Soonchul Lee

Brief Report: Human Perivascular Stem Cells and Nel‐Like Protein‐1 Synergistically Enhance Spinal Fusion in Osteoporotic Rats

Autologous bone grafts (ABGs) are considered as the gold standard for spinal fusion. However, osteoporotic patients are poor candidates for ABGs due to limited osteogenic stem cell numbers and function of the bone microenvironment. There is a need for stem cell‐based spinal fusion of proven efficacy under either osteoporotic or nonosteoporotic conditions. The purpose of this study is to determine the efficacy of human perivascular stem cells (hPSCs), a population of mesenchymal stem cells isolated from adipose tissue, in the presence and absence of NELL‐1, an osteogenic protein, for spinal fusion in the osteoporosis. Osteogenic differentiation of hPSCs with and without NELL‐1 was tested in vitro. The results indicated that NELL‐1 significantly increased the osteogenic potential of hPSCs in both osteoporotic and nonosteoporotic donors. Next, spinal fusion was performed by implanting scaffolds with regular or high doses of hPSCs, with or without NELL‐1 in ovariectomized rats (n = 41). Regular doses of hPSCs or NELL‐1 achieved the fusion rates of only 20%–37.5% by manual palpation. These regular doses had previously been shown to be effective in nonosteoporotic rat spinal fusion. Remarkably, the high dose of hPSCs+NELL‐1 significantly improved the fusion rates among osteoporotic rats up to approximately 83.3%. Microcomputed tomography imaging and quantification further confirmed solid bony fusion with high dose hPSCs+NELL‐1. Finally, histologically, direct in situ involvement of hPSCs in ossification was shown using undecalcified samples. To conclude, hPSCs combined with NELL‐1 synergistically enhances spinal fusion in osteoporotic rats and has great potential as a novel therapeutic strategy for osteoporotic patients. Stem Cells 2015;33:3158–3163

Combining Smoothened Agonist and NEL-Like Protein-1 Enhances Bone Healing

Background: Nonhealing bone defects represent an immense biomedical burden. Despite recent advances in protein-based bone regeneration, safety concerns over bone morphogenetic protein-2 have prompted the search for alternative factors. Previously, the authors examined the additive/synergistic effects of hedgehog and Nel-like protein-1 (NELL-1) on the osteogenic differentiation of mesenchymal stem cells in vitro. In this study, the authors sought to leverage their previous findings by applying the combination of Smoothened agonist (SAG), hedgehog signal activator, and NELL-1 to an in vivo critical-size bone defect model. Methods: A 4-mm parietal bone defect was created in mixed-gender CD-1 mice. Treatment groups included control (n = 6), SAG (n = 7), NELL-1 (n = 7), and SAG plus NELL-1 (n = 7). A custom fabricated poly(lactic-co-glycolic acid) disk with hydroxyapatite coating was used as an osteoinductive scaffold. Results: Results at 4 and 8 weeks showed increased bone formation by micro–computed tomographic analyses with either stimulus alone (SAG or NELL-1), but significantly greater bone formation with both components combined (SAG plus NELL-1). This included greater bone healing scores and increased bone volume and bone thickness. Histologic analyses confirmed a significant increase in new bone formation with the combination therapy SAG plus NELL-1, accompanied by increased defect vascularization. Conclusions: In summary, the authors’ results suggest that combining the hedgehog signaling agonist SAG and NELL-1 has potential as a novel therapeutic strategy for the healing of critical-size bone defects. Future directions will include optimization of dosage and delivery strategy for an SAG and NELL-1 combination product.

Fibromodulin reduces scar size and increases scar tensile strength in normal and excessive-mechanical-loading porcine cutaneous wounds

Hypertrophic scarring is a major postoperative complication which leads to severe disfigurement and dysfunction in patients and usually requires multiple surgical revisions due to its high recurrence rates. Excessive‐mechanical‐loading across wounds is an important initiator of hypertrophic scarring formation. In this study, we demonstrate that intradermal administration of a single extracellular matrix (ECM) molecule—fibromodulin (FMOD) protein—can significantly reduce scar size, increase tensile strength, and improve dermal collagen architecture organization in the normal and even excessive‐mechanical‐loading red Duroc pig wound models. Since pig skin is recognized by the Food and Drug Administration as the closest animal equivalent to human skin, and because red Duroc pigs show scarring that closely resembles human proliferative scarring and hypertrophic scarring, FMOD‐based technologies hold high translational potential and applicability to human patients suffering from scarring—especially hypertrophic scarring.

