Design and fabrication of a low cost implantable bladder pressure monitor

In the frame of the Flemish Community funded project Bioflex we developed and fabricated an implant for short term (< 7 days) bladder pressure monitoring, and diagnosis of incontinence. This implant is soft and flexible to prevent damaging the bladder's inner wall. It contains a standard flexible electronic circuit connected to a battery, which are embedded in surface treated silicone to enhance the biocompatibility and prevent salt deposition. This article describes the fabrication of the pill and the results of preliminary cytotoxicity tests. The electronic design and its tests, implantation and the result of the in-vivo experimentation will be presented in other articles

Early pH Changes in Musculoskeletal Tissues upon Injury-Aerobic Catabolic Pathway Activity Linked to Inter-Individual Differences in Local pH

Local pH is stated to acidify after bone fracture. However, the time course and degree of acidification remain unknown. Whether the acidification pattern within a fracture hematoma is applicable to adjacent muscle hematoma or is exclusive to this regenerative tissue has not been studied to date. Thus, in this study, we aimed to unravel the extent and pattern of acidification in vivo during the early phase post musculoskeletal injury. Local pH changes after fracture and muscle trauma were measured simultaneously in two pre-clinical animal models (sheep/rats) immediately after and up to 48 h post injury. The rat fracture hematoma was further analyzed histologically and metabolomically. In vivo pH measurements in bone and muscle hematoma revealed a local acidification in both animal models, yielding mean pH values in rats of 6.69 and 6.89, with pronounced intra- and inter-individual differences. The metabolomic analysis of the hematomas indicated a link between reduction in tricarboxylic acid cycle activity and pH, thus, metabolic activity within the injured tissues could be causative for the different pH values. The significant acidification within the early musculoskeletal hematoma could enable the employment of the pH for novel, sought-after treatments that allow for spatially and temporally controlled drug release

Early pH changes in musculoskeletal tissues upon injury-aerobic catabolic pathway activity linked to inter-individual differences in local pH

Local pH is stated to acidify after bone fracture. However, the time course and degree of acidification remain unknown. Whether the acidification pattern within a fracture hematoma is applicable to adjacent muscle hematoma or is exclusive to this regenerative tissue has not been studied to date. Thus, in this study, we aimed to unravel the extent and pattern of acidification in vivo during the early phase post musculoskeletal injury. Local pH changes after fracture and muscle trauma were measured simultaneously in two pre-clinical animal models (sheep/rats) immediately after and up to 48 h post injury. The rat fracture hematoma was further analyzed histologically and metabolomically. In vivo pH measurements in bone and muscle hematoma revealed a local acidification in both animal models, yielding mean pH values in rats of 6.69 and 6.89, with pronounced intra- and inter-individual differences. The metabolomic analysis of the hematomas indicated a link between reduction in tricarboxylic acid cycle activity and pH, thus, metabolic activity within the injured tissues could be causative for the different pH values. The significant acidification within the early musculoskeletal hematoma could enable the employment of the pH for novel, sought-after treatments that allow for spatially and temporally controlled drug release

Bone regeneration via novel macroporous CPC scaffolds in critical-sized cranial defects in rats

Objectives. Calcium phosphate cement (CPC) is promising for dental and craniofacial applications due to its ability to be injected or filled into complex-shaped bone defects and molded for esthetics, and its resorbability and replacement by new bone. The objective of this study was to investigate bone regeneration via novel macroporous CPC containing absorbable fibers, hydrogel microbeads and growth factors in critical-sized cranial defects in rats. Methods. Mannitol porogen and alginate hydrogel microbeads were incorporated into CPC. Absorbable fibers were used to provide mechanical reinforcement to CPC scaffolds. Six CPC groups were tested in rats: (1) control CPC without macropores and microbeads; (2) macroporous CPC + large fiber; (3) macroporous CPC + large fiber + nanofiber; (4) same as (3), but with rhBMP2 in CPC matrix; (5) same as (3), but with rhBMP2 in CPC matrix + rhTGF-beta 1 in microbeads; (6) same as (3), but with rhBMP2 in CPC matrix + VEGF in microbeads. Rats were sacrificed at 4 and 24 weeks for histological and micro-CT analyses. Results. The macroporous CPC scaffolds containing porogen, absorbable fibers and hydrogel microbeads had mechanical properties similar to cancellous bone. At 4 weeks, the new bone area fraction (mean +/- sd; n = 5) in CPC control group was the lowest at (14.8 +/- 3.3)%, and that of group 6 (rhBMP2 + VEGF) was (31.0 +/- 13.8)% (p < 0.05). At 24 weeks, group 4 (rhBMP2) had the most new bone of (38.8 +/- 15.6)%, higher than (12.7 +/- 5.3)% of CPC control (p < 0.05). Micro-CT revealed nearly complete bridging of the critical-sized defects with new bone for several macroporous CPC groups, compared to much less new bone formation for CPC control. Significance. Macroporous CPC scaffolds containing porogen, fibers and microbeads with growth factors were investigated in rat cranial defects for the first time. Macroporous CPCs had new bone up to 2-fold that of traditional CPC control at 4 weeks, and 3-fold that of traditional CPC at 24 weeks, and hence may be useful for dental, craniofacial and orthopedic applications. (C) 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved

