Laminin deposition to type IV collagen enhances haptotaxis, chemokinesis, and adhesion of hepatoma cells through beta1-integrins

Integrin α2 and β1 Cross-Communication with mTOR/AKT and the CDK-Cyclin Axis in Hepatocellular Carcinoma Cells

Simple Summary

Hepatocellular carcinoma (HCC) progression depends on two major processes, tumor growth and invasion. The present study investigated how these events are linked. A panel of HCC cell lines were stimulated with insulin-like growth factor-1 (IGF1) and the biological behavior was evaluated. IGF1 activated the proliferation and invasion cascade by altering the expression level of integrin α subtypes, which were associated with the AKT-mTOR pathway and the CDK-Cyclin axis. We assume that HCC progression is controlled by a fine-tuned network between IGF1 driven integrin signaling, the Akt-mTOR pathway, and the CDK-Cyclin axis. Concerted targeting of these pathways may, therefore, become an innovative option to prevent cancer dissemination.

Abstract

Integrin receptors contribute to hepatocellular carcinoma (HCC) invasion, while AKT-mTOR signaling controls mitosis. The present study was designed to explore the links between integrins and the AKT-mTOR pathway and the CDK-Cyclin axis. HCC cell lines (HepG2, Huh7, Hep3B) were stimulated with soluble collagen or Matrigel to activate integrins, or with insulin-like growth factor 1 (IGF1) to activate AKT-mTOR. HCC growth, proliferation, adhesion, and chemotaxis were evaluated. AKT/mTOR-related proteins, proteins of the CDK-Cyclin axis, focal adhesion kinase (FAK), and integrin-linked kinase (ILK) were determined following IGF1-stimulation or integrin knockdown. Stimulation with collagen or Matrigel increased tumor cell growth and proliferation. This was associated with significant alteration of the integrins α2, αV, and β1. Blockade of these integrins led to cell cycle arrest in G2/M and diminished the number of tumor cell clones. Knocking down the integrins α2 or β1 suppressed ILK, reduced FAK-phosphorylation and diminished AKT/mTOR, as well as the proteins of the CDK-Cyclin axis. Activating the cells with IGF1 enhanced the expression of the integrins α2, αV, β1, activated FAK, and increased tumor cell adhesion and chemotaxis. Blocking the AKT pathway canceled the enhancing effect of IGF on the integrins α2 and β1. These findings reveal that HCC growth, proliferation, and invasion are controlled by a fine-tuned network between α2/β1-FAK signaling, the AKT-mTOR pathway, and the CDK–Cyclin axis. Concerted blockade of the integrin α2/β1 complex along with AKT-mTOR signaling could, therefore, provide an option to prevent progressive dissemination of HCC.

Biomaterials for intestinal organoid technology and personalized disease modeling

Recent advances in intestinal organoid technologies have paved the way for in vitro recapitulation of the homeostatic renewal of adult tissues, tissue or organ morphogenesis during development, and pathogenesis of many disorders. In vitro modelling of individual patient diseases using organoid systems have been considered key in establishing rational design of personalized treatment strategies and in improving therapeutic outcomes. In addition, the transplantation of organoids into diseased tissues represents a novel approach to treat currently incurable diseases. Emerging evidence from intensive studies suggests that organoid systems' development and functional maturation depends on the presence of an extracellular matrix with suitable biophysical properties, where advanced synthetic hydrogels open new avenues for theoretical control of organoid phenotypes and potential applications of organoids in therapeutic purposes. In this review, we discuss the status, applications, challenges and perspectives of intestinal organoid systems emphasising on hydrogels and their properties suitable for intestinal organoid culture. We provide an overview of hydrogels used for intestinal organoid culture and key factors regulating their biological activity. The comparison of different hydrogels would be a theoretical basis for establishing design principles of synthetic niches directing intestinal cell fates and functions. STATEMENT OF SIGNIFICANCE: Intestinal organoid is an in vitro recapitulation of the gut, which self-organizes from intestinal stem cells and maintains many features of the native tissue. Since the development of this technology, intestinal organoid systems have made significant contribution to rapid progress in intestinal biology. Prevailing methodology for organoid culture, however, depends on animal-derived matrices and suffers from variability and potential risk for contamination of pathogens, limiting their therapeutic application. Synthetic scaffold matrices, hydrogels, might provide solutions to these issues and deepen our understanding on how intestinal cells sense and respond to key biophysical properties of the surrounding matrices. This review provides an overview of developing intestinal models and biomaterials, thereby leading to better understanding of current intestinal organoid systems for both biologists and materials scientists.

