Effect of Computer-guided Operations on Improving the Distal Femoral Flexion Angle on the Sagittal Placement of Femoral Prosthesis in Total Knee Arthroplasty.

Background: The precise placement of prosthesis in total knee arthroplasty (TKA) surgery significantly impacts the postoperative outcomes and the long-term survival rate of prosthesis. While the optimal coronal position of femoral prosthesis has been extensively researched, there remains a gap in the study of sagittal placement. Therefore, our aim is to investigate the impact of the distal femoral flexion angle (DFFA) on the sagittal placement of femoral prosthesis in TKA. Methods: A total of 88 patients (90 knees) with osteoarthritis were enrolled in this study. To mitigate the impact of DFFA, they were randomly assigned to either the traditional operation group (50 cases) or the computer navigation operation group (40 cases). A comparison was made between the two groups regarding the sagittal femoral prosthesis flexion angle (SFPFA) and the sagittal femoral component angle (SFA). Additionally, linear regression analysis was conducted to analyze DFFA, SFA, and SFPFA. Results: The absolute values of DFFA were (2.27 ± 0.32)° in the navigation group and (2.15 ± 0.27)° in the traditional group (t=0. 30, P = .77). The absolute values of SFPFA were (0.63 ± 0.14)° in the navigation group and (2.40 ± 0.29)° in the traditional group (t =-5. 47, P = .05). The absolute values of SFA were (4.44 ± 0.62)° in the navigation group and (7.20 ± 0.57)° in the traditional group, with SFA being lower in the navigation group compared to the traditional group (t =-3. 28, P = .002). The regression equations between DFFA and SFA in navigation group and traditional operation group were SFA=5. 510-0.979×DFFA (P = .01) and SFA=7. 869-0.971×DFFA (P = .08), respectively. The regression equations between DFFA and SFPFA in navigation group and traditional operation group were SFPFA=0. 105-0.081×DFFA (P = .38) and SFPFA=-0. 96 +0.516 ×DFFA (P = .06), respectively. Conclusion: In TKA, the DFFA can impact the placement position of the femoral prosthesis in the sagittal position. When compared to traditional operation methods, computer-guided operations tend to provide a more precise and accurate sagittal position of femoral prosthesis. This study represents the first investigation into the influence of DFFA on the sagittal placement of femoral prostheses in TKA, addressing a research gap in this area. It further underscores the important role of computer-guided surgery in achieving accurate sagittal alignment of femoral prostheses, suggesting a potential adjunctive approach.

Temperature Distribution Simulation, Prediction and Sensitivity Analysis of Orthogonal Cutting of Cortical Bone.

Bone cutting plays an important role in spine surgical operations. The power devices with high speed employing in bone cutting usually leads to high cutting temperature of the bone tissue. This high temperature control is important in improving cutting surface quality and optimizing the cutting parameters. In this paper, the bone-cutting model was appropriately simplified for finite element (FE) based modeling of 2D orthogonal cutting to discuss the change law of cutting temperature of cortical bones for cervical vertebra, and to study the orthogonal cutting mechanism of the anisotropic cortical bone, a 3D FE simulation model had been also established in which longitudinal, vertical, and transversal cutting types were accomplished to investigate the effect of osteons orientation. Secondly, this response surface method was used to regress the simulation results, and establishes the prediction model of maximum temperature on cutting depth, cutting speed, and feed speed. Then, the Sobol method was used to analyze the sensitivity of the milling temperature prediction mathematical model parameters, in order to clarify and quantitatively analyze the influence of input milling parameters on the output milling temperature. Finally, the cutting temperatures obtained with the simulations were compared with the corresponding experimental results obtained from the bone milling tests. This study verifies the influence of key variables and the cutting parameters on thermo mechanical behavior of the bone cutting. The obtained cutting temperature distribution for the bone surfaces could be employed to establish a theoretical foundation for research on thermal damage control of bone tissues.

Downregulation of DNA-PKcs suppresses P-gp expression via inhibition of the Akt/NF-κB pathway in CD133-positive osteosarcoma MG-63 cells.

