The mechanism of biomineralization: Progress in mineralization from intracellular generation to extracellular deposition

A comprehensive review of recent advancements in microbial-induced mineralization: biosynthesis and mechanism, with potential implementation in various environmental, engineering, and medical sectors

Biomineralization has garnered profuse attention in multidisciplinary fields. Using this strategy, living things, including eukaryotes or prokaryotes, mediate the uptake of ions from the surrounding environment, followed by assembling and depositing them as greatly configured structures inside the organic matrix. The generated biominerals, including nanomaterials, possess outstanding hierarchical structures that exceed their chemically synthesized counterparts. Despite the significant progress achieved in microbial-mediated mineralization, several key knowledge gaps remain, including mechanisms controlling biomineralization pathways and the impact of environmental factors on mineral morphology, crystallinity, and stability. This review provides a comprehensive description of this biomineralization, which can be categorized into controlled, influenced, and induced biomineralization. Interestingly, we highlighted biologically-induced mineralization approaches, such as photosynthesis, methane oxidation, and nitrogen-based metabolic pathways, and identified various chemical interactions during mineral production following analytical chemistry. This review also extensively delineates updates on application of biominerals across all fields, commencing with the remediation of deleterious pollutants and biominerals exploited in industrial sectors, moving on to using them to reinforce soil, generate biocement for construction, and delving into their utilization in pharmaceutical applications to deliver drugs, repair teeth and bones, and combat cancer and pathogenic microorganisms. Moreover, the review outlines the drawbacks and adequate solutions for biomineralization, particularly CaCO₃-mediated processes, such as the generation of ammonium and nitrate during the CaCO₃ precipitation process and the relatively slow rate of microbial-mediated mineralization. Biomineralization inspired the fabrication of smart biomaterials, which combine biological advantages. Overall, this comprehensive review discusses updated research and highlights potential approaches to future studies.

Coupling of Intracellular Calcium Homeostasis and Formation and Secretion of Matrix Vesicles: Their Role in the Mechanism of Biomineralization

The human bone is a dynamic, highly vascularized tissue composed of 60-70% minerals, which include mainly calcium phosphate (CaP) in the form of hydroxyapatite (HA) crystals, 30% organic matrix composed of type I collagen fibers, and less than 5% water and lipids. The crystals are formed inside the matrix vesicles (MVs) and are then released in the organic collagen-based fibrous matrix. Extracellular matrix (ECM) formation and mineralization processes, named osteogenesis, are associated with human mesenchymal stem cells (hMSCs) undergoing differentiation into osteoblasts (osteoblastogenesis). Osteogenesis is regulated by multiple intracellular signaling and genetic pathways and by environmental factors. Calcium flow is finely regulated and plays a key role in both osteoblastogenesis and osteogenesis. The formation and accumulation of CaP, the biogenesis of MVs, their secretion, and the deposition of HA crystals to fill the organic bone matrix are the fundamental events in the biomineralization process. In this paper, I will describe and discuss the recent findings and hypothesis on the molecular mechanism regulating this process.

Ultrafast, cytocompatible mineralization of calcium phosphate in the formation of stratified nanoshells of artificial spores

Spatially controlled confinement of catalytic enzymes within nanoshells holds substantial potential for applications in bioreactors, synthetic cells, and artificial spores. The utilization of amorphous calcium phosphate (CaP) precursors enables the extremely rapid (<5 seconds) construction of thick (∼400 nm) CaP nanoshells, stratified with distinct enzymes, on various tannic acid-primed substrates. Saccharomyces cerevisiae cells are nanoencapsulated with enzyme-embedded, multilayered CaP nanoshells in a cytocompatible manner, providing an advanced chemical tool for interfacing living cells with functional entities in a spatially controlled configuration.

