H. Liu’s scientific contributions

BACKGROUND: Previous reports revealed that electric pulses can induce apoptosis in cancer cells. OBJECTIVE: To observe the effects of different pulses on the apoptosis and mitochondrial transmembrane potential of human cancer cells, in addition, to investigate the apoptosis effects of electric pulse. DESIGN, TIME AND SETTING: A controlled and observational experiment was performed at the Key Laboratory of Biorheological Science and Technology and State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Ministry of Education between March 2007 and March 2008. MATERIALS: Human hepatoma cell SMMC-7721 and normal human liver cell HL-7702 was purchased from China Center for Type Culture Collection. METHODS: SMMC-7721 and HL-7702 were stimulated with electric pulse (200 V/cm, 1.8 μs; 250 V/cm, 1.8 μs; 600 V/cm, 120 ns, respectively) for 1 minute, flow cytometry and DNA ladder were used to determine the apoptosis of cells, meanwhile, real-time changes of mitochondrial transmembrane potential were investigated by confocal microscopy when cells exposed to electric fields. MAIN OUTCOME MEASURES: The apoptosis rate of SMMC-7721 cells and changes of mitochondrial transmembrane potential of SMMC-772 after 10 minutes stimulation was investigated when cells exposed to different electric fields. RESULTS: The 1.8 μs, 200 V/cm and 250 V/cm electric fields could induce cells apoptosis, while 120 ns, 600 V/cm pulses didn't have significant apoptotic effect on cells. Cells apoptosis was confirmed by DNA ladder. When cells were treated with pulses in 600 V/cm, 120 ns, and the cleavage of DNA was different from the cells treated with 1.8 μs pulses. More low-molecular-weight DNA fragments were extracted in this cell group. And the electric stimulation decreased mitochondrial transmembrane potential. Interestingly, the mitochondrial transmembrane potential decreased more significantly in cells that were exposed to the 120 ns, 600 V/cm electric fields (67.09%) compared to the cells in 1.8 μs, 200 V/cm and 250 V/cm (23.71% and 28.44% respectively). CONCLUSION: Electric pulses can induce cell apoptosis and decrease the mitochondrial transmembrane potential, which depending on the duration and electric intensity of electric pulses. Moreover, shorter pulses have more effect on intracellular structure. However, the change of mitochondrial transmembrane potential is not directly related to cell apoptosis.

Calcium is one of the most important secondly messenger in cells, it plays an important role in apoptosis. Measuring the change of intracellular free calcium concentration ([Ca2+]i) is a useful method for apoptosis. Exposing liver cancer cell dyed with Fluo-3/AM to steep pulsed electric field (SPEF), we observed the change of [Ca2+]i using laser scanning confocal microscope (LSCM) to study the apoptosis effect of SPEF. The experiment results showed that steady state of [Ca2+] i changed in process of exposing to SPEF, the phenomenon kept up even after canceling SPEF, the changing quantity of [Ca2+]i had relations with parameter (peak value, pulse width, et al) of SPEF and extracellular environment (extracellular free calcium existing or not). The experiment results of flow cytometry (liver cancer cell dyed with Annexin V-FITC) approved that SPEF could induce apoptosis markedly (P < 0.01); SPEF with lower voltage (200V) and longer width (1.3μs) could induce apoptosis more effectively (P < 0.01) than SPEF with higher voltage (600V) and shorter width (100ns). These experiment results provide possible mechanism and parameter selection basis for tumor treatment using SPEF.

In order to research apoptosis effects of cancer cell induced by nanosecond pulsed electric fields (nsPEF), on the basis of combination of switching power supply technology with pulsed power technology, this paper developed a nsPEF generator whose output multiple parameters could be adjusted in a wide range and independently. The generator was composed of a high-voltage direct current power supply, a pulse forming circuit and an assistant circuit. The amplitude of output pulse could be adjusted continually from 0 V to 1.2 kV by means of adjusting the driving signal in high-voltage direct current power supply. The repeat rate of output pulse could be adjusted continually from 1 Hz to 1 kHz by means of adjusting the control circuit in assistant circuit. The width of output pulse could be adjusted to 100 ns, 200 ns, 600 ns and 1000 ns by means of switching to different energy storing capacitor in pulse forming circuit. The number of output pulse could be preset to any value and the rise time of output pulse was less than 30 ns. All above-mentioned parameters could be displayed via LED. Over-voltage, over-current and short circuit protections were also available. Debugging results in laboratory and medical cell experiment results show that nsPEF generator can be adjusted conveniently and operated stably. Furthermore, nsPEF can induce apoptosis of human liver cancer cell effectively. In conclusion, this nsPEF generator is competent for research of mechanism and optimal parameters for cancer cell apoptosis induction.

The objective of this study was to investigate the clinicopathologic features of epithelioid angiomyolipoma of kidney (KAML) and the histologic criteria of epithelioid KAML. Four cases of epithelioid KAML with HE and immunohistochemistry staining were included. Its histopathological and immunohistological characteristics, biologic behaviors and related literatures have been analyzed and reviewed. Of the four cases of epithelioid KAML, significant perivascular epithelioid cells were presented with invasive hyperplasia of atypical pleomorphism, hyperchromatic nuclei with frequent mitotic figures, giant neoplasic cells and extensive hemorrhagic necrosis immunohistochemcial staining showing a positive HMB45 and Ki-67 in most neoplasic cells. Multiple organ invasion, partly with remote metastases and necrosis of organs were found in the 4 cases including 1 case of tuberous sclerosis and 1 case of death. In conclusion, the most differences between the epithelioid AML and classic AML of kidney are the rare biological behavior of invasive proliferation, histological features of atypical hyperplasia, mitosis and immunohistochemcial presentation. The existence of malignant epithelioid AML is strongly suggested by the features of the involvement of multiple organs or remote metastases, and all above clincohistopathology and biological behavior of KAML.