Regenerative matching axial vascularisation of absorbable 3D-printed scaffold for large bone defects: A first in human series

BACKGROUND

We describe the first clinical series of a novel bone replacement technique based on regenerative matching axial vascularisation (RMAV). This was used in four cases: a tibial defect after treatment of osteomyelitis; a calvarial defect after trauma and failed titanium cranioplasty; a paediatric tibial defect after neoadjuvant chemotherapy and resection of Ewing sarcoma; and a paediatric mandibular deficiency resulting from congenital hemifacial microsomia.

METHOD

All patients underwent reconstruction with three-dimensional (3D)-printed medical-grade polycaprolactone and tricalcium phosphate (mPCL-TCP) scaffolds wrapped in vascularised free corticoperiosteal flaps.

OUTCOME

Functional volumes of load-sharing regenerate bone have formed in all cases after a moderate duration of follow-up. At 36 cm, case 1 remains the longest segment of load bearing bone ever successfully reconstructed. This technique offers an alternative to existing methods of large volume bone defect reconstruction that may be safe, reliable, and give predictable outcomes in challenging situations. It achieves this by using a bioresorbable scaffold to support and direct the growth of regenerate bone, driven by RMAV.

CONCLUSION

This technique may facilitate the reconstruction of bone defects previously thought unreconstructable, reduce the risk of long-term implant-related complications and achieve these outcomes in a hostile environment. These potential benefits must now be formally tested in prospective clinical trials.

Personalized, Mechanically Strong, and Biodegradable Coronary Artery Stents via Melt Electrowriting

Biodegradable coronary artery stents are sought-after alternatives to permanent stents. These devices are designed to degrade after the blood vessel heals, leaving behind a regenerated artery. The original generation of clinically available biodegradable stents required significantly thicker struts (∼150 μm) than nondegradable ones to ensure sufficient mechanical strength. However, these thicker struts proved to be a key contributor to the clinical failure of the stents. A current challenge lies in the fabrication of stents that possess both thin struts and adequate mechanical strength. In this contribution, we describe a method for the bottom-up, additive manufacturing of biodegradable composite stents with ultrathin fibers and superior mechanical properties compared to the base polymer. Specifically, we illustrate that melt electrowriting (MEW) can be used to 3D print composite structures with thin struts (60-80 μm) and a high degree of geometric complexity required for stenting applications. Additionally, this technology allows additive manufacture of personalized stents that are customized to a patient's unique anatomy and disease state. Furthermore, we illustrate that polycaprolactone-reduced graphene oxide nanocomposites have superior mechanical properties compared to original polycaprolactone without detriment to the material's cytocompatibility and that customizable stent-like structures can be fabricated from these materials with struts as thin as 60 μm, well below the target value for clinical use of 80 μm.

Abstract 3747: Radium 223 inhibits prostate cancer in bone via zonal cytotoxicity

Bone metastases are the initial site of progression and account for many complications experienced by men with metastatic prostate cancer (PCa), with limited therapeutic options. Targeting the bone environment has recently resulted in the approval of Radium-223 (Rad-223), a new life-prolonging therapy for patients with metastatic castrate-resistant prostate cancer. Rad-223 is a rare earth metal radioisotope that displays chemical properties similar to calcium, becomes enriched in bone after in vivo administration and emits alpha particles with locally high energy but limited penetrance in tissues (<100 µm). Confoundingly, the clinical response to Radium-223 is often followed by detrimental relapse and progression, and whether Radium-223 causes tumor-cell directed cytotoxicity in vivo remains unclear. We hypothesized that limited radiation penetrance in situ defines outcome and addressed the principles discriminating Radium-223 efficacy from failure by combining 3D intravital microscopy, in silico modeling and end-point analysis in preclinical PCa models in bone. Radium-223 induced profound but zonally confined cancer cell lethality along the bone interface (200-300 µm), while the more distant tumor core remained unperturbed. As consequence, macro-lesions persisted and grew, whereas micro-tumors in the bone niche showed severe growth delay or eradication. The relative inefficacy in controlling large tumors points to application of Radium-223 in secondary prevention of early bone-metastatic disease and regimens co-targeting the tumor core or broadening the zonal toxicity.

Citation Format: Eleonora Dondossola, Stefano Casarin, Claudia Paindelli, Elena De-Juan-Pardo, Dietmar Hutmacher, Christopher Logothetis, Peter Friedl. Radium 223 inhibits prostate cancer in bone via zonal cytotoxicity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3747.

