WO1999004720A1

WO1999004720A1 - Repair of intervertebral disks

Info

Publication number: WO1999004720A1
Application number: PCT/US1998/014380
Authority: WO
Inventors: Shawn E. Stovall
Original assignee: Reprogenesis Inc.
Priority date: 1997-07-11
Filing date: 1998-07-10
Publication date: 1999-02-04

Abstract

This invention is a method of using a cell containing hydrogel suspension for treating a herniated intervertebral disk (10) by implanting a cell suspension into a patient, thereby forming a cell containing hydrogel adherent to at least one surface of the annulus fibrosus (20) of the herniated disk (10), wherein the cells are chondro-cyte, fibroblasts or osteoblast.

Description

REPAIR OF INTERVERTEBRAL DISKS

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to the use of tissue engineering to repair a

herniated disk, and more particularly, to the use of disaggregated chondrocytes

with various matrix/delivery systems to perform such a repair.

Review of Related Art

An intervertebral disk is composed of an outer fibrous part (annulus

fibrosus) that surrounds a central gelatinous mass (nucleus pulposus). Both

tissues in the disk are chondrocytic in cell type. When a spinal disk injury

occurs (herniated disk, see Figure 1), the disk reacts much like a tire with a

bulge or blister. Over time the blister can become larger, leading to increased

interior space for the nucleus pulposus. This in turn, decreases the ability of

the disk to "cushion" the adjacent vertebrae. Depending on the location of the

herniation, the bulge may put pressure on the spinal cord which results in pain,

reduced mobility and other complications.

Current treatment modalities include two major surgical interventions:

the removal of the disk and fusion. Both of these procedures lead to limitation

in spinal motion. In some cases, a prosthetic disk is placed in the intervertebral space. However, problems with these devices include poor

biocompatibility of the device material, improper placement, or surgical complications of the procedure. Thus, there is a need for an improved method

for treating herniation of intervertebral disks. SUMMARY OF THE INVENTION

It is an object of this invention to provide a minimally invasive technique to repair a herniated disk rather than remove it altogether. This and

other objects of this invention are provided in one or more of the following

embodiments.

In one embodiment, this invention provides a method for treating a

ruptured intervertebral disk by aspirating all or part of a cell-containing

gel from the disk, thereby reducing the nucleus pulposus volume;

excising damaged tissue from the annulus fibrosus of the ruptured disk

leaving a hole therein; covering the hole with a layer containing cells,

said cells being attached to a porous matrix comprising a crosslinked

biocompatible polymer; and injecting a cell-containing suspension into

the disk through the annulus fibrosus to restore the nucleus pulposus

volume. In a preferred embodiment, the cell-containing suspension is

obtained by collecting a population of chondrocytic cells from the annulus fibrosus or the nucleus pulposus, and expanding the population

of chondrocytic cells.

In another embodiment, this invention provides a method for

treating a herniated intervertebral disk by applying over the damaged

area of the disk, a layer containing cells and a biocompatible polymer

which is crosslinked to form a porous matrix.

In yet another embodiment, this invention provides a method for

preparation of a suspension of chondrocytes suitable for injection into a

vertebral disk by expanding a population of chondrocytes obtained by

aspirating a portion of an intervertebral disk; and mixing the expanded

population of chondrocytes with a biocompatible polymer to form a

suspension of chondrocytes suitable for in vivo application onto the

exterior wall of an intervertebral disk where the suspension forms a cell-

containing hydrogel when implanted into the body of a patient.

In still another embodiment, this invention provides a method for

applying a suspension of chondrocytes to the surface of a herniated disk

for repair of the disk by mixing a population of chondrocytes with a

biocompatible polymer to form a suspension of chondrocytes that will

form a cell-containing hydrogel when implanted into the body of a patient; and applying the suspension to the surface of a herniated disk to

form one or more layers of cell-containing hydrogel adherent to the

exterior wall of the disk.

In yet another embodiment, this invention provides a method for

injecting a suspension of chondrocytes into a herniated disk for repair of

the disk, the method comprising the steps of mixing a population of

chondrocytes with a biocompatible polymer to form a suspension of

chondrocytes; and injecting the suspension into a herniated disk where

the suspension forms a cell-containing hydrogel in the disk.

