|Title of Invention||
METHOD FOR DECELLULARISING FOREIGN MATERIAL FOR THE PRODUCTION OF BIOPROSTHESES
|Abstract||A method for decelltflarizing allogenic and xenogenic foreign material using biodetergents to produce bioprostheses coated with endogenic cells from the recipient of the prosthesis, characterized in that the foreign material is initially treated with bile acid to kill the cells and to coat the cells as well as to separate the bond with the tissue matrix, then treated with alcohol to kill more cells, each of these steps being followed by a rinsing step and at least the last rinsing step being executed in a media flow so that the fluid forces act mechanically on the tissue matrix and the ceils.|
|Full Text||FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION (See Section 10, rule 13)
METHOD FOR DECELLULARISING FOREIGN MATERIAL FOR THE PRODUCTION OF BIOPROSTHESES
AUTOTISSUE GMBH of HESSISCHE STRASSE 3-4, D-10115 BERLIN, GERMANY GERMAN Company
The following specification particularly describes the nature of the invention and the manner in which it is to be performed : -
The present invention relates to a method for decellular-izind allogenic and xenogenic foreign material using bio¬detergents for the production of bioprostheses coated with endogenic cells of the recipient of the prosthesis.
It is required to provide an „acellular" structure that is free from foreign cells in order to prevent immu¬nological reactions and to ensure the growth and regen¬eration of the newly established endogenic cells for pro¬ducing bioprostheses from allogenic and xenogenic foreign material coated with endogenic cells of the later recipi¬ent. However the known decellularization methods and uses of biodetergents fail to extract the entire cell material from the tissue matrix so that viral - as yet unknown -effects, e.g. as can be produced by viruses contained in porcine tissue, cannot be excluded.
It is the problem of the present invention to specify a method for decellularizing foreign material intended for being coated with endogenic cells that ensures complete but gentle removal of cells from the foreign tissue.
This problem is solved according to the invention by a method comprising'the characteristics described in claim 1.
In other words, the inventive idea is to remove foreign cells from the initial allogenic or xenogenic product to be re-coated with endogenic cells by combining a treat¬ment with bile acid, a treatment with alcohol and up¬stream and downstream rinsing steps with the mechanical
impact of a flowing medium on the tissue cells to be removed at least in the last
matrix and the rinsing step.
The bile acid that is preferably used in the form of de¬oxycholic acid causes gradual - or with a mechanical im¬pact, accelerated - coating of the cells with the acid to ere cite a separating layer between the matrix made of col¬lagen and elastin (hereinafter called ^collagen matrix') and the cell and to detach the cell from the matrix. At the same time, deoxycholic acid has a cytolytic effect. Tirte detached cells and the deoxycholic acid are rinsed off in a subsequent rinsing step. The subsequent treat¬ment with alcohol, preferably with ethanol or propanol, completely disposes of any residual deoxycholic acid as it dissolves well in alcohol. The residual deoxycholic acid that may be present detaches any cells that remained in the matrix while the alcohol has a cytocidal and anti¬viral effect. The subsequent last rinsing step is a pref¬erably pulsating flow whose forces act upon the walls of the respective organ portion and expand the matrix but also apply a direct mechanical force onto residual cells and remove them from the expanded matrix.
It is conceivable that other or all steps of the method are connected with such mechanical action by a preferably pulsating flow. Thus the pulsating deoxycholic acid flow mentioned above results in faster formation of the sepa¬rating layer between the cell and the collagen matrix due to the movement and expansion of the matrix and makes de¬taching the cell easier due to the forces that act upon it.
The subclaims and the subsequent description of an em¬bodiment disclose other characteristics and advantageous improvements of the invention.
Using the proposed method, it is possible to provide
acellular initial products, i.e. organ portions such as
cardiac valves or vessels that are free from any cell ma-
terial and viruses for producing(bioprostheses°)by subse¬
quently coating these products with endogenic cells from
their respective recipient.
The apparatus for treating an organ portion consisting of a foreign material in a flowing medium includes a decel-lularization chamber that receives the respective organ portion and a pump that creates the medium flow, both se¬quentially incorporated in a ring line. The ring line in¬cludes inlet and outlet valves for feeding or draining |jhe respective treatment medium. The decellularization Cihamber can be detached from the ring line so that said Chamber and the organ portion in the medium it contains Can be moved. The organ portion to be treated is fixed and preloaded in the container by sewing it to adapters shaped like the organ portion and placing it lengthwise in,the direction of flow.