Conceptual design of a personalized radiation therapy patch for skin cancer

Radiation therapy is a valuable option for treatment of skin cancer. In order to deliver the radiation dose to the superficial skin tumor, an X-ray source, electron beam radiation therapy or a radioisotope is applied. The effectiveness of these procedures is well established in the literature. Findings of some recent studies have indicated that beta particles can be of particular interest in suppressing skin tumor growth. Betaemitting radioisotopes are favorable because of the short penetration depth of their emitted particles. Beta radiation can induce significant damage in superficial skin tumor, and at the same time, result in enhanced protection of the underlying healthy tissues. In this study, we propose the design of a patch that can be used in beta radiation therapy of skin cancer patients. For that, we describe the components of this radioactive patch, as well as a proposal for the subsequent clinical application procedure. A scaffold was used as a substrate for embedding the desired beta-emitting radioisotope, and two layers of hydrogel to provide protection and shielding for the radioactively labelled scaffold. The proposed design could provide a universal platform for all beta-emitting radioisotopes. Depending on the depth of the tumor spread, a suitable beta emitter for that specific tumor can be selected and used. This is of particular and critical importance in cases where the tumor is located directly on top of the bone and for which the depth of penetration of radiation should be limited to only the tumor volume. The proposed design has the mechanical flexibility to adapt to curved body regions so as to allow the use in anatomically challenging areas of the body.

Abstract 1165: A tissue-engineered bone mimetic in vitro model for monitoring metastatic PCa growth and therapy response

Despite recent advances in prostate cancer (PCa) treatment, the outcome of metastatic disease remains frequently fatal and the underlying biology poorly understood. Thus, the development of clinically relevant in vitro models to monitor PCa biology in organotypic bone-like environment is critical to uncover mechanisms of therapy resistance and identify more effective treatments. To establish a bone-mimetic culture, we combined the following components: (i) bioactive osteoblasts depositing bone-like calcified extracellular matrix, (ii) complex 3D surface geometries, (iii) multicellular tumor application as spheroids/organoids, and (iv) applicability for live-cell microscopy to monitor the development of lesions over time. Calcified polycaprolactone (PCL) scaffolds were functionalized with bone-derived human mesenchymal stem cells (hMSCs) differentiated to osteoblasts, to generate a 3D niche-like calcified scaffold. PCa spheroids (PC3, C4-2B, patient-derived xenografts) were on-planted and their growth and invasion longitudinally monitored by advanced microscopy. PCa spheroids seeded on the organotypic bone model could be maintained and expanded over weeks, sufficient for monitoring therapy response to docetaxel, a first-line therapy for advanced PCa. The bone mimetic culture further revealed resistance to docetaxel mainly at the invasive edges, through a mechanism depending on the presence of osteoblasts. Thus, this 3D in vitro organotypic model will be suitable for dissecting the physical and molecular PCa cell-osteoblast interaction involved in PCa growth and therapy resistance.

Citation Format: Claudia Paindelli, Dietmar Hutmacher, Peter Friedl, Eleonora Dondossola. A tissue-engineered bone mimetic in vitro model for monitoring metastatic PCa growth and therapy response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1165.

Effect of plasma immersion ion implantation on polycaprolactone with various molecular weights and crystallinity

Polycaprolactone with five different molecular weights was spin-coated on silicon wafers and plasma immersion ion implanted (PIII) with ion fluence in the range 5 × 10¹⁴-2 × 10¹⁶ ions/cm². The effects of PIII treatment on the optical properties, chemical structure, crystallinity, morphology, gel fraction formation and wettability were investigated. As in the case of a number of previously studied polymers, oxidation and hydrophobic recovery of the PIII treated PCL follow second order kinetics. CAPA 6250, which has the lowest molecular weight and the highest degree of crystallinity of the untreated PCL films studied, has the highest carbonization of the modified layer after PIII treatment. Untreated medical grade PCL films, mPCL PC12 (Perstorp) and mPCL Osteopore^TM have similar chemical structures and crystallinity. Accordingly, the chemical and structural transformations caused by PIII treatment and post-treatment oxidation are almost identical for these two polymers. In general, PIII treatment destroys the nano-scale lamellar structure and results in a reduction of PCL crystallinity. Examination after washing PIII treated PCL films in toluene confirmed our hypothesis that cross-linking due to PIII treatment is significantly higher in semi-crystalline PCL as compared with amorphous polymers.