In still another embodiment, this invention provides a method of

using a cell-containing hydrogel suspension for treating a herniated

intervertebral disk by implanting a cell suspension into a patient having

a herniated disk, thereby forming a cell-containing hydrogel adherent to

at least one surface of the annulus fibrosus of the herniated disk.

Preferably the cells are chondrocytes, fibroblasts or osteoblasts.

In the method of this invention, disaggregated chondrocytes,

fibroblasts or osteoblasts are suspended in a hydrogel or other

liquid/semiliquid carrier and painted, brushed, sprayed, or applied by other

means in a layer or layers to the exterior wall of the intervertebral disk to strengthen the wall construct or create replacement wall, and optionally

similarly suspended cells may be introduced into the interior of the disk as

well. A primary difference between the method of this invention and the

methods in use prior to this invention is that this method of repair allows for

the original tissue to remain in place rather than replacing it with a synthetic

material. Potential advantages of the present invention include better spinal

motion, less degeneration of surrounding area, shorter recovery time, and

overall improved results when compared to diskectomy, fusion or implantation

of a prosthetic disk.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows an portion of the spinal column having a herniated disk

between two vertebrae.

Figure 2 is a schematic representation of the steps in the method for

repair of a herniated disk.

Figure 3 is a schematic representation of the steps in the method for

strengthening the annulus fibrosus.

DETAILED DESCRIPTION OF THE EMBODIMENTS

This invention utilizes a minimally invasive technique to repair a herniated disk rather than remove it altogether as is the current standard of

care. Disaggregated chondrocytes, fibroblasts or osteoblasts are suspended in

a hydrogel or other liquid/semiliquid carrier and painted, brushed, sprayed, or

applied by other means in a layer or layers to the exterior wall of the

intervertebral disk. This method can reinforce the annulus fibrosus in the case

of a minor herniation or can be used as a "patch" when the herniated tissue is

removed. Either application should prevent further damage and/or rupture and

may lead to the restoration of full disk function.

Cell/Matrix Compositions

According to this invention, herniated disks are repaired using

materials made up of cells dispersed in a matrix. The cell-containing matrix

adheres to the disk. The cells may be suspended in a liquid/semiliquid carrier

which is applied to the disk and then hardens into a cell-containing matrix.

Alternatively, material which forms the matrix may be applied to the disk, and

the matrix subsequently seeded with cells. The matrix material may be

applied in the fluid state to conform to the shape of the disk surface and then

cure, crosslink or harden to form the matrix, or the matrix may be formed first

and then applied to the surface of the disk.

The matrix material is biocompatible and forms a porous matrix under physiological conditions, typically by cross-linking of biocompatible

polymers. The polymers may be natural or synthetic, biodegradable or non-

biodegradable, and the polymer(s) may be further modified for enhanced

properties. Typical materials for the matrix are described in European Patent

No. 0 299 010 or in International Patent Publication No. WO 94/25080, both

of which are incorporated herein by reference. In one preferred mode, the

matrix is a hydrogel, but use of other materials which form a porous, fibrous

network that can contain cells is also within the contemplation of this

invention. Suitable raw materials which may be used to produce the hydrogel

in which the cells are suspended include sodium alginate, which has been

tested with chondrocytes, as well as PLURONICS™ and TETRONICS™.

Procedures for preparing the matrices and seeding them with cells are

described in these publications, and the skilled worker will readily adapt those

procedures to this invention in view of the guidance provided herein. The

hydrogel-cell suspension may be prepared as described for products used in

treatment for vesicoureteral reflux using autologous auricular chondrocytes in

sodium alginate. Alternatively, the hydrogel-cell suspension may be prepared

as described in International Patent Publication No. WO 97/17038, by Vacanti,

et al., entitled "Hydrogel-cell composition - for generating new tissue on

surface of structure or organ," incorporated herein by reference. Other cell- containing suspensions which can be "painted" on physiological surfaces in an

equivalent manner to the hydrogel-cell suspension described herein may also

be used to repair intervertebral disks according to this invention.

