In vitro evaluation of the biofunctionality of osteoblasts cultured on DegraPol-foam

The role of Vitamin D as an adjunct for bone regeneration: A systematic review of literature

Background and objectives

In spite of bone's healing capacity, critical-size bone defect regeneration and peri-implant osseointegration are challenging. Tissue engineering provides better outcomes, but requires expensive adjuncts like stem cells, growth factors and bone morphogenic proteins. Vitamin D (Vit.D) regulates calcium and phosphorus metabolism, and helps maintain bone health. Vit.D supplements in deficient patients, accentuates bone healing and regeneration. Therefore the aim of this systematic review was to evaluate the role of adjunctive Vit.D on bone defect regeneration.

Methods

Comprehensive database search of indexed literature, published between January 1990 and June 2022, was carried out. English language articles fulfilling inclusion criteria (clinical/in vivo studies evaluating bone regeneration including osseointegration and in vitro studies assessing osteogenic differentiation, with adjunct Vit.D) were identified and screened.

Results

Database search identified 384 titles. After sequential title, abstract and full-text screening, 23 studies (in vitro - 9/in vivo - 14) were selected for review. Vit.D as an adjunct with stem cells and osteoblasts resulted in enhanced osteogenic differentiation and upregulation of genes coding for bone matrix proteins and alkaline phosphatase. When used in vivo, Vit.D resulted in early and increased new bone formation and mineralization within osseous defects, and better bone implant contact and osseointegration, around implants. Adjunct Vit.D in animals with induced systemic illnesses resulted in bone defect regeneration and osseointegration comparable to healthy animals. While systemic and local administration of Vit.D resulted in enhanced bone defect healing, outcomes were superior with systemic route.

Conclusions

Based on this review, adjunct Vit.D enhances bone defect regeneration and osseointegration. In vitro application of Vit.D to stem cells and osteoblasts enhances osteogenic differentiation. Vit.D is a potentially non-invasive and inexpensive adjunct for clinical bone regeneration and osseointegration. Long term clinical trials are recommended to establish protocols relating to type, dosage, frequency, duration and route of administration.

A new in vivo magnetic resonance imaging method to noninvasively monitor and quantify the perfusion capacity of three-dimensional biomaterials grown on the chorioallantoic membrane of chick embryos

Adequate vascularization in biomaterials is essential for tissue regeneration and repair. Current models do not allow easy analysis of vascularization of implants in vivo, leaving it a highly desirable goal. A tool that allows monitoring of perfusion capacity of such biomaterials noninvasively in a cheap, efficient, and reliable in vivo model would hence add great benefit to research in this field. We established, for the first time, an in vivo magnetic resonance imaging (MRI) method to quantify the perfusion capacity of a model biomaterial, DegraPol(®) foam scaffold, placed on the embryonic avian chorioallantoic membrane (CAM) in ovo. Perfusion capacity was assessed through changes in the longitudinal relaxation rate before and after injection of a paramagnetic MRI contrast agent, Gd-DOTA (Dotarem(®); Guerbet S.A.). Relaxation rate changes were compared in three different regions of the scaffold, that is, at the interface to the CAM, in the middle and on the surface of the scaffold (p<0.05). The highest relaxation rate changes, and hence perfusion capacities, were measured in the interface region where the scaffold was attached to the CAM, whereas the surface of the scaffold showed the lowest relaxation rate changes. A strong positive correlation was obtained between relaxation rate changes and histologically determined vessel density (R(2) = 0.983), which corroborates our MRI findings. As a proof-of-principle, we measured the perfusion capacity in different scaffold materials, silk fibroin either with or without human dental pulp stem cells. For these, three to four times larger perfusion capacities were obtained compared to DegraPol; demonstrating that our method is sensitive to reveal such differences. In summary, we present a novel in vivo method for analyzing the perfusion capacity in three-dimensional-biomaterials grown on the CAM, enabling the determination of the perfusion capacity of a large variety of bioengineered materials.

Prevention of peritendinous adhesions using an electrospun DegraPol polymer tube: a histological, ultrasonographic, and biomechanical study in rabbits

Purpose. One of the great challenges in surgical tendon rupture repair is to minimize peritendinous adhesions. In order to reduce adhesion formation, a physical barrier was applied to a sutured rabbit Achilles tendon, with two different immobilization protocols used postoperatively. Methods. Thirty New Zealand white rabbits received a laceration on the Achilles tendon, sutured with a 4-strand Becker suture, and half of the rabbits got a DegraPol tube at the repair site. While fifteen rabbits had their treated hind leg in a 180° stretched position during 6 weeks (adhesion provoking immobilization), the other fifteen rabbits were recasted with a 150° position after 3 weeks (adhesion inhibiting immobilization). Adhesion extent was analysed macroscopically, via ultrasound and histology. Inflammation was determined histologically. Biomechanical properties were analysed. Results. Application of a DegraPol tube reduced adhesion formation by approximately 20%—independently of the immobilization protocol. Biomechanical properties of extracted specimen were not affected by the tube application. There was no serious inflammatory reaction towards the implant material. Conclusions. Implantation of a DegraPol tube tightly set around a sutured tendon acts as a beneficial physical barrier and prevents adhesion formation significantly—without affecting the tendon healing process.

