AU2013231068B2 - Activation of bone and cartilage formation - Google Patents

Abstract

Abstract Provided is a method of activating osteogenic or chondrogenic activity at a site in a subject in need thereof. Also provided is a method of treating a bone or cartilage defect in a subject. Additionally, the use of a reduced pressure apparatus for treating a bone or cartilage defect adjacent to dura mater, periosteum, or endosteum is provided. Further provided is a composition for treating a bone or cartilage defect. Also, the use of a reduced pressure apparatus and a biocompatible scaffold for the manufacture of a composition for treating a bone or cartilage defect adjacent to dura mater, periosteum or endosteum is provided.

Description

ACTIVATION OF BONE AND CARTILAGE FORMATION BACKGROUND The present application is a divisional application of Australian Application 5 No. 2008270564 which is incorporated in its entirety herein by reference. 1. Field of the Invention The present invention relates generally to tissue treatment systems and in particular to a system and method for promoting the growth of new bone or cartilage tissue by activating dura mater, periosteum or endosteum through the application of 10 reduced pressure. 2. Description of Related Art Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common generally knowledge in the field. 15 Clinical studies and practice have shown that providing a reduced pressure in proximity to a tissue site augments and accelerates the growth of new tissue at the tissue site. The applications of this phenomenon are numerous, but application of reduced pressure has been particularly successful in treating wounds. This treatment (frequently referred to in the medical community as "negative pressure wound therapy," "reduced 20 pressure therapy," or "vacuum therapy") provides a number of benefits, including faster healing and increased formulation of granulation tissue. Typically, reduced pressure is applied to tissue through a porous pad or other manifolding device. The porous pad contains cells or pores that are capable of distributing reduced pressure to the tissue and channelling fluids that are drawn from the tissue. The porous pad often is incorporated 25 into a dressing having other components that facilitate treatment. Would healing may be broadly split into three overlapping basic phases: inflammation, proliferation, and maturation. The inflammatory phase is characterised by hemostasis and inflammation. The next phase consists mainly of angiogenesis, granulation tissue formation, collagen deposition and epithelialisation. The final phase 30 includes maturation and remodelling. The complexity of the wound healing process is augmented by the influence of local factors such as ischemia, edema, and infection, as well as systemic factors such as diabetes, age, hypothyroidism, malnutrition, and 1 obesity. The rate limiting step of wound healing, however, is often angiogenesis. In bone and cartilage healing, the periosteum is the primary source of precursor cells that develop into osteoblasts and chondroblasts. The bone marrow, endosteum, small blood vessels and fibrous connective tissue are secondary sources of precursor 5 cells. However, bone and, especially, cartilage healing is often slow and frequently inadequate. For this reason, the medical community has long sought to develop improved methods of tissue repair and replacement for bone and cartilage defects. With craniofacial defects, successful repair or replacement is greatly compromised without the endogenous osteogenic capacity of the dura mater. 10 Unfortunately, dura mater in 1a humans begins to lose its osteogenic capacity rapidly after humans reach about two years of age. Current reconstructive techniques for craniofacial defects use autogenous, allogeneic, and prosthetic materials to counter the osteogenic deficiency of mature dura mater. Growth factors also are commonly used to facilitate tissue regeneration. These 5 techniques may achieve some functional restoration of craniofacial defects, but all are inherently limited by factors such as donor-site morbidity, unpredictable graft resorption, insufficient autogenous resources, viral disease transmission, immunologic incompatibility, structural failure, unsatisfactory aesthetic results, and cost. Moreover, it has been shown that osteoblasts induced by growth factors are initially derived from 10 undifferentiated mesenchymal stem cells of the dura mater, and later, though limited, augmented by cells in the overlying connective tissue rather than from cells in the cranial bone surrounding the defect. Cytokines or other factors are required to induce bone forming cells derived from the dura and the overlying connective tissue. Methods that improve healing of bone and cartilage are thus desired. 