Ryusuke Honma

Development of Monoclonal Antibody LpMab-10 Recognizing Non-glycosylated PLAG1/2 Domain Including Thr34 of Human Podoplanin

Podoplanin (PDPN) is a type-I transmembrane sialoglycoprotein that possesses a platelet aggregation-stimulating (PLAG) domain in the N-terminus. PLAG domain includes three tandem repeats of eight amino acids: PLAG1, PLAG2, and PLAG3. Among the three PLAG domains, O-glycan on Thr52 of PLAG3 is critical for binding with C-type lectin-like receptor-2 (CLEC-2) and is essential for platelet-aggregating activity of PDPN. In contrast, the glycosylation of Thr34 of PLAG1 of human PDPN remains to be clarified. Herein, we developed and characterized a novel anti-PDPN monoclonal antibody, LpMab-10, which targets PLAG1/2 domain. LpMab-10 detects endogenous PDPN of cancer cells and normal cells independently of glycosylation. The minimum epitope of LpMab-10 was identified as Glu33-Gly45 of PDPN using Western blot and flow cytometry. The Thr34 of PLAG1 is critical for LpMab-10 recognition, and O-glycan is not included in LpMab-10 epitope, indicating that Thr34 of PLAG1 is not O-glycosylated. In immunocytochemical and immunohistochemical analyses, LpMab-10 strongly detected PDPN-expressing tumor cells. By using monoclonal antibodies against different Ser/Thr, including epitopes of PDPN, it becomes possible to determine whether Ser/Thr residues of PDPN are O-glycosylated.

Novel Monoclonal Antibody LpMab-17 Developed by CasMab Technology Distinguishes Human Podoplanin from Monkey Podoplanin

Podoplanin (PDPN) is a type-I transmembrane sialoglycoprotein, which possesses a platelet aggregation-stimulating (PLAG) domain in its N-terminus. Among the three PLAG domains, O-glycan on Thr52 of PLAG3 is critical for the binding with C-type lectin-like receptor-2 (CLEC-2) and is essential for platelet-aggregating activity of PDPN. Although many anti-PDPN monoclonal antibodies (mAbs) have been established, almost all mAbs bind to PLAG domains. We recently established CasMab technology to produce mAbs against membranous proteins. Using CasMab technology, we produced a novel anti-PDPN mAb, LpMab-17, which binds to non-PLAG domains. LpMab-17 clearly detected endogenous PDPN of cancer cells and normal cells in Western-blot, flow cytometry, and immunohistochemistry. LpMab-17 recognized glycan-deficient PDPN in flow cytometry, indicating that the interaction between LpMab-17 and PDPN is independent of its glycosylation. The minimum epitope of LpMab-17 was identified as Gly77-Asp82 of PDPN using enzyme-linked immunosorbent assay. Of interest, LpMab-17 did not bind to monkey PDPN, whereas the homology is 94% between human PDPN and monkey PDPN, indicating that the epitope of LpMab-17 is unique compared with the other anti-PDPN mAbs. The combination of different epitope-possessing mAbs could be advantageous for the PDPN-targeting diagnosis or therapy.

LpMab-12 Established by CasMab Technology Specifically Detects Sialylated O-Glycan on Thr52 of Platelet Aggregation-Stimulating Domain of Human Podoplanin

