Characterization of a cell cycle-dependent nuclear autoantigen

HIV nucleoside reverse transcriptase inhibitors efavirenz and tenofovir change the growth and differentiation of primary gingival epithelium

OBJECTIVES

An increasing number of HIV-infected patients are combating HIV infection through the use of antiretroviral drugs, including reverse transcriptase inhibitors. Oral complications associated with these drugs are becoming a mounting cause for concern. In our previous studies, both protease inhibitors and reverse transcriptase inhibitors have been shown to change the proliferation and differentiation state of oral tissues. This study examined the effect of a nonnucleoside and a nucleoside reverse transcriptase inhibitor on the growth and differentiation of gingival epithelium.

METHODS

Organotypic (raft) cultures of gingival keratinocytes were treated with a range of efavirenz and tenofovir concentrations. Raft cultures were immunohistochemically analysed to determine the effect of these drugs on the expression of key differentiation and proliferation markers, including cytokeratins and proliferating cell nuclear antigen (PCNA).

RESULTS

These drugs dramatically changed the proliferation and differentiation state of gingival tissues when they were present throughout the growth period of the raft tissue as well as when drugs were added to established tissue on day 8. Treatment with the drugs increased the expression of cytokeratin 10 and PCNA and, conversely, decreased expression of cytokeratin 5, involucrin and cytokeratin 6. Gingival tissue exhibited increased proliferation in the suprabasal layers, increased fragility, and an inability to heal itself.

CONCLUSIONS

Our results suggest that efavirenz and tenofovir treatments, even when applied in low concentrations for short periods of time, deregulated the cell cycle/proliferation and differentiation pathways, resulting in abnormal epithelial repair and proliferation. Our system could be developed as a potential model for studying the effects of HIV and highly active antiretroviral therapy (HAART) in vitro.

Effect of the HIV nucleoside reverse transcriptase inhibitor zidovudine on the growth and differentiation of primary gingival epithelium

OBJECTIVES

Oral complications associated with HIV infection and with the antiretroviral drugs used to treat it are of increasing concern in HIV-infected patients. Protease inhibitors have been shown to change the proliferation and differentiation state of oral tissues but the effect of nucleoside reverse transcriptase inhibitors is currently unknown. This study examined the effect of zidovudine on the growth and differentiation of the gingival epithelium.

METHODS

Gingival keratinocyte organotypic (raft) cultures were established. The raft cultures were treated with a range of zidovudine concentrations. Haematoxylin and eosin staining was performed to examine the effect of zidovudine on gingival epithelium growth and stratification. Raft cultures were immunohistochemically analysed to determine the effect of this drug on the expression of key differentiation and proliferation markers, including cytokeratins and proliferating cell nuclear antigen (PCNA).

RESULTS

Zidovudine dramatically changed the proliferation and differentiation state of gingival tissues both when it was present throughout the growth period of the tissue and when it was added to established tissue at day 8. Zidovudine treatment increased the expression of cytokeratin 10, PCNA and cyclin A. Conversely, cytokeratin 5, involucrin and cytokeratin 6 expression was decreased. The tissue exhibited characteristics of increased proliferation in the suprabasal layers as well as an increased fragility and an inability to heal itself.

CONCLUSIONS

Zidovudine treatment, even when applied at low concentrations for short periods of time, deregulated the cell cycle/proliferation and differentiation pathways, resulting in abnormal epithelial repair and proliferation. Our system could potentially be developed as a model for studying the effects of HIV and highly active antiretroviral therapy in vitro.

Hepatic proliferation after partial liver irradiation in Sprague-Dawley rats

The liver has powerful capability to proliferate in response to various injuries, but little is known as to liver proliferation after irradiation (IR) injury. This study investigated whether liver proliferation could be stimulated in low-dose irradiated liver by partial liver IR injury with high dose radiation. Sprague-Dawley rats were irradiated by 6-MV X-ray with single dose of 25 Gy to the right-half liver, while the left-half liver was shielded (0.7 Gy) or irradiated with single doses of 3.2, 5.6, and 8.0 Gy, respectively. Hepatic proliferation in the shielded and low-dose irradiated left-half liver was evaluated by serum hepatic growth factor (HGF), proliferating cell nuclei antigen (PCNA), liver proliferation index (PI), hepatocyte mitosis index (MI). The observation time was 0 day (before IR), 30, 60, 90, and 120 days after IR. Our results showed that serum HGF and hepatocyte HGF mRNA increased after IR with HGF mRNA peak on day 30 in the shielded and low-dose irradiated left-half livers, and their values increased as the dose increased to the left-half liver. Liver PI and PCNA mRNA peaked on day 60 with stronger expressions in higher doses-irradiated livers. MI increased after IR, with the peak noted on day 60 in the shielded and on day 90 in the low-dose irradiated left-half livers. There was a 30 day delay between MI peaks in the shielded and low-dose irradiated livers. In conclusion, 25 Gy partial liver IR injury could stimulate the shielded liver and low-dose irradiated liver to proliferate. In the livers receiving a dose range of 3.2-8.0 Gy, the proliferation was stronger in higher doses-irradiated liver than the low-dose irradiated. However, IR delayed hepatocyte mitosis.

A natural process of cirrhosis resolution and deceleration of liver regeneration after thioacetamide withdrawal in a rat model

Characteristics of thioacetamide (TAA)-induced liver cirrhosis in rat was observed for 120 days after TAA withdrawal as part of the radiobiological study of partial liver irradiation on TAA-induced cirrhotic rats. The natural process focused on cirrhosis and regeneration was recorded as a baseline condition for the interpretation of the outcome of the partial liver irradiation study. Cirrhosis in rats was successfully induced by drinking 0.03% TAA water orally for 29 weeks with a modeling rate of 96%. After establishment of the cirrhosis model, the rats were observed for 120 days upon TAA withdrawal to investigate the dynamic changes of cirrhosis and regeneration. The following characteristics were observed: (1) Histological changes; (2) Liver functions; (3) Cirrhosis: trichrome stain, quantification of hydroxyproline in hydrolysed liver tissue and TGF-β1; (4) Liver regeneration: liver index, hepatocyte mitotic index (MI), hepatocyte proliferation index (PI) by flow cytometry, PCNA labeling index (LI) by IHC and expression of PCNA mRNA; and (5) Growth factors: serum HGF, VEGF, TGF-α, and IL-6. After TAA withdrawal, gradual improvement in liver functions was noted with decreases of ALT, AST, and ALP, and increase of PA. The resolution of cirrhosis was evident by histological improvement with attenuation of collagen fiber and decrease of TGF-β1 IHC index, and also decrease of trichrome stain and hydroxyproline content. However, cirrhosis was still existed on 120 days after TAA withdrawal. Significant deceleration of liver regeneration was demonstrated with TAA withdrawal, evidenced by decrease of MI and PI, reduced expression of PCNA mRNA and PCNA LI. In conclusion, upon TAA withdrawal hepatic cirrhosis was continuously resolved, but persisted up to 120 days, and liver regeneration was significantly decelerated.