The influence of anisotropic nano- to micro-topography on in vitro and in vivo osteogenesis

AIM

Topographically modified substrates are increasingly used in tissue engineering to enhance biomimicry. The overarching hypothesis is that topographical cues will control cellular response at the cell-substrate interface.

MATERIALS & METHODS

The influence of anisotropically ordered poly(lactic-co-glycolic acid) substrates (constant groove width of ~1860 nm; constant line width of ~2220 nm; variable groove depth of ~35, 306 and 2046 nm) on in vitro and in vivo osteogenesis were assessed.

RESULTS & DISCUSSION

We demonstrate that substrates with groove depths of approximately 306 and 2046 nm promote osteoblast alignment parallel to underlined topography in vitro. However, none of the topographies assessed promoted directional osteogenesis in vivo.

CONCLUSION

2D imprinting technologies are useful tools for in vitro cell phenotype maintenance.

Abstract A54: Intravital microscopy of prostate cancer lesions in bone: Kinetics of osteolysis and therapy response

This abstract is being presented as a short talk in the scientific program. A full abstract is printed in the Proffered Abstracts section (PR04) of the Conference Proceedings.

Citation Format: Eleonora Dondossola, Stephanie Alexander, Steve Alexander, Boris Holzapfel, Christopher Logothetis, Dietmar Hutmacher, Peter Friedl. Intravital microscopy of prostate cancer lesions in bone: Kinetics of osteolysis and therapy response. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr A54.

Substrate topography: A valuable in vitro tool, but a clinical red herring for in vivo tenogenesis

Controlling the cell-substrate interactions at the bio-interface is becoming an inherent element in the design of implantable devices. Modulation of cellular adhesion in vitro, through topographical cues, is a well-documented process that offers control over subsequent cellular functions. However, it is still unclear whether surface topography can be translated into a clinically functional response in vivo at the tissue/device interface. Herein, we demonstrated that anisotropic substrates with a groove depth of ∼317nm and ∼1988nm promoted human tenocyte alignment parallel to the underlying topography in vitro. However, the rigid poly(lactic-co-glycolic acid) substrates used in this study upregulated the expression of chondrogenic and osteogenic genes, indicating possible tenocyte trans-differentiation. Of significant importance is that none of the topographies assessed (∼37nm, ∼317nm and ∼1988nm groove depth) induced extracellular matrix orientation parallel to the substrate orientation in a rat patellar tendon model. These data indicate that two-dimensional imprinting technologies are useful tools for in vitro cell phenotype maintenance, rather than for organised neotissue formation in vivo, should multifactorial approaches that consider both surface topography and substrate rigidity be established.

STATEMENT OF SIGNIFICANCE

Herein, we ventured to assess the influence of parallel groves, ranging from nano- to micro-level, on tenocytes response in vitro and on host response using a tendon and a subcutaneous model. In vitro analysis indicates that anisotropically ordered micro-scale grooves, as opposed to nano-scale grooves, maintain physiological cell morphology. The rather rigid PLGA substrates appeared to induce trans-differentiation towards chondrogenic and/or steogenic lineage, as evidence by TILDA gene analysis. In vivo data in both tendon and subcutaneous models indicate that none of the substrates induced bidirectional host cell and tissue growth. Collective, these observations indicate that two-dimensional imprinting technologies are useful tools for in vitro cell phenotype maintenance, rather than for directional neotissue formation, should multifactorial approaches that consider both surface topography and substrate rigidity be established.

A histomorphometric assessment of collagen-stabilized anorganic bovine bone mineral in maxillary sinus augmentation - a randomized controlled trial in sheep

OBJECTIVE

To histomorphometrically compare the use of collagen-stabilized anorganic bovine bone (ABBM-C) (test) to anorganic bovine bone + autogenous bone (ABBM + AB) (control) in maxillary sinus augmentation.

MATERIALS AND METHODS

Nine sheep underwent bilateral sinus augmentation. Each sinus was randomized to receive either control or test bone graft. Three animals were sacrificed at 8 weeks, and six animals were sacrificed at 16 weeks post-grafting. The 18 sinuses were processed for histomorphometry, which assessed the area fraction of new bone (%NB), residual graft (%RG) and soft tissue components (% STM), as well as graft particle osseointegration (% OI), within three zones equally distributed from the augmented sinus floor.

