Influence of α-1,3-glucan synthase gene agsE on protoplast formation for transformation of Aspergillus luchuensis

Aspergillus luchuensis NBRC4314 recently underwent genome sequencing. We have not used the frequently used protoplast-polyethylene glycol (PEG) method but have used agrobacterium-mediated transformation (AMT) to genetically engineer this strain because it was difficult to generate protoplasts using commercial cell wall lytic enzymes. In this study, we initially investigated the various conditions for protoplast formation in A. luchuensis. We found that A. luchuensis protoplasts could be generated using a minimal medium for the preculture medium, a static culture for the preculture condition, and Yatalase and α-1,3-glucanase as cell-wall lytic enzymes. These protoplasts could then be transformed with the protoplast-PEG method. Because α-1,3-glucanase was needed to form protoplasts in A. luchuensis, we investigated the role of the α-1,3-glucan synthase gene agsE in protoplast formation, one of five α-1,3-glucan synthase genes in A. luchuensis and a homolog of the major α-1,3-glucan synthase agsB in Aspergillus nidulans. We disrupted agsE in A. luchuensis (ΔagsE) with AMT and found that protoplast formation in ΔagsE was comparable with protoplast formation in Aspergillus oryzae with Yatalase. The ΔagsE protoplasts were also competent for transformation with the protoplast-PEG method. Hence, agsE appears to inhibit protoplast formation in A. luchuensis.

Platelet adhesion on commercially pure titanium plates in vitro I: effects of plasma components and involvement of the von Willebrand factor and fibronectin

Background

Platelet-rich plasma (PRP) is widely used in regenerative dentistry. Furthermore, it is often applied in the pretreatment of titanium implants to improve their surface bioaffinity and initial stability. However, effects of PRP application on implant surface at cellular and molecular levels remain poorly understood. Therefore, we examined platelet adhesion on commercially pure titanium (cp-Ti) plates, with a particular focus on fibrinogen (FGN), von Willebrand factor (vWF), and fibronectin (FN), in the presence or absence of plasma components.

Methods

Citrated blood samples were obtained from six healthy male volunteers, and pure-PRP (P-PRP) and pure platelet suspensions in phosphate-buffered saline (PBS) were prepared. Platelet adhesion on cp-Ti plate surface was evaluated by phalloidin staining and tetrazolium dye assay. Distribution of FGN, vWF, FN, albumin, CD62P, and CD63 was examined by immunocytochemical analysis.

Results

Platelets in PBS suspensions rapidly and time-dependently adhered to cp-Ti plate surface, but this adhesion was substantially disturbed by the presence of plasma components. FGN was most preferably adsorbed regardless of the presence or absence of plasma components, while vWF and FN showed greater accumulation on platelet adhesion area.

Conclusions

Although FGN is rapidly and abundantly adsorbed on cp-Ti plate surface, vWF and FN function as major platelet adhesion molecules in citrated blood samples. After pretreatment with P-PRP, however, platelets adhered to cp-Ti much less efficiently. Therefore, P-PRP pretreatment might not directly contribute to surface functionalization, initial stabilization, and osseointegration of machined or similar types of implants.

Electronic supplementary material

The online version of this article (10.1186/s40729-019-0160-z) contains supplementary material, which is available to authorized users.

Abstract P1-14-07: Randomized phase 3 study of anthracycline-containing regimens versus S-1 as first-line treatment for metastatic breast cancer (SELECT BC-CONFIRM)–A combined analysis of two randomized phase 3 studies (SELECT BC-CONFIRM and SELECT BC)–

