An in vitro 3D bone metastasis model by using a human bone tissue culture and human sex-related cancer cells

A mechanobiological model of bone metastasis reveals that mechanical stimulation inhibits the pro-osteolytic effects of breast cancer cells

Bone is highly susceptible to cancer metastasis, and both tumor and bone cells enable tumor invasion through a "vicious cycle" of biochemical signaling. Tumor metastasis into bone also alters biophysical cues to both tumor and bone cells, which are highly sensitive to their mechanical environment. However, the mechanobiological feedback between these cells that perpetuate this cycle has not been studied. Here, we develop highly advanced in vitro and computational models to provide an advanced understanding of how tumor growth is regulated by the synergistic influence of tumor-bone cell signaling and mechanobiological cues. In particular, we develop a multicellular healthy and metastatic bone model that can account for physiological mechanical signals within a custom bioreactor. These models successfully recapitulated mineralization, mechanobiological responses, osteolysis, and metastatic activity. Ultimately, we demonstrate that mechanical stimulus provided protective effects against tumor-induced osteolysis, confirming the importance of mechanobiological factors in bone metastasis development.

Volumetric Tissue Imaging of Surgical Tissue Specimens Using Micro-Computed Tomography: An Emerging Digital Pathology Modality for Nondestructive, Slide-Free Microscopy-Clinical Applications of Digital Pathology in 3 Dimensions

OBJECTIVES

Micro-computed tomography (micro-CT) is a novel, nondestructive, slide-free digital imaging modality that enables the acquisition of high-resolution, volumetric images of intact surgical tissue specimens. The aim of this systematic mapping review is to provide a comprehensive overview of the available literature on clinical applications of micro-CT tissue imaging and to assess its relevance and readiness for pathology practice.

METHODS

A computerized literature search was performed in the PubMed, Scopus, Web of Science, and CENTRAL databases. To gain insight into regulatory and financial considerations for performing and examining micro-CT imaging procedures in a clinical setting, additional searches were performed in medical device databases.

RESULTS

Our search identified 141 scientific articles published between 2000 and 2021 that described clinical applications of micro-CT tissue imaging. The number of relevant publications is progressively increasing, with the specialties of pulmonology, cardiology, otolaryngology, and oncology being most commonly concerned. The included studies were mostly performed in pathology departments. Current micro-CT devices have already been cleared for clinical use, and a Current Procedural Terminology (CPT) code exists for reimbursement of micro-CT imaging procedures.

CONCLUSIONS

Micro-CT tissue imaging enables accurate volumetric measurements and evaluations of entire surgical specimens at microscopic resolution across a wide range of clinical applications.

Modelling skeletal pain harnessing tissue engineering

Bone pain typically occurs immediately following skeletal damage with mechanical distortion or rupture of nociceptive fibres. The pain mechanism is also associated with chronic pain conditions where the healing process is impaired. Any load impacting on the area of the fractured bone will stimulate the nociceptive response, necessitating rapid clinical intervention to relieve pain associated with the bone damage and appropriate mitigation of any processes involved with the loss of bone mass, muscle, and mobility and to prevent death. The following review has examined the mechanisms of pain associated with trauma or cancer-related skeletal damage focusing on new approaches for the development of innovative therapeutic interventions. In particular, the review highlights tissue engineering approaches that offer considerable promise in the application of functional biomimetic fabrication of bone and nerve tissues. The strategic combination of bone and nerve tissue engineered models provides significant potential to develop a new class of in vitro platforms, capable of replacing in vivo models and testing the safety and efficacy of novel drug treatments aimed at the resolution of bone-associated pain. To date, the field of bone pain research has centred on animal models, with a paucity of data correlating to the human physiological response. This review explores the evident gap in pain drug development research and suggests a step change in approach to harness tissue engineering technologies to recapitulate the complex pathophysiological environment of the damaged bone tissue enabling evaluation of the associated pain-mimicking mechanism with significant therapeutic potential therein for improved patient quality of life.