An embodiment of the invention is explained in greater detail below with reference to the figures. Wherein:
Fig. 1 shows an apparatus for decellularizing a car¬diac valve in a flow circuit;
Fig. 2 shows a sectional view of the decellularization chamber that is incorporated in the flow cir¬cuit and receives the cardiac valve;
Fig. 3a shows § microscopic sectional view of an aortic valve wall that has been decellularized using the method according to the invention; and
Fig. 3b shows a magnified view of a medial tissue sec¬tion of the aortic valve wall according to Fig. 3a.
In the embodiment described here, a porcine aortic valve that was removed at a slaughterhouse is freed from fat, cut to size, measured, and checked for germs (fungi, aerobic and anaerobic bacteria, mycoplasma). Intermediate storage at a maximum temperature of 4°C should not exceed seven days.
The cardiac valve prepared in this way is put into a 1% to 2% deoxycholic acid solution (or a bile acid with a similar effect) and stored therein for 24 hours at 37°C. The deoxycholic acid is capable of forming so-called ad-ducts with a fatty acid in the form of inclusion com7 pounds jso that the deoxycholic acid can encompass the cell on all sides, thereby dissolving its adhesive bond with the tissue matrix. At the same time, deoxycholic acid has a cytocidal effect.
Subsequently, a cardiac valve treated in this way is rinsed under constant motion in a dilution set of a phos¬phate buffer solution (PBS) at decreasing concentrations to remove the cells treated with deoxycholic acid from the tissue matrix.
In a subsequent third step, the cardiac valve is treated at room temperature for about 10 minutes in 40 per cent alcohol to produce an antiviral effect and kill any re¬maining cells in the collagen structure. As alcohol is a good solvent, it at the same times rinses off any resid¬ual acid and detaches more cells.
Using another set of a phosphate buffer solution (PBS), the cardiac valve is rinsed once again and then treated
mechanically in a pulsation PBS inpdi.i flow. The pul^n linq media flow rhythmically widens I,ho cardiac valve thai is fixed and preloaded lengthwise to the flow in a decellu-
■— ■ A"'
larization chamber and at the same time exposed to me¬chanical forces. This step mechanically detaches any re¬maining cells, from the collagen structure so that an acellular structure is obtained from which all cell mate¬rial has been removed and which therefore cannot contain any viruses. A tissue matrix of the cardiac valve treated in this way which is free of cells and of the decellu-larization media used - as shown in Fig. 2 - is excel¬lently suited for re-coating with endogenic endothelial cells from the laterrecipient of such a bioprosthesis, and this bioprosthesis can be implanted into a human body without the risk of immunological reactions or viral in¬fluences..
The invention is not limited to the treatment variant de¬scribed herein, both regarding the type and origin of the foreign material used for producing bioprosthesis and re¬garding the procedural parameters as long as the essen¬tial steps of the method, i.e. treatment with an adduct-forming bile acid and alcohol with intermediate or down¬stream rinsing in combination with exposure of the re¬spective organ portion to a preferably pulsating flow for gentle mechanical action on the tissue, are executed. The method can also be carried out by running.not just the last rinsing step but, instead or in addition, by running other or all treatment steps in a flowing medium. This mechanically supports the effect of the respective me¬dium, whereby better, all-area access to the cells is achieved and the cells are easier detached or removed from the expanded collagen matrix due to the action of the pulsating flow.
An apparatus for dece.llularlz.ijig a cardiac valve is shown in Fig. 1. It includes a ring line 1 that incorporates a decellularization chamber 2 that receives the cardiac valve to be treated, a diaphragm pump 3 and a downstream Equalizing chamber 4. The diaphragm pump 3 is connected to a drive unit (not shown) via a hose line 5. An outlet valve 6 and an inlet valve 7 whose functions approxi¬mately correspond to that of a cardiac valve are inte¬grated into the two connections of the diaphragm pump 3 to the ring line 1. The outlet valve 6 can be omitted when treating cardiac valves as these have valve flaps.
The core of the apparatus is the decellularization cham¬ber 2 for decellularizing a porcine aortic valve 8 using the additional effect of fluid force. The decellulariza¬tion chamber 2 consists of a transparent hollow cylinder 9 made of piacryl into the open end faces of which the teflon adapters 10 and 11 are sealingly centered and fixed, said adapters being connected to the ring line 1 via fittings 12, 13, each of them comprising a fixing section 14, 15 that protrudes into the hollow cylinder 9 and has mounting holes 16, 17 radially spaced around its periphery for firmly holding the aortic valve 8 in a pre¬loaded state to the rims of the end faces. The outer di¬ameter of the two fixing sections 14, 15 of the adapters 10,11 approximately is the same as the diameter of the aortic valve 8. The rear adapter 11 can be braced via a bridge 18 and a first packing 27 on the inside of a ring land 20 that is 'connected to the hollow cylinder 9 by turning a threaded ring 21 whoso female thread engages in a male thread on the adapter 11. The adapter 10 comprises a collar 22 that rests against the end surface of the hollow cylinder 9 and can be braced using a threaded cap 23 with a female thread that engages in a male thread on the hollow cylinder 9. A second packing 19 is provided for leak proof mounting. The hose piece of the ring line
1 that is topped by the decellularization chamber is made of a flexible material (silicone) to ensure flow-through due. to the pulsating pumping effect.
