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

Pan-cancer analysis of the oncogenic role of the core osteosarcoma gene VCAN in human tumors

OBJECTIVE

Versican (VCAN), a member of the multifunctional glycoprotein family, is involved in various aspects of cancer progression. However, the role of VCAN in diverse cancers remains poorly defined. This research aimed to investigate the correlation between VCAN expression and the oncogenic role, as well as visualize its prognostic landscape in pan-cancer.

METHODS

Raw data in regard to VCAN expression in cancer patients were acquired from GEO GeneChip public database in NCBI. Besides, we selected microarray data GSE16088 for analysis. We retrieved the genes associated with osteosarcoma (OS) from the OMIM database and identified their intersection with the core module. VCAN was suggested to be a potential marker gene for OS. Subsequently, we conducted Gene Set Enrichment Analysis (GSEA) to explore gene functional enrichment. Moreover, we performed pan-cancer analysis on VCAN to gain a comprehensive understanding of its implications across various cancer types.

RESULTS

The VCAN expression in the tumor tissue was higher than that in normal tissue. Elevated expression of VCAN was associated with high the tumor stage and poor long-term survival. There was a significant positive correlation between VCAN and cancer fibroblasts in all pan cancers. Moreover, FBN1 was the intersection gene of VCAN-related genes and linker genes. ANTXR1, COL5A2, CSGALNACT2, and SPARC were the target genes of VCAN genes. GSEA analysis showed that VCAN was mainly enriched in the extracellular matrix (ECM) signaling pathway.

CONCLUSION

VCAN can be used as a marker molecule for the early diagnosis of OS and holds significance as a molecule in cases of OS with distant metastasis. The ECM signaling pathway may be a core pathway in OS development and distant metastasis. These findings shed new light on therapeutics of cancers.

Quantitative Threshold Determination of Auditory Brainstem Responses in Mouse Models

The auditory brainstem response (ABR) is a scalp recording of potentials produced by sound stimulation, and is commonly used as an indicator of auditory function. However, the ABR threshold, which is the lowest audible sound pressure, cannot be objectively determined since it is determined visually using a measurer, and this has been a problem for several decades. Although various algorithms have been developed to objectively determine ABR thresholds, they remain lacking in terms of accuracy, efficiency, and convenience. Accordingly, we proposed an improved algorithm based on the mutual covariance at adjacent sound pressure levels. An ideal ABR waveform with clearly defined waves I-V was created; moreover, using this waveform as a standard template, the experimentally obtained ABR waveform was inspected for disturbances based on mutual covariance. The ABR testing was repeated if the value was below the established cross-covariance reference value. Our proposed method allowed more efficient objective determination of ABR thresholds and a smaller burden on experimental animals.

A Novel Ex Vivo Bone Culture Model for Regulation of Collagen/Apatite Preferential Orientation by Mechanical Loading

The anisotropic microstructure of bone, composed of collagen fibers and biological apatite crystallites, is an important determinant of its mechanical properties. Recent studies have revealed that the preferential orientation of collagen/apatite composites is closely related to the direction and magnitude of in vivo principal stress. However, the mechanism of alteration in the collagen/apatite microstructure to adapt to the mechanical environment remains unclear. In this study, we established a novel ex vivo bone culture system using embryonic mouse femurs, which enabled artificial control of the mechanical environment. The mineralized femur length significantly increased following cultivation; uniaxial mechanical loading promoted chondrocyte hypertrophy in the growth plates of embryonic mouse femurs. Compressive mechanical loading using the ex vivo bone culture system induced a higher anisotropic microstructure than that observed in the unloaded femur. Osteocytes in the anisotropic bone microstructure were elongated and aligned along the long axis of the femur, which corresponded to the principal loading direction. The ex vivo uniaxial mechanical loading successfully induced the formation of an oriented collagen/apatite microstructure via osteocyte mechano-sensation in a manner quite similar to the in vivo environment.