Graphical abstract

Rationale underlying novel drug testing platform development. Pain detected by the central nervous system and following bone fracture cannot be treated or exclusively alleviated using standardised methods. The pain mechanism and specificity/efficacy of pain reduction drugs remain poorly understood. In vivo and ex vivo models are not yet able to recapitulate the various pain events associated with skeletal damage. In vitro models are currently limited by their inability to fully mimic the complex physiological mechanisms at play between nervous and skeletal tissue and any disruption in pathological states. Robust innovative tissue engineering models are needed to better understand pain events and to investigate therapeutic regimes.

Advancing Treatment of Bone Metastases through Novel Translational Approaches Targeting the Bone Microenvironment

Bone metastases represent a lethal condition that frequently occurs in solid tumors such as prostate, breast, lung, and renal cell carcinomas, and increase the risk of skeletal-related events (SREs) including pain, pathologic fractures, and spinal cord compression. This unique metastatic niche consists of a multicellular complex that cancer cells co-opt to engender bone remodeling, immune suppression, and stromal-mediated therapeutic resistance. This review comprehensively discusses clinical challenges of bone metastases, novel preclinical models of the bone and bone marrow microenviroment, and crucial signaling pathways active in bone homeostasis and metastatic niche. These studies establish the context to summarize the current state of investigational agents targeting BM, and approaches to improve BM-targeting therapies. Finally, we discuss opportunities to advance research in bone and bone marrow microenvironments by increasing complexity of humanized preclinical models and fostering interdisciplinary collaborations to translational research in this challenging metastatic niche.

Engineering the early bone metastatic niche through human vascularized immuno bone minitissues

Bone metastases occur in 65%-80% advanced breast cancer patients. Although significant progresses have been made in understanding the biological mechanisms driving the bone metastatic cascade, traditional 2Din vitromodels and animal studies are not effectively reproducing breast cancer cells (CCs) interactions with the bone microenvironment and suffer from species-specific differences, respectively. Moreover, simplifiedin vitromodels cannot realistically estimate drug anti-tumoral properties and side effects, hence leading to pre-clinical testing frequent failures. To solve this issue, a 3D metastatic bone minitissue (MBm) is designed with embedded human osteoblasts, osteoclasts, bone-resident macrophages, endothelial cells and breast CCs. This minitissue recapitulates key features of the bone metastatic niche, including the alteration of macrophage polarization and microvascular architecture, along with the induction of CC micrometastases and osteomimicry. The minitissue reflects breast CC organ-specific metastatization to bone compared to a muscle minitissue. Finally, two FDA approved drugs, doxorubicin and rapamycin, have been tested showing that the dose required to impair CC growth is significantly higher in the MBm compared to a simpler CC monoculture minitissue. The MBm allows the investigation of metastasis key biological features and represents a reliable tool to better predict drug effects on the metastatic bone microenvironment.

Development and characterization of a novel human 3D model of bone metastasis from breast carcinoma in vitro cultured

Breast cancer frequently metastasizes to the skeleton causing significant morbidity. None of the therapeutic strategies used to manage breast cancer bone metastases are really curative. Here, we set-up a novel and advanced model by using fresh tissue from human vertebral bone metastasis from breast carcinoma patients able to retain the tumor microenvironment. The tissue model is based on an ex-vivo culture for up to 40 days and on a constant monitoring of tissue viability, gene expression profile (IL10, IL1b, MMP1, MMP7, PTH1R, PTH2R, TNF, ACP5, SPI1, VEGFA, CTSK, TGF-β) and histological and immunohistochemical analyses (CDH1/E-cadherin, CDH2/N-cadherin, KRT8/Cytokeratin 8, KRT18/Cytokeratin 18, Ki67, CASP3/Caspase 3, ESR1/Estrogen Receptor Alpha, CD68 and CD8). Results confirmed the development of a reliable, reproducible and cost-effective advanced model of breast cancer bone metastasis able to preserve and maintain long-term tissue viability, as well as molecular markers, tissue histomorphology, tissue micro-architecture and antigen expression. The study provides for the first time the feasibility and rationale for the use of a human-derived advanced alternative model for cancer research and testing of drugs and innovative strategies, taking into account patient individual characteristics and specific tumor subtypes so predicting patient specific responses.

