecular networks composed of fibrillins (fibrillin-1 and fibrillin-2) and associated ligands form intricate cellular microenvironments which balance skin homoeostasis and direct remodelling. Fibrillins assemble into microfibrils which are not only indispensable for conferring elasticity to the skin, but also control the bioavailability of growth factors targeted to the extracellular matrix architecture. Fibrillin microfibrils (FMF) represent the core scaffolds for elastic fibre formation, and they also decorate the surface of elastic fibres and form independent networks. In normal dermis, elastic fibres are suspended in a three-dimensional basket-like lattice of FMF intersecting basement membranes at the dermal-epidermal junction and thus conferring pliability to the skin. The importance of FMF for skin homoeostasis is illustrated by the clinical features caused by mutations in the human fibrillin genes (FBN1, FBN2), summarized as "fibrillinopathies." In skin, fibrillin mutations result in phenotypes ranging from thick, stiff and fibrotic skin to thin, lax and hyperextensible skin. The most plausible explanation for this spectrum of phenotypic outcomes is that FMF regulate growth factor signalling essential for proper growth and homoeostasis of the skin. Here, we will give an overview about the current understanding of the underlying pathomechanisms leading to fibrillin-dependent fibrosis as well as forms of cutis laxa caused by mutational inactivation of FMF-associated ligands.

Human keratinocyte-derived microvesicle miRNA-21 promotes skin wound healing in diabetic rats through facilitating fibroblast function and angiogenesis

Skin wound healing is a complex physiological process that maintains the integrity of the skin tissues, involving a variety of distinct cell types and signaling molecules. The specific signaling pathways or extracellular cues that govern the healing processes remain elusive. Microvesicles (MVs) have recently emerged as critical mediators of cell communication by delivery of genetic materials to target cells. In this study, we found the direct delivery of HEKa-MVs expressing miR-21 mimics significantly promoted the healing of skin wound in diabetic rats. In-depth studies showed that MV miR-21 promoted fibroblast migration, differentiation, and contraction, induced a pro-angiogenic process of endothelial cells and mediated a pro-inflammatory response. Mechanically, MV miR-21 might target specific essential effector mRNA in fibroblasts such as MMP-1, MMP-3, TIMP3, and TIMP4 to increase MMPs expression and enzymatic activities. Moreover, MV miR-21 regulated ɑ-SMA and N-cadherin to induce fibroblast-myofibroblast differentiation. MV miR-21 up-regulated the IL-6 and IL-8 expressions and their secretion to amplify the immune response. Furthermore, MV miR-21 down-regulated PTEN and RECK in protein level, and activate MAPK/ERK signaling cascade, thereby promoting fibroblast functions. Thus, our study has provided for the first time the basis for the potential application of HEKa-MVs, and MV miR-21 in particular for wound healing.

Tissue Engineering: Understanding the Role of Biomaterials and Biophysical Forces on Cell Functionality Through Computational and Structural Biotechnology Analytical Methods

Within the past 25 years, tissue engineering (TE) has grown enormously as a science and as an industry. Although classically concerned with the recapitulation of tissue and organ formation in our body for regenerative medicine, the evolution of TE research is intertwined with progress in other fields through the examination of cell function and behaviour in isolated biomimetic microenvironments. As such, TE applications now extend beyond the field of tissue regeneration research, operating as a platform for modifiable, physiologically-representative in vitro models with the potential to improve the translation of novel therapeutics into the clinic through a more informed understanding of the relevant molecular biology, structural biology, anatomy, and physiology. By virtue of their biomimicry, TE constructs incorporate features of extracellular macrostructure, molecular adhesive moieties, and biomechanical properties, converging with computational and structural biotechnology advances. Accordingly, this mini-review serves to contextualise TE for the computational and structural biotechnology reader and provides an outlook on how the disciplines overlap with respect to relevant advanced analytical applications.

