Method and solution for preserving organs for transplantation

Abstract

This invention provides an immersion preservation method and preservation solution that maintain organs for transplantation in good condition for a longer period than conventional methods. [Solution] The present invention relates to a method for preserving organs for transplantation, which involves immersing the organs in a nitrogen-rich UW solution at a temperature suitable for immersion preservation, where the dissolved oxygen content is 1.0 mg / L or less and the nitrogen content is 90 mg / L or more at one atmosphere. As an example, a nitrogen-rich UW solution is prepared in which the dissolved oxygen content is 1.0 mg / L or less and the nitrogen content is 90 mg / L or more at one atmosphere and a temperature suitable for immersion preservation, and the organs for transplantation are immersed in the prepared nitrogen-rich UW solution. As another example, a nitrogen-rich UW solution is prepared in which the dissolved oxygen content is 1.0 mg / L or less and the nitrogen content is 90 mg / L or more at one atmosphere and room temperature, and the prepared nitrogen-rich UW solution is cooled to a temperature suitable for immersion preservation before the organs for transplantation are immersed in it.

Description

Technical Field

[0001] The present invention relates to a method for preserving transplant organs and a preservation solution.

Background Art

[0002] As methods for preserving transplant organs such as kidneys, livers, and pancreases removed for transplantation in a good state, there are mainly perfusion methods and immersion methods. It is difficult to establish appropriate conditions for the perfusion method. On the other hand, the immersion method is a method of maintaining the organ at a low temperature in a preservation solution to suppress cell metabolism, and is widely used in clinical practice as a simple and effective method. As preservation solutions, EuroCollins solution and University of Wisconsin (UW) solution are known. EuroCollins solution is effective for kidneys with high viability, but is insufficient for other organs. UW solution has a problem of being unstable as a preparation. Therefore, improvements have been made by adding various components to these preservation solutions.

[0003] The time during which transplant organs can be preserved in a good state from excision to transplantation by the immersion method varies depending on the organ. In the case of the liver, about 12 hours is considered the limit. If this preservation time can be extended, the opportunity for transplantation will increase and many patients can be saved.

[0004] In Patent Document 1, it is proposed to use nitrogen-substituted water in which oxygen contained in ordinary water is replaced with nitrogen as a preservation solution for transplant organs. In Patent Document 2, it is disclosed that nitrogen-substituted water or nitrogen-substituted ice is used for preservation in order to prevent oxidation and spoilage of fresh foods such as seafood.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

[0006] Patent Document 1 discloses a basic method for producing nitrogen-displaced water for use as a preservation solution, but it does not disclose specific conditions for nitrogen-displaced water for organ preservation or its organ preservation effects.

[0007] The present invention aims to provide an immersion preservation method and a preservation solution used therein that can maintain transplant organs in good condition for a longer period than conventional methods. [Means for solving the problem]

[0008] To solve the above problems, the present invention has the following configuration. A first aspect of the present invention is a method for immersion preservation of organs for transplantation, A method characterized by immersing an organ to be transplanted in a nitrogen-rich UW solution at a temperature suitable for immersion preservation, having an oxygen dissolved content of 1.0 mg / L or less and a nitrogen content of 90 mg / L or more at one atmosphere. In the above embodiment, a nitrogen-rich UW solution is prepared in which the dissolved oxygen content is 1.0 mg / L or less and the nitrogen content is 90 mg / L or more at one atmosphere and a temperature suitable for immersion storage, and the organ to be transplanted is immersed in the prepared nitrogen-rich UW solution. In the above embodiment, a nitrogen-rich UW solution is prepared having an oxygen content of 1.0 mg / L or less and a nitrogen content of 90 mg / L or more at one atmosphere and room temperature, and the prepared nitrogen-rich UW solution is cooled to a temperature suitable for immersion storage before immersing the organ to be transplanted. In the above embodiment, the nitrogen-rich UW solution is kept from coming into contact with air after preparation until the immersion of the organ to be transplanted is started. A second aspect of the present invention is a nitrogen-rich UW solution for use in immersion preservation of organs for transplantation, having an oxygen dissolved content of 1.0 mg / L or less and a nitrogen content of 90 mg / L or more at one atmosphere. [Effects of the Invention]

[0009] The present invention provides an immersion preservation method and preservation solution that maintains transplant organs in good condition for a longer period than conventional methods. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is an overall diagram showing an example of a nitrogen water production system used in the present invention. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the illustrative drawings. Organs intended for transplantation must be preserved until the transplant surgery while maintaining as much of their physiological and functional state as possible at the time of extraction.