Podoplanin (PDPN), also known as Aggrus, possesses three tandem repeat of platelet aggregation-stimulating (PLAG) domains in its N-terminus. Among the PLAG domains, sialylated O-glycan on Thr52 of PLAG3 is essential for the binding to C-type lectin-like receptor-2 (CLEC-2) and the platelet-aggregating activity of human PDPN (hPDPN). Although various anti-hPDPN monoclonal antibodies (mAbs) have been generated, no specific mAb has been reported to target the epitope containing glycosylated Thr52. We recently established CasMab technology to develop mAbs against glycosylated membrane proteins. Herein, we report the development of a novel anti-glycopeptide mAb (GpMab), LpMab-12. LpMab-12 detected endogenous hPDPN by flow cytometry. Immunohistochemical analyses also showed that hPDPN-expressing lymphatic endothelial and cancer cells were clearly labeled by LpMab-12. The minimal epitope of LpMab-12 was identified as Asp49–Pro53 of hPDPN. Furthermore, LpMab-12 reacted with the synthetic glycopeptide of hPDPN, corresponding to 38–54 amino acids (hpp3854: 38-EGGVAMPGAEDDVVTPG-54), which carries α2–6 sialylated N-acetyl-D-galactosamine (GalNAc) on Thr52. LpMab-12 did not recognize non-sialylated GalNAc-attached glycopeptide, indicating that sialylated GalNAc on Thr52 is necessary for the binding of LpMab-12 to hPDPN. Thus, LpMab-12 could serve as a new diagnostic tool for determining whether hPDPN possesses the sialylation on Thr52, a site-specific post-translational modification critical for the hPDPN association with CLEC-2.

Development of Sensitive Monoclonal Antibody PMab-2 Against Rat Podoplanin

Podoplanin (PDPN) is a platelet aggregation-inducing factor, which is known as an endogenous ligand of C-type lectin-like receptor-2 (CLEC-2). PDPN is also expressed in several normal tissues, such as lung type I alveolar cells and kidney podocytes. Although many monoclonal antibodies (MAbs) against human PDPN (hPDPN) or mouse PDPN (mPDPN) have been established, anti-rat PDPN (rPDPN) MAbs, especially against platelet aggregation-stimulating (PLAG) domain (29-54 amino acids) of rPDPN, have not been developed. Therefore, functional analysis of rPDPN in normal tissues has been limited. Here, we immunized mice with rPDPN peptides (38-51 amino acids) and developed a novel mouse anti-rPDPN MAb, PMab-2 (IgG1, kappa), which possesses high affinity compared with anti-hPDPN or mPDPN MAbs. The KD of PMab-2 was determined to be 5.9 × 10(-10) M. PMab-2 is useful, not only in flow cytometry and Western blot analysis against endogenous rPDPN, which is expressed in rat dermal fibroblast, but also in immunohistochemistry against normal tissues. PMab-2 showed extraordinarily high sensitivity in immunohistochemistry, indicating that PMab-2 is very advantageous for functional analysis of rPDPN.

Development and characterization of anti‐glycopeptide monoclonal antibodies against human podoplanin, using glycan‐deficient cell lines generated by CRISPR/Cas9 and TALEN

Human podoplanin (hPDPN), which binds to C‐type lectin‐like receptor‐2 (CLEC‐2), is involved in platelet aggregation and cancer metastasis. The expression of hPDPN in cancer cells or cancer‐associated fibroblasts indicates poor prognosis. Human lymphatic endothelial cells, lung‐type I alveolar cells, and renal glomerular epithelial cells express hPDPN. Although numerous monoclonal antibodies (mAbs) against hPDPN are available, they recognize peptide epitopes of hPDPN. Here, we generated a novel anti‐hPDPN mAb, LpMab‐21. To characterize the hPDPN epitope recognized by the LpMab‐21, we established glycan‐deficient CHO‐S and HEK‐293T cell lines, using the CRISPR/Cas9 or TALEN. Flow cytometric analysis revealed that the minimum hPDPN epitope, in which sialic acid is linked to Thr76, recognized by LpMab‐21 is Thr76–Arg79. LpMab‐21 detected hPDPN expression in glioblastoma, oral squamous carcinoma, and seminoma cells as well as in normal lymphatic endothelial cells. However, LpMab‐21 did not react with renal glomerular epithelial cells or lung type I alveolar cells, indicating that sialylation of hPDPN Thr76 is cell‐type‐specific. LpMab‐21 combined with other anti‐hPDPN antibodies that recognize different epitopes may therefore be useful for determining the physiological function of sialylated hPDPN.