Non-invasive functional molecular phenotyping of human smooth muscle cells utilized in cardiovascular tissue engineering

Smooth muscle cell (SMC) diversity and plasticity are limiting factors in their characterization and application in cardiovascular tissue engineering. This work aimed to evaluate the potential of Raman microspectroscopy and Raman imaging to distinguish SMCs of different tissue origins and phenotypes. Cultured human SMCs isolated from different vascular and non-vascular tissues as well as fixed human SMC-containing tissues were analyzed. In addition, Raman spectra and images of tissue-engineered SMC constructs were acquired. Routine techniques such as qPCR, histochemistry, histological and immunocytological staining were performed for comparative gene and protein expression analysis. We identified that SMCs of different tissue origins exhibited unique spectral information that allowed a separation of all groups of origin by multivariate data analysis (MVA). We were further able to non-invasively monitor phenotypic switching in cultured SMCs and assess the impact of different culture conditions on extracellular matrix remodeling in the tissue-engineered ring constructs. Interestingly, we identified that the Raman signature of the human SMC-based ring constructs was similar to the one obtained from native aortic tissue. We conclude that Raman microspectroscopic methods are promising tools to characterize cells and define cellular and extracellular matrix components on a molecular level. In this study, in situ measurements were marker-independent, fast, and identified cellular differences that were not detectable by established routine techniques. Perspectively, Raman microspectroscopy and MVA in combination with artificial intelligence can be suitable for automated quality monitoring of (stem) cell and cell-based tissue engineering products. STATEMENT OF SIGNIFICANCE: The accessibility of autologous blood vessels for surgery is limited. Tissue engineering (TE) aims to develop functional vascular replacements; however, no commercially available TE vascular graft (TEVG) exists to date. One limiting factor is the availability of a well-characterized and safe cell source. Smooth muscle cells (SMCs) are generally used for TEVGs. To engineer a TEVG, proliferating SMCs of the synthesizing phenotype are essential, whereas functional, sustainable TEVGs require SMCs of the contractile phenotype. SMC diversity and plasticity are therefore limiting factors, also for their quality monitoring and application in TE. In this study, Raman microspectroscopy and imaging combined with machine learning tools allowed the non-destructive, marker-independent characterization of SMCs, smooth muscle tissues and TE SMC-constructs. The spectral information was specific enough to distinguish for the first time the phenotypic switching in SMCs in real-time, and monitor the impact of culture conditions on ECM remodeling in the TE SMC-constructs.

Biomechanical and biomolecular characterization of extracellular matrix structures in human colon carcinomas

The extracellular matrix (ECM) is extensively remodeled in tumor tissues. Overproduction of collagens, pathological collagen crosslinking and alignment of fibers are major processes that ultimately result in an increased tissue stiffness. Although it is known that glycosaminoglycans (GAGs) play an important role in tumor signaling, their contribution to the biomechanical properties of tumor ECM is unknown. In this study, ECM structures of human colon carcinoma and normal (control) colon tissues were histologically identified. Using atomic force microscopy (AFM) nanoindentation, we show that the collagen-rich regions within the ECM of colon carcinoma tissues were significantly stiffer than the submucosal collagen-rich layer of control tissues. Screening of these regions with Raman microspectroscopy revealed significantly different molecular fingerprints for collagen fibers in colon carcinoma tissues compared to control tissues. We further showed an increased alignment of collagen fibers and elevated levels of GAG immuno-reactivity within the collagen network of colon carcinoma tissues. GAGs such as heparan sulfate and chondroitin sulfate were detected in significantly elevated levels in collagen fibers of carcinoma tissues. Moreover, immunodetection of the collagen-associated proteoglycan decorin was significantly decreased in carcinomas tissues of individual patients when compared with the corresponding control tissues. Overall a strong patient-to-patient variability was evident in the ECM composition, structure and biomechanics of individual colon carcinoma tissues. Although, biomechanical characteristics of tumor ECM were not directly impacted by GAG content, GAGs might play an important role during the mechanical and structural remodeling of pathological tumor ECM. To manipulate GAG expression and deposition in tumor microenvironments could represent a novel potential therapeutic strategy.