15 It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. SUMMARY According to a first aspect, the present invention provides a system for activating osteogenic or chondrogenic activity at a tissue site in a subject, the system comprising: 20 a source of reduced pressure; and a manifold formed from an open-cell reticulated foam having pore sizes between about 400 microns and about 600 microns and adapted to be fluidly connected to the source and adapted to be positioned adjacent dura mater for applying reduced pressure to the dura mater of the subject adjacent the tissue 25 site in the subject. According to a second aspect, the present invention provides a system for treating a bone or cartilage defect in a subject, the system comprising: a source of reduced pressure; and a manifold formed from an open-cell reticulated foam having pore sizes between 30 about 400 microns and about 600 microns, fluidly connected to the source and adapted to be positioned adjacent dura mater for applying reduced pressure to the dura mater that is adjacent the defect. 2 According to a third aspect, the present invention provides a system for treating a bone or cartilage defect in a subject, the system comprising: a source of reduced pressure; a scaffold adapted to be positioned into the defect; and 5 a manifold formed from an open-cell reticulated foam having pore sizes between about 400 microns and about 600 microns and adapted to be fluidly connected to the source and adapted to be positioned adjacent dura mater for applying reduced pressure to the dura mater adjacent the defect Unless the context clearly requires otherwise, throughout the description and the 10 claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to". In one embodiment, a method is provided that includes activating osteogenic or chondrogenic activity at a site in a subject in need thereof. The method comprises 15 applying reduced pressure to the dura mater, periosteum or endosteum at the site in the subject. In another embodiment, a method is provided that includes treating a bone or cartilage defect in a subject. The method comprises applying reduced pressure to the dura mater, periosteum or endosteum that is adjacent to the defect. 20 In a further embodiment, the use of a reduced pressure apparatus for treating a bone or cartilage defect adjacent to dura mater, periosteum, or endosteum is provided. In still another embodiment, a composition for treating a bone or cartilage defect is provided. The composition comprises a reduced pressure apparatus and a biocompatible scaffold. With this composition, the defect is adjacent to dura mater, periosteum or 25 endosteum. In still a further embodiment, the use of a reduced pressure apparatus and a biocompatible scaffold for the manufacture of a composition for treating a bone or cartilage defect adjacent to dura mater, periosteum or endosteum is provided. Other features, and advantages of the illustrative embodiments will become 30 apparent with reference to the drawings and detailed description that follow. 2a BRIEF DESCRIPTION OF THE DRAWINGS FIG I is a schematic diagram ofa tissue.caffbld applied to a cranial defect such that 5 the tissue staffold isicontactwith a dura mater FG. 2 is a photograph lustrating a bone inductionsystem and method according to an embodiment of the present invention being applied to a rabbit cranium to induce inew bone growth through os eogenic activasion ofintact dura mater. FIG. 3 is a micrograph of an animal speAcien illustrating the normal architecture of a 10 dural sheath in comparison to newly forming bone in a rabbit craim subjected to reduced pressure according to ertain embodiments of the invention. FIG. 4 is mirmgraphs ofexperimentalresuls. Panel A is a microgrph ofhan imal specimen illustrating the demarcation between areas of e. bone formaion and areas without new bone formation. Panel B is a mirograh of an animal specimen in which central nervous 15 system tissue and aise scaffold are not separated by intact dura mater. Panel CL micrograph of an animal specimen in which. ew bone formation is in intimate contact with nsact dura niembrane. FIG is a micograph of Ith suface of a nive undamaged rabbit crantal bone. FIG 6 s amicrograph of a bone that was in contact with GranuFoam@ or ix days 20 wi bout reduced pressure. FIGais a mirograph of hone thatwain contact with Granufoam with reduced pressure koTbsix days. FIG. another micrograph of a bone that wasin contact with GranuFoam@ with redued pressure for six days 25 F1G9 is a nmicrograph of the surface of an undamnaged bone with superflal muscle tissue overying the pcdosteun. The do denote te demarcation between he cortical bone and the thin layer of the periosteunt. FIlUM panels A and U, is micrographsshowing inductin of cartilage tissue in response to contact with GranuFoanig Und reduced pressure, 30 FIK I is micrographs (l0X) showing procion red staining of endosteal bone surfaces interfacing with marrow tissues, in a bone treated with reduced pressure through Granufoan@ (A) or an untreated contralatera) control (3). 