In vitro study on the promotion of osteogenic differentiation by mitochondrial-derived vesicles through activation of inflammation and reprogramming of metabolic pathways

The secretion of mitochondrial-derived vesicles (MDVs) has been found to increase during osteogenic differentiation, but their role in intercellular communication and osteogenic promotion remains unclear. In this study, we extracted translocase of outer mitochondrial membrane 20 (Tomm20) + MDVs from bone marrow stromal cells (BMSCs) at different osteogenic culture days using differential centrifugation and immunoprecipitation, then co-cultured them with BMSCs to assess osteogenic differentiation, immune response and metabolic levels. The results showed that osteogenic differentiation enhances MDVs' secretion and their mitochondrial DNA (mtDNA) content. In promoting osteogenic differentiation ability, osteogenic-induced MDVs (MDV-OMs, especially MDV-OM14 and MDV-OM21) significantly enhance mineralization with OD values 1.37-fold and 1.32-fold higher than those of MDV-OM7 (p < 0.05) after 21 days, respectively. However, these MDVs containing mtDNA activate immune responses by upregulating cGas, Sting, Caspase-9, Il-6, and Tnf-a mRNA levels, inducing cell apoptosis and oxidative stress. In addition, MDVs containing mitochondrial components also have metabolic regulatory functions. Metabolic level detection revealed that MDV-OMs downregulate lactate, promote tricarboxylic acid cycle (TCA) enzyme expression, and increase mitochondrial membrane potential. Among these MDVs, MDV-OM7, induced for 7 days, shows osteogenic function without strong immune response, possibly related to metabolic reprogramming. This study highlights the potential of osteogenic-induced MDVs for bone regeneration, cGAS-STING activation, and metabolic enhancement, and are expected to be used for the treatment of diseases such as tissue damage.

Copper doped bioactive glass promotes matrix vesicles-mediated biomineralization via osteoblast mitophagy and mitochondrial dynamics during bone regeneration

Bone defect repair remains a great challenge in the field of orthopedics. Human body essential trace element such as copper is essential for bone regeneration, but how to use it in bone defects and the underlying its mechanisms of promoting bone formation need to be further explored. In this study, by doping copper into mesoporous bioactive glass nanoparticles (Cu-MBGNs), we unveil a previously unidentified role of copper in facilitating osteoblast mitophagy and mitochondrial dynamics, which enhance amorphous calcium phosphate (ACP) release and subsequent biomineralization, ultimately accelerating the process of bone regeneration. Specifically, by constructing conditional knockout mice lacking the autophagy gene Atg5 in osteogenic lineage cells, we first confirmed the role of Cu-MBGNs-promoted bone formation via mediating osteoblast autophagy pathway. Then, the in vitro studies revealed that Cu-MBGNs strengthened mitophagy by inducing ROS production and recruiting PINK1/Parkin, thereby facilitating the efficient release of ACP from mitochondria into matrix vesicles for biomineralization during bone regeneration. Moreover, we found that Cu-MBGNs promoted mitochondrion fission via activating dynamin related protein 1 (Drp1) to reinforce mitophagy pathway. Together, this study highlights the potential of Cu-MBGNs-mediated mitophagy and biomineralization for augmenting bone regeneration, offering a promising avenue for the development of advanced bioactive materials in orthopedic applications.

Osteomimix: A Multidimensional Biomimetic Cascade Strategy for Bone Defect Repair

Despite advancements in biomimetic mineralization techniques, the repair of large-scale bone defects remains a significant challenge. Inspired by the bone formation process, a multidimensional biomimetic cascade strategy is developed by replicating the biomineralization cascade, emulating the hierarchical structure of bone, and biomimicking its biological functions for efficient bone regeneration. This strategy involves the photocrosslinking of sodium methacrylate carboxymethyl cellulose-stabilized amorphous magnesium-calcium phosphate with methacrylate-modified type I collagen to create a self-mineralizing hydrogel. The hydrogel is then integrated with either naturally derived or synthetic oriented bulk scaffolds. The resulting composite, named Osteomimix, provides excellent mechanical support and can be customized for irregular bone defects using CAD/CAM technology. Through in vitro and in vivo studies, this work finds that Osteomimix exhibits spontaneous in situ biomimetic mineralization in a cell-free environment, while modulating immune responses and promoting vascularized bone formation in a cell-dependent manner. Built on bone-specific insights, this strategy achieves biomimicry across temporal, spatial, and functional dimensions, facilitating the seamless integration of artificial constructs with the natural tissue repair dynamics.