RESULTS

At week 16, a significant increase in %NB was evident across all three zones in the control group when compared to week 8. A significantly greater %NB was evident in the control group when compared to the test group in zones 2 (P < 0.001) and 3 (P < 0.001). There was a significant increase in %OI in week 16 when compared to week 8 across all three zones in the control group (P < 0.001). %OI in the control group was significantly greater across all three zones when compared to the test group at week 16 (P < 0.001). Zone was found to be a significant main effect (P < 0.001) that was independent of time and treatment with decreasing %OI in distant zones. %RG did not significantly change with time for both groups. There was a significant reduction in %ST in week 16 when compared to week 8 across all three zones in the control group (P < 0.001). %ST in the test group was significantly greater across all zones when compared to the control group at week 16 (P < 0.001).

CONCLUSION

Both groups exhibited very similar histomorphometric measurements in the zones proximal to the resident sinus wall. The % NB and % OI were greatest in the zones proximal to resident bony walls and gradually decreased as the distance from the proximal walls increased. There was greater % NB and % OI in the control group when compared to the test group in the distant zone.

Cavin-1/PTRF alters prostate cancer cell-derived extracellular vesicle content and internalization to attenuate extracellular vesicle-mediated osteoclastogenesis and osteoblast proliferation

Background

Tumour-derived extracellular vesicles (EVs) play a role in tumour progression; however, the spectrum of molecular mechanisms regulating EV secretion and cargo selection remain to be fully elucidated. We have reported that cavin-1 expression in prostate cancer PC3 cells reduced the abundance of a subset of EV proteins, concomitant with reduced xenograft tumour growth and metastasis.

Methods

We examined the functional outcomes and mechanisms of cavin-1 expression on PC3-derived EVs (PC3-EVs).

Results

PC3-EVs were internalized by osteoclast precursor RAW264.7 cells and primary human osteoblasts (hOBs) in vitro, stimulating osteoclastogenesis 37-fold and hOB proliferation 1.5-fold, respectively. Strikin gly, EVs derived from cavin-1-expressing PC3 cells (cavin-1-PC3-EVs) failed to induce multinucleate osteoblasts or hOB proliferation. Cavin-1 was not detected in EVs, indicating an indirect mechanism of action. EV morphology, size and quantity were also not affected by cavin-1 expression, suggesting that cavin-1 modulated EV cargo recruitment rather than release. While cavin-1-EVs had no osteoclastogenic function, they were internalized by RAW264.7 cells but at a reduced efficiency compared to control EVs. EV surface proteins are required for internalization of PC3-EVs by RAW264.7 cells, as proteinase K treatment abolished uptake of both control and cavin-1-PC3-EVs. Removal of sialic acid modifications by neuraminidase treatment increased the amount of control PC3-EVs internalized by RAW264.7 cells, without affecting cavin-1-PC3-EVs. This suggests that cavin-1 expression altered the glycosylation modifications on PC3-EV surface. Finally, cavin-1 expression did not affect EV in vivo tissue targeting as both control and cavin-1-PC3-EVs were predominantly retained in the lung and bone 24 hours after injection into mice.

Discussion

Taken together, our results reveal a novel pathway for EV cargo sorting, and highlight the potential of utilizing cavin-1-mediated pathways to attenuate metastatic prostate cancer.

Eyes on 3D-current 3D biomimetic disease concept models and potential applications in age-related macular degeneration

Three-dimensional cellular models that mimic disease are being increasingly investigated and have opened an exciting new research area into understanding pathomechanisms. The advantage of 3D in vitro disease models is that they allow systematic and in depth studies of physiological and pathophysiological processes with less costs and ethical concerns that have arisen with animal models. The purpose of the 30 approach is to allow crosstalk between cells and microenvironment, and with cues from the microenvironment,cells can assemble their niche similar to in vivo conditions. The use of 3D models for mimicking disease processes such as cancer, osteoarthritis etc., Is only emerging and allows multidisciplinary teams consisting of tissue engineers, biologist biomaterial scientists and clinicians to work closely together. While in vitro systems require rigorous testing before they can be considered as replicates of the in vivo model, major steps have been made,suggesting that they will become powerful tools for studying physiological and pathophysiological processes. This paper aims to summarize some of the existing 3D models and proposes a novel 3D model of the eye structures that are involved in the most common cause of blindness in the Western World,namely age-related macular degeneration (AMD).