35 DETAILED DESCIPTION OF ILLUSTRATIVE FNIBODIMENTS ht the fo lowi ig detailed description of 'the illustrative embodimen's, reference is made t tho accompanying drawings that fann a pat hereet These embodiments are described 059ciem detail to enable those skilled in the art to practice the invention, and it is underttxx 6 that other embodiments may be utilized and that logical structural, mechanical, electrica, and chemical changes may be made without deparing from the spirit or scope of the invention. To avoid detail not necessary to enable those skilled in the art to praetee the embodints described herein, the description may ore cenain infomation known to those skilled in the art. The following detailed description is, thereforenot o be taken in a irniting sense, and the 10 scope of the illustrative embodiments are defined only by the appended claims, in the context of th is ecificaon the term "educed pressure" generalE refers to a pressure that les than the ambint Pressure at a tissue site that is subgced to threaten In most casethis ducer ure will be les than the atmospheric pre e oflte location at which the patient is located. Although the tenns acuum"and"negad pressure" may be 15 used to desaibe the pressure applied tthe tissue sethe aual pressureapplied to the tissue ste may be significantly heater tan the pressrenomaly assoiated with a complete vacuum, Consistent with this nomenclature, an increase in reduced pressure or vacuum pressure refersto a relative reduction of absolute pressurewhile a deease in reduced pressue er vacuum pressure refers to a relati e 'nceasesofabsohue pressure. n ous 20 methods and compodions deti&g reduced pressure treatment oftssue is descrberin h following patent publicationsi W080424S IA2, W 60803 6 1A2, W0036359A2, VO08036162A2. WON 83096A2.W007143060A2 WOtS6A2 M0071B5$A2, WOG071f6594A2, WO7106592A1 WC71691A2 WO i 0$A,, W O 0659A2, W007092397A2, WO0707615A2, WO033273A2 WOO 00948A W00410576A2 25 W00406018A2, WOO3092620A2 W003018098A. W00M06A ,'W0K03A75A, US20070123895 US7351250 US7346945 US7316672, US727%12 US7214202, US7186244 1 S710863, US707733 US7070584, US70049 1 156994702 U6951353, U56936037, US68568% U6814079 5 7334.S6695823 and U &6135116 Thikapplication is based on the discovery that the utliaion of reduced pressure on a 30 bone or catilage adjacent to dura mater, pedistau r eadosteurcauses induction of bone o at ihge formadon by the dr mater(where the defect is a canofacial defect), the pe'osteum or the endostea. The application of&a foam dresig tothe bone or cartilage can also induce new hone or cartilage formation butaot to the extent of reduce pressure treatment See amples4 4 Thus, in some emnbodients, the appication is directed to a method of activating osteogenic or chondrogenic activity at a site in a subject in need thereof. The method comprises applying reduced pressure to the dua mater, periosteum or endoastui at thesite in the subject. Preferabiy, the subject has a bone or cartilage defect adjacenT to the dura mater, 5 the periosteun. or the endosteum. H however, the application is not limited to sites of bone or cartilage defects. The subjects may, for example, be treated with these methods on the intact dura mater, periosteum or endasteum where there is no defect, and the resultant nev tissue transplanted to defect sites elsewhere in the body, in some embodiments the reduced pressure is applied to the dura mater: In other 10 embodiments, the reduced pressure is applied to the periosteum As shown in Example 4, endosrtum fluid flow in an intact hone is increased by a short exposure of the periosteum to reduced pressure It is believed that this increased fluid flow in the endosteta is indicative of increased osteogeni activity in the endosteum. Thus, endosteum osteogenic activity can be induced by applying reduced pressure to the periosteum, 16 in additional embodiments, the reduced pressure is applied to the etdosteum, Such a treatment would be useful, e.g., where applying reduced pressure to a gap in a bone to induce osteogenesis into a scaffold placed in the gap, These methods are not narrowly limited to the treatment of any particular type of defect. However, i is recognized that the predominant defects in subjects treated with these 20 methods are defects (a) from a wound, (b) due to cancer, (c) due to a degenerative disease (e., ostcoarthtis). or (d) congenital In some enmbodiments, the defect is a bone defect. In other embodients, the defect is a cartilage defect. Preferably, a biocompatible scaffold is paced at te site. Where the site comprises a defect the biocomapatible scaffold is preferably inserted into the defect. The methods are not 2 limited to the use of any particular biocompatible scaffold; numerous usefu biocompatible scaffolds are known in the at. In some embodiments, the biocomnpatible scaffod is a bioresorbable polymer, In preferred embodiments the bioresorhable polymer is a polylactide coglycolide (PLAGiA) polymecr or a polyethylene glycol-PLAGiA copolymer. The biocompatible scaffold can also include ccmponerts that facilitate wound healing. 