Engineered cartilage regeneration from adipose tissue derived-mesenchymal stem cells: A morphomolecular study on osteoblast, chondrocyte and apoptosis evaluation

Bioinspired collagen-gelatin-hyaluronic acid-chondroitin sulfate tetra-copolymer scaffold biomimicking native cartilage extracellular matrix facilitates chondrogenesis of human synovium-derived stem cells

The microenvironment plays a crucial role in stem cell differentiation, and a scaffold that mimics native cartilaginous extracellular components can promote chondrogenesis. In this study, a collagen-gelatin-hyaluronic acid-chondroitin sulfate tetra-copolymer scaffold with composition and architecture similar to those of hyaline cartilage was fabricated using a microfluidic technique and compared with a pure gelatin scaffold. The newly designed biomimetic scaffold had a swelling ratio of 1278 % ± 270 %, a porosity of 77.68 % ± 11.70 %, a compressive strength of 1005 ± 174 KPa, and showed a good resilience against compression force. Synovium-derived stem cells (SDSCs) seeded into the tetra-copolymer scaffold attached to the scaffold firmly and exhibited good mitochondrial activity, high cell survival with a pronounced glycosaminoglycan production. SDSCs cultured on the tetra-copolymer scaffold with chondrogenic induction exhibited upregulated mRNA expression of COL2A1, ChM-1, Nrf2, TGF-β1, and BMP-7. Ex vivo study revealed that the SDSC-tetra-copolymer scaffold regenerated cartilage-like tissue in SCID mice with abundant type II collagen and S-100 production. BMP7 and COL2A1 expression in the tetra-copolymer scaffold group was much higher than that in the gelatin scaffold group ex vivo. The tetra-copolymer scaffold thus exhibits strong chondrogenic capability and will facilitate cartilage tissue engineering.

Novel Sensing Technique for Stem Cells Differentiation Using Dielectric Spectroscopy of Their Proteins

Dielectric spectroscopy (DS) is the primary technique to observe the dielectric properties of biomaterials. DS extracts complex permittivity spectra from measured frequency responses such as the scattering parameters or impedances of materials over the frequency band of interest. In this study, an open-ended coaxial probe and vector network analyzer were used to characterize the complex permittivity spectra of protein suspensions of human mesenchymal stem cells (hMSCs) and human osteogenic sarcoma (Saos-2) cells in distilled water at frequencies ranging from 10 MHz to 43.5 GHz. The complex permittivity spectra of the protein suspensions of hMSCs and Saos-2 cells revealed two major dielectric dispersions, β and γ, offering three distinctive features for detecting the differentiation of stem cells: the distinctive values in the real and imaginary parts of the complex permittivity spectra as well as the relaxation frequency in the β-dispersion. The protein suspensions were analyzed using a single-shell model, and a dielectrophoresis (DEP) study was performed to determine the relationship between DS and DEP. In immunohistochemistry, antigen-antibody reactions and staining are required to identify the cell type; in contrast, DS eliminates the use of biological processes, while also providing numerical values of the dielectric permittivity of the material-under-test to detect differences. This study suggests that the application of DS can be expanded to detect stem cell differentiation.

BDNF-modified human umbilical cord mesenchymal stem cells-derived dopaminergic-like neurons improve rotation behavior of Parkinson's disease rats through neuroprotection and anti-neuroinflammation