Background: Anthracycline-containing regimens and taxane have been standard as the first-line chemotherapy for metastatic breast cancer (MBC). We conducted SELECT BC (randomized phase 3 study of taxane versus S-1 as first-line treatment for MBC) for evaluating the efficacy of S-1 for patients with HER2-negative MBC from 2006 to 2010 in Japan. This study demonstrated non-inferiority of S-1 in overall survival (OS) (median OS was 37.2 months in taxes group and 35.0 months in S-1 group (HR 1.05, 95% CI 0.86–1.27, p=0.015)), and superiority in health-related quality of life (HRQOL) to taxanes. S-1 was also shown as less toxic than taxane (Lancet Oncol 2016; 17: 90-98). S-1 might provide clinical benefit as first-line treatment for patients with HER2-negative MBC. To confirm this suggestion, we have conducted further study (randomized phase 3 study of anthracycline-containing regimens versus S-1 as first-line treatment for HER2-negative MBC: SELECT BC-CONFIRM) from 2011 to present, and a combined analysis of two randomized studies (SELECT-BC CONFIRM and SELECT-BC).

Methods: In SELECT BC-CONFIRM, 230 patients receiving first-line treatment for MBC were randomly assigned to either anthracycline group (n=115) or S-1 group (n=115). Anthracycline group patients received anthracycline-containing regimens (AC, EC, FAC, FEC, q3w) at the discretion of the treating physician. S-1 group patients received S-1 40–60 mg twice daily based on the patient's body surface area for 28 days on, 14-day off. The primary endpoint was OS, and secondary endpoints were progression-free survival (PFS), time to treatment failure (TTF), adverse events, HRQOL, and cost-effectiveness. The results were combined with SELECT-BC, to confirm the hypothesis that S-1 treatment is not inferior to the standard therapy (taxanes / anthracycline) for HER2-negative MBC.

Results: A combined analysis of the two studies showed that HR was 1.06, 95%CI 0.90-1.253, and p=0.0071 between the standard therapy group and S-1 group. In addition, the Bayesian posterior probability for which HR would be less than 1.333 was about 99.6%.

Conclusions: A combined analysis of SELECT BC-CONFIRM and SELECT BC clearly demonstrated that OS with S-1 was not inferior to that with the standard therapy in patients receiving first-line treatment for HER2-negative MBC. S-1 could become a standard therapy for this patient population.

Citation Format: Park Y, Akabane H, Watanabe T, Takahashi M, Sagara Y, Nishimura R, Tsurutani J, Takashima T, Fujisawa T, Hozumi Y, Uemura Y, Mukai H. Randomized phase 3 study of anthracycline-containing regimens versus S-1 as first-line treatment for metastatic breast cancer (SELECT BC-CONFIRM)–A combined analysis of two randomized phase 3 studies (SELECT BC-CONFIRM and SELECT BC)– [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-14-07.

Abstract P2-08-35: A significance of SUVmax levels on FDG-PET as a prognostic factor may be mediated by local immune environment of breast cancer

(Background) SUVmax levels (maximum radioactivity concentration per a pixel) on FDG-PET reflect glucose uptake and it is clinically useful as a prognostic factor. It is reported that breast cancer with high levels of SUVmax causes insufficient glucose concentration in stromal tissue, which results in suppressed cytotoxic T-lymphocytes function. These data may indicate that the prognostic significance of SUVmax levels is influenced by local immune environment of breast cancer. The aim of this study is to investigate whether local immune responses of breast cancer affect correlation of SUVmax levels and prognosis.

(Method) The 278 invasive breast cancer patients were recruited who underwent surgery at Hyogo College of Medicine Hospital and whose SUVmax levels in the breast were examined before surgery or neo-adjuvant therapy. The cutoff value of SUVmax levels was set at 3.585. Tumor infiltrate lymphocytes (TILs) were evaluated as a local immune response and the distributions of TILs were divided into three groups, inflamed (intra-tumoral lymphocytes, Inf), immune excluded (peri-tumoral lymphocytes, IE) and immune desert (very few lymphocytes, ID). During follow-up period (median 39 months), 21 patients relapsed.

(Results) Relapse free survival (RFS) in the SUVmax-high group was significantly worse than in the SUVmax–low group (p=0.0026). There was no correlation between TILs distribution patterns and RFS. In the IE+ID group (175 patients) SUVmax levels were not correlated with prognosis, but in the Inf group (103 patients) RFS of SUVmax-high was significantly worse than of SUVmax-low (p=0.0051). In the multivariate analysis including nodal status and nuclear grade, SUVmax levels of the Inf group was an independent prognostic factor.