30 Such components include cytokines, e.g., thse that promote angiogenesis or ceil growth such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFiG). pltelet derived grwth factor (PDGFV angiogenin, angiopoietin-, granuloyte coltny-stimulating factor (G-CSF), hepatocyt growth factor/scatter factor (F CF/SF), interleukin-t (IL-8), placental growth factor, platelet-derived endothelial cell growth factor (PD-ECG F), platelet 35 derived growth factor-BB (PDGF-BB), transforming growth factor-t (TGP-c), tonsforming 5 growth factor-l (TGf." tumor necrosis factor-o (TNF-), vascular endothelia growth factor (VEGF), or a matrix metalloproteinase (MMP). Other components that can usefully he included in the scaffld inside antibiotics, or cells tha are capable of becoming osteoblasts, chandroblasts, or vascular tissue, such as embryonic steim cells, adut hematopoietic stem 6 cells, bone marrow stromal cells. or mesenchymal stem cells. The cells may optionally be genetically engineered to express a useful protein, such as one of' the above cytokines. In preferred embodiments, the reduced pressure is applied to the defect through a manifold connected to a reduced pressure source, where the manifold is porous and is placed on or in the defect, t is also preferred that the manifold is from a flowable material that is 10 delivered through a manifold delivery tube to the tissue site such that the lowable material fills the defect, In some embodiments, the manifold is a bioresorbable polymer and is capable of serving as a biocompatible scaffold. Non-limiting examples of such a bioresorbable polymer include a polylactide-coglycolide (PLAGA) polymer or a polyethylene glycol PLAGA copolymer. 15 FIG. I shows a referred example ' i method as applied to a defect adjacent to the dura mater, It is noted that the same reduced pressure system can be utilized with periosteum or endosteum Referring to FIG. I, describing a non-dimiting embodiment of the instant application, a system 10 is provided that includes a reduced pressure source 14 fluidly connected to a 20 manifold 18 that is placed adjacent to and in contact with dura mater 22. The manifold 18 may include any bioompatible material that is capable of distributing the reduced pressure supplied by the reduced pressure source 14 to the dura mater 22. The manifold 18 may be formed from a porous material or may include flow channels that assist in distributing reduced pressure, In one embodiment, the manifold 18 may include a scaffold or the entire manifold 25 may be scaffold that is capable of supporting :he growth and integration of new tissue. The seadfold may be incorporated within the new tissue growth and remain in place following repair or regeneration of new tissue. The scafold may be formed from a bioabsorbable substance that is absorbed by the body following tissue repair or regeneration. A canister 30 may be fluidly connected between the reduced pressure source 14 and 30 the manifold 18 to trap and hold tissue exudates and other fluids that are withdrawn from areas adjacent the manifold 18 during the application of reduced pressure. Filters may be fluidly connected between the manifold 18 and the reduced pressure source 14 to prevent contamination of the reduced pressed source 4 by tissue fluids and bacteria Prefeably, the fluid connection between the reduced pressure source 14 and the manifold 18 (and any ot er 35 fuid components) is provided by medica-grade conduit 34. The conduit 34 may be fluidly attached to the mniiold 18 by a manifod adapter (nor shown) or by placing an end of she conduit 34 directly in contact with the manifold 18 such that the conduit 34 communicates directly with the poret or fluid channels associated with the manifold 18, in one embodiment, the manifold 18 is a bioabsorbable scaffold, and the reduced 5 pressure source 14 supplies reduced pressure to the dura mater 22 through thxe conduit 34 and the scaffold. Without being hound by any particular mechanism of action, it is believed that the presence of reduced pressure above the dura mater 22 imparts a strain on the dura mater 22 that activates a pherotypic expression of the durn mater 22 that is similar to that seen in neonatal, inmature dura mater. The timulation of the dura mater itself by imposing a reduced 10 pressure and strain on the dura mater is sufficient to populate a scaffold with new bone and supporting tissue See Example i. The reduced pressure treatment is not narrowly limited to any particular time of application. Example I establishes that a one day (24h) duration is sufficient to induce new bone fomation, bridging of a defect gap. and