The effect of polymeric chemistry on the expression of bone-related mRNAs and proteins by human bone-derived cells in vitro

Impaired coronary microvascular and left ventricular diastolic function in patients with inflammatory bowel disease

BACKGROUND AND AIM

Increased incidence of coronary vascular events in patients with inflammatory bowel disease (IBD) is known. However, the association between coronary microvascular function and IBD has not been fully defined. We aimed to investigate whether coronary flow reserve (CFR) and left ventricular diastolic function were impaired in IBD patients.

METHODS

Seventy-two patients with IBD (36 patients with ulcerative colitis [UC] and 36 Crohn's disease [CD]) were registered. Each subject was evaluated after a minimum 15-day attack-free period. For the control group, 36 age- and sex-matched healthy volunteers were included into the study. IBD clinical disease activity in UC was assessed by the Truelove-Witts Index (TWAS) and in CD by the Crohn's Disease Activity Index (CDAI). In each subject, CFR was measured through transthoracic Doppler echocardiography.

RESULTS

Compared to the controls, the CD group and UC group had significantly higher high-sensitivity C-reactive protein (hs-CRP) and erythrocyte sedimentation rate. Baseline diastolic peak flow velocity (DPFV) of the left anterior descending artery (LAD) was significantly higher in the IBD group (24.1±3.9 vs. 22. 4±2.9, p<0.05), and hyperemic DPFV (56.1±12.5 vs. 70.6±15.3, p<0.05) and CFR (2.34±0.44 vs. 3.14±0.54, p<0.05) were significantly lower in the IBD group than in the control group. In stepwise linear regression analysis, hs-CRP and lateral Em/Am ratio were independently correlated with CFR.

CONCLUSION

CFR, reflecting coronary microvascular function, is impaired in patients with IBD. CFR and left ventricular diastolic function parameters are well correlated with hs-CRP.

The incorporation of strontium and zinc into a calcium-silicon ceramic for bone tissue engineering

In this study we developed novel scaffolds through the controlled substitution and incorporation of strontium and zinc into a calcium-silicon system to form Sr-Hardystonite (Sr-Ca(2)ZnSi(2)O(7), Sr-HT). The physical and biological properties of Sr-HT were compared to Hardystonite (Ca(2)ZnSi(2)O(7)) [HT]. We showed that Sr-HT scaffolds are porous with interconnected porous network (interconnectivity: 99%) and large pore size (300-500 microm) and an overall porosity of 78%, combined with a relatively high compressive strength (2.16+/-0.52 MPa). These properties are essential for enhancing bone ingrowth in load-bearing applications. Sr-HT ceramic scaffolds induced the attachment and differentiation of human bone derived cells (HOB), compared to that for the HT scaffolds. Sr-HT scaffolds enhanced expression of alkaline phosphatase, Runx-2, osteopontin, osteocalcin and bone sialoprotein. The in vivo osteoconductivity of the scaffolds was assessed at 3 and 6 weeks following implantation in tibial bone defects in rats. Histological staining revealed rapid new growth of bone into the pores of the 3D scaffolds with the Sr-HT and HT, relative to the beta-tricalcium phosphate (beta-TCP). In vivo, HT and Sr-HT produced distinct differences in the patterns of degradation of the materials, and their association with TRAP positive osteoclast-like cells with HT appearing more resistant compared to both Sr-HT and beta-TCP.

