US 20060121438 A1
A method of preserving, storing and transplanting mammalian donor organs. The method includes the cooling of refrigeration preservation, loading pre-freezer preservation, cryopreservation and washing solutions at least containing polyvinylpyrrolidone, a calcium channel blocker, a nucleoside, potassium chloride, polyethylene glycol, at least one amino acid, and a steroid to a temperature of 2° to 4° C. and/or of 0° to 2° C., harvesting a donor organ, perfusing it with one or more of the solution, immersing it in one or more of the solutions and storing it at a temperature above 0° C. or at a temperatures below 0° C. The cryopreservation solution also contains cryopreservative agents. Preserved organs may be transplanted directly from refrigeration storage or from freezer storage by cooling the washing refrigeration preservation solutions to 2° to 4° C., perfusing the organ with washing solution and then preservation solution, and transplanting it.
1. A method of preserving mammalian donor organs or tissues at refrigeration temperatures comprising:
cooling a refrigeration preservation solution at least containing polyvinylpyrrolidone (PVP-40), a calcium channel blocker, a nucleoside, potassium chloride, polyethylene glycol, at least one amino acid, and a steroid to a temperature between 2° and 4° C.;
harvesting a donor organ;
perfusing the donor organ with the refrigeration preservation solution;
immersing the donor organ in refrigeration preservation solution; and
storing the donor organ in the refrigeration preservation solution at a refrigeration temperature above 0° C.
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removing the preserved donor organ from a refrigeration temperature above 0° C.; and
This application claims the benefit of U.S. Provisional Application No. 60/471,028, filed May 15, 2003, and U.S. Provisional Application No. 60/465,114 filed Apr. 23, 2003, both of which are incorporated herein by reference.
The invention relates generally to organ storage systems. More particularly, the invention relates to solutions and methods for preserving donor organs and storing them for extended periods of time before transplantation or other use in the future.
One of the greatest problems in donor organ transplantation is the storage and preservation of organs between the time of harvest from a donor and the time of transplantation into a recipient. The amount of time that can lapse between the two events is quite limited because the cells and tissues of the donor organ deteriorate over time, even if they are stored at refrigerated temperatures. Once harvested, cells and tissues are deprived of the oxygen that is required to maintain internal metabolism and cell volume integrity. To counteract the ill effects of low oxygen, standard techniques for modern organ preservation involve the exposure of a harvested organ to preservation solutions at cold temperatures not below 0° C. Although colder temperatures are a solution to oxygen deprivation in donor organ tissue, they present their own problems. Cold or hypothermic conditions may lead to cellular damage including a reduced ability to generate energy, maintain cell volume integrity, and also swelling and/or cell death.
A widely used preservation solution is commonly known as University of Wisconsin (UW) solution or Viaspan, which is manufactured by DuPont. However, the preservation of donor organs using Viaspan is generally limited to a 36-hour period in kidneys before the organs begin to deteriorate. For example, if kidneys are perfused with UW solution and packed on ice, surgeons will attempt to use them within 24 hours but not later than 36 hours after harvesting. A principal problem however is that the viability of the donor kidney decreases over time of storage so that by 36 hours there is at least some damage to the tubular cells. This generally results in decreased viability of the kidney cells so that urine production and proper kidney function are delayed after transplant. As a result, artificial kidney function or dialysis is generally required for full recovery of a recipient after transplantation.
Storage of organs at sub-zero temperatures is not possible or extremely difficult because the tissue and water in the organ usually freezes. These relatively lower temperature ranges cause damage or destruction to the cells and tissues. Today there are some solutions currently available for organ storage purposes such as Viaspan, but their capacity to store organs effectively is generally limited. There is a need for improved solutions and methods for effective organ preservation for extended periods of time.
The invention describes solutions and methods for preserving donor organs for use in transplantation or other medical purposes in the future. In accordance with one aspect of the invention, a variety of storage methods at different temperatures are provided. The invention provides for example a first series of methods for cold storage or storage at refrigerator temperatures (about 0° to about 6° C.), and a second series of methods for storage at sub-zero temperatures as low as about −20° C., which is generally the equivalent to a refrigerator freezer temperatures, or even lower temperatures including cryopreservation temperatures that drop to as low as about −80° C. Other aspects of the invention provide preservation solutions that can be designed to provide low temperature organ storage benefits including reduction of interstitial edema and endothelial swelling. These solutions can also provide antioxidant and anti-proteolytic protection, can preserve proper intracellular ion concentration, and can offer an energy source to support cellular functions including the Krebs cycle.