(Discussion and conclusion) SUVmax levels in primary lesions were correlated with prognosis only in the Inf group and were not in the IE+ID group. A significance of SUVmax levels as a prognostic factor may be diverse depending on the local immune environment of breast cancer. A novel therapeutic strategy such as inducing suppression of glucose uptake in cancer cells is suggested for breast cancer with immune inflamed.

Citation Format: Fujimoto Y, Higuchi T, Watanabe T, Hida AI, Imamura M, Kitajima K, Miyoshi Y. A significance of SUVmax levels on FDG-PET as a prognostic factor may be mediated by local immune environment of breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-08-35.

Abstract P1-13-09: Long-term follow-up of two randomized controlled trials (N-SAS-BC01 trial and CUBC trial) comparing oral tegafur-uracil (UFT) versus classical cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) as adjuvant therapy in early breast cancer

Background: Two randomized controlled trials comparing the efficacy of oral tegafur-uracil (UFT) (2 years) with that of classical cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) (6 courses) were conducted in patients with resected early breast cancer. UFT is an oral fluoropyrimidine that combines tegafur, a prodrug of 5-fluorouracil, with uracil in a 1:4 molar ratio. One study was the N-SAS-BC01 trial (Watanabe et al, J Clin Oncol 2009), which was conducted in patients with high-risk node-negative breast cancer (n=733). The other was the CUBC trial (Park et al, Br J Cancer 2009), which was performed in patients with node-positive breast cancer (n=377). We reported the pooled analysis of these two randomized control trials using individual patient data (Ohashi et al, Breast Cancer Res Treat 2010). This pooled analysis showed that UFT was non-inferior to CMF in terms of inhibiting recurrence of estrogen receptor (ER)-positive early breast cancer. In addition, an exploratory subgroup analysis showed that UFT may be more effective in ER-positive patients who were 50 years or older. The present study was conducted to investigate the long-term efficacy of UFT or CMF in patients with early breast cancer.

Methods: Long-term follow-up data for disease recurrence and survival were collected. Hazard ratios (HR) were determined using the Cox model stratified by study and adjusted for clinical characteristics, namely age, tumor size, nodal status, histological type, ER, and progesterone receptor (PgR). Survival curves were estimated by the Kaplan-Meier method. Hochberg multiplicity adjustment was applied in the previous pooled analysis, and non-inferiority of UFT versus CMF was shown in terms of relapse-free survival (RFS) in the ER-positive patient group. We investigated the non-inferiority of UFT in the same patient group with updated data. Restricted mean survival time (RMST) was calculated to consider the relative efficacy of UFT. This study is registered with JapicCTI-163321.

Results: In total, 1,057 patients were analyzed (CMF, n=528; UFT n=529). The median follow-up time was 11.1 years (12.1 years in the N-SAS-BC 01 trial and 8.3 years in the CUBC trial). Table 1 shows the 10-year RFS and overall survival (OS) in all patients and ER-positive patients. The difference in RMST between arms at 20 years in terms of RFS was -2.7 months in all patients and 3.4 months in ER-positive patients. Table 2 shows the HR for RFS according to ER status and age.

 UFT (%)CMF (%)UFT to CMF; HR (95% CI)10-year RFSall patients74.477.11.02 (0.81–1.30)ER-positive patients75.075.10.91 (0.66–1.27)10-year OSall patients86.886.90.98 (0.72–1.34)ER-positive patients89.987.90.86 (0.54–1.37)

 Age <50 yearsAge ≥50 yearsER negative1.76 (0.95–3.26)0.93 (0.58–1.51)ER positive1.29 (0.74–2.23)0.76 (0.50–1.16)

Conclusion: This study shows that UFT was shown to be non-inferior to CMF in terms of RFS in ER-positive early breast cancer. This result is similar to that of the previous pooled analysis.