Templated Three-Dimensional Engineered Bone Matrix as a Model for Breast Cancer Osteolytic Bone Metastasis Process

Purpose

Bone metastasis is one of the common causes of death relative to breast cancer. However, the evolvement of bone niche in cancer progression remains poorly understood. A three-dimensional (3D) engineered bone matrix was developed as an effective biomimetic model to explore the mechanism relative to bone cancer metastasis.

Methods

In the study, a 3D engineered bone matrix was developed via cell biomineralization templated by a biomimetic collagen template. The process of bone metastasis relative to breast cancer was investigated by co-culturing breast cancer MDA-MB-231-GFP cells with pre-osteogenic MC3T3-E1 cells on the 3D bone matrix.

Results

A typical bone matrix was obtained, where mineralized collagen fibers were packed into the bundle to form a 3D engineered bone matrix. As the cancer cells were invading along the way vertical to the alignment of mineralized collagen fiber, the bone matrix gradually became thinner, accompanied with the erosion of Col I and the loss of calcium and phosphorus. As a result, the disassembled structure of mineralized collagen fiber was observed, which may be attributed to osteolytic bone metastasis.

Conclusion

An engineered 3D bone-like matrix was successfully prepared via cell mineralization, which can act as a model for bone metastasis process. The study revealed mineralized collagen fiber disassembled at nanoscale relative to breast cancer cells.

Superior Alignment of Human iPSC-Osteoblasts Associated with Focal Adhesion Formation Stimulated by Oriented Collagen Scaffold

Human-induced pluripotent stem cells (hiPSCs) can be applied in patient-specific cell therapy to regenerate lost tissue or organ function. Anisotropic control of the structural organization in the newly generated bone matrix is pivotal for functional reconstruction during bone tissue regeneration. Recently, we revealed that hiPSC-derived osteoblasts (hiPSC-Obs) exhibit preferential alignment and organize in highly ordered bone matrices along a bone-mimetic collagen scaffold, indicating their critical role in regulating the unidirectional cellular arrangement, as well as the structural organization of regenerated bone tissue. However, it remains unclear how hiPSCs exhibit the cell properties required for oriented tissue construction. The present study aimed to characterize the properties of hiPSCs-Obs and those of their focal adhesions (FAs), which mediate the structural relationship between cells and the matrix. Our in vitro anisotropic cell culture system revealed the superior adhesion behavior of hiPSC-Obs, which exhibited accelerated cell proliferation and better cell alignment along the collagen axis compared to normal human osteoblasts. Notably, the oriented collagen scaffold stimulated FA formation along the scaffold collagen orientation. This is the first report of the superior cell adhesion behavior of hiPSC-Obs associated with the promotion of FA assembly along an anisotropic scaffold. These findings suggest a promising role for hiPSCs in enabling anisotropic bone microstructural regeneration.

Development of orthophosphosilicate glass/poly(lactic acid) composite anisotropic scaffolds for simultaneous reconstruction of bone quality and quantity

Reconstruction of organ-specific architecture is necessary to recover the original organ function. The anisotropic structure of bone tissue is strongly related to the collagen fibril alignment and bone apatite crystal direction. Bone regeneration indicates following two main process; first, restoration of bone mineral density (BMD; bone quantity), and second, restoring bone apatite c-axis orientation (bone quality). In addition to BMD, bone quality is the most important factor among bone mechanical properties. Recovery of the original bone function requires development of novel scaffolds with simultaneous reconstruction of bone quality and quantity. Herein, novel orthophosphosilicate glass (PSG)/poly(lactic acid) composite anisotropic scaffolds were developed to control cell alignment and enhance bone formation, which are important for the simultaneous reconstruction of bone quality and quantity. The strategy to control cell alignment and bone formation involved designing anisotropic scaffolds in combination with the release of therapeutic ions by PSGs. The morphology of fibrous scaffolds containing PSGs was quantitatively designed using electrospinning. This successfully modulated cell alignment and subsequent bone apatite c-axis orientation along the fiber-oriented direction. The released silicate and Mg2+ ions from PSGs in scaffolds improved cell adhesion, proliferation, and calcification. To best of our knowledge, this is the first report demonstrating that the anisotropic scaffolds containing bioactive glasses regenerate bone tissues with simultaneous reconstruction of bone quality and quantity via stimulating osteoblasts by inorganic ions and designing morphology of scaffolds.