Enhancement of In Vivo Bone Regeneration by the Carbohydrate Derivative DP2

Background/Objectives: Delays in bone healing and complications of remodeling constitute a major medical problem-particularly in older adults and patients with comorbidities. Current therapeutic approaches are based on strategies that promote bone regeneration. We recently identified a disaccharide compound (DP2) that enhances in vitro mineralization in human osteoblast cells via the early activation of Runx2 and the induction of osteoblast differentiation. Methods: First, a calcium quantification assay was performed to assess mineralization in MC3T3-E1 cells. Next, microcomputed tomography and histological analyses were used to examine in vivo bone repair in a rat 5 mm cranial defect model following the implantation of DP2 coupled to a micro/macroporous biphasic CaP ceramic (MBCP+) or collagen scaffold. Results: Here, we demonstrated that DP2 induced osteogenic differentiation and significantly elevated calcium matrix deposition in the murine preosteoblast cell line MC3T3-E1. We found that treatment with DP2 coupled to MBCP+ repaired the calvarial defect on post-implantation day 91. It significantly increased bone mineral density starting on day 29 post-treatment. In addition, DP2 did not induce ectopic bone formation. Conclusions: Taken as a whole, these results show that DP2 is a promising candidate treatment for delayed bone healing.

Inhibiting Autophagy by Chemicals During SCAPs Osteodifferentiation Elicits Disorganized Mineralization, While the Knock-Out of Atg5/7 Genes Leads to Cell Adaptation

SCAPs (Stem Cells from Apical Papilla), derived from the apex of forming wisdom teeth, extracted from teenagers for orthodontic reasons, belong to the MSCs (Mesenchymal Stromal Cells) family. They have multipotent differentiation capabilities and are a potentially powerful model for investigating strategies of clinical cell therapies. Since autophagy-a regulated self-eating process-was proposed to be essential in osteogenesis, we investigated its involvement in the SCAP model. By using a combination of chemical and genetic approaches to inhibit autophagy, we studied early and late events of osteoblastic differentiation. We showed that blocking the formation of autophagosomes with verteporfin did not induce a dramatic alteration in early osteoblastic differentiation monitored by ALP (alkaline phosphatase) activity. However, blocking the autophagy flux with bafilomycin A1 led to ALP repression. Strikingly, the mineralization process was observed with both compounds, with calcium phosphate (CaP) nodules that remained inside cells under bafilomycin A1 treatment and numerous but smaller CaP nodules after verteporfin treatment. In contrast, deletion of Atg5 or Atg7, two genes involved in the formation of autophagosomes and essential to trigger canonical autophagy, indicated that both genes could be involved differently in the mineralization process with a modification of the ALP activity while final mineralization was not altered.

Modulation of biomineralization morphology by phosphorylated collagen peptides: insights into osteogenesis imperfecta pathophysiology

Osteogenesis imperfecta (OI) is a hereditary skeletal disorder characterized by bone fragility and deformities, primarily attributed to defects in type I collagen, the most abundant structural protein in humans. Multiple phosphorylation sites have been detected within collagen, suggesting that phosphorylation may influence mineralization processes, thereby impacting the development of OI. In this study, we investigated the modulation of biomineralization morphology by phosphorylated collagen peptides mimicking Gly-Ser mutations in osteogenesis imperfecta. A series of collagen peptide sequences, including GPO13S, GPO13pS, GPO12S, GPO12pS, GPO11S, and GPO11pS, were synthesized to explore the role of phosphorylation in peptide stability and its templating effect on biomineralization. The CD results indicated that the phosphorylation of Gly-pSer mutants reduces the stability of collagen peptides. SEM images revealed that phosphorylated peptides acted as templates, guiding the morphology of calcium carbonate into either olive-like or spherical structures, depending on their conformational state of the peptides. Non-phosphorylated peptides maintained a calcite crystal structure. The XRD patterns predominantly exhibited peaks associated with calcite and vaterite for GPO13pS-CaCO3, GPO12pS-CaCO3, and GPO11pS-CaCO3, and peaks associated with calcite for GPO13S-CaCO3, GPO12S-CaCO3, and GPO11S-CaCO3, indicating a transformation of mesocrystals influenced by peptide phosphorylation. Our findings elucidate the crucial role of phosphorylated collagen peptides in mediating biomineralization morphology and polymorph selection, offering insights into the complex pathophysiology of OI.