Sponsor: Taiho Pharmaceutical Co., LTD

Citation Format: Yonemori K, Ohsumi S, Takao S, Tokuda Y, Ito Y, Nakagami K, Takahashi M, Yoshidome K, Nakayama T, Yamaguchi Y, Ohashi Y, Inaji H, Watanabe T. Long-term follow-up of two randomized controlled trials (N-SAS-BC01 trial and CUBC trial) comparing oral tegafur-uracil (UFT) versus classical cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) as adjuvant therapy in early breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-13-09.

78 Evaluation of the genomic estimated breeding value of carcass traits in blastocyst-stage embryos derived from Japanese Black cattle

Genomic selection based on a high-throughput microarray for genotyping single nucleotide polymorphism (SNP) is expected to accelerate genetic improvement in cattle. Recently, a genomic evaluation system for carcass traits, such as carcass weight and marbling score, is being established in Japanese Black cattle. To further increase genetic improvement efficiency in this breed, establishing a genomic evaluation system for pre-implantation embryos before embryo transfer (ET) is required. Here, we examined the correlation between genomic estimated breeding value (GEBV) of carcass traits calculated from embryonic (blastocyst) biopsy cells and from a corresponding calf produced by ET (Experiment 1); we also evaluated the pregnancy rate following ET of GEBV-evaluated blastocysts (GEBV blastocysts) preserved by vitrification (Experiment 2). In total, 16 Japanese Black dams and cryopreserved semen from 6 Japanese Black sires were used for producing in vivo blastocysts (Day 7-8). In Experiment 1, four blastocysts (IETS code 1) were divided into biopsy cells (15-20 cells) and biopsied embryos using a micromanipulator equipped with a micro blade. Biopsy cells were processed for DNA extraction and whole-genome amplification. Freshly biopsied embryos were transferred to recipient cows, and DNA was extracted from the blood or ear cells of the resulting 4 calves. Then SNP genotyping was performed using Illumina bovine LD BeadChip (Illumina, San Diego, CA, USA). The GEBV of 6 carcass traits (carcass weight, ribeye area, rib thickness, subcutaneous fat thickness, estimated yield percent, and marbling score) were calculated using phenotypic and genotypic data from 4,311 Japanese Black steers, and these were compared between biopsy cells and the corresponding calf. In Experiment 2, 134 blastocysts (IETS code 1 and 2) in total were biopsied (10-20 cells), and the biopsied embryos were vitrified by the cryotop method. Biopsy cells were processed for SNP genotyping as in Experiment 1, and the samples in which the call rate was more than 85% were used for GEBV calculation. Based on GEBV records, 24 vitrified GEBV blastocysts were warmed, cultured for 3 to 5h, and 22 GEBV blastocysts that survived (re-expanded) post-culture were transferred to recipient cows. Pregnancy in these cows was diagnosed using ultrasonography during Day 55 to 60 of gestation. In Experiment 1, the SNP call rates of the biopsy cells and corresponding calf were 98.5 to 99.3% and 99.7 to 99.8%, respectively. The GEBV of 6 carcass traits from biopsy cells and from the corresponding calf had almost the same values. In Experiment 2, the SNP call rates of the biopsy cells were ranged from 26.1 to 99.3%. The GEBV of 6 carcass traits varied among full-sib embryos. The pregnancy rate following ET of vitrified GEBV blastocysts was 40.9% (9/22). These results suggest the possible application of a genomic evaluation system for carcass traits at the blastocyst stage in Japanese Black cattle. Further large-scale assessment of pregnancy rates following ET of cryopreserved GEBV blastocysts is required for practical application of the evaluation system.

