In-vitro Strain and Modulus Measurements in Porcine Cervical Lymph Nodes

Abstract

Cervical lymph nodes are common sites of metastatic involvement in head and neck cancers. These lymph nodes are superficially located and palpation is a common practice for assessing nodal hardness and staging cancer which is, however, too subjective and with limited accuracy. In this study, the mechanical properties of pig lymph node tissues were investigated using ultrasound elastography and indentation test. Lymph nodes were excised from fresh pork pieces and embedded in an agar-gelatin phantom for strain imaging by elastography. A strain ratio reflecting the strain contrast of lymph node over agar-gelatin phantom was used to assess the elasticity of the lymph node. A cutting device was then custom-designed to slice the phantom into uniform slices for indentation test. The measurements revealed that there were significant differences in both the strain ratio and Young’s modulus between the peripheral and middle regions of the lymph nodes (both p < 0.05); however, the results appeared contradictory. Correlation between the results of the two measurements (modulus ratio vs. inversed strain ratio) showed their association was moderate for both the peripheral and middle regions (R2 = 0.437 and 0.424 respectively). As the tests were only performed on normal lymph nodes, comparison in stiffness between healthy and abnormal lymph nodes could not be made. Future studies should be conducted to quantify the stiffness change in abnormal lymph nodes.

Award Winner in the Young Investigator Category, 2017 Society for Biomaterials Annual Meeting and Exposition, Minneapolis, MN, April 05—08, 2017: Lymph node stiffness‐mimicking hydrogels regulate human B‐cell lymphoma growth and cell surface receptor expression in a molecular subtype‐specific manner

“…In contrast, magnetic resonance elastography techniques have reported stiffness of lymphoid tissues in the range of 1.5–3 kPa . Likewise, ultrasound elastography and indentation tests were used to determine mechanical properties of porcine cervical lymph nodes, however stiffness change in abnormal lymph nodes were not determined using these methods . To characterize the mechanical stiffness of lymphoid tissues and apply the same technique to engineered hydrogels, we used a micropipette aspiration method, reported earlier by us .…”

“…29 Likewise, ultrasound elastography and indentation tests were used to determine mechanical properties of porcine cervical lymph nodes, however stiffness change in abnormal lymph nodes were not determined using these methods. 30 To characterize the mechanical stiffness of lymphoid tissues and apply the same technique to engineered hydrogels, we used a micropipette aspiration method, reported earlier by us. 20,21 This technique quantified the elongation of tissues aspirated inside the pipette in response to applied vacuum pressure (Figure 2A).…”

Determining the elastography strain ratio cut off value for differentiating benign from malignant breast lesions: systematic review and meta-analysis

“…In fact, the only study in this review that reported using a vendor machine predetermined cut-off value fell in a subgroup that did not produce favourable threshold effects. Furthermore, there are pieces of literature that indicate quantified variance for in vitro and clinical applications of SR measurement [ 77 , 78 ]. We still propose more research on the manufacturer model calibration aspects.…”

Leukocytes as carriers for targeted cancer drug delivery

“…Conjugation of liposomes to the surface of NK cells was facilitated by antibody binding to CD57 (Figure 4C and D), a marker found on a subpopulation of NK cells [141]. As an in vitro model of SLNs, functionalized NK cells were seeded into microbubbles comprised of polydimethylsiloxane, which mimic both the size and elastic modulus of lymph nodes (Figure 4E) [142]. MDA-MB-231, COLO 205, and LNCaP cancer cells, which typically metastasize to lymph nodes, were then cultured within microbubbles containing functionalized NK cells.…”