[0012] The method for preserving organs for transplantation according to the present invention is an immersion preservation method in which the organs are immersed in a low-temperature preservation solution. The base of the preservation solution used in this method is a general UW solution. A general UW solution is prepared by adding components such as electrolytes (potassium chloride, disodium hydrogen phosphate, sodium dihydrogen phosphate), nutrients (D-glucose, L-ascorbic acid, L-ascorbic acid phosphate ester), and osmotic pressure regulators (raffinose, maltose, etc.) to water, which is the solvent. The majority of the UW solution is water, and since it is for medical use, it is purified water or distilled water. The UW solution used in the preservation method of the present invention is characterized in that the water portion is not ordinary water, but water that contains more nitrogen than ordinary water (hereinafter referred to as "nitrogen-rich water"). In this specification, a UW solution in which the water portion is nitrogen-rich water is referred to as "nitrogen-rich UW solution".

[0013] "Nitrogen-rich water" refers to water in which dissolved oxygen has been removed as much as possible from ordinary water, and nitrogen has been forcibly added. At one atmosphere and 20°C, the saturated dissolved amounts of ordinary water are approximately 9 mg / L for oxygen and approximately 17 mg / L for nitrogen. The lower the water temperature, the higher the saturated dissolved amounts of these gases. At one atmosphere and 4°C, the saturated dissolved amounts of ordinary water are approximately 11 mg / L for oxygen and approximately 27 mg / L for nitrogen. Dissolution of gas in water refers to the state in which gases are dissolved in water in molecular form. Since oxygen is more soluble in water than nitrogen, a higher proportion of oxygen is dissolved in water than the oxygen-to-nitrogen concentration ratio in the air.

[0014] In the nitrogen-rich UW liquid used in this invention, the water portion contains nitrogen in an amount greater than or equal to the saturation dissolved amount at that temperature. In this case, nitrogen up to the saturation dissolved amount is dissolved in water, and the nitrogen exceeding the saturation dissolved amount exists in the water as fine bubbles. Such bubbles can be generated using, for example, microbubble (diameter approximately 1 to 100 micrometers) or nanobubble (diameter less than approximately 1 micrometer) technology or pressurized dissolution technology. Such bubbles are known to exist stably in water for a long time. In this specification, the amount of nitrogen in the nitrogen-rich UW liquid is referred to as "nitrogen content" rather than "nitrogen dissolved amount".

[0015] Preferably, in a nitrogen-rich UW liquid at one atmosphere, the dissolved oxygen content is 1.0 mg / L or less, and the nitrogen content is 90 mg / L or more. These amounts correspond to approximately 0.1 times the saturated dissolved oxygen and approximately 5.3 times the saturated dissolved nitrogen at 20°C, and approximately 0.09 times the saturated dissolved oxygen and approximately 3.3 times the saturated dissolved nitrogen at 4°C.

[0016] The organ for transplantation must be immersed in a preservation solution at a temperature suitable for immersion preservation. The temperature suitable for immersion preservation is, for example, 4°C. Here, "4°C" is not a strict numerical value but a value including a predetermined range in line with the common sense of the general preservation temperature of the organ for transplantation. The organ for transplantation is immersed in the preservation solution filled in a bag or a container. Various known methods can be adopted for the cooling method of the preservation solution. The simplest method is to indirectly contact it with ice. For more accurate temperature control, a cooling system equipped with a temperature sensor and a control device may be used.

