Traumatic brain injury and bone healing: radiographic and biomechanical analyses of bone formation and stability in a combined murine trauma model

Introduction:The combination of traumatic brain injury (TBI) and long-bone fractures has previously been reported to lead to exuberant callus formation. The aim of this experimental study was to radiographically and biomechanically study the effect of TBI on bone healing in a mouse model.Materials and methods:138 female C57/Black6N mice were assigned to four groups (fracture (Fx) / TBI / combined trauma (Fx/TBI) / controls). Femoral osteotomy and TBI served as variables: osteotomies were stabilized with external fixators, TBI was induced with controlled cortical impact injury. During an observation period of four weeks, in vivo micro-CT scans of femora were performed on a weekly basis. Biomechanical testing of femora was performed ex vivo.Results:The combined-trauma group showed increased bone volume, higher mineral density, and a higher rate of gap bridging compared to the fracture group. The combined-trauma group showed increased torsional strength at four weeks.Discussion:TBI results in an increased formation of callus and mineral density compared to normal bone healing in mice. This fact combined with a tendency towards accelerated gap bridging leads to increased torsional strength. The present study underscores the empirical clinical evidence that TBI stimulates bone healing. Identification of underlying pathways could lead to new strategies for bone-stimulating approaches in fracture care.     

Enhanced epithelial-mesenchymal transition-like phenotype in N-acetylglucosaminyltransferase V transgenic mouse skin promotes wound healing

N-Acetylglucosaminyltransferase V (GnT-V) catalyzes the β1,6 branching of N-acetylglucosamine on N-glycans. GnT-V expression is elevated during malignant transformation in various types of cancer. However, the mechanism by which GnT-V promotes cancer progression is unclear. To characterize the biological significance of GnT-V, we established GnT-V transgenic (Tg) mice, in which GnT-V is regulated by a β-actin promoter. No spontaneous cancer was detected in any organs of the GnT-V Tg mice. However, GnT-V expression was up-regulated in GnT-V Tg mouse skin, and cultured keratinocytes derived from these mice showed enhanced migration, which was associated with changes in E-cadherin localization and epithelial-mesenchymal transition (EMT). Further, EMT-associated factors snail, twist, and N-cadherin were up-regulated, and cutaneous wound healing was accelerated in vivo. We further investigated the detailed mechanisms of EMT by assessing EGF signaling and found up-regulated EGF receptor signaling in GnT-V Tg mouse keratinocytes. These findings indicate that GnT-V overexpression promotes EMT and keratinocyte migration in part through enhanced EGF receptor signaling.     

Polycystin-1 may play an important role in mechanical modulation of bone growth and healing

Mechanical stress is known to modulate bone growth and healing. However, the mechanisms underlying the mechanotransduction are not fully understood. Previous studies show that PC1 is a promising candidate among proteins that may play a role in the mechanotransduction process as it has been shown to function as a flow sensor in renal epithelium and it is known to be important for the growth of for skeletal development. We hypothesized that PC1 plays an important role in bone responses to mechanical stress. PC1 is required for the proliferation, differentiation and survival of periosteal osteochondroprogenitor cells upon mechanical stimulation of bone. Using both genetically manipulated animal models and animals undergoing are necessary to test this hypothesis.     

毛脚鵟细胞体外培养体系建立及三种组织来源细胞特性分析

用组织块培养法对毛脚鵟不同组织进行原代培养,获得了3种不同组织来源的细胞,并成功对细胞进行了冷冻保存和复苏。在传代培养过程中,对比分析了3种组织来源细胞的形态学、生长曲线、贴壁率、核型等生物学特性。形态学方面,3种来源细胞均为成纤维样细胞。对于3种组织来源细胞的贴壁能力分析显示,输卵管源细胞最强,肺源细胞和气管源细胞次之。3种不同组织来源细胞的倍增时间分别为(29.91±0.39)、(33.18±0.21)和(30.67±0.28)h,群体倍增次数分别为3.54±0.01、4.52±0.02和4.38±0.03。毛脚鵟细胞的染色体数目为2n=68,性染色体为典型的ZW型。本实验为今后毛脚鵟细胞利用、遗传信息的保存及生物学特性的深入研究提供实验材料和依据。     

Delivering cellular therapies: lessons learned from ex vivo culture and clinical applications of hematopoietic cells

