Micro-biopsy for detection of gene expression changes in ischemic swine myocardium: A pilot study

Abstract

Micro-endomyocardial biopsy (micro-EMB) is a novel catheter-based biopsy technique, aiming to increase flexibility and safety compared to conventional EMB. The technique was developed and evaluated in healthy swine. Therefore, the ability to detect disease related tissue changes could not be evaluated. The aim of the present pilot study was to investigate the ability to detect disease related gene expression changes using micro-EMB. Myocardial infarction was induced in three swine by coronary artery balloon occlusion. Micro-EMB samples (n = 164) were collected before, during, and after occlusion. RNA-sequencing was performed on 85 samples, and 53 of these were selected for bioinformatic analysis. A large number of responding genes was detected from the infarcted area (n = 1911). The early responding genes (n = 1268) were mostly related to apoptosis and inflammation. There were fewer responding genes two days after infarction (n = 6), which were related to extra-cellular matrix changes, and none after 14 days. In contrast to the infarcted area, samples harvested from a non-infarcted myocardial region showed considerably fewer regulated genes (n = 33). Deconvolution analysis, to estimate the proportion of different cell types, revealed a higher proportion of fibroblasts and a reduced proportion of cardiomyocytes two days after occlusion compared to baseline (p < 0.02 and p < 0.01, respectively. S5 File). In conclusion, this pilot study demonstrates the capabilities of micro-EMB to detect local gene expression responses at an early stage after ischemia, but not at later timepoints.

Safety evaluation of high-risk myocardial micro-biopsy in a swine model

“…Although crude positional changes were still possible, the steering difficulties could be relevant in scenarios where an accurate targeting is needed, such as in patchy disease or extensive fibrosis. As discussed in our previous study, micro-EMB could potentially be used in conjunction with interventional MRI guidance, or other navigational tools, to refine accuracy even further [ 11 ].…”

“…It should also be noted that the diagnostic utility of micro-EMB depends on advances in molecular-based methods for diagnosis, since the samples are too small for conventional histology. In previous studies, we showed the capabilities to generate high quality RNA data from swine micro-biopsy samples, as well as detecting tissue changes after myocardial infarction [ 10 , 11 ]. Moreover, Halloran and colleagues have developed and explored a gene expression profile test for allograft rejection, based on standard EMB samples [ 18 ].…”

“…The sampling protocols should also be closer to real-world clinical scenarios, and preferably using a clinical grade micro-EMB device. Future studies should also assess the diagnostic capabilities of micro-EMB, as discussed elsewhere [ 11 ].…”

“…The novel method features a significantly miniaturized and flexible biopsy device coupled to low-input analysis methods such as RNA-sequencing. Our previous studies of LV-micro-EMB in swine showed favorable safety outcomes as well as other outcomes such as navigability, sample quality, and ability to detect disease related changes [ 10 , 11 ]. For instance, it was shown that each micro-EMB attempt caused an injured area of 0.3 mm 2 in the endomyocardium, compared to 18 mm 2 with a conventional device [ 10 ].…”