ENDOTHELIAL CELL HARVESTING KIT

Abstract: A cell harvesting kit, for harvesting cells from a vein of a patient, has a packaging container (11) containing three trays (12,14,31), a support (16) holding the components needed for cell harvesting, and three vials (28) containing enzyme solutions and salt solution, respectively. The three trays include an outer tray (12) having a lid (13) engaged therewith to preserve sterility, a component tray (14) within the outer tray, the component tray (14) having a sealed lid (17) and having a shelf about its perimeter for supporting the support (16) having depressions therein for holding the components needed in cell harvesting, and a third tray contained within the component tray, the third tray comprising a process tray (31) with a trough (30) in which an excised vein may be placed for harvesting. A method for harvesting cells from a vein of a patient is also provided.

Description: This invention relates to an endothelial cell harvesting kit which allows one to rapidly obtain viable human endothelial cells. Previous research efforts have been directed to develop antithrombogenic linings in synthetic vascular prostheses by endothelial cell seeding. In order to develop these linings natural endothelial cells must first be extracted from segments of human arteries and veins. Endothelial cell harvesting is a process for removing viable endothelial cells from a portion of autologous vein. (See for example, Eric A. Jaffe, "Biology of Endothelial Cells" (1984) Martinus Nijhoff Publishers) Cell harvesting is accomplished by mechanical scraping or rubbing, or enzymatic treatment. One use for the harvested cells is to "seed" vascular prostheses. Extensive animal experimentation and limited experience in humans indicate that seeded grafts endothelialize more quickly, induce less platelet reaction, and have better patency than non-seeded grafts. Adjunctive antiplatelet therapy may be required until the endothelial lining has developed. Antiplatelet therapy, however, is a standard procedure for patients receiving vascular grafts. Briefly, harvesting is performed as follows. A segment of autologous vein is excised from a subject and the endothelial cells are removed. The cells so derived are concentrated by centrifugation, suspended in an aliquot of the subject's blood, and placed in the vascular graft until a thin layer of clot is formed on the graft wall. The "seeded" graft is immediately implanted in the subject. Endothelial cells "seeded" into the graft subsequently grow to confluence on the luminal surface thus providing the graft with a true neointima. Only autologous cells are used in this process. The present invention provides a cell harvesting kit comprising a packaging container containing three trays, a support holding the components needed for cell harvesting and three vials, said vials containing enzyme, Hanks' Balanced Salt Solution (HBSS) for reconstituting the enzyme, and HBSS, respectively; said three trays comprising: (a) an outer tray having a lid sealingly engaged with said outer tray to preserve sterility of its contents; (b) a component tray within said outer tray, the component tray having a sealed lid and having a shelf about its perimeter for supporting a support member having depressions therein for holding said components needed in cell harvesting, said component tray also containing the third of said three trays, said third tray comprising; (c) a process tray having a trough in which an excised vein may be placed for harvesting cells therefrom. Hanks' Balanced Salt Solution is well known in the art for the preservation of mammalian tissue (Hanks, J.H. 1975, Tissue Culture Assn. Man. I (1): 3-4, and Hanks, J.H. and R.E. Wallace, 1949, Proc. Soc. Exp. Biol. and Med. 71: 196-200). It provides a balanced salt solution which meets most requirements for inorganic salts and pH control of mammalian cells being handled in an in vitro system. The balanced salt solution provides constant levels of ionized Ca at 5 mg% when mixed in any ratio with serum. The support member of the component tray of the cell harvesting kit further contains at least two disposable pipettes, two centrifuge tubes, two cannulae, two syringe tips in a case, and two syringe bottoms in a case. In an alternative embodiment of the process tray, the trough is offset from the centerline of the process tray and three depressions are located therein in which the three vials are held in place. A method for harvesting cells from a vein of a patient is also provided comprising the steps of excising a vein from the patient and placing the vein in the trough of the process tray and stretching the vein to its approximate in vivo length, flushing the vein with HBSS, filling the vein with neutral protease, allowing the neutral protease and cell solution to stand and transferring the solution to a centrifuge tube. Dispase I and II are preferably used as the neutral protease. The method steps for harvesting cells from a vein may be repeated. The invention will now be particularly described, by way of example, with reference to the accompanying drawings in which:- Figure 1 shows a top plan view of a cell harvesting kit according to the present invention; Figure 2 shows a side elevational view, partly in cross-section, of the cell harvesting kit of Figure 1; Figure 3 is a side elevational view, partly in cross-section, of the cell harvesting kit taken along line 3-3 of Figure 1; Figure 4 is a top plan