[0017] When using nitrogen-rich UW solution as the preservation solution, it is preferable that the liquid surface of the nitrogen-rich UW solution does not come into contact with air so that no new oxygen dissolves into the solution during the period from its preparation to the start of use and during the period from the start of use to the end of preservation. If there is residual air in the bag or container filled with the nitrogen-rich UW solution, there is a possibility that oxygen may dissolve into the nitrogen-rich UW solution. To prevent this, for example, it is suitable to seal the bag or container without leaving air inside, or to fill the space in the bag or container with nitrogen gas.

[0018] <Method for preparing the preservation solution> FIG. 1 is an overall configuration diagram showing an example of a production system for nitrogen-rich UW solution. Referring to FIG. 1, an example of the method for preparing nitrogen-rich UW solution will be described.

[0019] First, the storage tank 4 is filled with ordinary UW solution. Then, nitrogen gas is injected into the UW solution for a predetermined time. Thereby, the dissolved oxygen in the UW solution is expelled into the air, nitrogen is dissolved into the UW solution up to the saturated dissolved amount, and further nitrogen is included as fine bubbles exceeding the saturated dissolved amount. In this way, a nitrogen-rich UW solution with a rich nitrogen content is obtained.

[0020] The air compressor 1 is an air compressor (for example, an oil-free Bebicon (registered trademark) manufactured by Hitachi Industrial Equipment Systems Co., Ltd.) that compresses the atmosphere and sends it to the nitrogen gas extractor 2. One with a supply air pressure of 0.5 MPa to 0.9 MPa is used.

[0021] The nitrogen gas extractor 2 has a pressure vessel having a nitrogen separation membrane made of a polyimide hollow fiber membrane. The nitrogen gas extractor 2 is a degassing device that takes in compressed air from the air compressor 1 at one end of the pressure vessel, purges oxygen gas from the discharge port on the side of the pressure vessel, and sends out nitrogen gas from the other end of the pressure vessel. This degassing device utilizes the fact that the permeation rate of the membrane varies depending on the type of gas. The nitrogen gas sent out from the nitrogen gas extractor 2 is sent to the nitrogen gas injector 3.

[0022] The UW solution filled in the water storage tank 4 circulates between the nitrogen gas injector 3 by the circulation pump P2. By this circulation, the dissolved oxygen content of the UW solution in the water storage tank 4 gradually decreases, and the nitrogen content increases. A device integrating the nitrogen gas extractor 2 and the nitrogen gas injector 3 is commercially available (for example, the degassing device "Reprel" (registered trademark) manufactured by Katayama Chemical Industry Research Institute Co., Ltd.).

[0023] In one embodiment, 35 L of UW solution was filled in the water storage layer 4 at 20°C, and nitrogen gas was injected into the UW solution by circulating it for 30 minutes at a pump capacity of 2000 L / hour. UW liquid As a result, a nitrogen-rich UW solution with a nitrogen content of 99.7 mg / L and a dissolved oxygen content of 0.3 mg / L was obtained.

[0024] As an example, by performing nitrogen injection treatment while setting the temperature of the UW solution in the water storage tank 4 to the same temperature as the temperature suitable for organ preservation (for example, 4°C), a nitrogen-rich UW solution at a temperature suitable for immersion preservation can be obtained. Then, the temperature of the nitrogen-rich UW solution is maintained until the start of organ preservation. As another example, after performing nitrogen substitution treatment at room temperature (for example, 10 to 30°C), the nitrogen-rich UW solution may be cooled to a temperature suitable for immersion preservation (for example, 4°C) until the start of organ preservation. In either case, it is preferable to maintain the nitrogen-rich UW solution so that it does not come into contact with air as much as possible until the immersion of the transplant organ starts. For this purpose, it is preferable to remove the residual air in the bag or container storing the nitrogen-rich UW solution or replace the residual air with nitrogen gas.

[0025] <Experiment to confirm the effect of organ preservation by preservation solution> · Experimental method The livers of pigs slaughtered within two hours were used as samples. Each sample was divided into four equal parts, placed in a plastic container, and immersed in one of the following four preservation solutions, then stored at 4°C. Preservation solution 1: Nitrogen-rich UW solution Storage solution 2: UW solution Preservation solution 3: Nitrogen-rich water Preservation solution 4: Physiological saline Preservation solution 1 is a nitrogen-rich UW solution prepared by the same method as in the above-described examples. Preservation solution 2 is a UW solution that has not undergone nitrogen injection treatment. Preservation solution 3 is nitrogen-rich water that has undergone the same nitrogen injection treatment as preservation solution 1 with ordinary water.