Perspective on biomaterials used in the surgical treatment of morbid obesity

Morbid obesity is defined as having a body mass index greater than or equal to 40.0 kg m(-2), or 37.0 kg m(-2) with comorbidities. Bariatric surgery remains the most effective treatment for morbid obesity. Bariatric procedures such as sleeve gastrectomy, vertical banded gastroplasty and adjustable gastric banding all generate excess body-weight loss typically over 3-5 years. The biomaterials used during these procedures, namely silicone, polypropylene, expanded polytetrafluoroethylene and titanium, are all non-degradable biomaterials. Hence, their presence in vivo exceeds the functional requirement of an implant to treat morbid obesity. Accordingly, research into non-invasive and reversible surgical procedures has increased, particularly in light of the dramatic increase in paediatric obesity. Tissue engineering is an alternative approach to treat morbid obesity, as it incorporates both engineering and biological principles into the design and development of an implant to surgically treat morbid obesity. It is hypothesized that a biodegradable polymer to treat morbid obesity could be developed to effectively promote excess weight loss. The aim of this review is to discuss morbid obesity with regards to its aetiology, prevalence and current modalities of treatment. Specifically, the shortcomings of the biomaterials currently used to surgically treat morbid obesity shall be reviewed, and alternative biomaterials shall be proposed.

Biocompatibility of polyhydroxybutyrate microspheres: in vitro and in vivo evaluation

Microspheres have been prepared from the resorbable linear polyester of beta-hydroxybutyric acid (polyhydroxybutyrate, PHB) by the solvent evaporation technique and investigated in vitro and in vivo. Biocompatibility of the microspheres has been proved in tests in the culture of mouse fibroblast cell line NIH 3T3 and in experiments on intramuscular implantation of the microspheres to Wistar rats for 3 months. Tissue response to the implantation of polymeric microspheres has been found to consist in a mild inflammatory reaction, pronounced macrophage infiltration that increases over time, involving mono- and poly-nuclear foreign body giant cells that resorb the polymeric matrix. No fibrous capsules were formed around polymeric microparticles; neither necrosis nor any other adverse morphological changes and tissue transformation in response to the implantation of the PHB microparticles were recorded. The results of the study suggest that polyhydroxybutyrate is a good candidate for fabricating prolonged-action drugs in the form of microparticles intended for intramuscular injection.

Enhancing sealing of fetal membrane defects using tissue engineered native amniotic scaffolds in the rabbit model

OBJECTIVE

The purpose of this study was to compare the efficacy of native engineered amniotic scaffolds (AS) and polyesterurethane scaffolds (DegraPol) and document wound healing response when sealing iatrogenic fetal membrane defects in the rabbit model.

STUDY DESIGN

Native AS were engineered from freshly harvested membranes of 23 days' gestational age (GA; term = 31-2 d). Acellularity of AS was assessed by histology, light and scanning electron microscopy. Fetal membrane defects were created by 14 gauge-needle puncture at GA 23 days and primarily closed with AS (n = 10) or DegraPol (n = 10) or left unclosed (positive controls; n = 10). Sixty-one sacs served as negative controls. At GA 30 days a second look hysterotomy was performed to assess presence of amniotic fluid (AF) and harvest plugging sites for microscopic evaluation.

RESULTS

Engineered AS had a cell-free collagenous fiber network. AF was significantly higher only in the DegraPol group (78%; P < .05) compared to the AF in positive controls (17%). Integration of plugs in the fetal membrane defect was better with AS than DegraPol, with higher reepithelialization rates (AS: 52.5% +/- 6.5%; DegraPol: 11.6% +/- 2.6%; P < .001) and proliferation indices (AS: 0.47 +/- 0.03; DegraPol: 0.28 +/- 0.04; P = .001). In both treatment groups, cell proliferation in the myometrium was increased (P < .05).

CONCLUSION

Native AS seal iatrogenic fetal membrane defects better than DegraPol. Within a week, there is abundant reepithelilization and minimal local inflammation. This yields the proof of principle that engineered native, amniotic membrane scaffolds enhance fetal membrane wound healing response.