Parkinson's disease (PD) is a neurodegenerative disease still without any cure. Brain-derived neurotrophic factor (BDNF) has shown therapeutic potential in PD, which is limited by its short half-life and inability to penetrate the blood-brain barrier. Stem cells not only present migration, differentiation and neurotrophy characteristics, but also can be used as delivery vectors for BDNF. This study aimed to investigate the therapeutic effects and possible mechanisms of BDNF-modified human umbilical cord mesenchymal stem cells (hUC-MSCs)-derived dopaminergic (DAergic)-like neurons in the PD rats. Results showed that transplantation of BDNF-modified hUC-MSCs-derived DAergic-like neurons improved the apomorphine induced rotation behavior of PD rats, increased the dopamine concentration and the expression of glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule-1 (Iba-1) in the striatum, promoted the expression of tyrosine hydroxylase (TH), nuclear receptor-related factor 1 (Nurr1), pituitary homeobox 3 (Pitx3), BDNF, tyrosine kinase B (TrkB), phosphatidylinositol-3-hydroxykinase (PI3K), phosphorylated protein kinase B (p-Akt), heat shock protein 60 (Hsp60), toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88) and inhibited the neural apoptosis in the substantia nigra (SN) and striatum. Results suggest that BDNF-modified hUC-MSCs-derived DAergic-like neurons improve the rotation of PD rats might through neuroprotection and anti-neuroinflammation by regulating the BDNF-TrkB-PI3K/Akt and Hsp60-TLR4/MyD88 signaling pathways, respectively.

Three-Dimensional Bioprinting for Cartilage Tissue Engineering: Insights into Naturally-Derived Bioinks from Land and Marine Sources

In regenerative medicine and tissue engineering, the possibility to: (I) customize the shape and size of scaffolds, (II) develop highly mimicked tissues with a precise digital control, (III) manufacture complex structures and (IV) reduce the wastes related to the production process, are the main advantages of additive manufacturing technologies such as three-dimensional (3D) bioprinting. Specifically, this technique, which uses suitable hydrogel-based bioinks, enriched with cells and/or growth factors, has received significant consideration, especially in cartilage tissue engineering (CTE). In this field of interest, it may allow mimicking the complex native zonal hyaline cartilage organization by further enhancing its biological cues. However, there are still some limitations that need to be overcome before 3D bioprinting may be globally used for scaffolds’ development and their clinical translation. One of them is represented by the poor availability of appropriate, biocompatible and eco-friendly biomaterials, which should present a series of specific requirements to be used and transformed into a proper bioink for CTE. In this scenario, considering that, nowadays, the environmental decline is of the highest concerns worldwide, exploring naturally-derived hydrogels has attracted outstanding attention throughout the scientific community. For this reason, a comprehensive review of the naturally-derived hydrogels, commonly employed as bioinks in CTE, was carried out. In particular, the current state of art regarding eco-friendly and natural bioinks’ development for CTE was explored. Overall, this paper gives an overview of 3D bioprinting for CTE to guide future research towards the development of more reliable, customized, eco-friendly and innovative strategies for CTE.

Multipotential Role of Growth Factor Mimetic Peptides for Osteochondral Tissue Engineering

Articular cartilage is characterized by a poor self-healing capacity due to its aneural and avascular nature. Once injured, it undergoes a series of catabolic processes which lead to its progressive degeneration and the onset of a severe chronic disease called osteoarthritis (OA). In OA, important alterations of the morpho-functional organization occur in the cartilage extracellular matrix, involving all the nearby tissues, including the subchondral bone. Osteochondral engineering, based on a perfect combination of cells, biomaterials and biomolecules, is becoming increasingly successful for the regeneration of injured cartilage and underlying subchondral bone tissue. To this end, recently, several peptides have been explored as active molecules and enrichment motifs for the functionalization of biomaterials due to their ability to be easily chemically synthesized, as well as their tunable physico-chemical features, low immunogenicity issues and functional group modeling properties. In addition, they have shown a good aptitude to penetrate into the tissue due to their small size and stability at room temperature. In particular, growth-factor-derived peptides can play multiple functions in bone and cartilage repair, exhibiting chondrogenic/osteogenic differentiation properties. Among the most studied peptides, great attention has been paid to transforming growth factor-β and bone morphogenetic protein mimetic peptides, cell-penetrating peptides, cell-binding peptides, self-assembling peptides and extracellular matrix-derived peptides. Moreover, recently, phage display technology is emerging as a powerful selection technique for obtaining functional peptides on a large scale and at a low cost. In particular, these peptides have demonstrated advantages such as high biocompatibility; the ability to be immobilized directly on chondro- and osteoinductive nanomaterials; and improving the cell attachment, differentiation, development and regeneration of osteochondral tissue. In this context, the aim of the present review was to go through the recent literature underlining the importance of studying novel functional motifs related to growth factor mimetic peptides that could be a useful tool in osteochondral repair strategies. Moreover, the review summarizes the current knowledge of the use of phage display peptides in osteochondral tissue regeneration.