Impaired Alignment of Bone Matrix Microstructure Associated with Disorganized Osteoblast Arrangement in Malignant Melanoma Metastasis

Malignant melanoma favors spreading to bone, resulting in a weakened bone with a high fracture risk. Here, we revealed the disorganized alignment of apatite crystals in the bone matrix associated with the homing of cancer cells by developing an artificially controlled ex vivo melanoma bone metastasis model. The ex vivo metastasis model reflects the progressive melanoma cell activation in vivo, resulting in decreased bone mineral density and expression of MMP1-positive cells. Moreover, less organized intercellular connections were observed in the neighboring osteoblasts in metastasized bone, indicating the abnormal and randomized organization of bone matrix secreted by disconnected osteoblasts. Our study revealed that the deteriorated microstructure associated with disorganized osteoblast arrangement was a determinant of malignant melanoma-related bone dysfunction.

A Novel Role of Interleukin-6 as a Regulatory Factor of Inflammation-Associated Deterioration in Osteoblast Arrangement

Inflammatory disorders are associated with bone destruction; that is, deterioration in bone cell activities are under the control of the innate immune system. Macrophages play a central role in innate immunity by switching their polarized phenotype. A disturbed immune system causes aberrance in the ordered bone matrix microarrangement, which is a dominant determinant of bone tissue functionalization. However, the precise relationship between the immune system and bone tissue organization is unknown. In this study, the controlled in vitro co-culture assay results showed that M1-polarized macrophages disrupted the osteoblast alignment, which directly modulate the oriented bone matrix organization, by secreting pro-inflammatory cytokines. Notably, interleukin-6 was found to be a key regulator of unidirectional osteoblast alignment. Our results demonstrated that inflammatory diseases triggered bone dysfunction by regulating the molecular interaction between the immune system and bone tissue organization. These findings may contribute to the development of therapeutic targets for inflammatory disorders, including rheumatoid arthritis.

3D Printing of Anisotropic Bone-Mimetic Structure with Controlled Fluid Flow Stimuli for Osteocytes: Flow Orientation Determines the Elongation of Dendrites

Although three-dimensional (3D) bioprinting techniques enable the construction of various living tissues and organs, the generation of bone-like oriented microstructures with anisotropic texture remains a challenge. Inside the mineralized bone matrix, osteocytes play mechanosensing roles in an ordered manner with a well-developed lacunar-canaliculi system. Therefore, control of cellular arrangement and dendritic processes is indispensable for construction of artificially controlled 3D bone-mimetic architecture. Herein, we propose an innovative methodology to induce controlled arrangement of osteocyte dendritic processes using the laminated layer method of oriented collagen sheets, combined with a custom-made fluid flow stimuli system. Osteocyte dendritic processes showed elongation depending on the competitive directional relationship between flow and substrate. To the best of our knowledge, this study is the first to report the successful construction of the anisotropic bone-mimetic microstructure and further demonstrate that the dendritic process formation in osteocytes can be controlled with selective fluid flow stimuli, specifically by regulating focal adhesion. Our results demonstrate how osteocytes adapt to mechanical stimuli by optimizing the anisotropic maturation of dendritic cell processes.