view of the process tray of the kit; Figure 5 is a front elevation, partly in cross-section, of the process tray taken substantially along line 5-5 of Figure 4; Figure 6 shows an end elevational view of the process tray; Figure 7 shows a top plan view of an alternative embodiment of the process tray in which the trough for processing the vein is located to one side of the tray; Figure 8 shows a side elevational view of an alternative process tray according to the present invention, partly in cross-section, taken substantially along line 8-8 of Figure 7; Figure 9 shows an end elevational view of the alternative process tray; Figure 10 shows the method step of cannulating the vein; figure 11 shows the method step of mounting the vein and cannulae in the process tray; Figure 12 shows the method step of flushing the cells from the vein into a centrifuge tube; Figure 13 shows the method step of centrifuging the solution to form a pellet of cells at the bottom of the tube; Figure 14 shows the method step of drawing off the supernatent with the pipette after centrifugation; Figure 15 shows the method step of resuspending the cells in a small amount of blood; Figure 16 shows the method step of drawing the blood-cell mixture into the syringe, and Figure 17 shows the method step of injecting the blood-cell mixture into a graft. In the illustrated endothelial cell harvesting kit, a combination of components needed for harvesting, enzymes, and salt solutions are brought together for easy access in the harvesting of cells from veins. This kit may be used directly in the operating room and the harvesting of cells may occur during an operation. The preferred temperature of the solutions used during harvesting is in the range from about 20°C to 37°C. The temperature may be maintained by a supplementary heating element not provided in the kit. The neutral protease enzymes that may be used in this kit and with this method include Dispase I and Dispase II. In the cell harvesting kit, a rectangular container having a sealed lid and containing three trays and a support member is provided. The three trays include a generally rectangular process tray having a longitudinal trough in which a vein is to be placed for cell harvesting, contained with a component tray having a moulded support in which a plurality of depressions are located for utensils used in cell harvesting such as pipettes, cannulae, syringes, needles, and centrifuge tubes, all contained within an outer tray hermetically sealed for maintaining sterility of the component tray and the process tray contained within. In an alternative embodiment of the process tray, a plurality of depressions are located in the process tray in which are placed the vials containing neutral protease and salt solutions and the trough in which a vein is to be placed for cell harvesting is offset from the center line of the tray. In the embodiment illustrated in Figure 1, the harvesting kit 10 is comprised of a packaging container 11, and the three trays namely an outer tray 12 having a lid 13, a component tray 14 having a support 16 and lid 17, and a process tray 31. Preferably lids 13 and 17 are transparent plastic. As depicted in Figure 1, the support member 16 contains depressions 19,21,23,25 and 27 designed to hold components needed in harvesting of cells. The following components are found within this support member 16: two disposable pipettes 18 located in depressions 19, two 1.5 ml centrifuge tubes 20 located in depressions 21, two cannulae 22 in depressions 23, two syringe needle cases 24 containing needles 34 located in depressions 25, and two syringe cases 26 containing syringes 15 located in depressions 27. A longitudinal depression 29 provides easy access to the various components by the person using the kit. Three vials 28 are located outside of the support member 16, component tray 14, and outer tray 12 but within the container 11. The three vials contain the neutral protease enzyme, HBSS for reconstituting the enzyme, and HBSS for rinsing the vein and cells, respectively. In the sectional view of Figure 2 a trough 30 is seen in the process tray, the trough being designed to contain the excised vein. The components are placed within the support member 16 so that, in the case of pairs of components 18,20,22 and 26, the head of one component of the pair is adjacent to the bottom of the other component of the pair within their specific depressions. Thus, for example, the pipettes 18 viewed in Figure 2 show the head of one pipette adjacent the bottom of the other. As shown in the top plan view of Figure 4, the process tray 31, the trough 30 in which the vein is to be placed is located within the center of the tray 31, and at either end of trough 30 are located slots 32 for accepting the cannulae. In the alternative embodiment of the process tray 31′ shown in Figure 7,8 and 9 the trough 30′ for the vein is located to one side of process tray 31′ rather than in the center of the tray. There are also three depressions 33 within the tray 31′ for holding the vials 28. At either end of trough 30′ are located slots 32′ for accepting cannulae. Components which may also be needed but are not part of the kit include one clinical centrifuge capable of providing a centrifugal force of 300 times gravity with a rotor to accept 15 ml tubes, one heat block to warm the tray, and one valvulotome. Modifications may be made in the design of the container and trays, the packaging of the enzyme and