Evaluation of an injectable, photopolymerizable, and three-dimensional scaffold based on methacrylate-endcapped poly(D,L-lactide-co-ε-caprolactone) combined with autologous mesenchymal stem cells in a goat tibial unicortical defect model

An in situ crosslinkable, biodegradable, methacrylate-endcapped poly(D,L-lactide-co-epsilon-caprolactone) in which crosslinkage is achieved by photoinitiators was developed for bone tissue regeneration. Different combinations of the polymer with bone marrow-derived mesenchymal stem cells (BMSCs) and alpha-tricalcium phosphate (alpha-TCP) were tested in a unicortical tibial defect model in eight goats. The polymers were randomly applied in one of three defects (6.0 mm diameter) using a fourth unfilled defect as control. Biocompatibility and bone-healing characteristics were evaluated by serial radiographies, histology, histomorphometry, and immunohistochemistry. The results demonstrated cell survival and proliferation in the polymer-substituted bone defects. The addition of alpha-TCP was associated with less expansion and growth of the BMSCs than other polymer composites

Matrix elasticity of void-forming hydrogels controls transplanted-stem-cell-mediated bone formation

The effectiveness of stem cell therapies has been hampered by cell death and limited control over fate. These problems can be partially circumvented by using macroporous biomaterials that improve the survival of transplanted stem cells and provide molecular cues to direct cell phenotype. Stem cell behaviour can also be controlled in vitro by manipulating the elasticity of both porous and non-porous materials, yet translation to therapeutic processes in vivo remains elusive. Here, by developing injectable, void-forming hydrogels that decouple pore formation from elasticity, we show that mesenchymal stem cell (MSC) osteogenesis in vitro, and cell deployment in vitro and in vivo, can be controlled by modifying, respectively, the hydrogel’s elastic modulus or its chemistry. When the hydrogels were used to transplant MSCs, the hydrogel’s elasticity regulated bone regeneration, with optimal bone formation at 60 kPa. Our findings show that biophysical cues can be harnessed to direct therapeutic stem cell behaviours in situ

Matrix elasticity of void-forming hydrogels controls transplanted-stem-cell-mediated bone formation

The effectiveness of stem cell therapies has been hampered by cell death and limited control over fate. These problems can be partially circumvented by using macroporous biomaterials that improve the survival of transplanted stem cells and provide molecular cues to direct cell phenotype. Stem cell behaviour can also be controlled in vitro by manipulating the elasticity of both porous and non-porous materials, yet translation to therapeutic processes in vivo remains elusive. Here, by developing injectable, void-forming hydrogels that decouple pore formation from elasticity, we show that mesenchymal stem cell (MSC) osteogenesis in vitro, and cell deployment in vitro and in vivo, can be controlled by modifying, respectively, the hydrogel's elastic modulus or its chemistry. When the hydrogels were used to transplant MSCs, the hydrogel's elasticity regulated bone regeneration, with optimal bone formation at 60 kPa. Our findings show that biophysical cues can be harnessed to direct therapeutic stem cell behaviours in situ