A novel and validated prognostic nomogram based on liver fibrosis and tumor burden for patients with hepatocellular carcinoma after curative resection

BACKGROUND AND OBJECTIVES

Most conventional staging systems were formulated concerning the tumor burden rather than the severity of liver fibrosis, which plays a central role in tumor promotion. The aim of this study was to formulate a prognostic nomogram comprehensively considering these two aspects for HCC after hepatectomy.

METHODS

The prognostic significances of the four indicators namely laminin, hyaluronic acid, human procollagen type-III, and collagen type-IV that reflect liver fibrosis were explored in two independent cohorts. A nomogram was established based on the results of multivariate analysis. The predictive accuracy of the nomogram was measured by concordance index (C-index) and calibration. The decision curve analysis (DCA) was used to evaluate the clinical benefit of the nomogram.

RESULTS

Preoperative serum laminin level is an independent prognostic factor for overall survival in HCC patients after resection. The C-indices of the nomogram in the training and validation cohorts were 0.779 and 0.719, respectively. The calibration showed optimal agreement between the prediction by nomogram and actual observation. Moreover, the C-indices and DCA revealed that the nomogram provided better clinical benefit compared with the BCLC stage, CLIP score, and AJCC 7th edition.

CONCLUSIONS

The prognostic nomogram constructed on laminin represents a superior predictive model.

Hepatic stellate cells: central modulators of hepatic carcinogenesis

Hepatocellular carcinoma (HCC) represents the second most common cause of cancer-related death worldwide, and is increasing in incidence. Currently, our therapeutic repertoire for the treatment of HCC is severely limited, and therefore effective new therapies are urgently required. Recently, there has been increasing interest focusing on the cellular and molecular interactions between cancer cells and their microenvironment. HCC represents a unique opportunity to study the relationship between a diseased stroma and promotion of carcinogenesis, as 90 % of HCCs arise in a cirrhotic liver. Hepatic stellate cells (HSC) are the major source of extracellular proteins during fibrogenesis, and may directly, or via secreted products, contribute to tumour initiation and progression. In this review we explore the complex cellular and molecular interplay between HSC biology and hepatocarcinogenesis. We focus on the molecular mechanisms by which HSC modulate HCC growth, immune cell evasion and angiogenesis. This is followed by a discussion of recent progress in the field in understanding the mechanistic crosstalk between HSC and HCC, and the pathways that are potentially amenable to therapeutic intervention. Furthermore, we summarise the exciting recent developments in strategies to target HSC specifically, and novel techniques to deliver pharmaceutical agents directly to HSC, potentially allowing tailored, cell-specific therapy for HCC.

TSC2 modulates cell adhesion and migration via integrin-α1β1

Recent evidence suggests that the rare and progressive lung disease lymphangioleiomyomatosis (LAM) is metastatic in nature. Dysfunction of the tumor suppressor genes tuberous sclerosis complex (TSC), in particular mutational inactivation of TSC2, enhances both cell proliferation and migration. Although substantial progress has been made in understanding the role of TSC2 in abnormal LAM cell proliferation and its pharmacological targeting, the mechanisms underlying the enhanced migratory capacity in LAM are not well understood. In this study, we examined the role of TSC2 in cell attachment, spreading, and migration, processes that contribute to the metastatic phenotype. Here we show that loss of TSC2 increased both the attachment and spreading of mouse embryonic fibroblasts to the extracellular matrix proteins collagen type I and fibronectin and that reexpression of TSC2 reduced these effects. Integrin-α1β1 modulated cell migration with the β1-subunit involved in cell attachment and spreading as shown by using functional blocking antibodies. Loss of TSC2 increased integrin-α1 expression, and inhibition of this integrin subunit reduced cell migration. The enhanced attachment and spreading were independent of the intracellular signaling pathways mammalian target of rapamycin complex 1 and Rho-associated kinase, as pharmacological inhibition with rapamycin or Y27632, respectively, was without effect. Together, these data demonstrate that TSC2 controls cell migration, attachment, and spreading through the α1β1-integrin receptor and thus suggest a potential therapeutic target for the treatment of increased cell invasiveness in LAM.