Ex vivo Bone Models and Their Potential in Preclinical Evaluation

PURPOSE OF REVIEW

Novel therapies for damaged and diseased bone are being developed in a preclinical testing process consisting of in vitro cell experiments followed by in vivo animal studies. The in vitro results are often not representative of the results observed in vivo. This could be caused by the complexity of the natural bone environment that is missing in vitro. Ex vivo bone explant cultures provide a model in which cells are preserved in their native three-dimensional environment. Herein, it is aimed to review the current status of bone explant culture models in relation to their potential in complementing the preclinical evaluation process with specific attention paid to the incorporation of mechanical loading within ex vivo culture systems.

RECENT FINDINGS

Bone explant cultures are often performed with physiologically less relevant bone, immature bone, and explants derived from rodents, which complicates translatability into clinical practice. Mature bone explants encounter difficulties with maintaining viability, especially in static culture. The integration of mechanical stimuli was able to extend the lifespan of explants and to induce new bone formation. Bone explant cultures provide unique platforms for bone research and mechanical loading was demonstrated to be an important component in achieving osteogenesis ex vivo. However, more research is needed to establish a representative, reliable, and reproducible bone explant culture system that includes both components of bone remodeling, i.e., formation and resorption, in order to bridge the gap between in vitro and in vivo research in preclinical testing.

MINDIN Exerts Protumorigenic Actions on Primary Prostate Tumors via Downregulation of the Scaffold Protein NHERF-1

Advanced prostate cancer preferential metastasis to bone is associated with osteomimicry. MINDIN is a secreted matrix protein upregulated in prostate tumors that overexpresses bone-related genes during prostate cancer progression. Na+/H+ exchanger regulatory factor (NHERF-1) is a scaffold protein that has been involved both in tumor regulation and osteogenesis. We hypothesize that NHERF-1 modulation is a mechanism used by MINDIN to promote prostate cancer progression. We analyzed the expression of NHERF-1 and MINDIN in human prostate samples and in a premetastatic prostate cancer mouse model, based on the implantation of prostate adenocarcinoma TRAMP-C1 (transgenic adenocarcinoma of the mouse prostate) cells in immunocompetent C57BL/6 mice. The relationship between NHERF-1 and MINDIN and their effects on cell proliferation, migration, survival and osteomimicry were evaluated. Upregulation of MINDIN and downregulation of NHERF-1 expression were observed both in human prostate cancer samples and in the TRAMP-C1 model. MINDIN silencing restored NHERF-1 expression to control levels in the mouse model. Stimulation with MINDIN reduced NHERF-1 expression and triggered its mobilization from the plasma membrane to the cytoplasm in TRAMP-C1 cells. MINDIN-dependent downregulation of NHERF-1 promoted tumor cell migration and proliferation without affecting osteomimicry and adhesion. We propose that MINDIN downregulates NHERF-1 expression leading to promotion of processes involved in prostate cancer progression.

Relevance of humanized three-dimensional tumor tissue models: a descriptive systematic literature review

Despite numerous advances in tumor screening, diagnosis, and treatment, to date, tumors remain one of the leading causes of death, principally due to metastasis and the physiological damage produced by tumor growth. Among the main limits related to the study of tumor physiology there is the complex and heterogeneity nature of its environment and the absence of relevant, simple and inexpensive models able to mimic the biological processes occurring in patients allowing the correct clinical translation of results. To enhance the understanding of the mechanisms of tumors and to develop and evaluate new therapeutic approaches the set-up of advanced and alternative models is mandatory. One of the more translational approaches seems to be the use of humanized three-dimensional (3D) tissue culture. This model allows to accurately mimic tumor morphology and biology, maintaining the native microenvironment without any manipulation. However, little is still known on the real clinical relevance of these models for the study of tumor mechanisms and for the screening of new therapy. The aim of this descriptive systematic literature review was to evaluate and summarize the current knowledge on human 3D tumor tissue culture models. We reviewed the strategies employed by researchers to set-up these systems, also considering the different approaches and culture conditions used. All these aspects greatly contribute to the existing knowledge on tumors, providing a specific link to clinical scenarios and making the humanized 3D tumor tissue models a more attractive tool both for researchers and clinicians.