Establishment of Novel Monoclonal Antibody PMab-32 Against Rabbit Podoplanin.

Podoplanin (PDPN) is a type I transmembrane O-glycoprotein, which is known as a specific lymphatic marker. PDPN activates platelet aggregation by binding to C-type lectin-like receptor-2 (CLEC-2) on platelet. PDPN is also expressed in several normal tissues, including podocytes and type I alveolar cells. Although many monoclonal antibodies (MAbs) against human PDPN (hPDPN), mouse PDPN (mPDPN), and rat PDPN (rPDPN) have been established, useful antibodies against rabbit PDPN (rabPDPN) have not been developed. In this study, we immunized mice with the recombinant proteins of rabPDPN, and developed a novel anti-rabPDPN MAb, named PMab-32. PMab-32 could detect endogenous and exogenous rabPDPN in flow cytometry and Western blot analysis. The KD of PMab-32 was determined to be 6.2 × 10(-8) M by flow cytometry. Immunohistochemical analysis showed that PMab-32 is useful for detecting podocytes, type I alveolar cells, and lymphatic endothelial cells in normal rabbit tissues. PMab-32 is expected to be useful for various rabbit experiments.

Establishment of Mouse Monoclonal Antibody LpMab-13 Against Human Podoplanin

Podoplanin (PDPN)/Aggrus is a type-I transmembrane sialoglycoprotein, which possesses a platelet aggregation-stimulating (PLAG) domain. The O-glycosylation on Thr52 of human PDPN (hPDPN) is critical for the interaction of hPDPN with C-type lectin-like receptor-2 (CLEC-2), resulting in platelet aggregation. Many anti-hPDPN monoclonal antibodies (MAbs) against PLAG domains and non-PLAG domains have been established; however, mouse anti-PLAG2/3 MAb, the epitope of which is consistent with rat anti-PLAG2/3 MAb NZ-1, has not been established. NZ-1 inhibits the hPDPN-CLEC-2 interaction and is also useful for anti-PA tag MAb. We recently established CasMab technology to produce MAbs against membranous proteins. Herein, we produced a novel anti-hPDPN MAb, LpMab-13, which binds to PLAG2/3 domains. LpMab-13 recognized endogenous hPDPN of cancer cells, including glioblastoma, oral cancer, lung cancer, and malignant mesothelioma, and normal cells such as lymphatic endothelial cells and podocytes of kidney in Western blot, flow cytometry, and immunohistochemistry. LpMab-13 recognized glycan-deficient hPDPN in flow cytometry, indicating that the interaction between LpMab-13 and hPDPN is independent of its glycosylation. The minimum epitope of LpMab-13 was identified as Ala42-Asp49 of hPDPN using Western blot and flow cytometry. The combination of different epitope-possessing MAbs could be advantageous for the hPDPN-targeting diagnosis and therapy.

Complications of Distal Radius Fractures Treated by Volar Locking Plate Fixation

The current study investigated the incidence of complications after surgery for distal radial fractures. This multicenter retrospective study was conducted at 11 institutions. A total of 824 patients who had distal radius fractures that were treated surgically between January 2010 and August 2012 were identified. The study patients were older than 18 years and were observed for at least 12 weeks after surgery for distal radius fractures with a volar locking plate. Sex, age, fracture type according to AO classification, implants, wrist range of motion, grip strength, fracture consolidation rate, and complications were studied. Analysis included 694 patients, including 529 women and 165 men, with a mean age of 64 years. The mean follow-up period was 27 weeks. The fracture consolidation rate was 100%. There were 52 complications (7.5%), including 18 cases of carpal tunnel syndrome, 12 cases of peripheral nerve palsy, 8 cases of trigger digit, 4 cases of tendon rupture (none of the flexor pollicis longus), and 10 others. There was no rupture of the flexor pollicis longus tendon because careful attention was paid to the relationship between the implant and the tendon. Peripheral nerve palsy may have been caused by intraoperative traction in 7 cases, temporary fixation by percutaneous Kirschner wires in 3 cases, and axillary nerve block in 1 case; 1 case appeared to be idiopathic. Tendon ruptures were mainly caused by mechanical stress. [Orthopedics.2016; 39(5):e893-e896.].