Matrix metalloproteinase-2 cleavage of the β1 integrin ectodomain facilitates colon cancer cell motility

Cancer cell invasion is a key element in metastasis that requires integrins for adhesion/de-adhesion, as well as matrix metalloproteinases (MMPs) for focalized proteolysis. Herein we show that MMP-2 is up-regulated in resected colorectal tumors and degrades β1 integrins with the release of fragments containing the β1 I-domain. The β1 cleavage pattern is similar to that produced by digestion of α5β1 and α2β1 with MMP-2. Two such fragments, at 25 and 75 kDa, were identified after immunoprecipitation, with monoclonal antibody BD610468 reacting with the NH(2)-terminal I-like ectodomain followed by SDS-PAGE and microsequencing using electrospray (ISI-Q-TOF-Micromass) spectrometry. Cleavage of the β1 integrin can be abolished by inhibition of MMP-2 activity; it can be induced by up-regulation of MMP-2 expression, as exemplified by HT29 colon cancer cells transfected with pCMV6-XL5-MMP-2. Co-immunoprecipitation studies of colon cancer cells showed that the β1 integrin subunit is associated with MMP-2. The MMP-2-mediated shedding of the I-like domain from β1 integrins resulted in decreased adhesion of colon cancer cells to collagen and fibronectin, thus abolishing their receptivity. Furthermore, such cells showed enhanced motility as evaluated by a "wound healing-like" assay and time-lapse microscopy, indicating their increased invasiveness. Altogether, our data demonstrate that MMP-2 amplifies the motility of colon cancer cells, not only by digesting the extracellular matrix components in the vicinity of cancer cells but also by inactivating their major β1 integrin receptors.

Icariin attenuates cardiac remodelling through down-regulating myocardial apoptosis and matrix metalloproteinase activity in rats with congestive heart failure

Objectives

In this study, the anti-heart failure effect of icariin, a natural flavonol glycoside, and the underlying mechanisms were investigated.

Methods

Heart failure was induced by isoproterenol in male Sprague–Dawley rats. Matrix metalloproteinase activity was determined by gelatin zymography assay. The mRNA expression was determined by real-time PCR. The protein expression was determined by Western bolt. Mitochondria structure was examined by transmission electron microscopy.

Key findings

Isoproterenol administration resulted in a severe heart failure, as shown by the increased levels of left ventricular weight index, heart rate, left ventricular end diastolic pressure, maximal rate of left ventricular pressure decline (dp/dtmin), decreased levels of left ventricular systolic pressure and maximal rate of left ventricular pressure rise (dp/dtmax). Against these, icariin dose-dependently reversed the changes of these cardiac morphometric and haemodynamic parameters. In addition, icariin significantly inhibited serum levels of tumour necrosis factor-α, noradrenaline, angiotensin II and brain natriuretic peptide in rats with congestive hear failure and improved the histological changes, including cardiocyte hypertrophy, cardiocyte degeneration, inflammatory infiltration and cardiac desmoplasia. Furthermore, the expression and activity of matrix metalloproteinase (MMP)-2 and MMP-9, which regulate collagen production, were also blocked by icariin. Moreover, myocardial apoptosis was remarkably attenuated by icariin through regulating Bcl-2/Bax axle.

Conclusions

Icariin ameliorates left ventricular dysfunction and cardiac remodelling through down-regulating matrix metalloproteinase-2 and 9 activity and myocardial apoptosis in rats with congestive heart failure.

DNAzymes to mouse beta1 integrin mRNA in vivo: targeting the tumor vasculature and retarding cancer growth

Previously, we designed a DNAzyme (beta1DE) targeting the human beta1 integrin subunit, which efficiently digested the mRNA of the beta1 integrin subunit and downregulated beta1 integrin expression in endothelial cells. This DNAzyme blocked the adhesion of endothelial cells and abolished their ability to form microcapillary tubes in Matrigel. In our present study, we demonstrate that beta1DE effectively inhibited neovascularization in Matrigel plugs (BALB/c mice, n=20) and solid human carcinoma tumors developed in nude mice (BALB/cA nude (nu-/-)-B6.Cg-Foxn1(nu)) (n=30) using prostate carcinoma cells PC-3 (n=15) and colon adenocarcinoma cells CX1.1 (n=15). When injected intratumorally, it significantly reduced the tumor size and number of microvessels developed by both CX1.1 and PC-3 cells within the 3 weeks of experiment duration. Thus, DNAzymes targeting beta1 integrin genes can inhibit multiple key tumorigenic processes in vitro and in vivo and may serve as useful anti-cancer agents.