Abstract B11: Using three-dimensional (3-D) culture systems to delineate the role of RANKL in metastatic prostate cancer

Introduction and Objective: While prostate cancer (PCa) is curable at early diagnosis, metastatic PCa is terminal. Recent studies have shown that Receptor Activator of NF kappa-B Ligand, RANKL, markedly enhances bone metastasis (70-100%) by the LNCaP human PCa cell line in mice compared to neo controls (0%). Multivariable tumor and microenvironmental factors in vivo make it difficult to identify the specific cellular response induced by RANKL causing PCa cell homing and growth in bone. Current in vitro 2D cultures lack mechanical and biochemical properties mimicking the bone microenvironment. Our preliminary data showed integrin alpha2 is elevated in RANKL-over-expressing LNCaP cells. PCa interaction with the major bone matrix protein Col1 may contribute to the metastatic potential of LNCAP-RANKL cells. This study used 3D systems to explore the role of RANKL in PCa-bone matrix interactions.

Methods: 3D cultures of RANKL-expressing (highly metastatic) or non-metastatic LNCaP cells were evaluated in 2D, suspension cultures, on type 1 collagen (Col1) coated polymeric meshes, embedded in Col1 gel or hydrogel mixed with Col1 for growth, morphology, motility, and gene expression. Time-dependent cell migration was assessed by a time-lapse imaging system.

Results: LNCAP-RANKL cells and Neo-expressing controls grew as aggregates in all 3D cultures but not 2D cultures. Col1 promoted less compact and more widespread aggregation of LNCAP-RANKL cells in the 3D cultures, exhibiting more motile and directional migratory behavior. A molecular signature of 3D growth was generated and compared among different conditions. Consistent with 2D studies, 3D qRT-PCR data showed RANKL drove epithelial-to-mesenchymal transition (EMT), shown by increased expression of vimentin and N-cadherin but decreased E-cadherin. Decreased expression of androgen receptor and PSA was observed in RANKL-expressing PCa cells. Supporting the migration data, the presence of Col1 drove RANKL-expressing PCa cells to express higher levels of c-Met protooncogene, sensitizing PCa cell responses to the c-Met ligand, hepatocyte growth factor (HGF).

Conclusions: 3D culture systems were established to study interactions between Col1 and metastatic or non-metastatic PCa cells. 3D culture systems supported PCa cell growth, while maintaining their classical markers, validating the reliability of our 3D systems. Bone metastatic PCa cells preferentially exhibited EMT, increased expression of α2 integrin, and c-Met protooncogene. These 3D systems will be used to assess liquid biopsy specimens harvested from human PCa patients to improve prognosis and therapeutic follow-up.

Citation Format: Shabnam Ziaee, Shirly Sieh, Chia-Yi Chu, Ruoxiang Wang, Dietmar Hutmacher, Colleen Nelson, Chin-Lin Guo, Leland W.K. Chung. Using three-dimensional (3-D) culture systems to delineate the role of RANKL in metastatic prostate cancer. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr B11.

In vivo tracking of segmental bone defect healing reveals that callus patterning is related to early mechanical stimuli

This study addresses the hypothesis that callus formation, patterning, and mineralisation are impaired during the early phase of critical sized bone defect healing, and may relate to inter-fragmentary tissue strains within the bone defect area. Twenty four 12 week old Sprague Dawley rats were used for this study. They were divided into two groups defined by the femur bone defect size: (i) 1 mm resulting in normal healing (NH), and (ii) a large sized 5 mm defect resulting in critical healing (CH). Callus formation, patterning, and mineralisation kinetics in both groups were examined in the periosteal and osteotomy gap regions using a novel longitudinal study setup. Finite element analyses on µCT generated tomograms were used to determine inter-fragmentary tissue strain patterns and compared to callus formation and patterning over the course of time. Using a novel longitudinal study technique with µCT, in vivo tracking and computer simulation approaches, this study demonstrates that: (i) periosteal bone formation and patterning are significantly influenced by bone defect size as early as 2 weeks; (ii) osteotomy gap callus formation and patterning are influenced by bone defect size, and adapt towards a non-union in critical cases by deviating into a medullary formation route as early as 2 weeks after osteotomy; (iii) the new bone formation in the osteotomy gap enclosing the medullary cavity in the CH group is highly mineralised; (iv) inter-fragmentary strain patterns predicted during the very early soft callus tissue phase (less than 2 weeks) are concurrent with callus formation and patterning at later stages. In conclusion, bone defect size influences early onset of critical healing patterns.