significant scaffold infiltration. In various 15 embodiments, the reduced pressure can be applied for anywhere from 0.1 h to 144 h or more. In other embodimets, the reduced pressure is applied for at least 24 h. In other examples, the reduced pressure is applied for less than 24 h, e.g. 12 h. In additioml embodiments, the reduced pressure is applied for 12 h to 3 days. As established in Exarnples 2 and 3, simply placing a foam manifold (preferably 20 GtanuFoam@) at a sie of desired bone or cartilage grwth (e.g., in a defect) on a periosteui or endosteum induces one or cartilage growth, although the induction is not as great as with reduced pressure, Therefore, it is contemplated that a biocompatible foam may be advantageously placed on a defect adjacent to a dura mater, a periosteum or an endostcum without reduced pressure to induce bone or cartilage growth. 25 The present invention is also directed to a method of treating a bone or cartilage defect in a subject The met co prices applying reduced pressure to the ura mater, perosteun or endosteam that is adjacent to the defect. In some embodiments, the reduced pressure is applied to the dura mater. ln other embodiments, the reduced pressure is applied to the periosteum, i stil other embodiments, the reduced pressure is applied to the endosteum. 30 As with the method described above, in this method a biocompatible scaffold is preferably inserted into the defect. The btocompaible scaffold is preferably a binresorbable polymer, most preferably a polyjactide-coglycolide (PLAGA) polymer or a polyethylene lycol-PLAGA copolymner. In preferred embodiments, the reduced pressure is applied to the dura mater, 35 periosteum or endosteum through a manifold connected to a reduced pressure sorce. iere, the manifold is and is pleed on or in the defect More preferab y, the manifold is from a flowable material that is deinered through a manifold deliver, tube to the tissue site such that the ilowable material tills the defect. Even more preferably, the manifold comprises a bioresorbable polymer and is capable of serving as a biocompatible scaffold, The 5 bioresorbable polymer that is most preferred is a polylactide-cog ycolide (PLAGA) polymer or a polyethylene glycol@LAGA copolymer In these methods, the reduced pressure can be applied for anywhere from 0,1 Ih to 144 h or more, n many embodiments, the reduced pressure is applied for at least 24 h. The application is also directed to the use of a reduced pressure apparatus for treating a 10 bone or cartilage defect adjacent to dura meat, periosteom, or endostewm. As with the methods described above, the reduced pressure apparatus preferably comprises a manifold connected to a reduced pressure source, wherein the manifold is porous and is placed on or in the defet. More preferably, the manifdid ic from a flowable material that is delivered through a manifold delivery tube to the tissue size such that the Dowable material fills the defect. 15 l additional embodiments, te invention is directed to a composition for treating a bone or cartilage defect. The composition comprises a reduced pressure apparatus and a biocompatible scaffold, wherein the de fect is adjacent to dura mater, periosteam or endosteum. Preferably, the biocompatible scaffold is a bioresorbable polymer, most preferably a polylactide-coglycolide (PLAGA) polymer or a polyethylene glycolPLAGA copolymer. 20 In preferred compositions the reduced pressure apparats comprises a manifold connected to a reduced pressure source. The manifold in these embodiments is porous, Preferably, the manifold comprises the biocompatible scaffold, More preferably, the manifold comprises a bioresorbabie polymer, most preferably a polylactide-coglycolide (PL AGA) polymer or a polyethylene gly'ol-PL AGA copolymer, 25 in these embodiment the manifold is preferably fronm a tonable material that is delivered through a manifold delivery tube to the tissue site such that the flowable material fillsthedfect The application is further directed to the use of a reduced pressure apparatus and a biocompatible scaffold for the manufacture oa composition for treating a bone or cartilage 30 defect adjacet to dura mater periosteum or endosteum. Prefebly;the bilocompatibe saffold is a bioresorbable polymer, most preDerably a pdylactide-oglycolide (PLAGA) prrlymer or a polyethylene gly col-PLAGA copolymer, For this use, the reduced pressure apparatus prefablyonmpries a manifold connected to a reduced pressure source, where the man i fold is porous. More preferably, the manifold 35 comprises the biocomnpatibe scaffold Even more pretrably, she manifold comprises a boresorbable polymer, most preferably a polylactide-coglycolide (PT A GA) polymer or a polyethylene giycol-PL.AGA copolymer. In preferred embodiments, lb manifold is from a Iowable material that is delivered through a manifod delivery tube to the tissue site such that the