Three-Dimensional Cell Cultures as an In Vitro Tool for Prostate Cancer Modeling and Drug Discovery

In the last decade, three-dimensional (3D) cell culture technology has gained a lot of interest due to its ability to better recapitulate the in vivo organization and microenvironment of in vitro cultured cancer cells. In particular, 3D tumor models have demonstrated several different characteristics compared with traditional two-dimensional (2D) cultures and have provided an interesting link between the latter and animal experiments. Indeed, 3D cell cultures represent a useful platform for the identification of the biological features of cancer cells as well as for the screening of novel antitumor agents. The present review is aimed at summarizing the most common 3D cell culture methods and applications, with a focus on prostate cancer modeling and drug discovery.

Use of in vitro bone models to screen for altered bone metabolism, osteopathies, and fracture healing: challenges of complex models

Approx. every third hospitalized patient in Europe suffers from musculoskeletal injuries or diseases. Up to 20% of these patients need costly surgical revisions after delayed or impaired fracture healing. Reasons for this are the severity of the trauma, individual factors, e.g, the patients’ age, individual lifestyle, chronic diseases, medication, and, over 70 diseases that negatively affect the bone quality. To investigate the various disease constellations and/or develop new treatment strategies, many in vivo, ex vivo, and in vitro models can be applied. Analyzing these various models more closely, it is obvious that many of them have limits and/or restrictions. Undoubtedly, in vivo models most completely represent the biological situation. Besides possible species-specific differences, ethical concerns may question the use of in vivo models especially for large screening approaches. Challenging whether ex vivo or in vitro bone models can be used as an adequate replacement for such screenings, we here summarize the advantages and challenges of frequently used ex vivo and in vitro bone models to study disturbed bone metabolism and fracture healing. Using own examples, we discuss the common challenge of cell-specific normalization of data obtained from more complex in vitro models as one example of the analytical limits which lower the full potential of these complex model systems.

Impact of Culture Medium on Cellular Interactions in in vitro Co-culture Systems

Co-culturing of cells in in vitro tissue models is widely used to study how they interact with each other. These models serve to represent a variety of processes in the human body such as development, homeostasis, regeneration, and disease. The success of a co-culture is dependent on a large number of factors which makes it a complex and ambiguous task. This review article addresses co-culturing challenges regarding the cell culture medium used in these models, in particular concerning medium composition, volume, and exchange. The effect of medium exchange on cells is often an overlooked topic but particularly important when cell communication via soluble factors and extracellular vesicles, the so-called cell secretome (CS) is being studied. Culture medium is regularly exchanged to supply new nutrients and to eliminate waste products produced by the cells. By removing medium, important CSs are also removed. After every medium change, the cells must thus restore their auto- and paracrine communication through these CSs. This review article will also discuss the possibility to integrate biosensors into co-cultures, in particular to provide real-time information regarding media composition. Overall, the manner in which culture medium is currently used will be re-evaluated. Provided examples will be on the subject of bone tissue engineering.

Prostate Cancer Phenotype Influences Bone Mineralization at Metastasis: A Study Using an In Vitro Prostate Cancer Metastasis Testbed