Advances in stem cell biology and cellular therapy have led to promising treatments in a range of incurable diseases. However, it is unclear whether primitive stem cells can be delivered to damage tissue for regeneration of functional mature cells or stem cells must be stimulated to differentiate into mature cells in vitro and these cells delivered to patients. A range of other questions remains to be determined including how to formulate cellular products for in vivo delivery and how to undertake pharmacological testing of cellular products. Insights into these questions can be obtained from hematopoietic stem cells (HSC) which have been used for the past 50 years in bone marrow transplantation for regeneration of blood cells in patients undergoing high dose chemotherapy to treat cancer. The differentiation of HSC into mature blood cells is controlled by proteins called hematopoietic growth factors and these factors have been used to generate cellular products in vitro for clinical applications. This chapter will review some of the results of cellular therapies performed with HSC and the lessons that can be learned from these studies.     

Cytokines in adipose-derived mesenchymal stem cells promote the healing of liver disease

Adipose-derived mesenchymal stem cells(ADSCs) are a treatment cell source for patients with chronic liver injury. ADSCs are characterized by being harvested from the patient's own subcutaneous adipose tissue, a high cell yield(i.e., reduced immune rejection response), accumulation at a disease nidus, suppression of excessive immune response, production of various growth factors and cytokines, angiogenic effects, antiapoptotic effects, and control of immune cells via cellcell interaction. We previously showed that conditioned medium of ADSCs promoted hepatocyte proliferation and improved the liver function in a mouse model of acute liver failure. Furthermore, as found by many other groups, the administration of ADSCs improved liver tissue fibrosis in a mouse model of liver cirrhosis. A comprehensive protein expression analysis by liquid chromatography with tandem mass spectrometry showed that the various cytokines and chemokines produced by ADSCs promote the healing of liver disease. In this review, we examine the ability of expressed protein components of ADSCs to promote healing in cell therapy for liver disease. Previous studies demonstrated that ADSCs are a treatment cell source for patients with chronic liver injury. This review describes the various cytokines and chemokines produced by ADSCs that promote the healing of liver disease.     

藏羚与几种牛科动物成纤维细胞的特性比较

为研究高原低氧环境对哺乳动物细胞生长特性的影响,本文以高原低氧动物藏羚和同科的阿尔巴斯白绒山羊、蒙古绵羊及鲁西黄牛的耳源组织细胞为材料,利用DMEM /F12 培养液进行培养,建立了4 种动物的体外培养成纤维细胞系,并对其进行形态学观察、生长曲线绘制、凋亡检测、核型分析等生物学特性检测。结果表明:4 种动物的细胞经差异贴壁法联合消化排除法,可获得纯化的成纤维细胞,细胞形态一致且活力稳定,4 种动物细胞的形态与生长曲线无明显差异;藏羚、绒山羊、绵羊、牛同代次细胞生长倍增时间分别为26 h、22 h、23 h 和22 h;经流式细胞仪检测,细胞凋亡率分别为5.5% 、2. 7% 、8. 6% 和1.5% ;藏羚、绒山羊、绵羊与牛的染色体数目分别为60、60、54 和60。藏羚与绒山羊、牛染色体数目相同,且除性染色体外,其余均为端部着丝粒类型,而绵羊存在6 条中着丝粒类型染色体。该结果表明,在体外培养条件下,藏羚的体细胞生长特性与同科的其他物种的细胞生长特性存在明显差异。这为从细胞水平上研究藏羚对环境低氧适应的分子机理提供了基础。     

Epstein-Barr virus-transformed B lymphocytes produce low molecular mass molecules with autocrine growth factor and competence factor activity

A human Epstein-Barr virus (EBV)-positive lymphoblastoid B cell line, named BA-D10-4, produces a factor of a molecular mass less than 10 kDa that promotes cell proliferation of both BA-D10-4 cells and other human T or B lymphoid cell lines, either EBV-positive or -negative. The factor synergizes with higher molecular mass autocrine growth factors and makes both BA-D10-4 cells and B cell lines from Burkitt's lymphoma, but not cells from T cell leukemia, more responsive to interleukin-1 and interleukin-6. Therefore, this low molecular mass factor seems to be an autocrine growth factor per se and to have the characteristics of a competence factor.     