A persistent mineralization process in alveolar bone throughout the postnatal growth stage in rats

OBJECTIVE

Alveolar bone quality is essential for the maxillofacial integrity and function, and depends on alveolar bone mineralization. This study aims to investigate the in vivo changes in alveolar bone mineralization, from the perspective of mineral deposition and crystal transition in postnatal rats.

DESIGN

Nine postnatal time points of Wistar rats, ranging from day 1 to 56, were set to obtain the maxillary alveolar bone samples. Each time point consisted of ninety rats, with 45 females and 45 males. Macromorphology of alveolar bone was reconducted by Micro-Computed Tomography and the mineral content was quantified via Thermogravimetric analysis, Scanning Electron Microscope, High-Resolution Transmission Electron Microscopy and vibrational spectroscopy. Furthermore, the crystallinity and composition were characterized by vibrational spectroscopy, X-ray Diffraction, X-ray Photoelectron Spectroscopy and Selected Area Electron Diffraction.

RESULTS

The progressive increase of mineral deposition was accompanied by substantial growth in alveolar bone mass and volume in postnatal rats. Whereas the mineral percentage initially decreased and then increased, reaching a nadir on postnatal day 14 (P14) when tooth eruption was first observed. Besides, localized mineralization was initiated by the formation of amorphous precursors and then converted into mineral crystals, while there was no statistically significant change in the average crystallinity of the bone during growth.

CONCLUSION

Mineralization of alveolar bone is ongoing throughout the early growth in postnatal rats. Mineral deposition increases with age, whereas the crystallinity remains stable within a certain range. Besides, the mineral percentage reaches its lowest point on P14, which may be attributed to tooth eruption.

Seriation of Enzyme-Functionalized Multilayers for the Design of Scalable Biomimetic Mineralized Structures

Biomimetic hydroxyapatites are widely explored for their potential applications in the repair of mineralized tissues, particularly dental enamel, which is acellular and, thus, not naturally reformed after damage. Enamel is formed with a highly-controlled hierarchical structure, which is difficult to replicate up to the macroscale. A biomimetic approach is thus warranted, based on the same principles that drive biomineralization in vivo. Herein, a strategy for the design of enamel-like architectures is described, utilizing enzymes embedded in polyelectrolyte multilayers to generate inorganic phosphate locally, and provide a favorable chemical environment for the nucleation and growth of minerals. Moreover, a method is proposed to build up seriated mineral layers with scalable thicknesses, continuous mineral growth, and tunable morphology. Results show the outstanding growth of cohesive mineral layers, yielding macroscopic standalone fluoride and/or carbonate-substituted hydroxyapatite materials with comparable crystal structure and composition to native human mineralized tissues. This strategy presents a promising path forward for the biomimetic design of biomineral materials, particularly relevant for restorative applications, with an exquisite level of synthetic control over multiple orders of magnitude.

