Engineered tissue annulus fibrosis augmentation methods and apparatus

[0002] This application claims priority of U.S. provisional patent application Serial No. 60/159,488, filed Oct. 14, 1999, and is a continuation-in-part of U.S. patent application Ser. Nos. 09/638,726, filed now U.S. Pat. No. 6,340,369 Aug. 14, 2000; and Ser. No. 09/415,382, filed Oct. 8, 1999, the entire contents of each application being incorporated herein by reference.

[0003] This invention relates generally to the treatment of diseased or traumatized intervertebral discs, and more particularly, to the use of engineered disc tissues in conjunction with such treatment.

[0004] Intervertebral discs provide mobility and a cushion between the vertebrae. At the center of the disc is the nucleus pulposus. The nucleus pulposus is surrounded by the annulus fibrosis, which is comprised of cells (fibrocyte-like and chondrocyte-like), collagen fibers, and non-fibrillar extracellular matrix. The components of the annulus are arranged in 15-25 lamellae around the nucleus pulposus. The fibers in the lamellae alternate their direction of orientation by 30 degrees between each band.

[0005] The annulus fibrosis has three important functions. First, the annulus contains the nucleus pulposus. Second, the annulus fibrosis, with other ligaments, connects the vertebrae of the spine. Lastly, the annulus fibrosis helps to control movement between the vertebrae.

[0006] The fibers of the annulus can tear causing pain and possible extrusion of the nucleus pulposus. Extrusion of the nucleus pulposus is known as a disc herniation. Disc herniations can compress nerves or the spinal cord resulting in arm or leg pain and dysfunction. Surgery to repair disc herniations leaves a hole in the annulus fibrosis. The hole in the annulus acts as a pathway for additional material to protrude into a nerve, resulting in a recurrence of the herniation.

[0007] To date, the treatment of tears or defects of the annulus fibrosis has relied for the most part on eliminating the defective disc or disc function. This may be accomplished by fusing the vertebra on either side of the disc. In terms of replacement, prior-art techniques replace either the nucleus or the nucleus and annulus functions. My co-pending U.S. patent application Ser. No. 09/322,516, and Patent Cooperation Treaty Application Serial No. PCT/US/14708 describe methods and devices to occlude annular defects.

[0008] Although transplantation of living cells risks rejection by graft host reaction, this invention broadly recognizes that transplantation of the extracellular matrix of the annulus fibrosis is unlikely to incite graft host reaction. In the preferred embodiment, fibrocytes are harvested, cultured, then added to annulus fibrosis extracellular matrix obtained from recently deceased humans or animals. The combined annulus fibrosis is then introduced into the injured or diseased disc.

[0009] The cells or engineered tissues may be introduced using any surgical technique, including percutaneous or laparoscopic approaches. As one delivery mechanism, a passageway may be formed through the annulus fibrosis, with the cells or engineered disc tissue being introduced into the disc through the passageway. In particular, the engineered disc tissue may be sewn or otherwise adhered to the inside or outside of the existing annulus fibrosis using a surgical procedure performed from the posterior or anterior portion of the body.

[0010] The method of the invention may further include the step of adding one or more therapeutic substances to the cells or annular tissue prior to transplantation. Such therapeutic substances could include culture media, growth factors, differentiation factors, hydrogels, polymers, antibiotics, anti-inflammatory medications, immunosuppressive medications, or any useful combination thereof.

[0011] The teachings of this invention may be combined with any compatible nucleus replacement procedure, as well as the embodiments described in co-pending U.S. patent application Ser. No. 09/690,536 entitled “Annulus Fibrosis Augmentation Methods And Apparatus,” the entire contents of which are incorporated herein by reference.

[0012] Broadly according to the invention, fibrocytes are harvested, cultured, added to annulus fibrosis extracellular matrix material, then sewn or otherwise placed relative to an injured or diseased disc. The annulus fibrosis cells and extracellular matrix are preferably harvested from a live human, though recently deceased human or animal donors may alternatively be used. Depending upon the extent of the harvest, the recipient may function at least in part as a donor, or the tissues from others, including fetal sources, may be used, preferably having a familial relationship to minimize or avoid the need for immunosuppressive substances. Guidelines for tissue procurement including surgical technique of removal, number of hours between death of the donor and tissue procurement, and testing of the donor for infectious disease, are well described.