Combination of bone tissue engineering and BMP-2 gene transfection promotes bone healing in osteoporotic rats

OBJECTIVE: The aim of this study was to develop a feasible approach to promote bone healing in osteoporotic rats using autogenous bone tissue-engineering and gene transfection of human bone morphogenetic protein 2 (hBMP-2). METHODS: Bone marrow stromal cells (BMSCs) from the left tibia of osteoporotic rats were transfected with the hBMP-2 gene in vitro which was confirmed by immunohistochemistry, in situ hybridization and Western blotting. Autogenous transfected or untransfected BMSCs were seeded on macroporous coral hydroxyapatite (CHA) scaffolds. Each cell-scaffold construct was implanted into a defect site which was created in the ramus of the mandible of osteoporotic rats. Four or eight weeks after implantation in situ hybridization was performed in BMSCs transfected with hBMP-2, X-ray examinations, histological and histomorphological analyses were used to evaluate the effect of tissue-engineered bone on osseous defect repair. RESULTS: Newly formed bone was observed at the margin of the defect 4 weeks after implantation with BMSCs transfected with BMP-2. Mature bone was observed 8 weeks after treatment. In the control group there was considerably less new bone and some adipose tissue was observed at the defect margins 8 weeks after implantation. CONCLUSIONS: Autogenous cells transfected with hBMP-2 promote bone formation in osteoporotic rats. BMSC-mediated BMP-2 gene therapy used in conjunction with bone tissue engineering may be used to successfully treat bone defects in osteoporotic rats. This method provides a powerful tool for bone regeneration and other tissue engineering.     

Cell cycle regulation in the developing lens

Regulation of cell proliferation is a critical aspect of the development of multicellular organisms. The ocular lens is an excellent model system in which to unravel the mechanisms controlling cell proliferation during development. In recent years, several cell cycle regulators have been shown to be essential for maintaining normal patterns of lens cell proliferation. Additionally, many growth factor signaling pathways and cell adhesion factors have been shown to have the capacity to regulate lens cell proliferation. Given this complexity, understanding the cross talk between these many signaling pathways and how they are coordinated are important directions for the future.     

Comparative modeling and analysis of microfluidic and conventional DNA microarrays

A theoretical analysis was developed to predict molecular hybridization rates for microarrays where samples flow through microfluidic channels and for conventional microarrays where samples remain stationary during hybridization. The theory was validated by using a multiplexed microfluidic microarray where eight samples were hybridized simultaneously against eight probes using 60-mer DNA strands. Mass transfer coefficients ranged over three orders of magnitude where either kinetic reaction rates or molecular diffusion rates controlled overall hybridization rates. Probes were printed using microfluidic channels and also conventional spotting techniques. Consistent with the theoretical model, the microfluidic microarray demonstrated the ability to print DNA probes in less than 1 min and to detect 10-pM target concentrations with hybridization times in less than 5 min.     

Human blood-derived fibrin releasates: Composition and use for the culture of cell lines and human primary cells

We have evaluated the capacity of two human blood fractions to substitute for FBS as growth medium supplement for human and animal cell cultures. Non-anticoagulated blood from volunteer donors (N = 13) was centrifuged to isolate a supernatant serum (SS) and a platelet-rich fibrin (PRF) clot which was squeezed to extract the releasate (PRFR). Both materials were characterized for the content in PDGF-AB, TGF-β1, VEGF, bFGF, EGF, IGF, total protein, albumin, IgG, IgM IgA, fibrinogen, cholesterol, triglycerides, various chemistry analytes and hemoglobin. Cell growth promoting activity of pooled SS and PRFR at 1, 5, and 10% in growth medium was evaluated over 7 days using human (HEK293, MG-63) and animal (SIRC, 3T3) cell lines and two human primary cultures (gingival fibroblasts and periodontal ligaments). Viable cell count was compared to that in cultures in FBS free-medium and 10% FBS supplement. SS and PRFR at 1-10% stimulated cell growth significantly more than FBS-free medium and in a way similar to 10% FBS in all cultures apart from 3T3. These two human blood-derived fibrin releasates are equally efficient to substitute for FBS as supplement for cell cultures and could be useful for specialized applications in regenerative medicine, dentistry and oral implantology, or cell therapy.     