Toward understanding the cellular control of vertebrate mineralization: The potential role of mitochondria

This review examines the possible role of mitochondria in maintaining calcium and phosphate ion homeostasis and participating in the mineralization of bone, cartilage and other vertebrate hard tissues. The paper builds on the known structural features of mitochondria and the documented observations in these tissues that the organelles contain calcium phosphate granules. Such deposits in mitochondria putatively form to buffer excessively high cytosolic calcium ion concentrations and prevent metabolic deficits and even cell death. While mitochondria protect cytosolic enzyme systems through this buffering capacity, the accumulation of calcium ions by mitochondria promotes the activity of enzymes of the tricarboxylic acid (TCA/Krebs) cycle, increases oxidative phosphorylation and ATP synthesis, and leads to changes in intramitochondrial pH. These pH alterations influence ion solubility and possibly the transitions and composition in the mineral phase structure of the granules. Based on these considerations, mitochondria are proposed to support the mineralization process by providing a mobile store of calcium and phosphate ions, in smaller cluster or larger granule form, while maintaining critical cellular activities. The rise in the mitochondrial calcium level also increases the generation of citrate and other TCA cycle intermediates that contribute to cell function and the development of extracellular mineral. This paper suggests that another key role of the mitochondrion, along with the effects just noted, is to supply phosphate ions, derived from the breakdown of ATP, to endolysosomes and autophagic vesicles originating in the endoplasmic reticulum and Golgi and at the plasma membrane. These many separate but interdependent mitochondrial functions emphasize the critical importance of this organelle in the cellular control of vertebrate mineralization.

Understanding the bio-crystallization: An insight to therapeutic relevance

In the realm of biomedical engineering and materials science, the synthesis of biomaterials plays a pivotal role in advancing therapeutic strategies for regeneration of tissues. The deliberate control of crystallization processes in biomaterial synthesis has emerged as a key avenue for tailoring the properties of these materials, enabling the design of innovative solutions for a wide array of medical applications. This review delves into the interplay between controlled crystallization and biomaterial synthesis, exploring its multifaceted applications in the therapeutic domains. The investigation encompasses a wide spectrum of matrices, ranging from small molecules to large biomolecules, highlighting their unique contributions in modulating crystallization processes. Furthermore, the review critically assesses the analytical techniques and methodologies employed to probe and characterize the depths of crystallization dynamics. Advanced imaging, spectroscopic, and computational tools are discussed in the context of unraveling the intricate mechanisms governing nucleation and crystallization processes within the organic matrix. Finally we delve in the applications of such advance material in therapeutics of hard and soft tissues.

Transcriptomic and proteomic strategies to reveal the mechanism of Gymnocypris przewalskii scale development

BACKGROUND

Fish scales are typical products of biomineralization and play an important role in the adaptation of fish to their environment. The Gymnocypris przewalskii scales are highly specialized, with scales embedded in only specific parts of the dermis, such as the areas around the anal fin and branchiostegite, making G. przewalskii an ideal material for biomineralization research. In this study, we aimed to unveil genes and pathways controlling scale formation through an integrated analysis of both transcriptome and proteome, of which G. przewalskii tissues of the dorsal skin (no scales) and the rump side skin (with scales) were sequenced. The sequencing results were further combined with cellular experiments to clarify the relationship between genes and signaling pathways.

RESULTS

The results indicated the following: (1) a total of 4,904 differentially expressed genes were screened out, including 3,294 upregulated genes and 1,610 downregulated genes (with a filtering threshold of |log2Fold-Change|> 1 and p-adjust < 0.05). The identified differentially expressed genes contained family members such as FGF, EDAR, Wnt10, and bmp. (2) A total of 535 differentially expressed proteins (DEPs) were filtered out from the proteome, with 204 DEPs downregulated and 331 DEPs upregulated (with a filtering threshold of |Fold-Change|> 1.5 and p < 0.05). (3) Integrated analyses of transcriptome and proteome revealed that emefp1, col1a1, col6a2, col16a1, krt8, and krt18 were important genes contributing to scale development and that PI3K-AKT was the most important signaling pathway involved. (4) With the use of the constructed G. przewalskii fibroblast cell line, emefp1, col1a1, col6a2, col16a1, krt8, and krt18 were confirmed to be positively regulated by the PI3K-AKT signaling pathway.

CONCLUSION

This study provides experimental evidence for PI3K-AKT controlled scale development in G. przewalskii and would benefit further study on stress adaptation, scale biomineralization, and the development of skin appendages.