Quercetin modified electrospun PHBV fibrous scaffold enhances cartilage regeneration

It suggests that the poly (3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) scaffold can be used for cartilage tissue engineering, but PHBV is short of bioactivity that is required for cartilage regeneration. To fabricate a bioactive cartilage tissue engineering scaffold that promotes cartilage regeneration, quercetin (QUE) modified PHBV (PHBV-g-QUE) fibrous scaffolds were prepared by a two-step surface modification method. The PHBV-g-QUE fibrous scaffold facilitates the growth of chondrocytes and maintains chondrocytic phenotype resulting from the upregulation of SOX9, COL II, and ACAN. The PHBV-g-QUE fibrous scaffold inhibited apoptosis of chondrocyte and reduced oxidative stress of chondrocytes by regulating the transcription of related genes. Following PHBV-g-QUE fibrous scaffolds and PHBV fibrous scaffolds with adhered chondrocytes were implanted into nude mice for 4 weeks, it demonstrated that PHBV-g-QUE fibrous scaffolds significantly promoted cartilage regeneration compared with the PHBV fibrous scaffolds. Hence, it suggests that the PHBV-g-QUE fibrous scaffold can be potentially applied in the clinical treatment of cartilage defects in the future.

In Vitro Evaluation of the Anti-Inflammatory Effect of KMUP-1 and In Vivo Analysis of Its Therapeutic Potential in Osteoarthritis

Osteoarthritis is a degenerative arthropathy that is mainly characterized by dysregulation of inflammatory responses. KMUP-1, a derived chemical synthetic of xanthine, has been shown to have anti-inflammatory and antioxidant properties. Here, we aimed to investigate the in vitro anti-inflammatory and in vivo anti-osteoarthritis effects of KMUP-1. Protein and gene expressions of inflammation markers were determined by ELISA, Western blotting and microarray, respectively. RAW264.7 mouse macrophages were cultured and pretreated with KMUP-1 (1, 5, 10 μM). The productions of TNF-α, IL-6, MMP-2 and MMP- 9 were reduced by KMUP-1 pretreatment in LPS-induced inflammation of RAW264.7 cells. The expressions of iNOS, TNF-α, COX-2, MMP-2 and MMP-9 were also inhibited by KMUP-1 pretreatment. The gene expression levels of TNF and COX families were also downregulated. In addition, KMUP-1 suppressed the activations of ERK, JNK and p38 as well as phosphorylation of IκBα/NF-κB signaling pathways. Furthermore, SIRT1 inhibitor attenuated the inhibitory effect of KMUP-1 in LPS-induced NF-κB activation. In vivo study showed that KMUP-1 reduced mechanical hyperalgesia in monoiodoacetic acid (MIA)-induced rats OA. Additionally, KMUP-1 pretreatment reduced the serum levels of TNF-α and IL-6 in MIA-injected rats. Moreover, macroscopic and histological observation showed that KMUP-1 reduced articular cartilage erosion in rats. Our results demonstrated that KMUP-1 inhibited the inflammatory responses and restored SIRT1 in vitro, alleviated joint-related pain and cartilage destruction in vivo. Taken together, KMUP-1 has the potential to improve MIA-induced articular cartilage degradation by inhibiting the levels and expression of inflammatory mediators suggesting that KMUP-1 might be a potential therapeutic agent for OA.