Stem cells and growth factor delivery systems for cardiovascular disease

Coronary (CAD) and peripheral (PAD) artery diseases are major causes of morbidity and mortality, and millions of CAD and PAD patients are treated by various medications, bypass surgery or angioplasty around the world. Such patients might benefit from novel stem cells and tissue engineering strategies aimed at accelerating natural processes of postnatal collateral vessel formation and repairing damaged tissues. By combining three fundamental “tools”, namely stem cells, biomaterials and growth factors (GFs), such strategies may enhance the efficacy of cell therapy in several ways: (a) by supplying exogenous stem cells or GFs that stimulate resident cardiac stem cell (CSC) migration, engraftment and commitment to cardiomyocytes, and that induce and modulate arterial response to ischemia; (b) by supporting the maintenance of GFs and transplanted stem cells in the damaged tissues through the use of biocompatible and biodegradable polymers for a period of time sufficient to allow histological and anatomical restoration of the damaged tissue. This review will discuss the potential of combining stem cells and new delivery systems for growth factors, such as vehicle-based delivery strategies or cell-based gene therapy, to facilitate regeneration of ischemic tissues. These approaches would promote the ability of resident CSCs or of exogenous multipotent stem cells such as adipose tissue-derived mesenchymal stem cells (AT-MSCs) to induce the healing of damaged tissue, by recruiting and directing these cells into the damage area and by improving angiogenesis and reperfusion of ischemic tissues.     

Control of megakaryocyte expansion and bone marrow fibrosis by lysyl oxidase

Lysyl oxidase (LOX), a matrix cross-linking protein, is known to be selectively expressed and to enhance a fibrotic phenotype. A recent study of ours showed that LOX oxidizes the PDGF receptor-β (PDGFR-β), leading to amplified downstream signaling. Here, we examined the expression and functions of LOX in megakaryocytes (MKs), the platelet precursors. Cells committed to the MK lineage undergo mitotic proliferation to yield diploid cells, followed by endomitosis and acquisition of polyploidy. Intriguingly, LOX expression is detected in diploid-tetraploid MKs, but scarce in polyploid MKs. PDGFR-BB is an inducer of mitotic proliferation in MKs. LOX inhibition with β-aminopropionitrile reduces PDGFR-BB binding to cells and downstream signaling, as well as its proliferative effect on the MK lineage. Inhibition of LOX activity has no influence on MK polyploidy. We next rationalized that, in a system with an abundance of low ploidy MKs, LOX could be highly expressed and with functional significance. Thus, we resorted to GATA-1(low) mice, where there is an increase in low ploidy MKs, augmented levels of PDGF-BB, and an extensive matrix of fibers. MKs from these mice display high expression of LOX, compared with control mice. Importantly, treatment of GATA-1(low) mice with β-aminopropionitrile significantly improves the bone marrow fibrotic phenotype, and MK number in the spleen. Thus, our in vitro and in vivo data support a novel role for LOX in regulating MK expansion by PDGF-BB and suggest LOX as a new potential therapeutic target for myelofibrosis.     

HIV and bone disease

Advances in management have resulted in a dramatic decline in mortality for individuals infected with human immunodeficiency virus (HIV). This decrease in mortality, initially the result of improved prophylaxis and treatment of opportunistic infections but later mediated by the use of highly-active antiretroviral therapy (HAART) has led to the need to consider long-term complications of the disease itself, or its treatment. Bone disease is increasingly recognised as a concern.The prevalence of reduced BMD and possibly also fracture incidence are increased in HIV-positive individuals compared with HIV-negative controls. There are many potential explanations for this - an increased prevalence of established osteoporosis risk factors in the HIV-positive population, a likely direct effect of HIV infection itself and a possible contributory role of ARV therapy. At present, the assessment of bone disease and fracture risk remains patchy, with little or no guidance on identifying those at increased risk of reduced BMD or fragility fracture. Preventative and therapeutic strategies with bone specific treatments need to be developed. Limited data suggest bisphosphonates may be beneficial in conjunction with vitamin D and calcium supplementation in the treatment of reduced BMD in HIV-infected patients but larger studies of longer duration are needed. The safety and cost-effectiveness of these and other treatments needs to be evaluated.     

Wound healing enhancement in leg ulcers: A case report

Wound healing in the skin is a complex biological process in which numerous types of cells, cytokines, growth factors, proteases and extracellular matrix components act in concert to restore the integrity of injured tissue. Cultivated allogenic human keratinocytes have been used for the treatment of various skin defects like burnwounds, surgical wounds, in exfoliative skin diseases and chronic wounds. A new method for wound healing enhancement in leg ulcers using cultured allogenic keratinocytes suspended in fibrin glue and used in spray technique is introduced. Allogenic keratinocytes are supposed to enhance granulation tissue production and to stimulate reepithelisation due to their release of growth factors and thus are able to recreate an active wound. This revised version was published online in July 2006 with corrections to the Cover Date.     