hPSCs and NELL-1 Synergistically Enhance Spinal Fusion in Osteoporotic Rats

Autologous bone grafts (ABGs) are considered as the gold standard for spinal fusion. However, osteoporotic patients are poor candidates for ABGs due to limited osteogenic stem cell numbers and function of the bone microenvironment. There is a need for stem cell‐based spinal fusion of proven efficacy under either osteoporotic or nonosteoporotic conditions. The purpose of this study is to determine the efficacy of human perivascular stem cells (hPSCs), a population of mesenchymal stem cells isolated from adipose tissue, in the presence and absence of NELL‐1, an osteogenic protein, for spinal fusion in the osteoporosis. Osteogenic differentiation of hPSCs with and without NELL‐1 was tested in vitro. The results indicated that NELL‐1 significantly increased the osteogenic potential of hPSCs in both osteoporotic and nonosteoporotic donors. Next, spinal fusion was performed by implanting scaffolds with regular or high doses of hPSCs, with or without NELL‐1 in ovariectomized rats (n = 41). Regular doses of hPSCs or NELL‐1 achieved the fusion rates of only 20%–37.5% by manual palpation. These regular doses had previously been shown to be effective in nonosteoporotic rat spinal fusion. Remarkably, the high dose of hPSCs+NELL‐1 significantly improved the fusion rates among osteoporotic rats up to approximately 83.3%. Microcomputed tomography imaging and quantification further confirmed solid bony fusion with high dose hPSCs+NELL‐1. Finally, histologically, direct in situ involvement of hPSCs in ossification was shown using undecalcified samples. To conclude, hPSCs combined with NELL‐1 synergistically enhances spinal fusion in osteoporotic rats and has great potential as a novel therapeutic strategy for osteoporotic patients. Stem Cells 2015;33:3158–3163

Modification of Titanium Implant and Titanium Dioxide for Bone Tissue Engineering

Bone tissue engineering using titanium (Ti) implant and titanium dioxide (TiO2) with their modification is gaining increasing attention. Ti has been adopted as an implant material in dental and orthopedic fields due to its superior properties. However, it still requires modification in order to achieve robust osteointegration between the Ti implant and surrounding bone. To modify the Ti implant, numerous methods have been introduced to fabricate porous implant surfaces with a variety of coating materials. Among these, plasma spraying of hydroxyapatite (HA) has been the most commonly used with commercial success. Meanwhile, TiO2 nanotubes have been actively studied as the coating material for implants, and promising results have been reported about improving osteogenic activity around implants recently. Also porous three-dimensional constructs based on TiO2 have been proposed as scaffolding material with high biocompatibility and osteoconductivity in large bone defects. However, the use of the TiO2 scaffolds in load-bearing environment is somewhat limited. In order to optimize the TiO2 scaffolds, studies have tried to combine various materials with TiO2 scaffolds including drug, mesenchymal stem cells, Al2O3-SiO2 solid and HA. This article will shortly introduce the properties of Ti and Ti-based implants with their modification, and review the progress of bone tissue engineering using the TiO2 nanotubes and scaffolds.

A Protocol to Acquire the Degenerative Tenocyte from Humans

Tendinopathy, a painful condition that develops in response to tendon degeneration, is on the rise in the developed world due to increasing physical activity and longer life expectancy. Despite its increasing prevalence, the underlying pathogenesis still remains unclear, and treatment is generally symptomatic. Recently, numerous therapeutic options, including growth factors, stem cells, and gene therapy, were investigated in hopes of enhancing the healing potency of the degenerative tendon. However, the majority of these research studies were conducted only on animal models or healthy human tenocytes. Despite some studies using pathological tenocytes, to the best of our knowledge there is currently no protocol describing how to obtain human degenerative tenocytes. The aim of this study is to describe a standard protocol for acquiring human degenerative tenocytes. Initially, the tendon tissue was harvested from a patient with lateral epicondylitis during surgery. Then biopsy samples were taken from the extensor carpi radialis brevis tendon corresponding to structural changes observed at the time of surgery. All of the harvested tendons appeared to be dull, gray, friable, and edematous, which made them visually distinct from the healthy ones. Tenocytes were cultured and used for experiments. Meanwhile, half of the harvested tissues were analyzed histologically, and it was shown that they shared the same key features of tendinopathy (angiofibroblastic dysplasia or hyperplasia). A secondary analysis by immunocytochemistry confirmed that the cultured cells were tenocytes with the majority of the cells having positive stains for mohawk and tenomodulin proteins. The qualities of the degenerative nature of tenocytes were then determined by comparing the cells with the healthy control using a proliferation assay or qRT-PCR. The degenerative tenocyte displayed a higher proliferation rate and similar gene expression patterns of tendinopathy that matched previous reports. Overall, this new protocol might provide a useful tool for future studies of tendinopathy.

