Yuji Haishima

Calcium‐incorporated titanium surfaces influence the osteogenic differentiation of human mesenchymal stem cells

In this study, a titanium surface was chemically modified with calcium ions and assessed for its influence on osteogenic differentiation and molecular responses of human mesenchymal stem cells (hMSCs). Titanium disks were treated with NaOH (NaOH treatment), NaOH + CaCl2 (CaCl2 treatment), or NaOH + Ca(OH)2 (Ca(OH)2 treatment). Ca(OH)2 treatment caused significantly greater calcium incorporation onto the titanium surface and apatite formation than CaCl2 treatment. The morphology of hMSCs differed on CaCl2- and Ca(OH)2-treated disks. The osteopontin (OPN) expression in hMSCs cultured on CaCl2-treated titanium was significantly higher than that in cells cultured on NaOH-treated disks; OPN expression was significantly higher in cells cultured on Ca(OH)2-treated disks than on un-, NaOH-, and CaCl2-treated disks. Osteocalcin (OCN) protein expression in hMSCs cultured on Ca(OH)2-treated disks was significantly higher than that on all the other disks. Comparative expression profiling by DNA microarray and pathway analyses revealed that calcium modification of the titanium surface induced integrin β3 after OPN upregulation and promoted Wnt/β-catenin signaling in hMSCs. In addition, Ca(OH)2 treatment upregulated the expression of bone morphogenetic protein 2, cyclooxygenase 2, and parathyroid hormone-like hormone in comparison to CaCl2 treatment. These observations suggest that calcium-modified titanium surfaces affect osteogenic differentiation in hMSCs and that Ca(OH)2 treatment induced osteogenic differentiation in hMSCs, whereas CaCl2 treatment had a limited effect.

Screening study on hemolysis suppression effect of an alternative plasticizer for the development of a novel blood container made of polyvinyl chloride

The aim of this study is to identify a plasticizer that is effective in the suppression of the autohemolysis of the stored blood and can be used to replace di(2-ethylhexyl) phthalate (DEHP) in blood containers. The results of hemolysis test using mannitol-adenine-phosphate/red cell concentrates (MAP/RCC) spiked with plasticizers included phthalate, phthalate-like, trimeliate, citrate, and adipate derivatives revealed that di-isononyl-cyclohexane-1,2-dicarboxylate (Hexamoll(®) DINCH), di(2-ethylhexyl)-1,2,3,6-tetrahydro-phthalate (DOTP), and diisodecyl phthalate (DIDP) exhibited a hemolysis suppression effect almost equal to that of DEHP, but not other plasticizers. This finding suggested that the presence of 2 carboxy-ester groups at the ortho position on a 6-membered ring of carbon atoms may be required to exhibit such an effect. The hemolytic ratios of MAP/RCC-soaked polyvinyl chloride (PVC) sheets containing DEHP or different amounts of DINCH or DOTP were reduced to 10.9%, 9.2-12.4%, and 5.2-7.8%, respectively (MAP/RCC alone, 28.2%) after 10 weeks of incubation. The amount of plasticizer eluted from the PVC sheet was 53.1, 26.1-36.5, and 78.4-150 µg/mL for DEHP, DINCH, and DOTP, respectively. PVC sheets spiked with DIDP did not suppress the hemolysis induced by MAP/RCC because of low leachability (4.8-6.0 µg/mL). These results suggested that a specific structure of the plasticizer and the concentrations of least more than ∼10 µg/mL were required to suppress hemolysis due to MAP/RCC.

Development and performance evaluation of a positive reference material for hemolysis testing

This study deals with the development and performance evaluation of a positive reference material for hemolysis testing, which is used for evaluating the biological safety of medical devices. Genapol X-080, a nonionic detergent, was selected as a candidate hemolytic substance in a survey of 23 chemical compounds; it showed significant hemolytic activity against rabbit defibrinated blood at concentrations more than 20 µg/mL. A polyvinyl chloride (PVC) sheet spiked with 0.6% (w/w) of the compound exhibited weak hemolytic activity in direct contact and/or extract-based assays after 4 h incubation at 37°C. A PVC sheet containing 5.8% (w/w) Genapol X-080 induced complete hemolysis in both assays. The amount of Genapol X-080 eluted from each PVC sheet during hemolysis testing using the direct contact method increased time-dependently and reached 25.6 (former sheet) or 1154 (later sheet) µg/mL after 4 h incubation, which was similar to or much higher than the critical micelle concentration, respectively. Similar elution behavior was observed using the extract-based method, and the Genapol X-080 content in test solutions prepared by autoclave extraction of both sheets was 22.5 and 358 µg/mL, respectively, indicating a clear relationship between the degree of hemolytic activity and the eluted amount of Genapol X-080. Thus, a PVC sheet spiked with a compound exhibiting different hemolytic activity depending on its concentration may be useful as a positive reference material to validate the hemolysis tests.