flowable material tills the & defect. Preferred embodinents are described in the following examples, Other eIrbodiments within the scope of the claims herein will be apparent to one skilled in the art from consideration of the specification or practice of the invention as disclosed herein. It is intended that the specification, together with the examples, be considered exemplary oly, 10 with the scope and spirit of the invention being indicated by the claims, which fellow the examples. Example . Stimulatioof osteoenia ativitY hn the dura mater With reduced reassure Referrng toIG 2, a racial defect study was performed to evaluate the effects of 15 applyngredued pressuretintact. dara mater throughascaffol Critical size defects ere made inthe cranium of a rabbit wih dura mater leftntact. A scaffokdsiinaa to hat shown in H1 ie. manifold and/or seaffld 18) was phced in contact with the dura matr Several tests were conducted tha vaed the amount of time over whichrduced pressurevas apphed, A control test warn in which .no rduced presure was supplied to the scalffod placed in 20 contact vith te dun mater. Samples of the craniumand scao were examined flowing 12 weeks of infelkhealing for each particular defectjnclusivof themount oftime over which duced pressure was applied The measured value included the amount of new bone area observed, the percentage of quaitative brdge assessment; the percentageof tol scaffold infiltrationand new bone growth penetration into the upper half of the scaffold 25 These mnasiement ar presented in Table t belw, 9, Treatment New Boac Area Quantitative {Total Scaffold Upper-Half Assessment infiltration (Dim) Bridging infiTratioun Scaffold 4 _________ 1 (mm2 Control 6 589% 0.36 24 hrs 718 87% 8.9% 1.74 (n__-E) (p .ml) I (psO.027) (pcO,0097) (ps0.000 2 l) 4 days 690 82% 17.9% L79 ( (pay5 (pSO.048) (p<0 14) (p 0,0076) 6 days 785% 20.4% 230 (ptsO.0032) (p 0.040) ps0.003 1 (fps0.00023) 10 days 6,98 85% 20.6% 234 (u=7) | (p<O.0066) (pV0.040) (p 0.O 04 3) (lps00003) Tab e 1. "New-Bone" is the total area ofbone formed iathe scaffold. "Bridging Assessment" is the percent of the defect bidged'with bone from one side of the defect to the other, as measured through the cemer of the defect The bridging assessment is an important clinical 5 factor since it indicates the effectiveness of closing the defect "Percent Scaffold Infiltration" is the percent of the total availablespace in the scaffold that is f iled with hone. "Upper-Half ifiltratonis the amount of bone the upperha of the safTid As Table I ilustrates, application of reduced pressuresignifcantly increased all bone formation parameters tested, elative to the control specimens. During the study cae was 10 taken toinaintain intact dura prior to insertion of thetissue scaffold At each time point, red d pressure stimulated statistically greater amouns of new bone deposiio than the control ndicating that a threshold eventwas achieved after a sing e day of application Although application for longer dunItion did not increase bridging assessments longer duration did influence the distribution of bone deposition, particularly in the uppe-half of the 16 tissue scaffoldthatis fuher removed frmhe dura mater. Differences observed and quantified presumably relate to dual activatin sincesotiisse above the defect was not subjected to reduced pressure Referring to FIGS. 3-40 micrographs wre taken ofspecimens obtained in the tests described 'he; FIG. 3 iustrate amrographefa normalhitectar ofoa dural sheath 40 20 adjacent to newly forming bone 45 in a rabbit cranium Also present areosteoblasts 47 between the dura 0heath40 and new bone 45. Examination of new hone formation and integration into scaffold materialsubjected to reduced pressure confirm he influence of intact dur mater in the osteogenic response to the stiffold ma erialFG.4A is a miogaph ofan animal specimen illustrating the shape deaation between areas ofnewboe formation 55 25 and areas without new bone formation 60. A though both areas contain scaffold material 62 to the absence of intact dural membrane consistently corelates with the absence of new bone formation, In FIC. 4A new bone formaIon 55 is located in proximity to an intact dual membrane 64, FIG, 4B illustrates a specimen. in~ wich central nervous sy stem tissue 70 and a tissue scaffold 75 are not separated by intact dura mater. Noticeably absent from FIG. 4B is 5 new bone form aion. In contrast, FIG. 4C illustrates a weli defined dural membrane 80 and a large amount of new bone Cormiation 90 in intitnatecontact h the dural membrane 80, 10 A foam manifold and reduced pressure were evaluated for theirability to induce the periosteum to synthesize new bone. The onrtundamagedcranal peioseum of rabbit was esp sed. A GranuFoamg (CI Licensing Ins,, San Antonio TX) foam dressing was applied to the bone. In some treatments,the foamcovered bone was also subjtd to reduced pressure