The Implication of Substance P in the Development of Tendinopathy: A Case Control Study

It was reported that substance P had beneficial effects in the healing of acute tendon injury. However, the relationship between substance P and degenerative tendinopathy development remains unclear. The purpose of this study was to determine the role of substance P in the pathogenesis of tendinopathy. Healthy and tendinopathy tendon were harvested from human and tenocytes were cultured individually. The expression levels of genes associated with tendinopathy were compared. Next, substance P was exogenously administered to the healthy tenocyte and the effect was evaluated. The results showed that tendinopathy tenocytes had higher levels of COL3A1, MMP1, COX2, SCX, ACTA2, and substance P gene expression compared to healthy tenocytes. Next, substance P treatment on the healthy tenocyte displayed similar changes to that of the tendinopathy tenocytes. These differences between the two groups were also determined by Western blot. Additionally, cells with substance P had the tendinopathy change morphologically although cellular proliferation was significantly higher compared to that of the control group. In conclusion, substance P enhanced cellular proliferation, but concomitantly increased immature collagen (type 3 collagen). Substance P plays a crucial role in tendinopathy development and could be a future therapeutic target for treatment.

Cyst-Like Osteolytic Formations in Recombinant Human Bone Morphogenetic Protein-2 (rhBMP-2) Augmented Sheep Spinal Fusion

Multiple case reports using recombinant human bone morphogenetic protein-2 (rhBMP-2) have reported complications. However, the local adverse effects of rhBMP-2 application are not well documented. In this report we show that, in addition to promoting lumbar spinal fusion through potent osteogenic effects, rhBMP-2 augmentation promotes local cyst-like osteolytic formations in sheep trabecular bones that have undergone anterior lumbar interbody fusion. Three months after operation, conventional computed tomography showed that the trabecular bones of the rhBMP-2 application groups could fuse, whereas no fusion was observed in the control group. Micro-computed tomography analysis revealed that the core implant areas bone volume fraction and bone mineral density increased proportionately with rhBMP-2 dose. Multiple cyst-like bone voids were observed in peri-implant areas when using rhBMP-2 applications, and these sites showed significant bone mineral density decreases in relation to the unaffected regions. Biomechanically, these areas decreased in strength by 32% in comparison with noncystic areas. Histologically, rhBMP-2-affected void sites had an increased amount of fatty marrow, thinner trabecular bones, and significantly more adiponectin- and cathepsin K-positive cells. Despite promoting successful fusion, rhBMP-2 use in clinical applications may result in local adverse structural alterations and compromised biomechanical changes to the bone.

Brief Report: Human Perivascular Stem Cells andNel-Like Protein-1 Synergistically Enhance Spinal Fusion in Osteoporotic Rats: hPSCs and NELL-1 in Spinal Fusion for Osteoporosis

Autologous bone grafts (ABGs) are considered as the gold standard for spinal fusion. However, osteoporotic patients are poor candidates for ABGs due to limited osteogenic stem cell numbers and function of the bone microenvironment. There is a need for stem cell‐based spinal fusion of proven efficacy under either osteoporotic or nonosteoporotic conditions. The purpose of this study is to determine the efficacy of human perivascular stem cells (hPSCs), a population of mesenchymal stem cells isolated from adipose tissue, in the presence and absence of NELL‐1, an osteogenic protein, for spinal fusion in the osteoporosis. Osteogenic differentiation of hPSCs with and without NELL‐1 was tested in vitro. The results indicated that NELL‐1 significantly increased the osteogenic potential of hPSCs in both osteoporotic and nonosteoporotic donors. Next, spinal fusion was performed by implanting scaffolds with regular or high doses of hPSCs, with or without NELL‐1 in ovariectomized rats (n = 41). Regular doses of hPSCs or NELL‐1 achieved the fusion rates of only 20%–37.5% by manual palpation. These regular doses had previously been shown to be effective in nonosteoporotic rat spinal fusion. Remarkably, the high dose of hPSCs+NELL‐1 significantly improved the fusion rates among osteoporotic rats up to approximately 83.3%. Microcomputed tomography imaging and quantification further confirmed solid bony fusion with high dose hPSCs+NELL‐1. Finally, histologically, direct in situ involvement of hPSCs in ossification was shown using undecalcified samples. To conclude, hPSCs combined with NELL‐1 synergistically enhances spinal fusion in osteoporotic rats and has great potential as a novel therapeutic strategy for osteoporotic patients. Stem Cells 2015;33:3158–3163

Lateral Supramalleolar Flap for Reconstruction of Soft Tissue Defect around the Ankle Joint

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