Relationship between frontal car-to-car test result and vehicle crash compatibility evaluation in mobile progressive deformable barrier test

Objective: In 2020, the world's first crash compatibility rating test will be introduced in the European mobile progressive deformable barrier (MPDB) test. In this research, the quantitative change in partner protection performance of large vehicles in car-to-car (C2C) impacts was studied if these large vehicles were designed in future based on MPDB tests addressing crash compatibility ratings. Methods: Representative vehicles of the European fleet were selected and a Computer Aided Engineering (CAE) parameter study was conducted. In particular, by changing an indicator of structural interaction performance (SD; i.e., the degree of uniformity of barrier deformation)/mass/stiffness of large vehicles systematically in a step-by-step approach, the compatibility evaluation results of large vehicles in MPDB and the occupant injury score of small vehicles in C2C impacts were compared. The CAE result was evaluated compared to that of C2C physical impact tests. Results: The CAE parameter study showed that in the C2C impact condition, the effects on occupant injury in a small vehicle due to changes in the large vehicle were as follows: (1) SD change: The effect was minor except for small overlap condition. (2) Mass and stiffness change: The effect was relatively major. On the other hand, compatibility evaluation in the MPDB showed a tendency to overestimate the effect of SD change in comparison with the above-mentioned C2C impact condition. In addition, physical impact tests showed that, based on SD evaluation, the large vehicle with a relatively inferior compatibility rating compared to those with superior compatibility ratings showed a contradicting trend of better compatibility performance in the C2C test. Conclusions: The currently proposed compatibility evaluation method of the MPDB test showed some tendency to overestimate the effect of SD change and resulted in quantitatively inconsistent outcomes regarding occupant injury in the partner car in C2C impact conditions.

Terminal Ileac Ulcers Mimicked Post-transplantation Lymphoproliferative Disorder in a Heart Recipient Treated With Everolimus: A Case Report

Post-transplant lymphoproliferative disorder (PTLD) is a well-recognized and potentially fatal complication of cardiac transplantation that commonly involves the gastrointestinal tract. Herein, we report a case of life-threatening gastrointestinal bleeding from recurrent terminal ileac ulcers mimicking PTLD in a heart recipient treated with everolimus (EVL). A 40-year-old man underwent heart transplantation for dilated cardiomyopathy 3 years prior to the current admission and was treated with tacrolimus and EVL. He was admitted to a local hospital because of fever, abdominal pain, and diarrhea. His symptoms persisted and, 3 weeks later, hematochezia occurred; thus, he was transferred to our hospital. As computed tomography and ¹⁸F-fluorodeoxyglucose positron emission tomography showed bowel-wall thickening of the terminal ileum, gastrointestinal PTLD was initially suspected. However, although colonoscopy- performed after switching EVL to mycophenolate mofetil (MMF)-showed terminal ileac ulcers, the histologic examination revealed no findings corresponding to PTLD. As EVL may delay ulcer healing, MMF was maintained for 3 months. After repeated colonoscopy showed ulcer healing, MMF was switched back to EVL for cardiac allograft vasculopathy prevention. Three weeks later, he was emergently admitted to a local hospital for life-threatening gastrointestinal bleeding from a recurrent terminal ileal ulcer, which required hemostatic forceps hemostasis. As EVL is suspected to be associated with recurrent ileal ulcers, EVL was again switched back to MMF. The ileal ulcers resolved, without recurrence in 3 months of clinical follow-up. This case demonstrates that cases of life-threatening gastrointestinal bleeding from recurrent terminal ileac ulcers can mimic PTLD in a heart recipient treated with EVL.

Microwave plasmonic mixer in a transparent fibre-wireless link

To cope with the high bandwidth requirements of wireless applications1, carrier frequencies are shifting towards the millimetre-wave and terahertz bands2-5. Conversely, data is normally transported to remote wireless antennas by optical fibres. Therefore, full transparency and flexibility to switch between optical and wireless domains would be desirable6,7. Here, we demonstrate for the first time a direct wireless-to-optical receiver in a transparent optical link. We successfully transmit 20 and 10 Gbit/s over wireless distances of 1 and 5 m at a carrier frequency of 60 GHz, respectively. Key to the breakthrough was a plasmonic mixer directly mapping the wireless information onto optical signals. The plasmonic scheme with its subwavelength feature and pronounced field confinement provides a built-in field enhancement of up to 90'000 over the incident field in an ultra-compact and CMOS compatible structure. The plasmonic mixer is not limited by electronic speed and thus compatible with future terahertz technologies.