Biological response of human bone cells to zinc-modified Ca-Si-based ceramics

Calcium silicate (CaSiO(3)) ceramics have received considerable attention in recent years due to their excellent bioactivity and degradability. However, their poor chemical stability limits their biological applications. Hardystonite (Ca(2)ZnSi(2)O(7)) ceramics are Ca-Si-based materials developed by incorporating zinc into the Ca-Si system to improve their chemical stability. However, the biological responses of Ca(2)ZnSi(2)O(7) to bone cells are unknown. The objective of this study is to investigate and compare the in vitro responses of human osteoblast-like cells (HOBs) and osteoclasts when cultured on Ca(2)ZnSi(2)O(7) and CaSiO(3) ceramic disks. The ability of Ca(2)ZnSi(2)O(7) ceramics to support HOB attachment, cytoskeleton organization, proliferation and differentiation was assessed by scanning electron microscopy, confocal microscopy, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, alkaline phosphatase activity and quantitative real-time polymerase chain reaction. Our results show that Ca(2)ZnSi(2)O(7) supported HOB attachment with a well-organized cytoskeleton structure, and significantly increased cellular proliferation and differentiation compared to CaSiO(3). In addition, Ca(2)ZnSi(2)O(7) showed increased expression levels of osteoblast-related mRNAs (alkaline phosphatase, collagen type I, osteocalcin, receptor activator of NF(kappa)B ligand and osteoprotegerin) compared to CaSiO(3). Ca(2)ZnSi(2)O(7) ceramic supported the formation of mature and functional osteoclasts and formed resorption imprints. On CaSiO(3) ceramics, the cells failed to differentiate from the monocytes into osteoclasts. Taken together, these results indicate that Hardystonite ceramics are conducive to both types of bone cells, osteoblast-like cells and osteoclasts, suggesting their potential use for skeletal tissue regeneration and as coatings onto currently available orthopedic and dental implants.

The functional expression of human bone-derived cells grown on rapidly resorbable calcium phosphate ceramics

The use of biodegradable bone substitutes is advantageous for alveolar ridge augmentation, since it avoids second-site surgery for autograft harvesting. This study examines the effect of novel, rapidly resorbable calcium phosphates on the expression of bone-related genes and proteins by human bone-derived cells (HBDC) and compares this behavior to that of tricalciumphosphate (TCP). Test materials were alpha-TCP, and four materials which were created from beta-Rhenanite and its derivatives: R1-beta-Rhenanite (CaNaPO(4)); R1/M2 composed of CaNaPO(4) and MgNaPO(4); R1+SiO(2) composed of CaNaPO(4) and 9% SiO(2) (wt%); and R17-Ca(2)KNa(PO(4))(2). HBDC were grown on the substrata for 3, 5, 7, 14 and 21 days, counted and probed for various mRNAs and proteins (Type I collagen, osteocalcin, osteopontin, osteonectin, alkaline phosphatase and bone sialoprotein). All substrata supported continuous cellular growth for 21 days. At day 21, surfaces of R1+SiO(2) and R17 had the highest number of HBDC. At 14 and 21 days, cells on R1 and on R1+SiO(2) displayed significantly enhanced expression of all osteogenic proteins. Since all novel calcium phosphates supported cellular proliferation together with expression of bone-related proteins at least as much as TCP, these ceramics can be regarded as potential bone substitutes. R1 and R1+SiO(2) had the most effect on osteoblastic differentiation, thus suggesting that these materials may possess a higher potency to enhance osteogenesis than TCP.

Proliferation and bone-related gene expression of osteoblasts grown on hydroxyapatite ceramics sintered at different temperature

Human osteoblast-like cells SaOS-2 (ATCC HTB85) were seeded onto three kinds of hydroxyapatite (HA) ceramics sintered at different temperature (1200 degrees C, 1000 degrees C and 800 degrees C). Scanning electron microscopy (SEM) was conducted to detect the surface microstructure. Cells were cultured on these substrates for 6 and 12 days and cell proliferation rate and mRNA expression for osteocalcin, osteonectin, type I collagen and alkaline phosphatase and protein production for osteocalcin, bone sialoprotein and osteonectin were detected with quantitative in situ hybridization and immunocytochemistry techniques. SEM revealed that crystal particle size was affected by sintering temperature. Result showed that cell proliferation rate on HA ceramics sintered at 1200 degrees C was the highest. Osteonectin and type I collagen mRNA expression was not altered by sintering temperature. After 12 days in culture, bone sialoprotein, osteocalcin and osteonectin proteins levels were significantly (p<0.05) higher when SaOS-2 cells were cultured on HA sintered at 1200 degrees C, compared to the other two surfaces, suggesting that HA sintered at high temperature may be a better candidate for in vivo implantation. This result provides valuable information concerning the clinic application of HA ceramics sintered at different temperature.