The development of chemoresistance is closely linked to the plateau of the survival rate in osteosarcoma (OS) patients. CD133-positive (CD133+) OS cells are known as cancer stem cells (CSCs) in OS and exhibit the characteristic of chemoresistance. In this study, CD133+ and CD133­negative (CD133­) MG­63 cells were isolated by magnetic activated cell sorting (MACS). We verified that CD133+ MG­63 cells were more resistant to cisplatin (CDDP) than CD133­ MG­63 cells. DNA­dependent protein kinase catalytic subunit (DNA­PKcs) and P­glycoprotein (P­gp) were expressed at higher levels in the CD133+ MG­63 cells compared with those levels in the CD133­ MG­63 cells, whereas downregulation of DNA­PKcs by small interfering RNA (siRNA) decreased chemoresistance to CDDP and P­gp expression at the mRNA and protein levels in these cells. This indicated that DNA­PKcs was correlated with P­gp expression in the CD133+ MG­63 cells. The Akt/NF­κB pathway was hyperactivated in the CD133+ MG­63 cells, whereas inhibition of the Akt/NF­κB pathway downregulated P­gp expression. In addition, downregulation of DNA­PKcs suppressed the activity of the Akt/NF­κB pathway. These results revealed that downregulation of DNA­PKcs could decrease P­gp expression via suppression of the Akt/NF­κB pathway in CD133+ MG­63 cells. Therefore, inhibition of DNA­PKcs decreases P­gp expression and sensitizes OS CSCs to chemotherapeutic agents in vitro, which needs to be further validated in vivo.

Putative roles of hepatitis B x antigen in the pathogenesis of chronic liver disease.

Under most circumstances, hepatitis B virus (HBV) is noncytopathic. However, hepatocellular regeneration that accompanies each bout of hepatitis appears to be associated with increased integration of HBV DNA fragments expressing the virus encoded hepatitis B x antigen (HBxAg). Intrahepatic HBxAg staining correlates with the intensity and progression of chronic liver disease (CLD), and additional work has shown that HBxAg blocks immune mediated killing by Fas and by tumor necrosis factor alpha (TNFalpha). This is not only associated with the blockage of caspase activities by HBxAg, but also by the constitutive stimulation of hepatoprotective pathways, such as nuclear factor kappa B (NF-kappaB), phosphoinositol 3-kinase (PI3K), and beta-catenin (beta-catenin). HBxAg also appears to promote fibrogenesis, by stimulating the production of fibronectin. HBxAg also stimulates the production and activity of transforming growth factor beta1 (TGFbeta1) by several mechanisms, thereby promoting the profibrogenic and tumorigenic properties of this important cytokine. In addition, HBxAg appears to remodel the extracellular matrix (ECM) by altering the expression of several matrix metalloproteinases (MMPs), which may promote tumor metastasis. Hence, HBxAg appears to promote chronic infection by preventing immune mediated apoptosis of infected hepatocytes, by promoting the establishment and persistence of fibrosis and cirrhosis preceding the development of HCC, and by promoting the remodeling of EMC during tumor progression.

The hepatitis B x antigen effector, URG7, blocks tumour necrosis factor alpha-mediated apoptosis by activation of phosphoinositol 3-kinase and beta-catenin.

Hepatitis B x antigen (HBxAg) contributes significantly to the pathogenesis of chronic infection and development of hepatocellular carcinoma. To discern some of its operative pathways, HepG2 cells were stably transduced with HBx or the bacterial chloramphenicol acetyltransferase (CAT) gene. Differential gene expression has previously revealed an upregulated gene, clone 7 (URG7), that conferred resistance to anti-Fas killing on HepG2X cells. Given that tumour necrosis factor alpha (TNFalpha) is also an important mediator of chronic hepatitis, and partially shares signalling with Fas, experiments were designed to test whether URG7 blocks TNFalpha killing of HepG2X cells. HepG2X cells expressing URG7 and HepG2 cells overexpressing URG7 in the absence of HBxAg were resistant to TNFalpha killing compared with HepG2CAT cells. URG7 small interfering RNA restored the sensitivity of HepG2X cells to TNFalpha killing. Killing was associated with the activation of caspases 3 and 8, suggesting that URG7 blocked these caspases. This resistance was also associated with activation of phosphoinositol 3-kinase/Akt. Given that Akt and HBxAg also activate beta-catenin, experiments were designed to determine whether URG7 blocked apoptosis via activation of beta-catenin. Both HBxAg and URG7 activated fragments of the beta-catenin promoter, and also promoted expression of beta-catenin target genes. Hence, URG7 inhibits TNFalpha-mediated killing by blocking one or more caspases in the apoptotic pathway and by activating phosphoinositol 3-kinase and beta-catenin, thereby overriding the apoptotic signalling of TNFalpha. This suggests that URG7 helps to protect virus-infected hepatocytes during chronic hepatitis B virus infection.

Hepatitis B virus X antigen (HBxAg) and cell cycle control in chronic infection and hepatocarcinogenesis.

