Possibilities of stimulating regeneration with fetal and biological materials in liver cirrhosis

The dissertation is devoted to an experimental study of the possibilities of stimulating liver regeneration in cirrhosis using fetal and biological materials. It considers the etiology and pathogenesis of chronic hepatitis and liver cirrhosis, current surgical and cell-based technologies for their treatment, and the limitations of orthotopic liver allotransplantation as a radical method. On an experimental model of cirrhosis, a comparative morphofunctional analysis of regenerative processes was carried out with intrahepatic administration of an allogeneic dispersed biomaterial, with preperitoneal implantation of fetal liver tissue, and with their combined application. It is shown that the combined use of two materials with different mechanisms of action provides the most complete involution of cirrhotic changes and enhancement of restorative processes in the parenchyma and vascular bed of the liver.

Relevance of the topic

Diffuse liver diseases — chronic hepatitis and liver cirrhosis — are among the most severe pathologies of the hepatopancreatoduodenal region [64].

The incidence of acute hepatitis in the population of our country has increased by a factor of 2–2.5 over the past three years alone. The actual figures are considerably higher, since only icteric forms are officially registered, and these account for 25 % of all cases. Chronization of the process occurs in 30–40 % of patients, and approximately half of them develop liver cirrhosis within the following 10 years [19, 77]. In economically developed countries, liver cirrhosis is among the six leading causes of death in persons aged 36–64 years [50]. Despite certain advances in understanding the pathogenesis and therapy of these diseases, the prognosis in chronic hepatitis and liver cirrhosis remains unsatisfactory, and mortality shows a steady tendency to rise. A positive effect in the treatment of chronic hepatitis and early stages of liver cirrhosis has been noted in only 30–50 % of all patients with this disease [3]. In patients at the compensation stage, five-year survival is 62 %, and ten-year survival is 51 %; at the decompensation stage, these figures are 19 % and 9.9 %, respectively [30].

At present, the radical surgical method of treating liver cirrhosis is orthotopic liver allotransplantation [46, 53]; however, its technical complexity, the shortage of donor organs, and the high cost of treatment limit the broad introduction of this operation into clinical practice and stimulate the search for more accessible methods of treatment. The main alternative to organ transplantation is considered to be stimulation of liver regeneration.

Existing methods aimed at enhancing reparative liver regeneration in most cases yield a certain positive effect but do not fundamentally resolve the problem of liver regeneration [84, 36].

One of the ways to correct the pathological process in chronic hepatitis and liver cirrhosis by influencing the regeneration of liver cells is the use of a dispersed biomaterial. It has been shown in experimental and clinical studies that its intrahepatic administration activates the resorption of the liver's own excess collagen [26, 27, 32, 33].

In recent years, transplantation of human fetal tissues has been considered promising [7]. Specific and nonspecific mechanisms of action of fetal tissues are distinguished. The specific mechanism of action is substitutive cell therapy. The nonspecific mechanism of action is the stimulation of regenerative processes by stage-specific proteins and peptides (growth factors, cytokines, tissue hormones). In addition, fetal tissues do not provoke a rejection reaction, since during the 1st and 2nd trimesters of gestation histocompatibility proteins of classes 1 and 2 are not yet expressed, and fetal tissues are able to use the evolutionarily more ancient energy pathway — glycolysis — and therefore possess greater resistance to hypoxia [74].

In view of the different mechanisms of the stimulating effect of the allogeneic dispersed biomaterial and human fetal tissues on liver regeneration, a hypothesis was advanced about the potentiation of their effect when used together.

Aim of the work

On the basis of the foregoing, the aim of the work was to investigate regenerative processes in the liver in experimental cirrhosis under the action of fetal and biological materials.

Objectives of the work

1. In experimental cirrhosis, to study the features of restoration of anatomical structures of the liver with the use of the allogeneic dispersed biomaterial.