Other goals and advantages of the invention will be further appreciated and understood when considered in conjunction with the following description and accompanying drawings. While the following description may contain specific details describing particular embodiments of the invention, this should not be construed as limitations to the scope of the invention but rather as an exemplification of preferable embodiments. For each aspect of the invention, many variations are possible as suggested herein that are known to those of ordinary skill in the art. A variety of changes and modifications can be made within the scope of the invention without departing from the spirit thereof.
The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:
Current organ preservation, storage and transplantation procedures are limited because organs are so vulnerable to damage after removal from a donor. Once harvested, cells and tissues are deprived of the oxygen that is required to maintain internal metabolism and cell volume integrity. This low oxygen state is called ischemia and leads to hypoxia, which prevents oxygen from being delivered to the organ tissue. Without oxygen, cellular tissue can suffer injury as cell metabolism fail and individual cells can be subject to swelling or inflammation.
To counteract the ill effects of ischemia, standard techniques for modern organ preservation involve the exposure of a harvested organ to preservation solutions at cold temperatures not below 0° C. This treatment essentially creates hypothermic conditions that reduce a cell's need for metabolic oxygen. Components of the solution and the cold environment combine to protect the cell from ischemic conditions and thereby prevent the onset of injury. This procedure is known as cold flush preservation, in which the preservation solutions are designed to eliminate chemical potential gradients across the cell membranes of the cells composing the organ. By doing so the solution tends to mimic the intracellular environment and prevent the donor organ cells from activating metabolic pathways. Although hypothermia is a solution to oxygen deprivation in donor organ tissue, it presents its own problems. The cells of an organ preserved under hypothermic conditions lose their ability to source of ATP, and therefore cannot produce the energy required to regulate the sodium-potassium pump, which is one of the most important modulators of internal cell volume. Also the hypoxic environment induces the release of intracellular calcium and elevated concentrations of calcium can lead to subsequent activation of multiple metabolic inflammatory pathways. As a result, the cells may exhibit endothelial cell swelling, a loss of blood vessel integrity, including the reduction in the internal diameter of blood vessels called a vasospasm, and even cell death in tubules.
One of the most widely used solutions in organ preservation and storage is known as University of Wisconsin (UW) solution or Viaspan, which is manufactured by DuPont. However, preservation of donor organs using Viaspan is generally limited to a 36-hour period in kidneys before the organs begin to deteriorate.
In general, the current limitations on donor organ preservation time seriously hamper the capacity of organ transplantation procedures. The 36-hour time frame allowed for kidneys does not always provide sufficient time for accurate cross-matching of donors and recipients, which is needed to increase the chances of a successful transplant. In addition, the time required for transnational and trans-international transport of donor organs and of recipients may exceed the viability period of organs preserved under current procedures.
Methods for Preservation Storage and Transplantation
The invention provides improved methods and solutions for storing organs for future medical uses such as organ transplants into a recipient. In one aspect of the invention, methods are provided using various preservation solutions and cryopreservation solutions to prepare and store a donor organ after it is harvested. The preserved organ can then be placed in storage at an appropriate temperature for prolonged periods of time that can be greater than 36 hours. With respect to another embodiment of the invention, when the preserved organ is required for transplantation, the combination of a preservation solution and a washing solution can be utilized to thaw the organ from storage and transplant it into a recipient.
At the time a donor organ becomes available, a potential recipient may not yet have been identified. One embodiment of the invention addresses such a problem as follows. The donor organ may be prepared as above in steps 101-103, and then stored at an appropriate temperature as in step 104. At a later date when the appropriate recipient for the stored donor organ becomes available, it can be thawed and transplanted as in step 105. One embodiment of the invention utilizes a washing solution that is followed by a preservation solution to thaw the stored organ in preparation for the transplantation procedure.