Hepatitis B and related viruses that infect mammalian hosts encode the "X" protein that has been shown to contribute importantly to the pathogenesis of chronic liver disease (CLD) and to the development of hepatocellular carcinoma (HCC). In a variety of tissue culture systems, hepatitis B virus (HBV) X antigen, or HBxAg, has been shown to trigger apoptosis, while other evidence suggests that HBxAg inhibits apoptosis and stimulates the cell cycle by constitutively activating a number of signaling pathways that are important for hepatocellular growth and survival. These apparently contrasting properties of HBxAg may be associated with differences in the X protein itself, since carboxy-terminal truncated forms of HBxAg appear to be associated with HCC lesions. Alternatively, or in addition, these differences may be due to the cell type, state of cell differentiation, and whether expression occurs in resting or dividing cells. Further, the association between HBxAg expression and chromosomal instability, may also contribute to the apparently contrasting fates of HBxAg positive cells. It is proposed that in many of these systems, the different outcomes of HBxAg expression may be due to the nature of the cellular response to HBxAg, and not due to differences in the fundamental properties of HBxAg, the latter of which promote cell survival, cell cycle progression, and the development of HCC.

Hepatitis C virus replication in stably transfected HepG2 cells promotes hepatocellular growth and tumorigenesis.

HepG2 cells stably transfected with a full-length, infectious hepatitis C virus (HCV) cDNA demonstrated consistent replication of HCV for more than 3 years. Intracellular minus strand HCV RNA was present. Minus strand synthesis was NS5B dependent, and was sensitive to interferon alpha (IFN alpha) treatment. NS5B and HCV core protein were detectable. HCV stimulated HepG2 cell growth and survival in culture, in soft agar, and accelerated tumor growth in SCID mice. These mice became HCV RNA positive in blood, where the virus was also sensitive to IFN alpha. The RNA banded at the density of HCV, and was resistant to RNase prior to extraction. Hence, HCV stably replicates in HepG2 cells, stimulates hepatocellular growth and tumorigenesis, and is susceptible to IFN alpha both in vitro and in vivo.

Early molecular and genetic determinants of primary liver malignancy.

Although the overview above provides a partial molecular picture of the early stages of stepwise hepatocarcinogenesis. it should be emphasized that tumor and nontumor liver contain multiple changes, and that there is variability in their profile among different patients even within single studies. Variability in the number and types of genetic changes has also been observed geographically, and may be dependent upon the etiology of the tumor (viral, chemical or both). Interestingly, HBxAg inactivates tumor suppressors (such as p53 [by direct binding] and Rb [by stimulating its phosphorylation]) early in carcinogenesis that are mutated later during tumor progression. HBxAg also constitutively activates signal transduction pathways, such as those involving c-jun and ras, and activates oncogenes,such as c-nloc, that are otherwise activated by 3-catenin mutations. These findings suggest common molecular targets in hepatocarcinogenesis, despite different mechanisms of activation or inactivation. These observations need to be exploited in future drug discovery and in the development of new therapeutics. Heterogeneity in the mechanisms of tumor development, evidenced by the differences in the up- and down regulated genes reported in micro array analyses, as well as in the genetic loci that undergo mutation or LOH indifferent reports, has now been well documented. This suggests that there are multiple pathways to HCC, and that there is redundancy in the pathways that regulate cell growth and survival. These findings also reflect that,although hepatocarcinogenesis is multistep, the molecular changes that underpin histopathological changes in tumor development are likely to be different or only partially overlapping in individual tumors. Overall, the consequences of these changes suggest that the pathogenesis of HCC is accompanied by a progressive loss of differentiation, loss of normal cell adhesion, loss of the ECM, and constitutive activation of selected signal transduction pathways that promote cell growth and survival. Although mechanisms are important, attention also has to be paid to the target genes whose altered expression actually mediate the neoplastic phenotype. Other key avenues of work need to be explored. For example, it will be important to try to identify germline mutations in HBV-infected patients that are passed on to their children, resulting in the development of HCC in childhood. Clinical materials will also be important for the validation of new markers with diagnostic or prognostic potential. In this context, there is an urgent need to establish simple and low-cost tests based upon molecular changes that are hallmarks of HCC development. Identification of patients with early HCC will also significantly increase survival through its impact upon treatment. The discovery and validation of HCC markers may permit accurate staging of lesions, determine the proximity of such lesions to malignancy, and determine whether lesions with a particular genetic profile are still capable of remodeling through appropriate therapeutic intervention. The efficient reintroduction of the relevant tumor suppressors, or the inhibition of oncogene expression by siRNA, provide just some of the additional opportunities that will ultimately be useful in patient treatment. Together, these approaches will go far in reducing the very high morbidity and mortality associated with HCC.