Proliferation and differentiation of rat calvarial osteoblasts on type I collagen-coated titanium alloy

Several attempts have been made to improve osseointegration of titanium alloy as an implant material by modification of its surface. In the present study, proliferation, differentiation, and mineralization of osteoblasts on type I collagen-coated Ti6Al4V were investigated. The activity of alkaline phosphatase and the accumulation of calcium by osteoblasts grown on titanium alloy were significantly higher compared to cells grown on polystyrene. Precoating of the implant surface with type I collagen did not extensively affect proliferation, the activity of alkaline phosphatase, collagen synthesis, calcium accumulation, or the mRNA levels for collagen I alpha1, osteopontin, osteocalcin, MMP-2, and TIMP-2. Maximum collagen synthesis by osteoblasts was observed at day 4 of culture independent of the type of implant material. The specific activity of alkaline phosphatase reached its maximum at day 18 of culture. Accumulation of calcium and elevated mRNA levels for osteocalcin were found at day 22. These results indicate that collagen-coating alone is not sufficient to accelerate differentiation of rat calvarial osteoblasts on Ti6Al4V.

Protein adsorption and cell attachment to patterned surfaces

To better understand the events involved in the generation of defined tissue architectures on biomaterials, we have examined the mechanism of attachment of human bone-derived cells (HBDC) to surfaces with patterned surface chemistry in vitro. Photolithography was used to generate alternating domains of N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (EDS) and dimethyldichlorosilane (DMS). At 90 min after seeding, HBDC were localized preferentially to the EDS regions of the pattern. Using sera specifically depleted of adhesive glycoproteins, this spatial organization was found to be mediated by adsorption of vitronectin (Vn) from serum onto the EDS domains. In contrast, fibronectin (Fn) was unable to adsorb in the face of competition from other serum components. These results were confirmed by immunostaining, which also revealed that both Vn and Fn were able to adsorb to EDS and DMS regions when coated from pure solution, i.e., in the absence of competition. In this situation, each protein was able to mediate cell adhesion across a range of surface densities. Cell spreading was constrained on the EDS domains, as indicated by cell morphology and the lack of integrin receptor clustering and focal adhesion formation. This spatial constraint may have implications for the subsequent expression of differentiated function.

Titanium substrata composition influences osteoblastic phenotype: In vitro study

In spite of observed differences at the interface between boon and either commercially pure titanium [Ti(cpi)] or titanium alloy (Ti-6Al-4V), the mechanism of such a response is ill understood. This prompted further investigation of the influence of similar metals on human bone-derived cells (HBDCs). This study investigated the influence of Ti(cpi) and its alloy on osteoblastic proteins formed by HBDCs grown for 5, 7, 10, and 14 days on these metals and compared them to cells grown on tissue culture polystyrene plates. Messenger RNA and translated proteins that form an array of osteogenic parameters were determined: alkaline phosphatase (ALP), thrombospondin, osteopontin, osteocalcin (OC), osteonectin (ON/SPARC), type I collagen (Col I) and bone sialoprotein (BSP). At the four predetermined time points, cells grown on either Ti(cpi) or Ti-6Al-4V generally expressed similar mRNA levels, while levels of their respective proteins differed. Cells on Ti(cpi) had peak levels for most proteins at day 7, whereas those on Ti-6Al-4V peaked at either day 5 and/or day 7. At day 5 cells grown on Ti-6Al-4V had higher levels of ALP, Col I, ON/SPARC, OC, and BSP than those in Ti(cpi); this difference was not maintained at later time points in culture. The differential regulation of proteins occurring between cells from the same patient grown on titanium and its alloy implies that HBDCs respond to small differences in the surface chemistry and/or microcrystallinity.