The flowchart in
In another embodiment of the invention as shown in
FIGS. 3A-B provide flowcharts that illustrate the methodology and operation of alternative embodiments of the invention. A preserved organ can either be removed from refrigeration temperatures and transplanted as shown in
An alternate embodiment of the invention provides suitable solutions and methods for organ storage at cryofreezer temperatures. The steps described in
Solutions Used for Preservation, Storage and Transplantation
One of the most widely used solutions in organ preservation and storage is known as University of Wisconsin (UW) solution or Viaspan, which is manufactured by DuPont. However, preservation of donor organs using Viaspan is generally limited to a 36-hour period in kidneys before the organs begin to deteriorate. The solutions described herein may allow for significantly longer storage periods.
A variety of organ preservation and storage solutions are provided herein in accordance with invention. These preservation solutions may contain one or more of the following ingredients: a large molecule hydrophilic polymer used for cellular protection of the organ, agents for reducing interstitial edema or fluid buildup inside cells, an energy source for cellular functions, agents for maintaining cellular ion concentrations including a variety of salts, and series of one or more amino acids that can help prevent proteolysis and to scavenge free radicals as antioxidants. Other solution additives may include cell membrane stabilizers and anti-inflammatory agents.
The table in
It is important to note that the NaCl concentration is generally higher in Solution #2 than in Solutions #3 and #4 because the organ is being dehydrated slightly. This removal of water from the cell will reduce the likelihood that ice crystals will be formed during the freezing process of the organ. The DMSO in Solution #3 also plays a role by replacing the lost water from the cell. As DMSO has a lower freezing point, the cell will be less likely to form ice crystals.
Solution #4, the washing solution, generally contains the same ingredients as found in Solutions #1 and #2, except the concentration of NaCl is typically lower than in Solution #1. This allows Solution #4 to wash out the cryosolution, Solution #3, and rehydrate the cell. The DMSO from Solution #3 that had replace water in the cell prior to freezing is washed out and water is added back as the temperature of the stored organ is restored to normal.
It is important to note that the concentrations and the ranges of concentrations of each ingredient of Solutions #1-#4 are relatively low compared to other organ preservation/storage solutions currently available, such as Viaspan. Viaspan contains ingredients in higher concentrations than the solutions described herein. Higher ingredient concentration however generally increases the toxicity of the solution to the donor organ.
Kit for Organ Preservation, Storage and Transplantation
In accordance with yet another aspect of the invention, each of the Solutions #1, #2, #3 and #4 described herein can be stored in separate containers within a single package or a kit. Such kits may be marketed to entities engaged in the business or activities of harvesting, storing, preserving and/or transplanting donor organs. These kits may include instructions for methods of organ preparation and storage as described elsewhere herein. In accordance with an aspect of the invention, various types of mammalian organs can be treated and prepared for storage over extended periods of time. While experiments were conducted in the following examples with rat kidneys, the invention here can be applied to human subjects or other mammals and their respective organs.
Organ Storage at Cold Storage or at Refrigerator Temperatures
Donor rat kidneys were harvested by usual methods and perfused with Solution #1 (described below), comprised of ingredients listed in the table below. This solution is a mixture designed to reduce interstitial edema and endothelial swelling, contains antioxidants and anti-proteolytic amino acids, and preserves proper intracellular concentrations of ions including magnesium, sodium, and potassium. This solution is comprised of macromolecules, impermeable molecules, amino acids, energy sources that support the Krebs cycle, and salts. The pH of this solution is about 7.3+/−0.1.
The kidneys that were perfused with Solution #1 were stored in a refrigerator at about 2° to 4° C. for 36 hours and then transplanted into anephric rats using a published method. The transplanted kidneys were observed to quickly turned pink with fresh blood and immediately began producing urine.
In contrast, donor kidneys perfused with UW solution and stored for 36 hours in the refrigerator did not turn as bright with blood nor did they make appropriate amounts of urine after transplantation.
Organs perfused or stored in a solution such as this Solution #1 or equivalent solution can be stored for extended periods and recover and function rapidly after transplantation. Specifically, kidneys can be stored for 36 hours, 40 hours, 48 hours, 50 hours, or longer and then transplanted and are viable and they function.
