Production enhancement of human adipose-derived mesenchymal stem cells by low-intensity ultrasound stimulation.

Low-intensity ultrasound (LIUS) enhances the proliferation rate of various mammalian stem cells through mechanical stimulation. This study quantitively finds suitable LIUS stimulation parameters for increasing the proliferation rate of human adipose-derived mesenchymal stem cells (hAdMSCs) for mass production. Various stimulation conditions of LIUS were assessed based on the beam pattern of the ultrasonic transducer and the attenuation of the sound waves. Using optimal LIUS stimulation parameters for enhancing proliferation of hAdMSCs taken from bromodeoxyuridine (BrdU) incorporation assay, long-term culture of hAdMSCs was performed for 16 days. The resultant hAdMSCs were characterized for various biomarkers such as CD34-, CD45-, CD73+, CD95+, CD105+ and cytological staining and a cytokine array assay. LIUS stimulation parameters found for enhancing the hAdMSCs proliferation were the frequency of 5 MHz, an intensity of 300 mWcm-2, a duration of 10 min per day, and continuous waves with a 100% duty cycle. The LIUS stimulated hAdMSCs group showed a 3.25-fold increase in the cell number compared to the control group after 16 days of culture. By confirming the effects of quantitatively measured LIUS stimulation on the enhancement of hAdMSCs proliferation, this study may be a foundation for the applications of LIUS stimulation in the industrial-scale production of hAdMSCs.

Choroidal Thickness in Different Patterns of Diabetic Macular Edema.

This observational study investigated the changes in choroidal thickness (ChT) in different patterns of diabetic macular edema (DME) based on image processing using enhanced-depth imaging spectral-domain optical coherence tomography (EDI-SD-OCT). Participants with ocular conditions affecting the fundus view, including retinal diseases, were excluded. After observing the patient's medical record, multicolor fundus photos, thickness maps, and subtypes of DME were diagnosed according to the criteria reported by the Early Treatment Diabetic Retinopathy Study (ETDRS). Edema was classified as focal or diffuse and was subdivided into cystic macular edema (CME), CME with subretinal fluid (CME+), and spongy macular edema (SME). Image processing was performed on the B-scan images from SD-OCT to segment the choroid layer and obtain the choroid thickness. A total of 159 eyes of 81 patients (46 males and 35 females; 57.53 ± 9.78 years of age), and 57 eyes of 30 healthy individuals (age 57.34 ± 8.76 years) were enrolled in this study. Out of 159 eyes, 76 had focal macular edema (FME), 13 exhibited SME, and 51 presented CME. Among those with cystic macular edema, 19 eyes showed subretinal fluid (CME+). The average choroidal thickness in FME, diffuse SME, CME, and CME+ was 216.95 ± 52.94 µm, 243.00 ± 46.34 µm, 221.38 ± 60.78 µm, and 249.63 ± 53.90 µm, respectively. The average choroidal thickness in age-matched controls was 213.88 ± 45.60 µm. Choroidal thickness increases with the severity of edema; choroidal thickness was higher in diffuse macular edema than in FME. However, choroidal thickness increased in cystic macular edema with subretinal fluid (CME+).

Changes in ultrasonic properties of liver tissue in vitro during heating-cooling cycle concomitant with thermal coagulation.

The present work considers the ultrasonic properties of porcine liver tissue in vitro measured during heating concomitant with thermal coagulation followed by natural cooling, so as to provide information about changes in the ultrasonic properties of the tissue after thermal coagulation. The excised liver samples were heated in a degassed water bath up to 75°C and naturally cooled down to 30°C. The tissue was observed to begin thermally coagulating at temperatures lower than 75°C. The ultrasonic parameters considered include the speed of sound, the attenuation coefficient, the backscatter coefficient and the nonlinear parameter of B/A. They were more sensitive to temperature when heating than during natural cooling. All of the parameters were shown to rise significantly on completion of the heating-cooling cycle. At 35°C after thermal coagulation, the B/A value was increased by 96%, the attenuation and backscatter coefficients were increased by 50%∼68% and 33%∼37%, respectively, in the typical frequency ranges of 3 MHz∼5 MHz used for ultrasonic imaging and the speed of sound was increased by 1.4%. The results of this study added to the evidence that tissue characterization, in particular, based on the B/A could be valuable for ultrasonically imaging the thermal lesions following high-intensity focused ultrasound (HIFU) surgery.

The acute effects of smoking on the cyclic variations in blood echogenicity of carotid artery.

The objective of this research is to study the cyclic variations in echogenicity (CVE) as an acute response to smoking. CVEs, caused by the aggregation of red blood cells (RBC) were measured from the cross-sectional images of the common carotid artery using coded harmonic imaging of a commercial ultrasound system. The amplitude of the CVE (A(cve)) was analyzed among 28 smokers before and after smoking. A(cve) was increased in 22 smokers and decreased in six smokers after 1-2 cigarettes were smoked. Heart rate (HR) was also estimated from the ultrasonic images before and after smoking. The smokers were optimally divided into two clusters with respect to the change in A(cve) and the intrinsic characteristics of smokers (i.e., daily consumed cigarettes and smoking years) through a two-step cluster analysis (TSCA). The increase in A(cve) after smoking was significantly higher in the heavy smoker cluster compared with the light smoker cluster. The results suggest that the acute changes in A(cve) in response to smoking are different between heavy smokers and light smokers. This preliminary study demonstrates the potential application of coded harmonic ultrasound imaging to detect or characterize RBC aggregation. In addition, the results may be useful for understanding the acute physiologic changes caused by smoking.

Influence of cell packing by centrifugation on 40-MHz ultrasound backscatter.

High-frequency ultrasound (HFUS) signals backscattered from RBL-2H3 cell pellets prepared under different centrifugal forces were analyzed to investigate the packing effect of cell aggregates. The measurements were performed in a pulse-echo setup with a 40-MHz transducer. The changes of ultrasound signals from cell pellet in backscattered power, statistical parameter, and pellet thickness were monitored after centrifugation at between 100g and 1600g. Experimental results showed that the HFUS backscattered power from cell pellets was inversely proportional to centrifugal force and increased to a plateau within 1-2h after centrifugation. The initial thickness of cell pellets decreased with higher centrifugal force, but the changes in thickness and time that took to reach a plateau increased at higher centrifugal force. The envelope statistics of backscattered signals with Nakagami distribution indicates that the centrifugal force and elapsed time after centrifugation affected the backscattering characteristics. The present study suggests that centrifugal force and data acquisition time after cell pellet formation should be considered in in vitro cell packing method with centrifugation to emulate the tissue in vivo.

Ultrasonic backscatter from rat blood in aggregating media under in vitro rotational flow.

Ultrasonic backscatter from flowing and static rat red blood cells (RBCs) in autologous plasma and in 360 kDa polyvinylpyrrolidone (PVP 360) solution was measured as a function of hematocrit. The flow speed was varied by a stirring magnet in a cylindrical chamber. The radio-frequency (RF) signals backscattered by RBC samples were measured over 5 min in a pulse-echo setup with a 5 MHz focused transducer. Although the intact rat blood has poor RBC aggregability, RBC aggregation of rat blood was enhanced by replacing its plasma with a higher molecular weight polymer solution. The experimental results showed that the nonlinear relationship between hematocrit and ultrasonic backscatter from rat RBCs in plasma and aggregating media is affected by flow speed, which may provide a unified insight into hematocrit dependence of RBC aggregation under flowing and static conditions.