Influences of age and mechanical stability on volume, microstructure, and mineralization of the fracture callus during bone healing: is osteoclast activity the key to age-related impaired healing?

Earlier studies have shown that the influence of fixation stability on bone healing diminishes with advanced age. The goal of this study was to unravel the relationship between mechanical stimulus and age on callus competence at a tissue level. Using 3D in vitro micro-computed tomography derived metrics, 2D in vivo radiography, and histology, we investigated the influences of age and varying fixation stability on callus size, geometry, microstructure, composition, remodeling, and vascularity. Compared were four groups with a 1.5-mm osteotomy gap in the femora of Sprague-Dawley rats: Young rigid (YR), Young semirigid (YSR), Old rigid (OR), Old semirigid (OSR). Hypothesis was that calcified callus microstructure and composition is impaired due to the influence of advanced age, and these individuals would show a reduced response to fixation stabilities. Semirigid fixations resulted in a larger DeltaCSA (Callus cross-sectional area) compared to rigid groups. In vitro microCT analysis at 6 weeks postmortem showed callus bridging scores in younger animals to be superior than their older counterparts (p<0.01). Younger animals showed (i) larger callus strut thickness (p<0.001), (ii) lower perforation in struts (p<0.01), and (iii) higher mineralization of callus struts (p<0.001). Callus mineralization was reduced in young animals with semirigid fracture fixation but remained unaffected in the aged group. While stability had an influence, age showed none on callus size and geometry of callus. With no differences observed in relative osteoid areas in the callus ROI, old as well as semirigid fixated animals showed a higher osteoclast count (p<0.05). Blood vessel density was reduced in animals with semirigid fixation (p<0.05). In conclusion, in vivo monitoring indicated delayed callus maturation in aged individuals. Callus bridging and callus competence (microstructure and mineralization) were impaired in individuals with an advanced age. This matched with increased bone resorption due to higher osteoclast numbers. Varying fixator configurations in older individuals did not alter the dominant effect of advanced age on callus tissue mineralization, unlike in their younger counterparts. Age-associated influences appeared independent from stability. This study illustrates the dominating role of osteoclastic activity in age-related impaired healing, while demonstrating the optimization of fixation parameters such as stiffness appeared to be less effective in influencing healing in aged individuals.

009. KALLIKREIN-RELATED PROTEASES AS NOVEL THERAPEUTIC TARGETS IN PROSTATE AND OVARIAN CANCER

The kallikrein-related (KLKs) peptidases are implicated in prostate and ovarian cancer invasion/metastasis via activation of growth factors, proteases and extracellular matrix degradation involved in. In our published work, we used cell biology approaches to show novel associations of KLK peptidases with processes indicative of metastasis and the potential of our novel sunflower trypsin inhibitor scaffold-engineered KLK4 inhibitor. Our current studies are directed towards discovering the precise KLK target proteins/substrates and the subsequent signalling pathways involved in these events in order to determine their therapeutic target potential. In this regard, we are using novel tissue engineered biomimetic 3D gel matrices to better mimic the in vivo micro-environment of prostate cancer cells especially in bone metastasis and peritoneal invasion in ovarian cancer. Pilot studies show that PC3 cells cultured on an osteoblast-derived bone matrix undergo an EMT-like change but remain dispersed on the cell surface. In contrast, LNCaP cells cluster aligning with the fibrillar structure as they invade into the bone matrix as typically seen in vivo. KLK4 proteolysis of the osteoblast-derived bone matrix has identified additional novel substrates. In addition, we are exploring the cell biology that underlies the reported high KLK4 or KLK7 levels associated with poorer outcome in women with epithelial ovarian cancer (EOC). Of note, KLK4 or KLK7 transfected SKOV3 EOC cells have increased chemoresistance to taxol and/or cisplastin suggesting a mechanism for this poor outcome. Furthermore, KLK7 transfected SKOV-3 cells form multicellular aggregates (MCA) in agarose suspension (a process indicative of peritoneal tumour cell spread seen in ascites fluid clinically) which can be reversed by a KLK7 blocking antibody indicating the critical role played by KLK7 in this event. These new paradigms are providing novel information on the role of KLK peptidases in prostate and ovarian cancer progression and their potential as novel therapeutic targets.