Organ Storage at Sub-Zero Temperatures (Below 0° C.)
Two solutions are used in sequence to perfuse or wash organs in preparation for sub-zero storage (Solution #2 and Solution #3 described below). After storage at sub-zero temperature, Solution #3 is washed out with Solution #4 (described below) followed by washing with Solution #1, and the organ is transplanted. These solutions #2, #3, and #4 are similar to Solution #1 with some modifications for use in cryopreservation (storage at sub-zero temperatures). Solution #3 (cryosolution) contains cryoprotectants. All solutions are cold at about 2 to 4° C. when used for perfusing or washing organs.
The donor rat kidneys were perfused for 30 minutes at 2° to 4° C. with Solution #2 which is the same as Solution #1 except that sodium chloride is at 2.5% and amounts of PEG and sucrose are increased. Then the donor kidneys were perfused at 2° to 4° C. for 30 minutes with Solution #3 (cryopreservation solution). The kidneys were placed into a refrigerator's freezer at about −20° C. Kidneys were stored for days, but could be stored for much longer periods or weeks or months.
The kidneys did not freeze because of the use of the perfusion solutions and the system utilized as indicated above.
After removing the kidneys from the freezer, the kidneys were perfused with a washing solution (Solution #4), which is identical to Solution #2 except that the amount of NaCl is 10 mM. Finally, kidneys were perfused for 30 minutes with Solution #1 and transplanted. The transplanted kidneys were observed to turn pink in color as they were reperfused with blood and immediately produced urine.
The solutions used in this example are comprised as listed in the tables below.
By following the method stated above and using the invented solutions described, or essentially equivalent solutions, organs can be stored at sub-zero temperatures for extended periods of time of days, weeks, or months, until used for transplantation by following the stated method of this invention.
Solutions listed below are all at a pH of about 7.3+/−0.1 in a phosphate buffer comprised of 950 ml water, 10 ml 1M monobasic phosphate, and 40 ml 1M dibasic phosphate.
The following is a description of a procedure in accordance with the invention for organ storage of four rat kidneys at temperatures as low as about −80° C. The same solutions described herein may be applied for storage at temperatures generally in this range.
Each of the kidneys can be dissected in a standard manner isolating the renal flow with silk. The venous drainage is opened which may be accomplished usually by sectioning the renal vein. A 27 g needle may be inserted in the isolated arterial system so flushing of the kidney can start immediately. It is desirable to avoid air circulation or the introduction of air bubbles into the system during this process. An infusion with 1 ml of volume of the loading hypertonic solution (Solutions #2) may be performed in about 1 minute at 2 to 4° C. Then the organ is removed and immediately immersed in the same solution at 0 to 2° C., and is maintained at this temperature in the loading solution for 30 minutes. Then the infusion of 10 ml of the subzero solution (anti-freeze Solution #3) is initiated at 0.300 ml per minute, and the kidney is maintained at 0 to 2° C. during this infusion. The graft immersed in the antifreeze solution is subsequently placed in the freezer at −20° C. for 12 hours, and then placed in the cryo-freezer at −80° C. for cryo-preservation.
To warm up the organ after its storage at −80° C. for cryo-preservation, it is initially placed in a −20° C. surrounding for 12 hours (regular freezer). Afterwards it is placed at a 0 to 2° C. environment, and then 10 ml of the washing solution (Solution #4) is introduced at 0.300 ml per minute. The kidney is maintained at 0 to 2° C. during this infusion. Subsequently the graft is placed in a refrigerator at 2 to 4° C. for at least one hour. Each of the kidneys were then transplanted in a customary fashion and then allowed circulation of blood. The Reperfusion Damage Index was measured during the first 15 minutes. The graft was removed at 60 minutes of reperfusion and placed in buffered formal in 10% for histology (H&E) and pictures taken at 600×. The histology yielded positive results with intact glomeruli and the cellular structure in the kidneys were generally maintained following organ storage at −80° C. in accordance with the invention herein.
As evidenced by the examples mentioned above, the methods and solutions herein provide organ storage at temperatures as low as −20° C. or even lower at about −80° C. These techniques may be applied to other mammalian organs including human kidneys.
While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.