After treatment, the animals wer sacrifi ed and the treated bone was subjected to 15 paraffin embedig, sectioning and staining to evaluate the effect of the treatment on new bone formation. FiG. S shows a naive undamaged periosteum in a rabbit The arrow denotes the location ofthe thin 1ayer of the peristeus The periostem is thin and unremarkable. By contrast, FIG 6 shows induction ofgrmulation tissuoveding t periosteum wherethe 20 foam wamaimained in contact with the bony surface for day without reduced pressure. Granlation tssue was induced byexposure of the bone to the foam without a reduced pressure treatnnt This demonstrates foam induction of granulation tissue overying the periosteunt, FIG. shows treatment ofbone 'with foam and reduced pressure (125m igh New bone formatonwas enhanced over te foam treatmen akne. Fi. 8 shows another 25 section of a bone subjected to foam and reduced pressure, sov'ing new bone deposition tinder newlyformed granuat ton u The fne one erlies the origial periosteak onrical interface In conclusionths Example shows the inducton of new bone when foam alone is applied. More rapid and extensive bon formation occars with application of reduced pressure 30 through the fbam. E e 1duttion ofrcan e fissuefiornation Cartilage fomiatiortwas observed response to the application of oedused pressure therapy to the suraile o' intact cranial periosteal membranes, These observations are of 35 significance in that cantiage formation in response to a therapy is unique and of great interest in the field of tissue engineerng These tornations were observed in the absence of caffotd materials and only with the application of educed pressure. No cartilage formation was obseved in controls. Cartilage degeneration caused by congenital abnormalides or disease and trauma is of 5 great clinical oonsegnne. Because of the lack of blood supply and subsequent wound healing response, damage to cartilage general results in an incompleterepair by the body Fullthickness articular cartilage damage or osteochondral lesionsallowfor he normaI iflammatozy response, but result In inferior fibrocartiage fnnatin Surgial intervention is ofen the o y option. Treatments for repair of canilage damage are ofen less tan 10 satisfactory, and rarely restore full functieno return the tissue to its native normal state This Example demonstrates the induction of new cartilage from pedosteum using GianuFOWin® and reduced pressure treatment. A foam manifold and reduced pressure were evaluated fortheir ability to induce the periosteun to synthesize new cartilage The intact, undamaged crania of rabbits were 15 posed, AGrantFoam@(KC Liensingc, San Antonio TX) foam dressing as applied to thebone With some atmentsthe Foam-covered bone was also subjected to reduced pressure. Atier treatment the animals were sacrificed and the treated bone was subjected to paraffin embedding sectining and stainirg to evaluate the ef fect of the treatment on new bone fornatio. 20 FIG. 9 shows a nave, undamaged periosteun in rabbit cranium. The dots denote the demarcation between the coical bone and the thin layer of the penosteum. By contrast, Fi. 10A, B show that, with the use of Grt-anuFoam® and reduced pressure (-125 mm Hg), extensive cartilage issues was induced overlying the periosteum, 25 E xamte4~Adution of endosteal actijy The effect of reduced pressure treatment on induction of endosteal osteogenic activity was evaluated. Contralatend sheep metacarpal bones were used. The dye procion red (0.8%) was introduced lot the canmulated median arteries of the bones for 310 minutes. One bone was aso subjected to reduced pressure (-125 mm Hg). The contralateral bone was not subjected to 30 reduced pressure. After the treatment, the bones were fixed in 80% ethyl alcohol en subjected to fuoromicroscopy through a green filer. FI It bows the result The bone treated with reduced pressure (Panel A) showed much greater circulation of the endosteal surface (as measured by intensity of procion red staining thante untreated bone (Panel U), indicaingincreased fhtd I w by educed pressure, even though therapy was applied to the 35 outer periosteal surface i2 In vew ofthe above, it will be seen that the several advantages of ihe in enn re achieved and other advantages attained. As various changes could be made inthe above methods and compositionsvwthout 5 departing from the sope 1fthe invention, it is intended that all matter contaed in thyabove descrition and shown in the accompanying drawings sall be interpreted as illustrate e and not in a limiting sense All referencesited in this specification are hereby incorporated by reference The discussion ofthe references herein is intended merely to summarize the assertions made by the 10 authors and no admission is made that any reference constitutes prior art. Applicants reserve the right to challenge the accuracy and pertinence of the cited references.