Cell delivery systems for bone tissue engineering

Bone is a very active and dynamic tissue that is constantly remodelled in response to mechanical stress and hormonal stimuli. The cells of the bone are capable of restoring bone defects and fractures in their original state. However, in certain circumstances, the spontaneous repair process is hampered, resulting in non-unions and/or the formation of fibrous scar tissue. When the repair process of the bone fails, additional treatment is needed to aid the healing and to preserve the integrity of the bone. The standard treatment consists of transplanting bone grafts in the defects. These grafts can be harvested from the patient (autograft) or from other human (allograft) or animal (xenograft) origin. Autologous bone grafting is still the golden standard treatment, but as with allograft and/or xenograft treatment, several drawbacks have been reported. The search for the ideal treatment for bone defects is ongoing to optimise the bone repair process. Especially the field of bone tissue engineering receives a lot of attention. Tissue engineered implants are constructs of a biomaterial (scaffold, carrier) and bioactive factors. These factors can be cells and/or growth factors that stimulate the hosts repair response. The goal is to mimic as closely as possible the organization, functionality and structure of bone. It was the aim of this thesis to find a new tissue engineered construct (TEC) to augment the bone repair process. This has been carried out in close collaboration with the Polymer Chemistry and Biomaterials Research Group of Prof. Etienne Schacht for the fabrication of new biomaterials and with the group of Prof. Frank Gasthuys from the Department of Surgery and Anaesthesiology of Domestic Animals for the evaluation of the TEC in an animal model. Since most bone defects are irregular in shape, it is difficult to fit in a preformed scaffold. That is why a scaffold that is formed inside the defect by an in situ polymerization technique is preferred. Moreover, the biomaterial can be delivered in a minimal invasive way through injection. Cells, i.e. bone marrow derived mesenchymal stem cells (BMSC), can be mixed with the biomaterial prior to injection. Cells were first cultured on a porous carrier system to offer the cells protection during the mixing in and the curing of the biomaterial and to offer these anchorage dependent cells a substrate for attachment and proliferation. Two types of in situ forming materials were investigated i.e. a poly(D,L-lactide-co-ε-caprolactone) polyester with a cross-linkable methacrylate end group and a UV cross-linkable chemically modified form of the Pluronic® F127 hydrogel with N-methacryloyl depsipeptide end groups. The porous carrier systems were on the one hand the commercially available gelatine microcarrier CultiSpher-S® and on the other hand a hydroxyapatite (HA) carrier developed at VITO. Implantation of cell loaded CultiSpher-S® carriers mixed in the lactide-caprolactone polyester in unicortical tibia defects in goats showed the survival of the cells on the encapsulated carriers, but there was no formation of new bone originating from the added cell source. The limited porosity of the polymer combined with the slow degradation rate of the polymer hampered the ingrowth of new blood vessels and bone. As an alternative, a chemically modified form of the FDA approved Pluronic® F127 hydrogel was tested in vitro and in vivo in the same goat model. There were clear indications of new bone formation originating from the implanted cells on the CultiSpher-S® carriers. Furthermore there was a general tendency of better bone formation in comparison to the natural bone healing capacity of the untreated control defect. However when the cells were cultured on the HA carriers and encapsulated into the same modified hydrogel, there was no formation of newly formed bone originating from the cells on the HA carriers. Further research is needed to find an explanation for these unexpected results with the HA carriers. Finally, the possibility of cryopreservation of cell loaded carriers was investigated so that the in vitro culture time before implantation could be decreased. Different mixtures of cryoprotective agents were tested for their contribution to cell survival. Each mixture contained dimethyl sulphoxide (Me2SO) either in a 10vol% concentration or in 5vol% concentration with 5vol% of a non-penetrating cryoprotectant. Best results were obtained after cryopreservation in the presence of 10vol% Me2SO. Cryopreservation of BMSC and MC3T3-E1 preosteoblasts cultured on CultiSpher-S® carriers showed immediately after thawing a decline in cell viability but the same level of cell colonization on the carriers as before cryopreservation was obtained after an additional three days of culture. This study indicates that cryopreservation of cell loaded CultiSpher-S® carriers is possible and could indeed reduce the in vitro culture time prior to implantation

The 24th annual meeting of the European Tissue Repair Society (ETRS) in Edinburgh, Scotland

From the 10th to 12th of September 2014, in the midst of the Scottish Independence debate, the European Tissue Repair Society descended on Edinburgh for their 24th Annual Meeting. In the beautiful and historic setting of the Royal College of Surgeons of Scotland, Professors David Thomas (Chair), Phil Stephens, Chris Lloyd, and their teams from Cardiff hosted an educational and inspiring program