Critical Epitope of Anti-Rabbit Podoplanin Monoclonal Antibodies for Immunohistochemical Analysis

Podoplanin (PDPN) is a type I transmembrane sialoglycoprotein, which is expressed in several normal cells, including lymphatic endothelial cells throughout the body, podocytes of the kidney, and lung type I alveolar cells of the lung. We have established many monoclonal antibodies (mAbs) against human PDPN, mouse PDPN, and rat PDPN. In addition, we recently produced an anti-rabbit PDPN mAb, PMab-32, which was established by immunizing mice with recombinant proteins of rabbit PDPN. Herein, we compared the reactivity of PMab-32 with that of newly established anti-rabbit PDPN mAbs, PMab-33 and PMab-21, against normal tissues in immunohistochemistry. PMab-32 reacted with podocytes, type I alveolar cells, and lymphatic endothelial cells, whereas PMab-33 detected only podocytes and type I alveolar cells but not lymphatic endothelial cells. PMab-21 was not useful in immunohistochemistry. We identified the epitope of PMab-32 and PMab-33 as Ser61-Ala68 of rabbit PDPN using western blot and flow cytometric analyses. In contrast, the epitope of PMab-21 was identified as Leu44-Glu48, which is corresponding to platelet aggregation-stimulating (PLAG) domain, indicating that Ser61-Ala68 of rabbit PDPN is a more appropriate epitope for immunohistochemistry compared with PLAG domain. PMab-32 could be useful for uncovering the function of rabbit PDPN.

Comparison of the Effects of Osteochondral Autograft Transplantation With Platelet-Rich Plasma or Platelet-Rich Fibrin on Osteochondral Defects in a Rabbit Model

Background: Although osteochondral autograft transplantation (OAT) provides satisfactory outcomes for osteochondral defects, for large defects OAT is often inadequate because of graft availability. Osteochondral allograft transplantation is an alternative treatment for large defects, but this approach is limited by graft storage constraints and carries disease transmission risks. Platelet-rich fibrin (PRF) is a second-generation platelet concentrate, and its positive effect on articular cartilage has been reported. However, the effect of PRF with OAT of osteochondral defects is unknown. Purpose: To compare the effects of OAT with platelet-rich plasma (PRP) and PRF on osteochondral defects in a rabbit model. Study Design: Controlled laboratory study. Methods: Forty-two juvenile rabbits were divided into control, PRP, and PRF groups. In the control and PRP groups, a cylindrical osteochondral defect (5 mm in diameter and 2 mm in depth) was created on the patellar groove, and an osteochondral graft (3.5 mm in diameter and 5 mm in length) harvested from the contralateral side was inserted into the distal portion of the defect. After wound closure, either normal saline or PRP was injected in the knee. In the PRF group, a PRF clot was placed in the defect before grafting. The surgical site was macroscopically and histologically assessed after 3 and 12 weeks. Results: At 3 weeks, the PRF group (n = 8) was macroscopically healed compared with the other 2 groups (control, n = 7; PRP, n = 6) (P < .005). Histologically, osteochondral graft cartilage of the PRF group had normal cellularity and higher amounts of safranin O staining relative to the other 2 groups (P < .005). At 12 weeks, all 3 groups (n = 8 per group) were macroscopically healed with normal or nearly normal cartilage, and osteochondral graft cartilage was histologically hyaline cartilage. In contrast, the PRF group healed with hyaline-like cartilage at nongrafted defects, whereas the other 2 groups healed with fibrocartilage (P < .001). Conclusion: OAT with PRF maintained hyaline cartilage, and the nongrafted defect healed with hyaline-like cartilage. Clinical Relevance: PRF has the potential to improve clinical outcomes of OAT used to treat osteochondral lesions.