BMP5 silencing inhibits chondrocyte senescence and apoptosis as well as osteoarthritis progression in mice

In this study, we using the in vivo destabilization of the medial meniscus (DMM) mouse model to investigate the role of bone morphogenetic protein 5 (BMP5) in osteoarthritis (OA) progression mediated via chondrocyte senescence and apoptosis. BMP5 expression was significantly higher in knee articular cartilage tissues of OA patients and DMM model mice than the corresponding controls. The Osteoarthritis Research Society International scores based on histological staining of knee articular cartilage sections were lower in DMM mice where BMP5 was knocked down in chondrocytes than the corresponding controls 4 weeks after DMM surgery. DMM mice with BMP5-deficient chondrocytes showed reduced levels of matrix-degrading enzymes such as MMP13 and ADAMTS5 as well as reduced cartilage destruction. BMP5 knockdown also decreased chondrocyte apoptosis and senescence by suppressing the activation of p38 and ERK MAP kinases. These findings demonstrate that BMP5 silencing inhibits chondrocyte senescence and apoptosis as well as OA progression by downregulating activity in the p38/ERK signaling pathway.

Connexin expression decreases during adipogenic differentiation of human adipose-derived mesenchymal stem cells

Adipose-derived stem cells (ASCs) represent a valuable tool for regenerative medicine being able to differentiate toward several cell lines, such as adipocytes, chondrocytes and osteocytes. During ASC adipogenic differentiation, changes in connexin (Cx) expression were evaluated in the present study. Three different Cxs were investigated: Cx43, Cx32 and Cx31.9. Cx43 is the most abundant in human tissues, Cx32 is prevalently found in nervous tissue and Cx31.9 is found at the myocardial level. Human ASCs undergoing adipogenic differentiation were isolated from raw lipoaspirate and characterized as mesenchymal stem cells. After multiple days of culture (1, 7, 14, 21 and 28 days), adipogenic differentiation was assessed by Oil Red O staining and Acetyl-CoA carboxylase (ACC) levels by western blotting. Cx expression was evaluated by western blotting at the same time points. In treated ASCs, lipidic vacuoles were detected from day 7 of treatment. Their number and size progressively increased over the entire period of observation. A parallel increase of ACC expression was also found. Lower levels of Cx expression were detected during adipogenic differentiation. Such decreases were particularly evident for Cx32, already after the first day of treatment. Cx31.9 and Cx43 also decreased, but starting from day 7. Our results suggest that ASCs may initially be equipped with a variety of Cxs, which is not surprising assuming their multipotential differentiation ability. Although some Cxs may be selectively enhanced depending on specific induction strategies toward different tissues, they seem markedly downregulated during adipogenic differentiation.

Co-culture and Mechanical Stimulation on Mesenchymal Stem Cells and Chondrocytes for Cartilage Tissue Engineering

Defects in articular cartilage injury and chronic osteoarthritis are very widespread and common, and the ability of injured cartilage to repair itself is limited. Stem cell-based cartilage tissue engineering provides a promising therapeutic option for articular cartilage damage. However, the application of the technique is limited by the number, source, proliferation, and differentiation of stem cells. The co-culture of mesenchymal stem cells and chondrocytes is available for cartilage tissue engineering, and mechanical stimulation is an important factor that should not be ignored. A combination of these two approaches, i.e., co-culture of mesenchymal stem cells and chondrocytes under mechanical stimulation, can provide sufficient quantity and quality of cells for cartilage tissue engineering, and when combined with scaffold materials and cytokines, this approach ultimately achieves the purpose of cartilage repair and reconstruction. In this review, we focus on the effects of co-culture and mechanical stimulation on mesenchymal stem cells and chondrocytes for articular cartilage tissue engineering. An in-depth understanding of the impact of co-culture and mechanical stimulation of mesenchymal stem cells and chondrocytes can facilitate the development of additional strategies for articular cartilage tissue engineering.