A development and biological safety evaluation of novel PVC medical devices with surface structures modified by UV irradiation to suppress plasticizer migration

This study examines the chemical, physicochemical, and biological properties of PVC sheets treated with UV irradiation on their surfaces to suppress the elution of a plasticizer, di-(2-ethylhexyl) phthalate (DEHP), for developing novel polyvinyl chloride (PVC) medical devices. The PVC sheets irradiated under conditions 1 (52.5 μW/cm(2), 136 J/cm(2)) and 2 (0.45 mW/cm(2), 972 J/cm(2)) exhibited considerable toxicity in cytotoxicity tests and chromosome aberration tests due to the generation of DEHP oxidants, but no toxicity was detected in the PVC sheet irradiated under condition 3 (8.3 mW/cm(2), 134 J/cm(2)). The release of DEHP from the surface irradiated under condition 3 was significantly suppressed, and mono-(2-ethylhexyl) phthalate (MEHP) converted from a portion of DEHP could be easily removed from the surface by washing with methanol. The physicochemical properties of the surface regarding the suppression of DEHP elution remained stable through all sterilizations tested, but MEHP elution was partially recrudesced by the sterilizations except for gamma irradiation. These results indicated that UV irradiation using a strong UV-source over a short time (condition 3) followed by methanol washing and gamma sterilization may be useful for preparing novel PVC products that did not elute plasticizers and do not exhibit toxicity originating from UV irradiation.

Development of an in vitro screening method for safety evaluation of nanomaterials

To evaluate the role of particle size in cytotoxicity tests of nanomaterials (NMs), we exposed Chinese hamster cells to polystyrene (PS) spheres with defined diameters ranging from 0.1 to 9.2 microm. We found that the 4.45-microm PS particles were most cytotoxic while sizes 0.1 and 0.2 microm showed no cytotoxicity up to 1000 microg/ml. In the chromosome aberration test, the 4.45-microm PS particles induced polyploidy in a mass concentration-dependent manner in 24- and 48-h treatments. The 5.26-microm PS particles induced polyploidy only at 1000 microg/ml for 48 h. Next, we performed the cytotoxicity test with as-grown single walled carbon nanohorns (NHas). These were suspended in DMSO and then transferred into the culture medium followed by sonication. Six suspensions differently sonicated showed the same apparent toxicity, although the total particle size distributions differed. However, the sizes of NHas particles predicted to be most toxic from the experiments with PS particles, i.e. 1.01-4.47 microm constituted 40-60% of all particles in all six suspensions. The results suggest that the cytotoxicity of NMs in suspension depends on specific sizes of aggregates and therefore suspensions should be checked with regard to particle size distributions in assays of toxic effects. The uptake of particles into cells was confirmed by confocal microscopy.

A biological study establishing the endotoxin limit of biomaterials for bone regeneration in cranial and femoral implantation of rats.

The purpose of this study was to accurately quantify the risk of endotoxin contamination in biomaterials for bone regeneration in order to establish the acceptable endotoxin limit. Collagen sheets containing varying amounts of purified endotoxin from Escherichia coli and dried, heat-killed E. coli or Staphylococcus aureus cells were implanted into cranial or femoral defects in rats. These defects were artificially prepared to a size of 5 × 5 mm or a diameter of 1 mm, respectively. The degree of osteoanagenesis was assessed by soft X-ray radiography and histopathology at 1 and 4 weeks after implantation. The collagen sheet containing the dried E. coli cells showed a dose-dependent delay in cranial and/or femoral osteoanagenesis at endotoxin activities of more than 33.6 EU/mg, at which no inflammatory response was observed. In contrast, no such observation occurred with the collagen sheet containing S. aureus cells. These results suggest that endotoxins may affect the process of osteoanagenesis. Additionally, the no-observed-adverse-effect level was 9.6 EU/mg, corresponding to 255 EU/kg body weight in rats. Interestingly, no delay in osteoanagenesis was induced by the implantation of collagen sheets containing purified endotoxin at any dose tested. This suggested that pure endotoxin implanted into tissues having poor circulation of bodily fluids without bleeding may not be recognized as a foreign substance and may not induce a significant biological response.