Pathological Crosstalk between Metastatic Breast Cancer Cells and the Bone Microenvironment

Bone is the most common metastatic site in breast cancer. Upon arrival to the bone, disseminated tumor cells can undergo a period of dormancy but often eventually grow and hijack the bone microenvironment. The bone marrow microenvironment consists of multiple cell types including the bone cells, adipocytes, endothelial cells, and nerve cells that all have crucial functions in the maintenance of bone homeostasis. Tumor cells severely disturb the tightly controlled cellular and molecular interactions in the bone marrow fueling their own survival and growth. While the role of bone resorbing osteoclasts in breast cancer bone metastases is well established, the function of other bone cells, as well as adipocytes, endothelial cells, and nerve cells is less understood. In this review, we discuss the composition of the physiological bone microenvironment and how the presence of tumor cells influences the microenvironment, creating a pathological crosstalk between the cells. A better understanding of the cellular and molecular events that occur in the metastatic bone microenvironment could facilitate the identification of novel cellular targets to treat this devastating disease.

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.

Bone apatite anisotropic structure control via designing fibrous scaffolds

Bone tissue has an anisotropic structure, associated with the collagen fibrils' orientation and the c-axis direction of the bone apatite crystal. The bone regeneration process comprises two main phases: bone mineral density restoration (bone quantity), and subsequent recovery of bone apatite c-axis orientation (bone quality). Bone quality is the determinant factor for mechanical properties of bone. Control of osteoblast alignment is one of the strategies for reconstructing bone quality since the collagen/apatite matrix orientation in calcified tissues is dependent on the osteoblast orientation. In this work, fibrous scaffolds designed for reconstruction of bone quality via cell alignment control was investigated. The fibrous scaffolds were fabricated using the electrospinning method with poly(lactic acid) at various fiber collecting speeds. The degree of fiber alignment in the prepared fibrous scaffolds increased with increasing fiber collecting speed, indicating that the fibers were oriented in a single direction. The alignment of osteoblasts on the fibrous scaffolds as well as the subsequent apatite c-axis orientation increased with increasing fiber collecting speed. We successfully controlled cell alignment and apatite c-axis orientation using the designed morphology of fibrous scaffolds. To the best of our knowledge, this is the first report demonstrating that adjusting the degree of fiber orientation for fibrous scaffolds can manipulate the regeneration of bone quality.

Osteoblast alignment on the fibrous scaffolds as well as the subsequent apatite c-axis orientation increased with increasing fiber collecting speed. We successfully controlled cell alignment and apatite c-axis orientation using the designed morphology of fibrous scaffolds.

Extracellular Matrix Alterations in Metastatic Processes

The extracellular matrix (ECM) is a complex network of extracellular-secreted macromolecules, such as collagen, enzymes and glycoproteins, whose main functions deal with structural scaffolding and biochemical support of cells and tissues. ECM homeostasis is essential for organ development and functioning under physiological conditions, while its sustained modification or dysregulation can result in pathological conditions. During cancer progression, epithelial tumor cells may undergo epithelial-to-mesenchymal transition (EMT), a morphological and functional remodeling, that deeply alters tumor cell features, leading to loss of epithelial markers (i.e., E-cadherin), changes in cell polarity and intercellular junctions and increase of mesenchymal markers (i.e., N-cadherin, fibronectin and vimentin). This process enhances cancer cell detachment from the original tumor mass and invasiveness, which are necessary for metastasis onset, thus allowing cancer cells to enter the bloodstream or lymphatic flow and colonize distant sites. The mechanisms that lead to development of metastases in specific sites are still largely obscure but modifications occurring in target tissue ECM are being intensively studied. Matrix metalloproteases and several adhesion receptors, among which integrins play a key role, are involved in metastasis-linked ECM modifications. In addition, cells involved in the metastatic niche formation, like cancer associated fibroblasts (CAF) and tumor associated macrophages (TAM), have been found to play crucial roles in ECM alterations aimed at promoting cancer cells adhesion and growth. In this review we focus on molecular mechanisms of ECM modifications occurring during cancer progression and metastatic dissemination to distant sites, with special attention to lung, liver and bone. Moreover, the functional role of cells forming the tumor niche will also be reviewed in light of the most recent findings.