[0026] For each immersed sample, observation samples measuring approximately 10 mm x 10 mm were thinly sliced ​​and extracted from the liver margin at 3, 6, 9, 10, 11, 12, 13, 14, 15, 18, 21, 24, and 48 hours after the start of preservation. After fixing the extracted samples with formalin, they were stained with HE and PAS, and observed under a light microscope. The preservation solution was changed every 6 hours.

[0027] Observations using a light microscope were performed in a blind test by experts with extensive experience in analyzing organ tissue images, and each sample was evaluated. For evaluation, each sample stained with HE staining and PAS staining was scored based on the degree of cytotoxicity and neutrophil infiltration, with mild damage at 1 point, moderate damage at 2 points, and severe damage at 3 points. Mild damage corresponds to a condition suitable for transplantation, while moderate and severe damage correspond to a condition unsuitable for transplantation.

[0028] • Experimental results The evaluation results for each sample are shown in Table 1. [Table 1]

[0029] Samples preserved in nitrogen-rich UW solution showed increasing levels of damage after 21 hours (approximately 23 hours after slaughter), but the organs remained in the mildest damaged state for the longest period. In both the UW solution and nitrogen-rich water-preserved samples, the degree of damage increased after 12 hours (approximately 14 hours after slaughter). Samples preserved in physiological saline solution already showed increased levels of damage after 3 hours (approximately 5 hours after slaughter).

[0030] The experimental results showed that nitrogen-rich UW solution has better organ preservation performance compared to general UW solution, nitrogen-rich water, and physiological saline.

[0031] Although the above experiment was conducted on pig livers, pig organs are relatively similar to human organs, so the preservation effect of nitrogen-rich UW solution on human organs can be reasonably inferred. The liver is an organ that is vulnerable to ischemia and easily deteriorates. Since nitrogen-rich UW solution has been confirmed to have a good preservation effect on livers, it is thought to be effective in preserving organs for transplantation such as the heart, pancreas, kidneys, and small intestine. According to the above experimental results, liver preservation using nitrogen-rich UW solution was started 2 hours after slaughter, and the liver remained in good condition even after being preserved for 18 hours. With general UW solution, preservation has been limited to about 12 hours after organ removal, but with the nitrogen-rich UW solution of the present invention, preservation for up to about 20 hours is expected. According to the present invention, it will be possible to significantly extend the preservation time of organs for transplantation. [Explanation of symbols]

[0032] 1. Air compressor 2. Nitrogen gas extractor 3. Nitrogen gas injector 4. Water storage tank

Claims

1. A method for immersion preservation of organs for transplantation, A method characterized by immersing an organ to be transplanted in a nitrogen-rich UW solution at a temperature suitable for immersion preservation, having an oxygen dissolved content of 1.0 mg / L or less and a nitrogen content of 90 mg / L or more at one atmosphere.

2. The method according to claim 1, characterized by preparing a nitrogen-rich UW solution having an oxygen content of 1.0 mg / L or less and a nitrogen content of 90 mg / L or more at one atmosphere and a temperature suitable for immersion storage, and immersing the organ to be transplanted in the prepared nitrogen-rich UW solution.

3. The method according to claim 1, characterized in that a nitrogen-rich UW solution is prepared having an oxygen dissolved content of 1.0 mg / L or less and a nitrogen content of 90 mg / L or more at one atmosphere and room temperature, and the prepared nitrogen-rich UW solution is cooled to a temperature suitable for immersion storage before immersing the organ to be transplanted.

4. The method according to 2 or 3, characterized in that, after the preparation of the nitrogen-rich UW solution, the nitrogen-rich UW solution is kept from coming into contact with air until the immersion of the organ to be transplanted is started.

5. A nitrogen-rich UW solution for immersion preservation of organs for transplantation, having an oxygen content of 1.0 mg / L or less and a nitrogen content of 90 mg / L or more at one atmosphere.

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