HBSS, the number and size of the syringes, the number of pipettes, the number of centrifuge tubes, and/or the method of cell collection after harvesting. Figures 10 through 17 show the method steps undertaken in the use of the kit to harvest endothelial cells. Generally, to use the kit,while a patient is being prepared for vascular reconstructive or bypass surgery, a small segment of vein 35 is removed. As depicted in Figure 10, the removed vein is cannulated with the cannulae 22 at each end of the vein. As shown in Figure 11, the vein 35 and cannulae 22 are then mounted in the process tray 31 within the trough 30. The lumen of the vein is gently rinsed by flushing with HBSS. If obstructive valves are encountered, they are to be cut with a valvulotome. The vein is filled with the reconstituted neutral protease preferably Dispase. After five minutes, the enzyme solution is withdrawn and replaced with fresh enzyme. Ten minutes later, the vein 35 is again drained. Both collections of enzyme solution are combined in one of the centrifuge tubes 20 as shown in Figure 12. The vein is then rinsed with HBSS which is collected and divided between both centrifuge tubes 20. After equalizing solution levels in the two tubes with HBSS, the solutions are centrifuged in a centrifuge 40 at 300 times gravity for three minutes as shown in Figure 13. A pellet should be visible at the bottom of one or both trays after centrifugation. As shown in Figure 14, the supernatent is carefully aspirated from over the cell pellet in the centrifuge tube 20 containing the enzyme solutions with a pipette 18. Fresh HBSS is poured into the tube 20 and the cells are resuspended by gentle agitation. The supernatent in the second tube 20 is also carefully aspirated, and the cell pellet is resuspended in the cell suspension of the first tube 20 by gentle agitation. One drop of the cell suspension is removed and placed on the microscope slide so that the presence of cells may be confirmed. Twenty minutes prior to graft implantation, 10 to 20 ml of nonheparinized blood are withdrawn from the patient. A small amount of fresh nonheparinized blood is mixed with the cell suspension in the first tube 20 as shown in Figure 15. This step is done immediately before seeding the vascular graft 42. A small amount of nonheparinized blood is also used to coat the inner surface of the vascular graft 42. This is done by closing one end of the graft with an atraumatic clamp and injecting the blood into the graft. The graft is gently massaged to completely coat the inner surface. After five minutes, any excess blood is poured out of the graft. Next, the blood-cell suspension is drawn into syringe 15 as shown in Figure 16 and is then injected into the graft 42 as shown in Figure 17 and the open end clamped. The blood-cell suspension is distributed over the surface of the graft by gentle tipping, turning, and massaging. Modifications of the kit may be made to improve the ease of handling of the vein and endothelial cells, increase the yield of endothelial cells, and/or reduce the time required for cell harvesting and seeding.

Claims: A cell harvesting kit comprising a packaging container (11) containing three trays (12, 14, 31), a support holding the components needed for cell harvesting and three vials, said vials containing enzyme, Hanks' Balanced Salt Solution (HBSS) for reconstituting the enzyme, and HBSS, respectively; said three trays comprising: (a) an outer tray (12) having a lid (13) sealingly engaged with said outer tray to preserve sterility of its contents; (b) a component tray (14) within said outer tray, the component tray having a sealed lid (17) and having a shelf about its perimeter for supporting a support member (16) having depressions therein for holding said components needed in cell harvesting, said component tray also containing the third of said three trays, said third tray comprising; (c) a process tray (31) having a trough (30) in which an excised vein may be placed for harvesting cells therefrom. A cell harvesting kit according to claim 1 in which said support member contains at least two disposable pipettes (18), two centrifuge tubes (20), two cannulae (22), two syringe tips (34) and two syringe bottoms (15). A cell harvesting kit according to claim 1 wherein said trough (30) in said process tray (31) is offset from the centerline of the process tray and said process tray has three depressions (33) therein in which said three vials are held in place. A method for harvesting cells from a vein of a patient using a cell harvesting kit, said kit having a process tray (31) containing a trough (30), the method comprising the steps of (a) placing an excised vein in the trough of said process tray and stretching said vein to its approximate in vivo length, (b) flushing said vein with Hanks' Balanced Salt Solution (HBSS), (c) filling said vein with a neutral protease and allowing the protease and cell solution to stand, and (d) transferring said protease and cell solution to a centrifuge tube for further processing. A method according to claim 4 in which said neutral protease is Dispase I. A method according to claim 4 in which said neutral protease is Dispase II. A method according to claim 4 in which steps b, c, and d are repeated.

Inventors: BOWMAN, PHILLIP DALTON, FISHER, JOHN LEWIS, WORKINGER, DAVID MARK
Applicants: W.L. GORE & ASSOCIATES, INC.
Application year: 1987
Main classification: A61F2
IPC codes: A61B10, A61F2, A61B5, C12N5, A61L27