Noninvasive image analysis of 3D construct mineralization in a perfusion bioreactor

Although the beneficial effects of perfusion on cell-mediated mineralization have been demonstrated in several studies, the size of the mineralized constructs produced has been limited. The ability to quantify mineralized matrix formation non-invasively within 3D constructs would benefit efforts to optimize bioreactor conditions for scaling-up constructs to clinically relevant dimensions. In this study, we report a micro-CT imaging-based technique to monitor 3D mineralization over time in a perfusion bioreactor and specifically assess mechanisms of construct mineralization by quantifying the number, size, and distribution of mineralized particle formation within constructs varying in thickness from 3 to 9 mm. As expected, mineralized matrix volume and particle number increased with construct thickness. Analyzing multiple concentric volumes inside each construct indicated that a greater proportion of the mineral volume was found within the interior of the perfused constructs. Interestingly, intermediate-sized 6mm thick constructs were found to have the highest core mineral volume fraction and the largest mineralized particles. Two complementary mechanisms of increasing total mineral volume were observed in the 6 and 9 mm constructs: increasing particle size and increasing the number of mineralized particles, respectively. The rate of mineralized matrix formation in the perfused constructs increased from 0.69 mm(3)/week during the first 3 weeks of culture to 1.03 mm(3)/week over the final 2 weeks. In contrast, the rate of mineral deposition in the static controls was 0.01 mm(3)/week during the first 3 weeks of culture and 0.16 mm(3)/week from week 3 to week 5. The ability to monitor overall construct mineralization non-invasively coupled with quantitative analysis of mineralized particle size, number, and distribution offers a powerful tool for elucidating how mineral growth mechanisms are affected by cell type, scaffold material and architecture, or bioreactor flow conditions.

Temporal expression of proteoglycans in the rat limb during bone healing

Proteoglycans found in the bone extracellular matrix and on the cell surface can complex with HBGFs such as the FGFs, TGFs and BMPs which are known to play key roles in regulating fracture healing. Here we have studied the expression of key PGs during the bone repair process in order to determine the relationship between PG expression and healing status. We created non-critical sized trephine defects just proximal to the distal end of the tibial crest of adult male Wistar rats and examined the healing process histologically as well as by monitoring the temporal expression of mRNA transcripts for ALP, OP and OC, together with HSPG, CSPG and FGF-FGF receptor expression. Following surgery, animals were allowed to recover, and then euthanized after 7, 14, 21 and 28 days post-surgery, at which time tissue was harvested for histological examination and total RNA extracted and the mRNA transcripts examined by quantitative real-time PCR. HS and CSPG expression was generally observed to increase in the days immediately following injury, reaching peak expression two weeks post-surgery. This was followed by a gradual return to basal levels by day 28. The expression patterns of PGs were broadly similar with those of ALP, OP and FGFRs. The increase of mRNA expression for many key PGs detected during bone healing coincided with the elevation of bone markers and FGFRs, and provides further evidence that PGs involved in bone repair act in part through susceptible growth factors, including the FGF/FGFR system. The data presented here indicates that increased proteoglycan expression is involved in the early stages of bone healing at a time when previous studies have shown that the levels of HBGFs are maximal. Hence there exists a rationale for an exploration of the use of exogenous PGs as an adjunct therapy to potentiate the powerful effects of these factors and to augment the natural healing response.

Evaluation of a new bioresorbable barrier to facilitate guided bone regeneration around exposed implant threads. An experimental study in the monkey

The aim of this study was to evaluate the effectiveness of a new bioresorbable barrier alone or in combination with BioOss for guided bone regeneration around dental implants with exposed implant threads. Five adult Macaca fascicularis monkeys were used in this investigation. After extraction of all premolars and first molars, two endosteal oral implants were installed in each quadrant and the bony defects were randomly treated with either: 1) placement of the new bioresorbable device alone (group 1); 2) placement of the new bioresorbable barrier in combination with BioOss (group 2); 3) placement of an ePTFE barrier in combination with BioOss (group 3); or (4) control (group 4). After a period of six months the animals were killed and the histological processing was performed. There was a significant difference in the amount of new bone regeneration around the implants between the four groups (i.e. groups 1, 2, 3 and 4) (P=0.0122). There was no difference, however, between group 2 and group 3. It can be concluded that the new bioresorbable barrier in combination with BioOss appears to obtain the same results in this type of bony defects as the grafting material in combination with an ePTFE barrier.