In this study, two types of prostate cancer cell lines, highly metastatic PC-3 and low metastatic MDA PCa 2b (PCa) were cultured on bone mimetic scaffolds to recapitulate metastasis to bone. A unique in vitro 3D tumor model that uses a sequential culture (SC) of human mesenchymal stem cells followed by seeding with cancer cells after bone formation was initiated to study the phenotype-specific interaction between prostate cancer cells and bone microenvironment. The PCa cells were observed to be less prolific and less metastatic, and to form multicellular tumoroids in the bone microenvironment, whereas PC-3 cells were more prolific and were highly metastatic, and did not form multicellular tumoroids in the bone microenvironment. The metastatic process exhibited by these two prostate cancer cell lines showed a significant and different effect on bone mineralization and extracellular matrix formation. Excessive bone formation in the presence of PC-3 and significant osteolysis in the presence of PCa were observed, which was also indicated by osteocalcin and MMP-9 expression as measured by ELISA and qRT-PCR. The field emission scanning electron microscopy images revealed that the structure of mineralized collagen in the presence of PC-3 is different than the one observed in healthy bone. All experimental results indicated that both osteolytic and osteoblastic bone lesions can be recapitulated in our tumor testbed model and that different cancer phenotypes have a very different influence on bone at metastasis. The 3D in vitro model presented in this study provides an improved, reproducible, and controllable system that is a useful tool to elucidate osteotropism of prostate cancer cells. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

A Comparison of Osteoblast and Osteoclast In Vitro Co-Culture Models and Their Translation for Preclinical Drug Testing Applications

As the population of western societies on average ages, the number of people affected by bone remodeling-associated diseases such as osteoporosis continues to increase. The development of new therapeutics is hampered by the high failure rates of drug candidates during clinical testing, which is in part due to the poor predictive character of animal models during preclinical drug testing. Co-culture models of osteoblasts and osteoclasts offer an alternative to animal testing and are considered to have the potential to improve drug development processes in the future. However, a robust, scalable, and reproducible 3D model combining osteoblasts and osteoclasts for preclinical drug testing purposes has not been developed to date. Here we review various types of osteoblast-osteoclast co-culture models and outline the remaining obstacles that must be overcome for their successful translation.

Deregulated miRNAs in osteoporosis: effects in bone metastasis

Starting from their role exerted on osteoblast and osteoclast differentiation and activity pathways, microRNAs (miRNAs) have been recently identified as regulators of different processes in bone homeostasis. For this purpose, in a recent review, we highlighted, as deregulated miRNAs could be involved in different bone diseases such as osteoporosis. In addition, recent studies supported the concept that osteoporosis-induced bone alterations might offer a receptive site for cancer cells to form bone metastases, However, to date, no data on specific-shared miRNAs between osteoporosis and bone metastases have been considered and described to clarify the evidence of this link. The main goal of this review is to underline as deregulated miRNAs in osteoporosis may have specific roles in the development of bone metastases. The review showed that several circulating osteoporotic miRNAs could facilitate tumor progression and bone-metastasis formation in several tumor types, i.e., breast cancer, prostate cancer, non-small-cell lung cancer, esophageal squamous cell carcinoma, and multiple myeloma. In detail, serum up-regulation of pro-osteoporotic miRNAs, as well as serum down-regulation of anti-osteoporotic miRNAs are common features of all these tumors and are able to promote bone metastasis. These results are of key importance and could help researcher and clinicians to establish new therapeutic strategies connected with deregulation of circulating miRNAs and able to interfere with pathogenic processes of osteoporosis, tumor progressions, and bone-metastasis formation.

Cell communication and signaling: how to turn bad language into positive one

Cell-to-cell communication has a critical role during tumor development and progression, allowing cancer cell to re-program not only the surrounding tumor microenvironment, but also cells located at distant sites. The crosstalk between neoplastic cells and accessory elements, such as immune and stromal cells, fosters several processes that are necessary for tumor progression and dissemination, such as angiogenesis, immune-escape, epithelial-to-mesenchymal transition, invasion and multi-drug resistance. There are several means by which cells communicate to each other, either by direct cell interactions through membrane receptors and ligands, or by releasing soluble molecules, such as growth factors, cytokines and chemokines. More recently, additional means of cell communication have been identified, such as microRNAs and extracellular vesicles. These two peculiar ways of cell-to-cell interaction were the focus of the 31st Annual Conference of the Italian Association of Cell Cultures (AICC).