Experimental study on transarterial administration of GRGDSP combined with transarterial chemoembolization in rats with hepatic carcinoma

PURPOSE

To evaluate the effects of transarterial administration of an integrin antagonist, GRGDSP (Gly-Arg-Gly-Asp-Ser-Pro), combined with transarterial chemoembolization (TACE) to treat hepatic carcinoma in rats.

METHODS

Walker-256 tumor was implanted beneath the liver capsule in 26 Wistar rats. Animal subjects were assigned to groups based on which treatment was injected into the hepatic artery: group A, GRGDSP + TACE; group B, TACE alone; and group C, normal saline. Magnetic resonance imaging (MRI), tumor pathology, and immunohistochemistry were performed to assess each treatment.

RESULTS

The ratios of the post-treatment to pretreatment tumor volumes (V2/V1) in groups A, B, and C were 4.42 +/- 0.48, 6.98 +/- 1.09, and 13.00 +/- 1.68, respectively. The metastatic potential of the tumors was assessed by tumor cell nest counts, which were 5.00 +/- 1.25, 6.63 +/- 1.60, and 7.22 +/- 1.92 in groups A, B, and C, respectively. Microvessel density (MVD) was quantified by measuring von Willebrand factor density values, which were 0.18 +/- 0.02, 0.22 +/- 0.02, and 0.23 +/- 0.02 in groups A, B, and C, respectively.

CONCLUSIONS

Transarterial infusion of GRGDSP combined with TACE noticeably inhibited the growth of hepatic carcinoma and intrahepatic metastases in rats.

Osmoregulation of bile formation

Bile secretion by liver parenchymal cells is the result of vectorial transcellular transport of solutes and involves the coordinated action of transport proteins at the basolateral (sinusoidal) and apical (canalicular) membranes of the hepatocyte. A complex network of signals controls uptake and efflux transporters on a long- and a short-term timescale, including regulation at the level of gene transcription, protein translation and maturation, covalent modification, and dynamic localization of transporter proteins, as well as substrate availability. Evidence has shown that the hepatocellular hydration state exerts powerful control on the transcellular transport of solutes, such as conjugated bile acids and glucuronide and glutathione conjugates. This is of physiological significance because liver cell hydration is a dynamic parameter, which changes within minutes under the influence of hormones, nutrients, and oxidative stress. Thus, osmoregulation of bile formation is of physiological and pathophysiological interest.

Role of four major components in the effect of Si-Ni-San, a traditional Chinese prescription, against contact sensitivity in mice

Previously, we demonstrated the inhibitory effects of Si-Ni-San, a traditional Chinese prescription, on picryl chloride-induced ear contact sensitivity (PCl-CS). This study aimed to evaluate the role of the four major constituents contained in the prescription (saikosaponins, paeoniflorin, naringin and glycyrrhizin) in the inhibitory effect. When administered during the induction phase, saikosaponin a and glycyrrhizin showed significant inhibitory effects, while paeoniflorin and naringin did not. These components in Si-Ni-San also inhibited the activation and proliferation of T lymphocytes as well as the production of cytokines such as tumour necrosis factor-alpha and interferon-gamma to different extents. Saikosaponin a and paeoniflorin dose-dependently reduced the splenocyte adhesion to type I collagen, while glycyrrhizin only showed a slight tendency. Furthermore, treatment with glycyrrhizin or saikosaponin a, rather than paeoniflorin or naringin, moderately inhibited the matrix metalloproteinase (MMP)-2 activity of the splenocytes from PCl-CS mice, and the combination of all four components showed a strong inhibition against MMP-2. Moreover, the components markedly decreased the serum level of nitric oxide in PCl-sensitized mice. The results indicated that saikosaponin a and glycyrrhizin may be the major contributors in the alleviation effect of Si-Ni-San on contact sensitivity, and paeoniflorin and naringin may exhibit a co-operative effect.