Hepatitis B virus X antigen promotes transforming growth factor-beta1 (TGF-beta1) activity by up-regulation of TGF-beta1 and down-regulation of alpha2-macroglobulin.

Hepatitis B virus (HBV) X antigen (HBxAg) may contribute to the development of hepatocellular carcinoma (HCC) by activation of signalling pathways such as NF-kappaB. To identify NF-kappaB target genes differentially expressed in HBxAg-positive compared to -negative cells, HepG2 cells consistently expressing HBxAg (HepG2X cells) were stably transfected with pZeoSV2 or pZeoSV2-IkappaBalpha. mRNA from each culture was isolated and compared by PCR select cDNA subtraction. The results showed lower levels of alpha(2)-macroglobulin (alpha(2)-M) in HepG2X-pZeoSV2 compared to HepG2X-pZeoSV2-IkappaBalpha cells. This was confirmed by Northern and Western blotting, and by measurement of extracellular alpha(2)-M levels. Elevated transforming growth factor-beta1 (TGF-beta1) levels were also seen in HepG2X compared to control cells. Serum-free conditioned medium (SFCM) from HepG2X cells suppressed DNA synthesis in a TGF-beta-sensitive cell line, Mv1Lu. The latter was reversed when the SFCM was pretreated with exogenous, activated alpha(2)-M or with anti-TGF-beta. Since elevated TGF-beta1 promotes the development of many tumour types, these observations suggest that the HBxAg-mediated alteration in TGF-beta1 and alpha(2)-M production may contribute importantly to the pathogenesis of HCC.

Hepatitis Bx antigen stimulates expression of a novel cellular gene, URG4, that promotes hepatocellular growth and survival.

Hepatitis B virus encoded X antigen (HBxAg) may contribute to the development of hepatocellular carcinoma (HCC) by up- or downregulating the expression of cellular genes that promote cell growth and survival. To test this hypothesis, HBxAg-positive and -negative HepG2 cells were constructed, and the patterns of cellular gene expression compared by polymerase chain reaction select cDNA subtraction. The full-length clone of one of these upregulated genes (URG), URG4, encoded a protein of about 104 kDa. URG4 was strongly expressed in hepatitis B-infected liver and in HCC cells, where it costained with HBxAg, and was weakly expressed in uninfected liver, suggesting URG4 was an effector of HBxAg in vivo. Overexpression of URG4 in HepG2 cells promoted hepatocellular growth and survival in tissue culture and in soft agar, and accelerated tumor development in nude mice. Hence, URG4 may be a natural effector of HBxAg that contributes importantly to multistep hepatocarcinogenesis.

Genetic mechanisms of hepatocarcinogenesis.

The development of hepatocellular carcinoma (HCC) is a multistep process associated with changes in host gene expression, some of which correlate with the appearance and progression of tumor. Preneoplastic changes in gene expression result from altered DNA methylation, the actions of hepatitis B and C viruses, and point mutations or loss of heterozygosity (LOH) in selected cellular genes. Tumor progression is characterized by LOH involving tumor suppressor genes on many chromosomes and by gene amplification of selected oncogenes. The changes observed in different HCC nodules are often distinct, suggesting heterogeneity on the molecular level. These observations suggest that there are multiple, perhaps redundant negative growth regulatory pathways that protect cells against transformation. An understanding of the molecular pathogenesis of HCC may provide new markers for tumor staging, for assessment of the relative risk of tumor formation, and open new opportunities for therapeutic intervention.

Hepatitis B virus X protein protects against anti-Fas-mediated apoptosis in human liver cells by inducing NF-kappa B.

The hepatitis B virus-encoded X antigen (HBxAg) may contribute to the development of liver cancer, in part, by stimulating the growth and survival of infected cells in the face of ongoing immune responses. Given that the Fas ligand/receptor system contributes to the pathogenesis of chronic hepatitis B, experiments were designed to test the hypothesis that HBxAg mediates resistance of liver cells to anti-Fas killing. Accordingly, when HBxAg was introduced into HepG2 cells, it rendered these cells partially resistant to killing by anti-Fas. In HepG2 cells replicating virus, protection against anti-Fas killing was also observed, but to a lesser extent. Survival correlated with the activation of nuclear factor kappa B (NF-kappa B) by HBxAg. Sensitivity to anti-Fas was observed in control cells, and was re-established in HepG2X cells stably transfected with the dominant negative inhibitor of NF-kappa B, I kappa B alpha. HBxAg activation of NF-kappa B was also associated with decreased levels of endogenous I kappa B alpha mRNA. Hence, HBxAg stimulation of NF-kappa B promotes the survival of liver cells against Fas killing. This may contribute to the persistence of infected hepatocytes during chronic infection.