[0013] Following annulus fibrosis harvest, the tissue is processed to kill the living cells. Care is taken to preserve the extracellular matrix. Guidelines for processing the harvested annulus fibrosis as described are well known to those skilled in the art. For example, the tissue could be frozen and thawed.

[0014] Fibrocytes are obtained from a tendon of the patient. For example, a palmaris longus tendon could be removed from one arm of the patient. The harvested fibrocytes are isolated and cultured using standard techniques. The harvested sterile tendon is morselized and washed with phosphate buffered saline. The cells are released from the extracellular matrix with 0.2% clostridial collagenase (Worthington CLS II, 140 u/mg) and agitated. See Klagsburn, “Methods in Enzvmology, Vol. VII. The resulting suspension is filtered with 153.mu.g.nylon sieve (Tetko, Elmford, N.Y.).

[0015] The filtered solution is then centrifuged at 1800 rpm to remove the cells. The supernatant above the cells is removed with a micropipette until the cell concentration reaches 5.times.10.sup7 cells/cc. The harvested cells are grown in Hamm's F-12 culture media, 10% fetal calf serum, L-glutamine (292.mu.g/cc), penicillin (100 u/cc), streptomycin (100.mu.g/cc), and asorbic acid (5.mu.g/cc) at 37° C. The above method is described in U.S. Pat. No. 6,060,053, which is incorporated in its entirety herein by reference.

[0016] Precursor cells of the annulus fibrosis, annulus fibrosis cells, chondrocytes, or other living cells that could function like annulus fibrosis cells or that could differentiate into cells to build a functional annulus fibrosis may also be used.

[0017] The living cells from cell culture are implanted into the donor extracellular matrix to form a living annulus fibrosis. In the preferred embodiment, the cells are injected into small holes drilled into the donor extracellular matrix.

[0018] The living cells and extracellular matrix may be added to the patient's disc immediately after combination or after a period of time to allow attachment of the cells to the matrix. Naturally, in the delayed embodiment, the cells would preferably be supported with culture media.

[0019] The engineered annulus is added to the inside or the outside of a patient's annulus. Surgical procedures to access the inner or outer surface of the annulus fibrosis are well known to those skilled in the art. The engineered annulus could be sutured, placed against, or “glued” to the patient's annulus. Platelet rich plasma combined with calcium and thrombin or “fibrin glue” could be used to glue the annular tissues together.

[0020] Additional therapeutic substances could be added to the transplanted annulus. For example, resorbable culture medium, tissue growth or differentiation factors (recombinant generated morphogenetic proteins, PDGF, TGF-β, EGF/TGF-α, IGF-I, βFGF), hydrogels, absorbable or nonresorbable synthetic or natural polymers (collagen, fibrin, polyglycolic acid, polylactic acid, polytetrafluoroethylene, etc.), antibiotics, anti-inflammatory medication, immunosuppressive medications, etc. may be used.

[0021] In an alternative embodiment, living cells are not added to the harvested annulus fibrosis. The harvested annulus fibrosis is processed as described above to kill the living host annulus cells.

[0022] Although annulus fibrosis augmentation and/or transplantation is being described herein in detail, the invention is not limited to treatment of the intervertebral disc. For example, the invention could also be used to treat other tissues of the body such as the meniscus of the knee. In such cases, a meniscus would be removed from recently deceased humans. The harvested meniscus would be processed to kill the cells but preserve the extracellular matrix. Fibroctyes harvested as described above would then be added to the extracellular matrix prior to insertion of the engineered meniscus into a patient's knee. Similarly, chondrocytes could be harvested and added to the meniscus extracellular matrix as described in my pending U.S. Pat. Ser. No. 09/639,309 09/628,727, 09/638,726, and 09/638,242.

[0023] Similarly, the process could be used to repair or replace other tissues or organs of the body such as the pancreas, liver, kidney, heart, etc. Healthy live cells would be obtained thorough biopsy and tissue culture. The live cells would be added to the extracellular matrix of tissues or organs harvested to recently deceased human or animals.