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Nitric oxide inhibits T cell adhesion and migration by down-regulation of β1-integrin expression in immunologically liver-injured mice

Our previous study has reported that nitric oxide (NO) exerts a protective role in immunologically liver-injured mice induced by delayed-type hypersensitivity to picryl chloride. To explore the mechanism of the protection, we have now examined the effect of NO on T cell adhesion and migration. First, we isolated hepatocytes and nonparenchymal cells from the liver-injured mice and separated the nonparenchymal cells into Kupffer cell-enriched and lymphocyte-enriched populations. When these hepatocytes or the fractions of nonparenchymal cells were co-cultured with spleen T cells of the liver-injured mice in a Transwell system, the adhesive potential of the T cells was significantly inhibited in the presence of hepatocytes or the Kupffer cell-enriched population but not the lymphocyte-enriched population of nonparenchymal cells. This effect was dependent on NO production. The NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA) could reverse this inhibition of cell adhesion and also decrease NO production. To confirm this effect of NO on T cells, we further examined the role of exogenous or endogenous NO on the adhesive activity of the Jurkat T cell line. As a result, the NO donor, S-nitroso-N-acetyl penicillamine (SNAP) caused a dose-dependent inhibition of the adhesion of Jurkat T cells. Furthermore, the binding ability of Jurkat T cells to collagen decreased gradually after co-incubation with macrophages stimulated by LPS+IFN-gamma, an effect which correlated well with the increasing NO level in the medium. Such opposite changes in cell adhesion and in NO production were also markedly reversed by L-NMMA. Moreover, treatment with SNAP reduced adhesion, transmigration, matrix metalloproteinase-9 production and beta1-integrin expression of spleen T cells of the liver-injured mice. Taken together, these findings suggest that NO can function as a down-regulator of T cell mobility, which might be one of the mechanisms by which NO exerts its protective effect in T cell-mediated liver injury.

Selective depletion of glycyrrhizin from Si-Ni-San, a traditional Chinese prescription, blocks its effect on contact sensitivity in mice and recovers adhesion and metalloproteinases production of T lymphocytes

In the present study, we performed to selectively deplete glycyrrhizin from Si-Ni-San, a traditional Chinese prescription that consists of 4 Chinese herbs including Radix Glycyrrhizae Uralensis, and examined its influence on the suppressing activity of Si-Ni-San against contact sensitivity in mice. An immunoaffinity column was made by covalently coupling the polyclonal antibody, obtained by the immunization with glycyrrhizin–BSA conjugate, to CNBr-activated Sepharose 4B. By using this column, glycyrrhizin in Si-Ni-San was selectively and almost completely depleted from the whole extract, which was confirmed by high-performance liquid chromatography (HPLC). Both 200 mg/kg of Si-Ni-San and 10 mg/kg of glycyrrhizin, the dose corresponding to its proportion contained in Si-Ni-San, significantly reduced the ear swelling of picryl chloride (PCl)-induced ear contact sensitivity in mice and the inhibition by Si-Ni-San was stronger than that by glycyrrhizin. The adhesion activity to type IV collagen of the isolated spleen cells from PCl-sensitized mice was significantly decreased by both Si-Ni-San and glycyrrhizin. However, the glycyrrhizin-depleted sample of Si-Ni-San (Si-Ni-San^GL−) only showed a slight inhibition on the cell adhesion. Furthermore, the spleen cells from PCl-sensitized mice produced more matrix metalloproteinase (MMP)-2 and -9 than naive spleen cells did, and both Si-Ni-San and glycyrrhizin remarkably reduced MMP-2 and MMP-9 production. In contrast, Si-Ni-San^GL− only showed a slight inhibition. These results suggest that glycyrrhizin may act as one of the active constituents of Si-Ni-San in inhibiting delayed-type hypersensitivity reaction via down-regulating the MMP production and the cell adhesion to extracellular matrix. The present study also provides a new approach to recognize and validate an active constituent in traditional prescription through a selective depletion.