The cells in the matrix may be any suitable cell type, but preferably the

cells will be derived from the structure to be repaired (i.e., cells from the

herniated disk, or cells of the same cell type, will be used). Typically the cells

are chondrocytes, although osteoblasts or fibroblasts may be used.

Chondrocytes may be obtained from any cartilaginous tissue in the patient, or

may be allogeneic chondrocytes, so long as care is taken to mitigate any

adverse reactions to the allogeneic cells. Alternatively, other cell types known

in the field of tissue engineering to proliferate on the matrix of this invention

may be used in this method.

Cells obtained for use in the matrix may be used directly or expanded

by culture under suitable conditions. Standard cell culture conditions may be

used, taking into account that results of this cell expansion process must be

suitable for re-introduction into the patient. The cell suspension may contain

additives, such as growth factors, colony stimulating factors, cytokines,

adhesion peptides, antibiotics, cell nutrients, physiologically compatible

buffers and salts, and the like. The components of the cell suspension may be

combined using any procedure which preserves viability of a substantial portion of the cells (typically 35% of the cells, preferably at least 50%). Such

procedures are known to those skilled in the art of tissue engineering, and

suitable procedures are described in the patent publications incorporated herein

by reference.

Treatment Modalities

This invention is directed to the repair of intervertebral disks.

Defect(s) which may be overcome by the method of this invention include

damage of, abnormal development of, weakness of, or missing sections of

exterior or outer intervertebral disk wall. This method may be used for repair

of spinal/skeletal injuries by augmenting existing tissue which would result in

increased strength, improved or restored function, or providing a bridge for

missing sections. In a preferred embodiment, the method of this invention is

used as a first step/additional treatment in combination with spinal cord pain

management/reconstruction by removing fluid from inside the disk thus

reducing pressure on the outer wall of the disk. The cells in the fluid may then

be expanded in vitro and re-implanted once the disk wall has been

strengthened by application of the cell-matrix structure according to this

invention.

The method described herein can be performed in open surgery or endoscopically. A typical procedure is illustrated in Figure 2. Figure 2-1

shows a side view of herniated disk 10 in which the wall (annulus fibrosus 20)

has a damaged section 30. Figure 2-2 shows the first step in the repair

procedure. Herniated tissue 30 is removed. Usually, a small fragment of

undamaged annulus fibrosus will be taken at the same time and sent to a cell

culture facility for isolation and expansion of the cell population. After cell

expansion, a second procedure would seed cells into the interior of the disk

and/or onto the matrix. Preferably, all or a part of the nucleus pulposus (40) of

herniated disk 10 is aspirated. Removal of part of nucleus pulposus 40

relieves the pressure on the ruptured wall and/or the patch placed over the

rupture as described in the following paragraph. The aspirated material may

be stored for later re-introduction into the interior of the disk; any method of

cell storage which maintains adequate viability for future use is within the

contemplation of this invention. Alternatively, the cell population contained

in the aspirate may be expanded.

As shown in Figure 2-3, a matrix "patch" 50 is placed over the

resulting hole 60 in the annulus fibrosus. Patch 50 may be formed from a fluid

composition containing a polymer that will harden when in contact with

biological tissue to form a porous matrix, or it may be a preformed layer of

fibrous material that can be applied to the exterior disk wall. A preformed porous patch applied during an open surgical procedure may be sutured in

place, or fibrin glue may be used to secure the patch in either endoscopic or

open surgery. The fluid composition may contain cells in suspension, or cells

may be seeded 70 onto the matrix once it has formed (See Figure 2-4).

After hole 60 in the annulus fibrosus has been closed, the volume of

the nucleus pulposus is preferably restored by injection 80 of stored aspirate or

a cell suspension, which preferably contains expanded cells described above,

and more preferably, contains material that will have fluid consistency similar

to the original nucleus pulposus, e.g., polymers that crosslink under

physiological conditions to form a hydrogel with the desired properties.

Suitable procedures for injecting material for volume restoration are analogous

to the surgical procedures for introducing and removing arterial catheters.