Management of De Novo Mycobacterial Infection After Lung Transplantation Without Rifampicin: Case Series of a Single Institution

BACKGROUND AND OBJECTIVES

To treat organ transplant patients with mycobacterial infection, physicians need to pay attention to interaction between drugs used against mycobacteria and immunosuppressants. The purpose of this report is to describe the clinical features of and treatment for mycobacterial infection in lung transplant (LTx) recipients.

METHODS

To investigate the incidence, treatment, and outcome for mycobacterial infection, we retrospectively reviewed 100 LTx recipients in our program since 2000.

RESULTS

Four recipients (4.0%) developed mycobacterial infection. Three recipients took tacrolimus, and 1 received cyclosporine with mycophenolate mofetil and a steroid for immunosuppression. Tuberculosis (TB) was isolated from 2 recipients, and non-tuberculous mycobacteriosis (NTM) was detected in the other 2. We treated the patients with levofloxacin + isoniazid + pyrazinamide + ethambutol (EB) for TB and clarithromycin (CLM) + EB for NTM to avoid interaction of calcineurin inhibitors (CNI: 8-10 ng/mL in trough level) with rifampicin (RFP). In treating the patients with NTM, we were able to maintain an adequate blood concentration of CNI by decreasing the dosage from one-half to one-quarter. All mycobacterial infections were controlled with treatment. In 1 patient with chronic obstructive pulmonary disease (COPD) infected with TB in the native lung, the forced expiratory volume in 1 second (FEV1) unexpectedly increased from 1890 mL before infection to 2320 mL possibly due to organization of the native lung.

CONCLUSIONS

We were able to manage the mycobacterial infections using drugs other than RFP without any cases of acute rejection under adequate immunosuppression. Organization of the native lung with TB infection unexpectedly resulted in improvement of FEV1 in a COPD patient.

Spectrophotometric determination of platelet counts in platelet-rich plasma

BACKGROUND

Platelet-rich plasma (PRP) is widely used in regenerative dentistry and other medical fields. However, its effectiveness has often been questioned. For better evaluation, the quality of individual PRP preparations should be assured prior to use. We proposed a spectrophotometric method for determination of platelet counts and validated its applicability using two types of PRP preparations.

METHODS

Blood samples were obtained from healthy male volunteers and pure PRP (P-PRP) and leukocytes-rich PRP (L-PRP) were prepared using the double-spin method. In serial dilutions, platelet counts in P-PRP and L-PRP were determined using an automated hematology analyzer and a compact spectrophotometer. For validation, P-PRP and L-PRP independently prepared by three well-trained operators were used for comparison of the calculated and measured platelet counts.

RESULTS

In the two types of PRP samples evaluated, platelet counts were almost equal and greater amount of both white blood cells (WBCs) and red blood cells (RBCs) were included in L-PRP preparations. The calibration curve obtained from serially diluted P-PRP showed a strong correlation (R2 = 0.995), whereas that of L-PRP was relatively weaker (R2 = 0.975). In validation testing, the scatter plot of the calculated platelet counts versus the measured values showed a strong correlation in P-PRP (R2 = 0.671), whereas that of L-PRP showed a much weaker correlation (R2 = 0.0605).

CONCLUSIONS

This method can precisely determine platelet counts in PRP preparations when the inclusion of WBCs or RBCs is minimized. Therefore, we recommend that clinicians use this method for quality assurance of individual PRP preparations.

