Normal bone physiology, remodelling and its hormonal regulation

Physical and chemical characterization of femur during and after body development period in male and female rats

The aim of this study was to determine the physical and chemical characteristics of the bone structures during four developmental periods. Forty Wistar Albino rats (20 male and 20 female) were divided into four groups including prepubertal period (group I), period between adolescence and adulthood (group II) and later (young adult period as group III and old adult period as group IV). The bones were analysed by morphometric measurements, XRF (X-ray fluorescence) analysis for mineral levels and BET analysis (Brunaurer-Emmett-Teller) for surface area and porosity. In morphometric measurements, the GL (greatest length) and the GLC (greatest length from caput femoris) values increased gradually from the first to the fourth group, and these values were higher in the males than the females. Phosphorus and calcium values were higher in the males in adult groups (third and fourth) compared to that for the females; however, they were higher in the females in groups up to adulthood (first and second). While the Ca/P ratio reached the highest value in the second group in the male, it decreased gradually afterwards. In females, the rate, which was close to each other in the first three groups, increased in the fourth group. Surface area size in the female and the male rats was the highest in the second group. In conclusion, changes in the rat bone structure during the development and adulthood periods of the body were revealed, and it was determined that the gender factor was effective in these changes.

The application of 3D bioprinting in urological diseases

Urologic diseases are commonly diagnosed health problems affecting people around the world. More than 26 million people suffer from urologic diseases and the annual expenditure was more than 11 billion US dollars. The urologic cancers, like bladder cancer, prostate cancer and kidney cancer are always the leading causes of death worldwide, which account for approximately 22% and 10% of the new cancer cases and death, respectively. Organ transplantation is one of the major clinical treatments for urological diseases like end-stage renal disease and urethral stricture, albeit strongly limited by the availability of matching donor organs. Tissue engineering has been recognized as a highly promising strategy to solve the problems of organ donor shortage by the fabrication of artificial organs/tissue. This includes the prospective technology of three-dimensional (3D) bioprinting, which has been adapted to various cell types and biomaterials to replicate the heterogeneity of urological organs for the investigation of organ transplantation and disease progression. This review discusses various types of 3D bioprinting methodologies and commonly used biomaterials for urological diseases. The literature shows that advances in this field toward the development of functional urological organs or disease models have progressively increased. Although numerous challenges still need to be tackled, like the technical difficulties of replicating the heterogeneity of urologic organs and the limited biomaterial choices to recapitulate the complicated extracellular matrix components, it has been proved by numerous studies that 3D bioprinting has the potential to fabricate functional urological organs for clinical transplantation and in vitro disease models.

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Outline the advantages and characteristics of 3D printing compared with traditional methods for urological diseases.

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Guide the selection of 3D bioprinting technology and material in urological tissue engineering.

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Discuss the challenges and future perspectives of 3D bioprinting in urological diseases and clinical translation.

Application Progress of Modified Chitosan and Its Composite Biomaterials for Bone Tissue Engineering

In recent years, bone tissue engineering (BTE), as a multidisciplinary field, has shown considerable promise in replacing traditional treatment modalities (i.e., autografts, allografts, and xenografts). Since bone is such a complex and dynamic structure, the construction of bone tissue composite materials has become an attractive strategy to guide bone growth and regeneration. Chitosan and its derivatives have been promising vehicles for BTE owing to their unique physical and chemical properties. With intrinsic physicochemical characteristics and closeness to the extracellular matrix of bones, chitosan-based composite scaffolds have been proved to be a promising candidate for providing successful bone regeneration and defect repair capacity. Advances in chitosan-based scaffolds for BTE have produced efficient and efficacious bio-properties via material structural design and different modifications. Efforts have been put into the modification of chitosan to overcome its limitations, including insolubility in water, faster depolymerization in the body, and blood incompatibility. Herein, we discuss the various modification methods of chitosan that expand its fields of application, which would pave the way for future applied research in biomedical innovation and regenerative medicine.

Antigen receptor therapy in bone metastasis via optimal control for different human life stages

In this work we propose a bone metastasis model using power law growth functions in order to describe the biochemical interactions between bone cells and cancer cells. Experimental studies indicate that bone remodeling cycles are different for human life stages: childhood, young adulthood, and adulthood. In order to include such differences in our study, we estimate the model parameter values for each human life stage via bifurcation analysis. Results reveal an intrinsic relationship between the active period of remodeling cycles and the proliferation of cancer cells. Subsequently, using optimal control theory we analyze a possible antigen receptor therapy as a new treatment for bone metastasis. Theoretical results such as existence of optimal solutions are proved. Numerical simulations for late stages of bone metastasis are presented and a discussion of our results is carried out.

Unique bone marrow blood vessels couple angiogenesis and osteogenesis in bone homeostasis and diseases

Blood vessels serve as a versatile transport system and play crucial roles in organ development, regeneration, and stem cell behavior. In the skeletal system, certain capillaries support perivascular stem cells or osteoprogenitor cells and thereby regulate bone formation. Recent studies reported that a specialized capillary subtype, termed type H vessels, is shown to couple angiogenesis and osteogenesis in rodents and humans. They can be distinguished by specific cell surface markers, as the endothelial cells in the metaphysis and endosteum highly express the junctional protein CD31 and the sialoglycoprotein endomucin. Here, we provide an overview of the role of type H vessels in bone homeostasis and summarize their linkage with various cytokines to control bone cell behavior and bone formation. We also discuss the potential clinical application for bone disorders by targeting these specific vessels according to their physiological and pathobiological settings.

Nanoparticle-mediated siRNA delivery assessed in a 3D co-culture model simulating prostate cancer bone metastasis

siRNA has emerged as a potential therapeutic for the treatment of prostate cancer but effective delivery remains a major barrier to its clinical application. This study aimed to develop and characterise a 3D in vitro co-culture model to simulate prostate cancer bone metastasis and to assess the ability of the model to investigate nanoparticle-mediated siRNA delivery and gene knockdown. PC3 or LNCaP prostate cancer cells were co-cultured with hFOB 1.19 osteoblast cells in 2D on plastic tissue culture plates and in 3D on collagen scaffolds mimicking the bone microenvironment. To characterise the co-culture model, cell proliferation, enzyme secretion and the utility of two different gene delivery vectors to mediate siRNA uptake and gene knockdown were assessed. Cell proliferation was reduced by∼50% by day 7 in the co-culture system relative to monoculture (PC3 and LNCaP co-cultures, in 2D and 3D) and an enhanced level of MMP9 (a marker of bone metastasis) was secreted into the media (1.2-4-fold increase depending on the co-culture system). A cationic cyclodextrin gene delivery vector proved significantly less toxic in the co-culture system relative to the commercially available vector Lipofectamine 2000(®). In addition, knockdown of both the GAPDH gene (minimum 15%) and RelA subunit of the NF-κB transcription factor (minimum 20%) was achieved in 2D and 3D cell co-cultures. Results indicate that the prostate cancer-osteoblast in vitro co-culture model was more physiologically relevant vs the monoculture. This model has the potential to help improve the design and efficacy of gene delivery formulations, to more accurately predict in vivo performance and, therefore, to reduce the risk of product failure in late-stage clinical development.