Characterization of a slowly degrading biodegradable polyesterurethane for tissue engineering scaffolds

The purpose of this research was to develop and characterize a novel, slowly degrading polyester-urethane. In this study, a polyester-urethane with a crystalline segment of poly((R)-3-hydroxybutyric acid)-diol linked by a diisocyanate to an amorphous segment of poly(epsilon-caprolactone-co-glycolide)-diol was synthesized. Porous and nonporous scaffolds were processed using electrospinning and solvent casting respectively. The morphology, pore size, and filament diameter of the mesh and film were characterized using scanning electron microscopy (SEM). The thermal properties were examined using differential scanning calorimetry (DSC). A degradation study was initiated to characterize the change in mechanical properties, molecular weight, and surface morphology over 12 months using tensile testing, gel permeation chromatography (GPC), and SEM respectively. Concomitantly, cell morphology and viability on these variants were investigated using fibroblasts. The mechanical test data indicated a gradual decrease in the ultimate tensile strength and strain to break while the modulus of elasticity remained stable. GPC data suggested a slow decrease in the molecular weight while SEM examination revealed changed surface morphologies. The in vitro studies implied that the novel polyester-urethane was not cytotoxic and that the mesh was a more favorable scaffold towards cell viability. The summation of these results suggests that this polyester-urethane has the potential for tissue engineering applications.

The functional response of U937 macrophage-like cells is modulated by extracellular matrix proteins and mechanical strain

Extracellular matrix proteins (ECMs) play a significant role in the transfer of mechanical strain to monocyte-derived macrophages (MDMs) affecting morphological changes in a foreign body reaction. This study investigated how the functional responses of U937 macrophage-like cells differed when subjected to 2 dynamic strain types (nonuniform biaxial or uniform uniaxial strain) while cultured on siloxane membranes coated with either collagen type I or RGD peptide repeats (ProNectin®). Biaxial strain caused an increase in intracellular esterase and acid phosphatase (AP) activities, as well as monocyte-specific esterase (MSE) protein levels in cells that were seeded on either uncoated surfaces (shown previously) or collagen, but not ProNectin®. Released AP activity, but not released esterase activity, was increased on all surfaces. Biaxial strain increased IL-6, but not IL-8 on all surfaces. When cells were subjected to uniaxial strain, intracellular esterase increased on coated surfaces only, whereas intracellular AP activity was unaffected. Both esterase and AP released activities increased on all surfaces. Uniaxial strain increased the release of IL-6 on all surfaces, but IL-8 on coated surfaces only. This study demonstrated for the first time that ECM proteins could specifically modulate cellular responses to different types of strain. Using this approach with an in vitro cell system may help to unravel the complex function of MDMs in the foreign-body reaction.

Biodegradable Elastomeric Polyurethane Membranes as Chondrocyte Carriers for Cartilage Repair

Autologous chondrocyte implantation in combination with an autologous periosteal patch has become a clinically accepted procedure for the treatment of articular cartilage defects. The use of periosteum has, however, several drawbacks. We have been able to fabricate thin elastomeric biodegradable polyurethane (PU) membranes that may possibly have an application as a tissue-engineered substitute for the periosteal patch. Three types of membranes varying in pore size and surface texture were used as substrates for bovine chondrocytes in culture. The membranes, marked as P-I, P-II, and P-R, had average pore sizes of 10 to 20 microm, 40 to 60 microm, and less than 5 microm, respectively. A poly(L/DL-lactide) 80/ 20% micro-porous membrane (PLA) with an average pore size in the range of 10 to 70 microm was used as a control. There was no difference in the cell proliferation profile among the 4 membranes. In terms of proteoglycan and collagen production, P-I, P-R, and PLA performed similarly to one another. The rate of matrix production appears to be greater in the PU membranes than in the PLA membrane in the first 10 days, although by day 30, the PLA membrane had caught up. In all comparisons, the performance of P-II lagged behind those of the other materials. In conclusion, this preliminary study supports the potential use of this novel group of PUs as a periosteal flap substitute or perhaps as a chondrocyte carrier for matrix-assisted chondrocyte implantation and related techniques. Further studies will be necessary to better define their role in clinical applications for cartilage repair.

Evaluation of 45S5 Bioactive Glass Combined as a Bone Substitute in the Reconstruction of Critical Size Calvarial Defects in Rabbits