An on-site preparable, novel bone-grafting complex consisting of human platelet-rich fibrin and porous particles made of a recombinant collagen-like protein

Platelet‐rich fibrin (PRF) is widely used in regenerative medicine. Nonetheless, major issues include its controversial effects on bone regeneration and a lack of quality‐assured glass tubes required for coagulation. We used porous particles (FBG) comprising a recombinant RGD motif‐enriched collagen I‐like protein to activate the coagulation pathway and examined the effects of the resulting PRF–FBG complex on bone regeneration. Human whole‐blood samples were mixed with FBG in plastic tubes and centrifuged to prepare a PRF–FBG complex. Platelet‐derived growth factor‐BB (PDGF‐BB) levels and cell growth activity were determined by ELISA and a bioassay using osteoblasts. Bone regenerative activity was assessed using a mouse model of calvarial bone defect. FBG facilitated PRF‐like matrix formation during centrifugation. In this PRF–FBG complex, the microstructure of fibrin fibers was similar to that of PRF prepared conventionally in glass tubes. PDGF‐BB levels and mitogenic action were not significantly influenced by FBG. In the bone defect model, although PRF did not exert any significant positive effects on its own, in combination with FBG, it synergistically stimulated new bone formation. This study demonstrated that incorporation of FBG into whole‐blood samples induces PRF formation without the aid of glass tubes. The resulting PRF–FBG complex could be a promising bone grafting material in clinical settings. © 2018 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1420–1430, 2019.

Direct activation of platelets by addition of CaCl2 leads coagulation of platelet-rich plasma

Background

Based on the notion that full activation of platelets is required for a growth factor release, in regenerative dentistry, platelet-rich plasma (PRP) in liquid form is usually clotted by addition of CaCl₂ in glassware before topical implantation. However, there has been no evidence as to which is better, full or partial activation of platelets, for minimizing the loss of growth factors and improving the controlled release of growth factors from coagulated PRP. To address this matter, here, we primarily examined direct effects of CaCl₂ on platelets in PBS and on coagulation in citrated PRP.

Methods

PRP was prepared from healthy volunteers’ blood. Platelets’ actions were monitored by scanning electron microscopy, flow cytometry, digital holographic microscopy, and immunofluorescent staining. Clot formation was examined in plasma.

Results

In plasma-free PBS, 0.1% CaCl₂ immediately upregulated CD62P and CD63, causing a release of microparticles and fibrinogen/fibrin; consequently, platelets aggregated and adhered to polystyrene culture dishes with enlargement of their attachment area. In a clot formation assay in plasma, CaCl₂ initially induced platelet aggregation, which triggered loop-like matrix formation and subsequently induced coagulation on a watch glass. Such changes were not clearly observed either with PRP in a plastic dish or in platelet-poor plasma on a watch glass: coagulation was delayed in both conditions.

Conclusions

These findings indicate that besides the well-known coagulation pathway, which activates platelets via thrombin conversion in a coagulation cascade, CaCl₂ directly activates platelets, which then facilitate clot formation independently and in cooperation with the coagulation pathway.

Quantitative evaluation of morphological changes in activated platelets in vitro using digital holographic microscopy

Platelet activation and aggregation have been conventionally evaluated using an aggregometer. However, this method is suitable for short-term but not long-term quantitative evaluation of platelet aggregation, morphological changes, and/or adhesion to specific materials. The recently developed digital holographic microscopy (DHM) has enabled the quantitative evaluation of cell size and morphology without labeling or destruction. Thus, we aim to validate its applicability in quantitatively evaluating changes in cell morphology, especially in the aggregation and spreading of activated platelets, thus modifying typical image analysis procedures to suit aggregated platelets. Freshly prepared platelet-rich plasma was washed with phosphate-buffered saline and treated with 0.1% CaCl₂. Platelets were then fixed and subjected to DHM, scanning electron microscopy (SEM), atomic force microscopy, optical microscopy, and flow cytometry (FCM). Tightly aggregated platelets were identified as single cells. Data obtained from time-course experiments were plotted two-dimensionally according to the average optical thickness versus attachment area and divided into four regions. The majority of the control platelets, which supposedly contained small and round platelets, were distributed in the lower left region. As activation time increased, however, this population dispersed toward the upper right region. The distribution shift demonstrated by DHM was essentially consistent with data obtained from SEM and FCM. Therefore, DHM was validated as a promising device for testing platelet function given that it allows for the quantitative evaluation of activation-dependent morphological changes in platelets. DHM technology will be applicable to the quality assurance of platelet concentrates, as well as diagnosis and drug discovery related to platelet functions.