m-calpain Activation Is Regulated by Its Membrane Localization and by Its Binding to Phosphatidylinositol 4,5-Bisphosphate

m-calpain plays a critical role in cell migration enabling rear de-adhesion of adherent cells by cleaving structural components of the adhesion plaques. Growth factors and chemokines regulate keratinocyte, fibroblast, and endothelial cell migration by modulating m-calpain activity. Growth factor receptors activate m-calpain secondary to phosphorylation on serine 50 by ERK. Concurrently, activated m-calpain is localized to its inner membrane milieu by binding to phosphatidylinositol 4,5-bisphosphate (PIP₂). Opposing this, CXCR3 ligands inhibit cell migration by blocking m-calpain activity secondary to a PKA-mediated phosphorylation in the C2-like domain. The failure of m-calpain activation in the absence of PIP₂ points to a key regulatory role, although whether this PIP₂-mediated membrane localization is regulatory for m-calpain activity or merely serves as a docking site for ERK phosphorylation is uncertain. Herein, we report the effects of two CXCR3 ligands, CXCL11/IP-9/I-TAC and CXCL10/IP-10, on the EGF- and VEGF-induced redistribution of m-calpain in human fibroblasts and endothelial cells. The two chemokines block the tail retraction and, thus, the migration within minutes, preventing and reverting growth factor-induced relocalization of m-calpain to the plasma membrane of the cells. PKA phosphorylation of m-calpain blocks the binding of the protease to PIP₂. Unexpectedly, we found that this was due to membrane anchorage itself and not merely serine 50 phosphorylation, as the farnesylation-induced anchorage of m-calpain triggers a strong activation of this protease, leading notably to an increased cell death. Moreover, the ERK and PKA phosphorylations have no effect on this membrane-anchored m-calpain. However, the presence of PIP₂ is still required for the activation of the anchored m-calpain. In conclusion, we describe a novel mechanism of m-calpain activation by interaction with the plasma membrane and PIP₂ specifically, this phosphoinositide acting as a cofactor for the enzyme. The phosphorylation of m-calpain by ERK and PKA by growth factors and chemokines, respectively, act in cells to regulate the enzyme only indirectly by controlling its redistribution.     

Bioimmunoadjuvants for the treatment of neoplastic and infectious disease: Coley's legacy revisited

In the nineteenth century, William B. Coley induced durable remission of inoperable metastatic sarcoma by repeatedly injecting live streptococcus bacilli and, subsequently, heat-killed bacterial extracts into the primary tumor. While Coley's contemporaries debated the veracity of his results, this bold treatment protocol established the new scientific field of immunology. In Coley's era, the scientific and medical communities lacked the prerequisite knowledge to validate and understand his treatment protocols. Today, a more comprehensive understanding of the human immune system, anchored by the discovery of the mammalian Toll-like receptor gene family in the 1990s, permits a mechanistic understanding of his results. Coley's cocktail of TLR agonists likely stimulated a complex cascade of cytokines, each of which plays a unique and vital role in the orchestration of the immune response. Here we explore Coley's legacy: a dissection of those cytokines which possess the immunostimulatory properties necessary to modulate the immune system and ameliorate human disease. The discussion is limited to molecules that have been able to show therapeutic promise in the clinical setting.     

Proteomic identification of pleckstrin‐associated proteins in platelets: Possible interactions with actin

Pleckstrin (plek)‐null platelets from a knockout mouse have been shown to be defective in granule secretion, aggregation and actin polymerization. However, the mechanism of plek signaling is currently unknown. Therefore, we sought to identify plek‐binding proteins in platelets by using GST pulldown assays and immunoprecipitation to isolate proteins from extracts of protein kinase C‐activated or inhibited human platelets. Co‐purified plek‐binding proteins were resolved by SDS‐PAGE and identified via nanospray quadruple TOF MS. Identified proteins may be involved in various cellular processes including cytoskeletal reorganization (moesin, radixin and α‐actinin) and signal transduction (serum deprivation response protein, 17 β‐hydroxysteroid dehydrogenase 4 and factor XIIIA). Both platelet aggregation and/or secretion require actin polymerization. However, studies have shown no direct association between plek and actin. Based on our findings we propose indirect associations between plek and actin through 17 β‐hydroxysteroid dehydrogenase 4, α‐actinin, moesin, radixin and factor XIIIA, which in turn suggest new roles for plek in platelet biology.