Due to the design and arrangement of the adapters 10, 11 as described above, a suitably prepared aortic valve 8 can be sfewed outside the hollow cylinder 9 to the oppo¬site fixing sections 14, 15 of the adapters 10, 11. The aortic valve 8, fixed as described above, is inserted into the hollow cylinder 9. First, the deoxycholic acid is introduced into the decellularization chamber 2 and the ring line 1 via an inlet and outlet valve 24, 25 in the ring line 1 or one of the fittings 13, 14; then, the diaphragm pump 3 is activated so that a pulsating flow of deoxycholic acid continuously flows by or through the aortic valve 8, and the mechanical force this flow exerts on the tissue completes the detachment and removal of cells that are foreign to the recipient of the cardiac valve. Physiological saline or phosphate buffer solution is filled into the apparatus after discharging the deoxy¬cholic acid, and the tissue is rinsed until all the de¬oxycholic acids and any troxic constituents are removed. After this rinsing step, treatment of the aortic valve 8 with alcohol and another rinsing step in phosphate buffer solution follow..
All treatment steps of the decellularization method take place in the apparatus described above in a pulsating flow of the respective medium. The direction of flow is the natural flow direction when the bioprosthesis is im¬planted. The inlet and outlet valves 24, 25 are used for media replacement, however fresh rinsing solution can be supplied, and used rinsing solution can be discharged, continuously for the rinsing step.
treatment steps disconnected from the ring line and dia¬phragm pump without any nuxl i. urn Mowing through t:ho docel-lula-rization chamber, which optionally may be turned manually or using a motor, or, as s.tated above, to carry out individual treatment steps outside the decellulariza-tion chamber.
1. A method for decelltflarizing allogenic and xenogenic foreign material using biodetergents to produce bioprostheses coated with endogenic cells from the recipient of the prosthesis, characterized in that the foreign material is initially treated with bile acid to kill the cells and to coat the cells as well as to separate the bond with the tissue matrix, then treated with alcohol to kill more cells, each of these steps being followed by a rinsing step and at least the last rinsing step being executed in a media flow so that the fluid forces act mechanically on the tissue matrix and the ceils.
2. The method as claimed in claim 1 wherein the media flow is pulsating.
3. The method as claimed in claim 1, wherein that a cell-encompassing deoxycholic acid is used to detach the cells with bile acid.
4. The method as claimed in claim 3 wherein 1% to 2% deoxycholic acid is used.
5. The method as claimed in claim 1 wherein 30% to 60% alcohol is used to kill the cells.
6. The method as claimed in claim 5 wherein 40% alcohol is used.
7. The method as claimed in claim 1 wherein a phosphate buffer solution is used as rinsing medium.
8. The method as claimed in claim 7 wherein decreasing concentrations of the rinsing medium are used for rinsing with non-flowing medium.
9. The method as claimed in claims 1 through 7 wherein that the deoxycholic acid treatment in nonflowing medium takes up to 24 hours, alcohol treatment takes about 20 minutes, and rinsing takes about 60 minutes.
10. The method as claimed in claims 1 through 7 wherein that the treatment of the foreign material in deoxycholic acid and/or alcohol and/or the intermediate rinsing cycle are carried out in a pulsating medium flow that comes close to the natural flow conditions in the respective organ.
11. The method as claimed in claims 1 and 10 wherein the speed of the flowing media can be varied.
12. The method as claimed in claims 1, 10 and 11 wherein that the flowing rinsing medium is replaced continuously or discontinuously.
13. The method as claimed in claim 11, wherein that the concentration of the detergent flow is gradually reduced.
14. The method as claimed in any one of claims 1 and 10 through 13, wherein that the foreign material to be treated is held in a preloaded state in the respective media flow.
Dated this 29th day of April, 2003.
|Indian Patent Application Number||462/MUMNP/2003|
|PG Journal Number||26/2007|
|Date of Filing||29-Apr-2003|
|Name of Patentee||AUTO TISSUE GMBH|
|Applicant Address||HESSISCHE STRASSE 3-4, D-10115 BERLLN, GERMANY.|
|PCT International Classification Number||A61L 2/02|
|PCT International Application Number||PCT/DE01/04646|
|PCT International Filing date||2001-12-05|