Human ex vivo 3D bone model recapitulates osteocyte response to metastatic prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer deaths among American men. Unfortunately, there is no cure once the tumor is established within the bone niche. Although osteocytes are master regulators of bone homeostasis and remodeling, their role in supporting PCa metastases remains poorly defined. This is largely due to a lack of suitable ex vivo models capable of recapitulating the physiological behavior of primary osteocytes. To address this need, we integrated an engineered bone tissue model formed by 3D-networked primary human osteocytes, with conditionally reprogrammed (CR) primary human PCa cells. CR PCa cells induced a significant increase in the expression of fibroblast growth factor 23 (FGF23) by osteocytes. The expression of the Wnt inhibitors sclerostin and dickkopf-1 (Dkk-1), exhibited contrasting trends, where sclerostin decreased while Dkk-1 increased. Furthermore, alkaline phosphatase (ALP) was induced with a concomitant increase in mineralization, consistent with the predominantly osteoblastic PCa-bone metastasis niche seen in patients. Lastly, we confirmed that traditional 2D culture failed to reproduce these key responses, making the use of our ex vivo engineered human 3D bone tissue an ideal platform for modeling PCa-bone interactions.

Dynamic Collision Behavior Between Osteoblasts and Tumor Cells Regulates the Disordered Arrangement of Collagen Fiber/Apatite Crystals in Metastasized Bone

Bone metastasis is one of the most intractable bone diseases; it is accompanied with a severe mechanical dysfunction of bone tissue. We recently discovered that the disorganized collagen/apatite microstructure in cancer-bearing bone is a dominant determinant of the disruption of bone mechanical function; disordered osteoblast arrangement was found to be one of the principal determinants of the deteriorated collagen/apatite microstructure. However, the precise molecular mechanisms regulating the disordered osteoblast arrangement triggered by cancer invasion are not yet understood. Herein, we demonstrate a significant disorganization of bone tissue anisotropy in metastasized bone in our novel ex vivo metastasis model. Further, we propose a novel mechanism underlying the disorganization of a metastasized bone matrix: A dynamic collision behavior between tumor cells and osteoblasts disturbs the osteoblast arrangement along the collagen substrate.

Evaluation of RNA from human trabecular bone and identification of stable reference genes

The isolation of good quality RNA from tissues is an essential prerequisite for gene expression analysis to study pathophysiological processes. This study evaluated the RNA isolated from human trabecular bone and defined a set of stable reference genes. After pulverization, RNA was extracted with a phenol/chloroform method and then purified using silica columns. The A260/280 ratio, A260/230 ratio, RIN, and ribosomal ratio were measured to evaluate RNA quality and integrity. Moreover, the expression of six candidates was analyzed by qPCR and different algorithms were applied to assess reference gene stability. A good purity and quality of RNA was achieved according to A260/280 and A260/230 ratios, and RIN values. TBP, YWHAZ, and PGK1 were the most stable reference genes that should be used for gene expression analysis. In summary, the method proposed is suitable for gene expression evaluation in human bone and a set of reliable reference genes has been identified.

From Chemotherapy to Combined Targeted Therapeutics: In Vitro and in Vivo Models to Decipher Intra-tumor Heterogeneity

Recent advances in next-generation sequencing and other omics technologies capable to map cell fate provide increasing evidence on the crucial role of intra-tumor heterogeneity (ITH) for cancer progression. The different facets of ITH, from genomic to microenvironmental heterogeneity and the hierarchical cellular architecture originating from the cancer stem cell compartment, contribute to the range of tumor phenotypes. Decoding these complex data resulting from the analysis of tumor tissue complexity poses a challenge for developing novel therapeutic strategies that can counteract tumor evolution and cellular plasticity. To achieve this aim, the development of in vitro and in vivo cancer models that resemble the complexity of ITH is crucial in understanding the interplay of cells and their (micro)environment and, consequently, in testing the efficacy of new targeted treatments and novel strategies of tailoring combinations of treatments to the individual composition of the tumor. This challenging approach may be an important cornerstone in overcoming the development of pharmaco-resistances during multiple lines of treatment. In this paper, we report the latest advances in patient-derived 3D (PD3D) cell cultures and patient-derived tumor xenografts (PDX) as in vitro and in vivo models that can retain the genetic and phenotypic heterogeneity of the tumor tissue.