Biomaterial research and tissue engineering have guided new developments in bone replacement. In this study, the osteoconductive and osteoinductive properties of 45S5 Bioglass (Novabone-C/M, Porex Surg., Newnan, GA), granules as a bone replacement material for large calvarial defects were evaluated. Rabbit periosteal cells were expanded in culture and used in vivo. Alkaline-phosphatase assay, collagen type I, and calcium expression were applied to confirm osteoblast phenotype. In the in vivo phase, a 15-mm diameter critical size calvarial defect was created in rabbits (n = 14). The defect was reconstructed according to four treatment groups: autogenous bone (n = 2), Bioglass alone (n = 2), Bioglass + bone (n = 5), Bioglass + periosteal cells (n = 5). The animals were killed 12 weeks after surgery, and the samples were analyzed. Periosteal cells grew successfully in vitro. Because of their fast proliferation and potential to differentiate into osteoblasts, they were an excellent source of cells for bone tissue engineering. The best ossification was seen when autogenous bone was used (79.4% ossified), whereas only 8.2% of the defect in the Bioglass group showed ossification. Addition of bone or cells to the Bioglass increased the area of ossification to 42.7% and 30.2%, respectively. Defects replaced with Bioglass showed varying degrees of inflammatory reaction because of the intense cell-mediated biodegradation process. Based on these findings, the use of Bioglass granules to repair large craniofacial defects cannot be advised.

Changes in macrophage function and morphology due to biomedical polyurethane surfaces undergoing biodegradation

Monocytes are recruited to the material surface of an implanted biomedical device recognizing it as a foreign body. Differentiation into macrophages subsequently occurs followed by fusion to form foreign body giant cells (FBGCs). Consequently, implants can become degraded, cause chronic inflammation or become isolated by fibrous encapsulation. In this study, a relationship between material surface chemistry and the FBGC response was demonstrated by seeding mature monocyte-derived macrophages (MDMs) on polycarbonate-based polyurethanes that differed in their chemical structures (synthesized with poly(1,6-hexyl 1,2-ethyl carbonate) diol, and either (14)C-hexane diisocyanate and butanediol (BD) (referred to as HDI) or 4,4'-methylene bisphenyl diisocyanate and (14)C-BD (referred to as MDI)) and material degradation assessed. At 48 h of cell-material interaction, the FBGC attached to HDI were more multinucleated (73%) compared to MDI or the polystyrene (PS) control (21 and 36%, respectively). There was a fivefold increase in the synthesis and secretion of a protein with an approximate molecular weight of 48 kDa and a pI of 6.1 (determined by two-dimensional gel electrophoresis) only from cells seeded on HDI. Immunoprecipitation confirmed that MSE and CE were synthesized and secreted de novo. Immunoblotting also showed an increase in secreted monocyte-specific esterase (MSE) and cholesterol esterase (CE) from cells seeded on HDI relative to PS and MDI. Significantly more radiolabel ((14)C) release and esterase activity were elicited by MDMs on HDI than MDI (P < 0.05). The material that was more degradable (HDI), elicited greater protein synthesis and esterase secretion as well as more multinucleated MDMs than MDI, suggesting that the material surface chemistry modulates the function of MDM at the site of an inflammatory response to an implanted device.

Adhesion, apoptosis and cytokine release of human mononuclear cells cultured on degradable poly(urethane urea), polystyrene and titanium in vitro

Early interactions between materials and mononuclear cells may influence the viability and secretory response of the cells. Such effects may in turn influence the subsequent inflammatory and repair phases around the materials. In the present study, it was examined if mononuclear cells cultured in vitro either unstimulated or stimulated with lipopolysaccharide (LPS) (10ng/ml) revealed differences regarding cell viability and apoptosis. A major interest was to study the influence of different material properties on the parameters of the inflammatory response upon cell adhesion to materials with widely different surface chemical properties but similar surface topography: degradable poly(urethane urea) (PUUR), cell culture treated polystyrene (PS) surfaces, and commercially pure (c.p.) titanium (Ti). Finally, the secretion of the proinflammatory tumor necrosis factor-a (TNF-alpha) and the downregulating interleukin-10 (IL-10) cytokines was examined in the supernatants from 24h mononuclear cell cultures. No differences in cell viability as measured by lactate dehydrogenas (LDH) were observed between the three materials. The number of material-surface adherent cells was higher on PUUR than the more hydrophilic PS and Ti as judged by quantification of material surface-associated DNA, light microscopic morphological examination of DAPI-stained cells and SEM. LPS increased the number of adherent cells, irrespective of the type of material. The lowest number of apoptotic (annexin-V) and necrotic (propidium iodide) mononuclear cells was detected on PUUR. LPS decreased the number of both apoptotic and necrotic cells, irrespective of material. Low TNF-alpha levels were detected in unstimulated conditions, irrespective of material types. A significantly lower amount of TNF-alpha was found with unstimulated cells on PUUR than on Ti. A significantly higher IL-10 level was detected in unstimulated Ti cultures compared with PUUR and PS. Secretion of IL-10 was predominantly stimulated by LPS on PUUR and Ti. The data indicate that material-related differences are expressed in differences in cell adherence, apoptosis and cytokine secretion. Further, degradable PUUR has equal or less cell-activating properties than Ti and PS under in vitro conditions.