Development and clinical application of titanium minipins for fixation of nonresorbable barrier membranes

Clinical applications of the principle of guided bone regeneration in oral and maxillofacial surgery include preimplant reconstruction of atrophied bone defects and coverage of endosseous implants that were incompletely covered by bone through primary intention. Nonresorbable polytetrafluoroethylene membranes are used. Over the past several years, the use of periosteal sutures to fix membranes has been supplemental or replaced by the use of metallic fixation systems. Five-year clinical results with a membrane pin set developed for fixation of such membranes are reported. Application of the titanium pin limits the relative movement between the membrane and surrounding bone and/or between and surrounding soft tissue flaps. Moreover, the titanium pin expands the range of applications for such membranes, particularly to topographically complicated bone defects at sites where clinically secure and biologically functioning placement of the membrane is not always easy.

A review of material properties of biodegradable and bioresorbable polymers and devices for GTR and GBR applications

Use of bioresorbable and biodegradable materials for guided tissue and guided bone regeneration is under intense investigation and is being tested in clinical trials. This study presents a basic overview of material properties of bioresorbable and biodegradable polymers and devices for guided tissue and guided bone regeneration treatment. Collagens and aliphatic polyesters, such as poly(glycolic acid), poly(lactic acid), and poly(epsilon-caprolactone), are discussed, as well as biocompatibility, mechanical properties, and sterilization.

The use of basic fibroblast growth factor (bFGF) for enhancement of bone ingrowth into pyrolized bovine bone

This pilot study aimed to investigate whether in vivo cultivation of bone in porous scaffolds can be enhanced by the use of growth factors. Four adult Göttingen minipigs received subperiosteal implantation of a block of pyrolized bovine bone on either side of the mandible. The blocks were covered with polylactic membrane. On one side, the implants were loaded with 240 micrograms of lyophilized basic fibroblast growth factor (bFGF). After 5 months, bone ingrowth was found throughout the whole block into the peripheral pore layers regardless of whether or not the scaffolds had been loaded with bFGF. Fluorescence labels likewise showed no significant differences in bone formation.

Experimental transplantation of hydroxylapatite-bone composite grafts

PURPOSE

This study was undertaken to determine if autogenous bone can be cultivated in vivo in a porous hydroxylapatite (HA) matrix by ingrowth from underlying bone and if this autogenous HA-bone composite graft can then be transplanted.

PATIENTS AND METHODS

Five Göttingen minipigs received subperiosteal implantation of one HA block each (40 x 10 x 10 mm), covered by a polylactic membrane, on the ascending ramus of the mandible. After 5 months, half of each implant was harvested and transplanted as an onlay graft to the horizontal ramus of the mandible with simultaneous insertion of a titanium implant. Polychrome fluorescence labeling was done 1, 2, 4, and 8 weeks postoperatively. After 3 months, the vascular system of the animals was filled with BaSO4 for microangiographic examination, and all blocks were retrieved.

RESULTS

Fluorescence microscopy showed that there was a significant decrease in deposition of the label in the grafted blocks at 1 week when compared with later labels. After the second week, there were no significant changes. A 20% to 30% decrease in the frequency of fluorochrome staining was noted in the upper third of each block. In this region, microangiography demonstrated highly vascularized tissue and limited bone resorption.

CONCLUSION

It was concluded that cultivation of mandibular bone in a porous matrix under guided bone regeneration is possible and that this autogenous HA-bone composite graft can be transplanted at a later date.

Enhancement of bone ingrowth into a porous hydroxylapatite-matrix using a resorbable polylactic membrane: an experimental pilot study

The objective of this pilot study was to study bone ingrowth into porous hydroxylapatite (HA) blocks using a polylactic membrane for guided tissue regeneration. Porous HA blocks were placed on both sides of the mandible and of the ilium in five Göttingen minipigs. On one side a polylactic membrane was used to cover the blocks. After 5 months, the blocks with the membrane covering showed complete bony penetration of the HA matrix both in the mandible and the ilium. The blocks without the membrane covering showed substantially less and irregular bone ingrowth after placement on the mandible and poor ingrowth after placement on the ilium. The newly formed bone in the blocks from the ilium showed a cancellous structure while bone tissue inside the blocks from the mandible exhibited a dense cortical appearance. The polylactic membrane was nearly completely degraded at the time of investigation.