Claims (20)

1. A system for activating osteogenic or chondrogenic activity at a tissue site in a subject, the system comprising: a source of reduced pressure; and a manifold formed from an open-cell reticulated foam having pore sizes between about 400 microns and about 600 microns and adapted to be fluidly connected to the source and adapted to be positioned adjacent dura mater for applying reduced pressure to the dura mater of the subject adjacent the tissue site in the subject.

2. The system of claim 1, wherein the manifold includes a biocompatible scaffold.

3. The system of claim 2, wherein the biocompatible scaffold is a bioresorbable polymer.

4. The system of claim 3, wherein the bioresorbable polymer is a polylactide coglycolide (PLAGA) polymer or a polyethylene glycol-PLAGA copolymer.

5. The system of claim 1, wherein the tissue site is a bone or cartilage defect adjacent to the dura mater.

6. The system of claim 1, wherein the reduced pressure induces endosteum osteogenic activity.

7. The system of claim 5, wherein the defect is (a) from a wound, (b) due to cancer, (c) due to a degenerative disease, or (d) congenital.

8. The system of claim 5, wherein a biocompatible scaffold is inserted into the defect.

9. The system of claim 8, wherein the biocompatible scaffold is a bioresorbable polymer.

10. The system of claim 9, wherein the bioresorbable polymer is a polylactide coglycolide (PLAGA) polymer or a polyethylene glycol-PLAGA copolymer. 14

11. The system of claim 1, wherein the manifold is porous and formed from a flowable material that is delivered through a manifold delivery tube to the tissue site such that the flowable material fills the defect.

12. The system of claim 1, wherein the manifold is a porous, bioresorbable polymer capable of serving as a biocompatible scaffold.

13. The system of claim 1, wherein the reduced pressure is applied for a period of time between about 12 hours and about 3 days.

14. A system for treating a bone or cartilage defect in a subject, the system comprising: a source of reduced pressure; and a manifold formed from an open-cell reticulated foam having pore sizes between about 400 microns and about 600 microns, fluidly connected to the source and adapted to be positioned adjacent dura mater for applying reduced pressure to the dura mater that is adjacent the defect.

15. The system of claim 14, wherein a biocompatible scaffold is inserted into the defect.

16. The system of claim 15, wherein the biocompatible scaffold is a bioresorbable polymer.

17. The system of claim 16, wherein the bioresorbable polymer is a polylactide coglycolide (PLAGA) polymer or a polyethylene glycol-PLAGA copolymer.

18. The system of claim 14, wherein the manifold is porous and formed from a flowable material that is delivered through a manifold delivery tube to the defect such that the flowable material fills the defect.

19. The system of claim 14, wherein the manifold is a porous, bioresorbable polymer capable of serving as a biocompatible scaffold. 15

20. A system for treating a bone or cartilage defect in a subject, the system comprising: a source of reduced pressure; a scaffold adapted to be positioned into the defect; and a manifold formed from an open-cell reticulated foam having pore sizes between about 400 microns and about 600 microns and adapted to be fluidly connected to the source and adapted to be positioned adjacent dura mater for applying reduced pressure to the dura mater adjacent the defect. 16