Fourier transform infrared spectroscopy to quantify collagen and elastin in an in vitro model of extracellular matrix degradation in aorta

Abstract

Extracellular matrix (ECM) is a key component and regulator of many biological tissues including aorta. Several aortic pathologies are associated with significant changes in the composition of the matrix, especially in the content, quality and type of aortic structural proteins, collagen and elastin. The purpose of this study was to develop an infrared spectroscopic methodology that is comparable to biochemical assays to quantify collagen and elastin in aorta. Enzymatically degraded porcine aorta samples were used as a model of ECM degradation in abdominal aortic aneurysm (AAA). After enzymatic treatment, Fourier transform infrared (FTIR) spectra of the aortic tissue were acquired by an infrared fiber optic probe (IFOP) and FTIR imaging spectroscopy (FT-IRIS). Collagen and elastin content were quantified biochemically and partial least squares (PLS) models were developed to predict collagen and elastin content in aorta based on FTIR spectra. PLS models developed from FT-IRIS spectra were able to predict elastin and collagen content of the samples with strong correlations (RMSE of validation = 8.4% and 11.1% of the range respectively), and IFOP spectra were successfully used to predict elastin content (RMSE = 11.3% of the range). The PLS regression coefficients from the FT-IRIS models were used to map collagen and elastin in tissue sections of degraded porcine aortic tissue as well as a human AAA biopsy tissue, creating a similar map of each component compared to histology. These results support further application of FTIR spectroscopic techniques for evaluation of AAA tissues.

Correlations between transmural mechanical and morphological properties in porcine thoracic descending aorta

“…The same procedure was repeated for a spectroscopic band centered at 1338 cm −1 to map structural proteins, i.e, collagen and elastin and reported as SPR (structural proteins). This band has been observed in the spectra of both collagen and elastin and confirmed with published spectra for these molecules (Cheheltani et al, 2014; Wetzel et al, 2005).…”

“…These include monitoring arterial remodeling after injury (Herman et al, 2009), identification and characterization of vulnerable plaques using characteristic absorption bands of lipids and total protein (Colley et al, 2004; Kazarian and Chan, 2006; Palombo et al 2009), differentiation of normal and aneurysmal human aortas on biopsies of human ascending aortas (Bonnier et al, 2006 and 2008; Rubin et al, 2008), and quantification of collagen and elastin in aortic degradation (Cheheltani et al , 2014). The results of this study showed that the transmural variations of structural proteins and total protein, as measured by FT-IRIS, are consistent with microstructural parameters, and two distinct regions of inner half and outer half could be identified.…”

“…Aorta cross sections were mounted on MirrIR low-e microscope slides (Kevley Technologies, Chesterland, OH) according to a previously published protocol (Cheheltani et al , 2012). FT-IRIS images were acquired at 25μm pixel resolution and 8 cm −1 spectral resolution with 2 co-added scans using a Perkin Elmer Spotlight 400 spectrometer.…”

Hybrid cardiovascular sourced extracellular matrix scaffolds as possible platforms for vascular tissue engineering

“…H&E staining confirmed the removal of the DNA content from the two tissue types after decellularization, and the Picrosirius red staining confirmed that the collagenous structure of the ECM was maintained during decellularization (Figure b). The FTIR results for the two ECMs showed peaks in the areas associated with structural proteins such as collagen and elastin, suggesting that the decellularizing process maintained the protein's integrity (Cheheltani, McGoverin, Rao, et al, ).…”

Evaluation of catheter-induced tribological damage to porcine aorta using infra-red spectroscopy

“…Destructive tissue damage characterization methods are suitable only for ex-vivo tissue testing and include histology (with chemical or cryogenic tissue fixation) [8], optical (light) microscopy [9], scanning electron microscopy (SEM) [10][11], and environmental SEM [12][13]. Non-destructive methods are more suited for in vivo tissue testing and include techniques such as optical coherence tomography (OCT) [14][15], ultrasound [16], white light interferometry [17], Raman spectroscopy [18][19], and infrared (IR) spectroscopy [20][21][22]. Of these approaches the most promising for further exploration are the methods based on Raman and IR spectroscopy.…”