Evaluating the durability of UHMWPE biomaterials used for articulating surfaces of joint arthroplasty using delamination tests

Ultra-high molecular weight polyethylene (UHMWPE) is the most popular material used for the articulating surface of joint replacements. Delamination is a common fatigue-related failure mode in UHMWPE components; however, the relationship between delamination resistance and fatigue crack growth has not been reported. Here, the delamination resistance of contemporary UHMWPE materials, including highly cross-linked UHMWPE (HXLPE), vitamin E blended UHMWPE (VEPE), and vitamin E blended HXLPE (VEXLPE), was measured to verify a previously proposed accelerated test method using a U-shaped sliding motion; the results were compared with those of fatigue crack growth tests. The oxidative stability of each material was estimated using Fourier transform infrared analysis. UHMWPE sterilized by gamma irradiation in an inert atmosphere and annealed HXLPE had lower delamination resistance than virgin UHMWPE after artificial aging. This was consistent with previous findings from retrieval studies, and in vitro knee simulator and ball-on-flat unidirectional reciprocation wear studies. In contrast, remelted HXLPE, VEPE, and VEXLPE showed excellent delamination resistance after artificial aging. The results of the delamination tests were not consistent with those of fatigue crack growth tests, indicating the complex delamination mechanism and importance of evaluating these factors separately.

A biological study establishing the endotoxin limit for in vitro proliferation of human mesenchymal stem cells

Introduction Multipotent mesenchymal stem cells (MSCs) are widespread in adult organisms and are implicated in tissue maintenance and repair, regulation of hematopoiesis, and immunologic responses. Human (h)MSCs have applications in tissue engineering, cell-based therapy, and medical devices but it is unclear how they respond to unfavorable conditions such as hypoxia or inflammation after in vivo transplantation. Although endotoxin testing is a requirement for evaluating the quality and safety of transplanted MSCs, there have been no reports on the dose response to endotoxins to establish limits for in vitro MSC culture systems. The present study aimed to accurately quantify the risk of endotoxin contamination in cell culture systems in order to establish the acceptable endotoxin limit for hMSC proliferation. Methods Three types of bone marrow-derived hMSC (hMSC-1: 21 years, M/B; hMSC-2: 36 years, M/B; hMSC-3: 43 years, M/C) and adipose-derived stem cells (ADSCs; StemPro Human) were cultured in medium from commercial kits containing various concentrations of endotoxin (0.1–1000 ng/ml). The proliferative capacity of cells was estimated by cell counts using a hemocytometer. To clarify the molecular mechanism underlying the effect of endotoxin on hMSCs proliferation, cellular proteins were extracted from cultured cells and subjected to liquid chromatograph-tandem mass spectrometry shotgun proteomics analysis. The expression of Cu/Zn-type superoxide dismutase (SOD1) and Fe/Mn-type superoxide dismutase (SOD2) induced in hMSCs by endotoxin stimulation were evaluated by enzyme-linked immunosorbent assay (ELISA), and the effect of SOD2 on hMSC proliferation was also estimated. Results Although there was no change in cell morphology during the culture period, proliferative capacity increased with endotoxin concentration to over 0.1 ng/ml for ADSCs, 1 ng/ml for hMSC-1, and 100 ng/ml for hMSC-2; hMSC-3 proliferation was unaffected by the presence of endotoxin. A proteomic analysis of hMSC-1 revealed that various proteins related to the cell cycle, apoptosis, and host defense against infection were altered by endotoxin stimulation, whereas SOD2 expression was significantly and consistently upregulated during the culture period. The latter was also confirmed by ELISA. Moreover, recombinant SOD2 increased proliferative capacity in hMSC-1 cells in a manner similar to endotoxin. These results suggest that endotoxin protects MSCs from oxidative stress via upregulation of SOD2 to improve cell survival. Conclusions Since endotoxins can affect various cellular functions, an endotoxin limit should be set for in vitro MSC cultures. The lowest observed adverse effect level was determined to be 0.1 ng/ml based on the effect on MSC proliferation.