In a alternative embodiment (shown in Figure 3), minor herniated

tissue can be strengthened with layers of the cell suspension as needed. Disk

15 in Figure 3-1 has a minor herniation which weakens the wall (25) without

significantly changing the volume of disk 15. As shown in Figure 3-2,

annulus fibrosus 25 may be strengthened by applying a layer (55) over

damaged section 35 which is a fibrous matrix containing cells. Preferably, the

layer is applied as a cell-containing suspension which is painted, sprayed or

brushed on an area corresponding to at least damaged section 35 of the exterior disk wall. Suitable procedures for preparation of such a cell suspension as

well as procedures that may be adapted for applying the suspension to the disk

wall are described in International Patent Publication No. WO 97/17038.

Treatment according to this invention may optionally include

administration of drugs and/or other biological materials as appropriate. For

example, one or more antibiotics, one or more growth factors for maintenance

or stimulation of the cells, or nutrient medium components to support cell

viability may be included in the cell suspension. Alternatively, such

components may be administered separately, preferably by direct application

in the region of the disk. Preferably, local administration of antibiotics is

included in the method to reduce the risk of infection in the procedure. Where

the cell suspension contains allogeneic cells or other foreign immunogenic

material, immunosuppressive drugs may also be included.

Work reported by Ashton and Eisenstein in Spine, Feb 15, 1996, pages

421-426, states that the neuropeptide, Substance P had a small stimulatory

effect on disk cell proliferation in vitro. Their conclusion is that further

investigation is required to establish if Substance P has a biologic relevance to

the maintenance or repair of the intervertebral disk. Substance P may be used

according to this invention to help in the expansion and growth of cells used in

the procedure. Application of Substance P for cell expansion in vitro may use conditions analogous to those described by Ashton and Eisenstein. Suitable

conditions for use of Substance P in vivo will be readily determined by the

skilled clinician in view of the disclosures of Ashton and Eisenstein.

For purposes of clarity of understanding, the foregoing invention has

been described in some detail by way of illustration and example in

conjunction with specific embodiments, although other aspects, advantages

and modifications will be apparent to those skilled in the art to which the

invention pertains. The foregoing description and examples are intended to

illustrate, but not limit the scope of the invention. Modifications of the

above-described modes for carrying out the invention that are apparent to

persons of skill in the art of tissue engineering, medicine, and surgery, and/or

related fields are intended to be within the scope of the invention, which is

limited only by the appended claims.

All publications and patent applications mentioned in this specification

are indicative of the level of skill of those skilled in the art to which this

invention pertains. All publications and patent applications are herein

incorporated by reference to the same extent as if each individual publication

or patent application was specifically and individually indicated to be

incorporated by reference.

Claims

Claims:

1. A method of using a cell-containing hydrogel suspension for treating a herniated intervertebral disk, said method comprising: implanting a cell suspension into a patient having a herniated disk, thereby forming a cell-containing hydrogel adherent to at least one surface of the annulus fibrosus of the herniated disk, wherein the cells are chondrocytes, fibroblasts or osteoblasts.

2. A method for applying a suspension of chondrocytes to the surface of a herniated disk for repair thereof, said method comprising: mixing a population of chondrocytes with a biocompatible polymer to form a suspension of chondrocytes, said suspension forming a cell-containing hydrogel when implanted into the body of a patient; and applying the suspension to the surface of a herniated disk to form one or more layers of cell-containing hydrogel adherent to the exterior wall of the disk.

3. A method for injecting a suspension of chondrocytes into a herniated disk for repair thereof, said method comprising: mixing a population of chondrocytes with a biocompatible polymer to form a suspension of chondrocytes; and injecting the suspension into a herniated disk, wherein the suspension forms a cell-containing hydrogel in the disk.

4. A method for preparation of a suspension of chondrocytes suitable for injection into a vertebral disk, said method comprising expanding a population of chondrocytes obtained by aspirating a portion of an intervertebral disk; and mixing the expanded population of chondrocytes with a biocompatible polymer to form a suspension of chondrocytes, said suspension forming a cell- containing hydrogel when implanted into the body of a patient, wherein the suspension is suitable for in vivo application onto the exterior wall of an intervertebral disk.