2. To study experimentally the effectiveness of using fetal liver tissue in liver cirrhosis.

3. To assess the effect on the cirrhotic process in the liver of the allogeneic dispersed biomaterial and fetal liver tissue when they are used in combination.

4. To develop practical recommendations for the introduction into clinical practice of the technique of combined use of fetal and biological materials.

Scientific novelty of the work

For the first time, using biochemical, morphometric, histological, and electron-microscopic methods on experimental material, the regenerative activity of the liver in cirrhosis was determined against the background of various types of surgical stimulation of regeneration, and the morphofunctional dynamics of restorative processes was assessed. On the basis of a comparative analysis of the results of surgical stimulation of liver regeneration in experimental cirrhosis, it was shown that with the combined use of the dispersed biomaterial and fetal tissue the most complete involution of cirrhotic changes is achieved. It was established that, with preperitoneal implantation of fetal tissue, the main factor in the restoration of the parenchyma is the increase in the functional activity of hepatocytes, which manifests itself in the early terms of treatment (7–14 days). Liver regeneration upon intrahepatic administration of the dispersed biomaterial is expressed in active resorption of excess connective tissue and proliferation of hepatocytes, so the therapeutic effect prevails on days 21–30 after surgery. The studies carried out have proved the expediency of the combined use of the dispersed biomaterial and fetal liver tissue, since the activity of restorative processes in the liver increases owing to the different mechanisms of action on the liver in its diffuse diseases. For the first time, a morphological and theoretical substantiation is given for the effectiveness of the combined clinical use of the allogeneic dispersed biomaterial and human fetal tissue in the treatment of diffuse liver lesions.

Implementation of the results of the work

On the basis of the scientific data, the possibility of potentiating the stimulating effect on liver regeneration by the combined use of the allogeneic dispersed biomaterial and transplantation of fetal tissue has been substantiated. The results of experimental studies made it possible to begin the clinical application of transplantation of human fetal liver tissue at the G. G. Kuvatov Republican Clinical Hospital. The theoretical propositions and practical recommendations of the dissertation are used in the training program for students, medical interns, clinical residents, and postgraduate students at the Department of General Surgery of BSMU.

Main propositions submitted for defense

1. Polyploidy of liver cells, expressed in enlargement of hepatocyte nuclei and hypertrophy of the cells themselves, is the main factor in the restoration of the parenchyma upon preperitoneal implantation of fetal liver tissue in diffuse liver diseases.

2. An increase in the number and activity of liver macrophages and intensive proliferation of hepatocytes after the administration of the allogeneic biomaterial lead to involution of connective tissue and restoration of liver structure.

3. The combined use of the allogeneic material and transplantation of fetal tissue exerts a stimulating influence on liver regeneration in its cirrhotic lesion and leads to restoration of the liver structure and the capillary vascular bed in the experiment.

4. The activity of liver regeneration is higher with their combined use, since the activity of connective-tissue resorption and hepatocyte proliferation observed under the influence of the allogeneic biomaterial increases with greater hypertrophy and polyploidization of hepatocyte nuclei arising under the action of fetal tissues.

Approval of the work

The results of the work were reported and discussed at the 5th scientific-practical conference of students and young scientists of BSMU (Ufa, 2004), at a meeting of the Association of Surgeons of the Republic of Bashkortostan (Ufa, 2005), at the First Congress of Moscow Surgeons "Emergency and Specialized Surgical Care" (Moscow, 2005), and at the V Congress of the Scientific Society of Gastroenterologists of Russia and the XXXII Session of the Central Research Institute of Gastroenterology of the Moscow Department of Health (2005).

Publications

On the topic of the dissertation, 6 printed works have been published. Of these, 3 are in central publications.

Scope and structure of the dissertation

The dissertation consists of an introduction, a review of the literature, a presentation of the materials and methods of research, two chapters of original research, a conclusion, conclusions, and practical recommendations. The work is presented on 137 pages of typewritten text, contains 67 figures, 7 tables, and a bibliography of 161 works, including 86 domestic and 75 foreign sources.