Pilot study on novel blood containers with alternative plasticizers for red cell concentrate storage

Di (2-ethylhexyl) phthalate (DEHP), a typical plasticizer used for polyvinyl chloride (PVC) blood containers, is eluted from the blood containers and exerts protective effects on red blood cells. However, a concern for detrimental effects of DEHP on human health has led to the development of potential DEHP substitutes. Here, we compared the red blood cell preservation ability of two types of non-DEHP blood containers with safe alternative plasticizers to that of DEHP blood containers. Red cell concentrates in mannitol-adenine-phosphate solution (MAP/RCC) were stored for 6 weeks in PVC blood bags containing DEHP, di-isononyl-cyclohexane-1,2-dicarboxylate (DINCH) and di (2-ethylhexyl) 4-cyclohexene-1,2-dicarboxylate (DOTH), or 4-cyclohexene-1,2-dicarboxylic acid dinonyl ester (DL9TH) and DOTH. There was no significant difference in the total amount of plasticizer eluted into MAP/RCC (till 3 weeks from the beginning of the experiment), hemolysis of MAP/RCC, and osmotic fragility of MAP/RCC between the non-DEHP blood containers and DEHP blood containers. Hematological and blood chemical indices of MAP/RCC in all containers were nearly the same. Thus, DOTH/DINCH and DOTH/DL9TH blood containers demonstrate the same quality of MAP/RCC storing as the DEHP blood containers. Since DOTH, DINCH, and DL9TH were reported to be safe, DOTH/DINCH and DOTH/DL9TH blood containers are promising candidate substitutes for DEHP blood containers.

A biological study establishing the endotoxin limit for osteoblast and adipocyte differentiation of human mesenchymal stem cells

Introduction Multipotent mesenchymal stem cells (MSCs) are widespread in adult organisms and are implicated in tissue maintenance and repair, regulation of hematopoiesis, and immunologic responses. Human (h)MSCs have applications in tissue engineering, cell-based therapy, and medical devices but it is unclear how they respond to unfavorable conditions, such as hypoxia or inflammation after transplantation in vivo. Although endotoxin testing is required for evaluating the quality and safety of transplanted MSCs, no reports on their dose response to endotoxins are available to establish the limits for in vitro MSC culture systems. In the present study, we aimed to accurately quantify the risk of endotoxin contamination in cell culture systems to establish an acceptable endotoxin limit for the differentiation of hMSC osteoblasts and adipocytes. Methods Three types of bone marrow-derived hMSCs (hMSC-1: 21-year-old, M/B; hMSC-2: 36-year-old, M/B; hMSC-3: 43-year-old, M/C) and adipose-derived stem cells (ADSCs; StemPro Human) were cultured in osteogenic or adipogenic differentiation media, respectively, from commercial kits, containing various concentrations of endotoxin (0.01–100 ng/ml). The degree of adipocyte and osteoblast differentiation was estimated by fluorescent staining of lipid droplets and hydroxyapatite, respectively. To clarify the molecular mechanism underlying the effect of endotoxin on hMSC differentiation, cellular proteins were extracted from cultured cells and subjected to liquid chromatograph-tandem mass spectrometry shotgun proteomics analysis. Results Although endotoxin did not effect the adipocyte differentiation of hMSCs, osteoblast differentiation was enhanced by various endotoxin concentrations: over 1 ng/ml, for hMSC-1; 10 ng/ml, for hMSC-2; and 100 ng/ml, for hMSC-3. Proteomic analysis of hMSC-1 cells revealed up-regulation of many proteins related to bone formation. These results suggested that endotoxin enhances the osteoblast differentiation of MSCs depending on the cell type. Conclusions Since endotoxins can affect various cellular functions, an endotoxin limit should be established for in vitro MSC cultures. Its no-observed-adverse-effect level was 0.1 ng/ml based on the effect on the hMSC osteoblast differentiation, but it may not necessarily be the limit for ADSCs.