Aqueous extract from aerial parts of Artemisia vestita, a traditional Tibetan medicine, reduces contact sensitivity in mice by down-regulating the activation, adhesion and metalloproteinase production of T lymphocytes

In the present paper, the effect of the aqueous extract from aerial parts of Artemisia vestita (AV-ext), a traditional Tibetan medicine, on ear contact sensitivity was examined. AV-ext significantly reduced the ear swelling when administered during the induction phase of picryl-chloride (PCl)-induced ear contact sensitivity in mice. The extract also showed a dose-dependent inhibition on lymphocyte proliferation and IL-2 production in Con A-activated spleen cells. The proliferation inhibition was confirmed in the mixed lymphocytes reaction. Furthermore, the adhesion of the isolated spleen cells from PCl-sensitized mice to type IV collagen was significantly decreased in a dose-dependent manner by AV-ext. Such decrease was also seen in AV-ext-treated Jurkat T cells and the T cells purified from above spleen cells. The purified spleen T cells from PCl-sensitized mice produced more matrix metalloproteinase-9 (MMP-9) than naive T cells, and AV-ext remarkably reduced MMP-9 production both in vivo and in vitro. These results suggest that AV-ext may alleviate contact sensitivity through blocking the activation of T lymphocytes and decreasing their localization to the inflammatory sites via down-regulating the potential of cell adhesion and metalloproteinase production.

Si-Ni-San, a traditional Chinese prescription, and its drug-pairs suppress contact sensitivity in mice via inhibition of the activity of metalloproteinases and adhesion of T lymphocytes

In this paper, the effect of Si-Ni-San, a famous traditional Chinese prescription, on ear contact sensitivity was examined. Si-Ni-San significantly inhibited the ear swelling when administered during the induction phase of picryl-chloride-induced ear contact sensitivity in mice. The adhesion to type I collagen of isolated spleen cells was significantly decreased in the Si-Ni-San group, especially in the presence of protein kinase C activator, phorbol 12,13-dibutyrate. The inhibition of adhesion was seen in purified T cells from the spleen, as well as in Jurkat cells. Furthermore, the adhesion to collagen involves the production of matrix metalloproteinase-2 and -9 in spleen cells, and the oral administration of Si-Ni-San remarkably reduced the matrix metalloproteinase production. Three drug-pairs composed in Si-Ni-San were used for comparison. The combination of Chaihu and Shaoyao showed a similar effect to Si-Ni-San, while Chaihu and Zhishi, and Shaoyao and Gancao only showed a tendency in most situations. These results suggest that Si-Ni-San may contribute to the treatment of immunologically related diseases by down-regulating the activation and function of T lymphocytes, especially the cell adhesion and matrix metalloproteinase production. Its effect is mainly displayed by the combination of Chaihu and Shaoyao.

Tumoral angiogenesis and tissue factor expression during hepatocellular carcinoma progression in a transgenic mouse model

BACKGROUND/AIMS

The hypervascularity described in hepatocellular carcinoma varies according to the progression and the differentiation of the tumor, suggesting an angiogenic switch during tumor development.

METHODS

We used a transgenic mouse model of hepatocellular carcinoma induced by the expression of SV40-T antigen, in which male mice developed hepatic tumors at various temporal and histological stages, whereas female mice remained tumor-free. We analyzed, by immunostaining and reverse transcription-polymerase chain reaction, factors involved in tumoral angiogenesis.

RESULTS

We demonstrated that tumoral angiogenesis occurred before the development of diffuse hepatocarcinoma. We showed that some SV40-T-positive cells with an endothelial phenotype are involved in angiogenic processes, suggesting a partial vasculogenic mimicry. This tumoral angiogenesis is associated with platelet activation due to tissue factor expression in endothelial cells and invading macrophages. Normal and transgenic livers exhibited different pattern of expression of hypoxia-inducible factor 1 alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) mRNA.

CONCLUSIONS

This model of hepatocellular carcinoma displays marked tumoral angiogenesis, with proliferation, remodeling and arterialization of hepatic sinusoids, probably associated with a partial vasculogenic mimicry. Abnormal angiogenesis observed in hepatocarcinoma was associated with platelet activation by tissue factor (TF) produced by endothelial cells and invading macrophages. In this transgenic model, HIF-1alpha, VEGF, and TF play a crucial role in tumoral angiogenesis.

Composition options for tissue-engineered bone

The logical assembly of tissue-engineered bone is ultimately directed by the clinical status of the patient. The basic elements for tissue-engineered bone should include signaling molecules, cells, and extracellular matrix. The assembly of these basic elements may need to be modified by tissue engineers to account for patient variables of age, gender, health, systemic conditions, habits, and anatomical implant. Moreover, different regions of the body will have different functional loads and vascularity. This review discusses several basic options that may be necessary to engineer bone, including spatial and temporal assembly of signaling factors, cells, and biomimetic extracellular matrices. Moreover, the importance of the health care status of the patient who may be receiving the tissue-engineered composition is emphasized.