Mesenchymal stem cells regulate inflammatory milieu within degenerative nucleus pulposus cells via p38 MAPK pathway

It has been established that excessive apoptosis of nucleus pulposus cells (NPCs) are responsible for pathogenesis of human intervertebral disc degeneration (IDD). The present study aimed to shed light on the molecular mechanisms underlying the protective effects of mesenchymal stem cells (MSCs) on NPCs in an inflammatory environment. NPCs were treated with TNF-α to induce inflammation and then co-cultured with Wharton's Jelly-derived MSCs (WJ-MSCs)without direct interaction. The levels of inflammation markers (IL-1β, IL-6 and IL-8) in NPCs were detected by performing enzyme-linked immunosorbent assay (ELISA), and expression of metalloproteases and aggrecan, as well as the activity of p38 MAPK pathway were determined through immunoblotting. SB-203580 was used to inhibit p38 signaling, prior to evaluation of the effects of Wharton's Jelly-derived MSCs (WJ-MSCs) on inflammatory response within the co-cultured NPCs. After TNF-α treatment, the levels of inflammatory cytokines, MMP-3, and MMP-13 in NPCs were increased whereas aggrecan was decreased, which was then dramatically reversed by WJ-MSCs co-culture. Likewise, WJ-MSCs suppressed TNF-α-induced phosphorylation of p38 MAPK signaling components including p38, ASK-1, MKK-3 and MKK-6. Blocking p38 MAPK pathway enhanced the anti-inflammatory impact of WJ-MSCs, and there was no significant difference between NPCs co-cultured with WJ-MSCs or the cells cultured alone. WJ-MSCs co-culture mitigate TNF-α-induced inflammatory response and ECM degeneration in NPCs, the major pathological events are implicated in IDD development, probably by suppressing the p38 MAPK signaling cascade.

Lingzhi and San-Miao-San with hyaluronic acid gel mitigate cartilage degeneration in anterior cruciate ligament transection induced osteoarthritis

Objective

To investigate the mitigate efficacy of Chinese medicine Lingzhi (LZ) and San-Miao-San (SMS) combined with hyaluronic acid (HA)-gel in attenuating cartilage degeneration in traumatic osteoarthritis (OA).

Methods

The standardized surgery of anterior cruciate ligament transection (ACLT) was made from the medial compartment of right hind limbs of 8-week-old female SD rats and resulted in a traumatic OA. Rats (n ​= ​5/group) were treated once intra-articular injection of 50 ​μl HA-gel, 50 ​μl HA-gel+50 ​μg LZ-SMS, 50 ​μl of saline+50 ​μg LZ-SMS and null (ACLT group) respectively, except sham group. Limbs were harvested for μCT scan and histopathological staining 3-month post-treatment. Inflammatory cytokines from plasma and synovial fluid were detected using Immunology Multiplex Assay kit. The putative targets of active compounds in LZ-SMS and known therapeutic targets for OA were combined to construct protein–protein interaction network. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis was adopted to predict the potential targets and signaling pathway of LZ-SMS in OA through the tool of DAVID Bioinformatics.

Results

In vivo, HA-gel ​+ ​LZ-SMS treatment resulted in a higher volume ratio of hyaline cartilage (HC)/calcified cartilage (CC) and HC/Sum (total volume of cartilage), compared to ACLT and HA-gel groups. In addition, histological results showed the elevated cartilage matrix, chondrogenic and osteoblastic signals in HA-gel ​+ ​LZ-SMS treatment. Treatment also significantly altered subchondral bone (SCB) structure including an increase in BV/TV, Tb.Th, BMD, Conn.Dn, Tb.N, and DA, as well as a significant decrease in Tb.Sp and Po(tot), which implied a protective effect on maintaining the stabilization of tibial SCB microstructure. Furthermore, there was also a down-regulated inflammatory cytokines and upregulated anti-inflammatory cytokine IL-10 in HA+LZ-SMS group. Finally, 64 shared targets from 37 active compounds in LZ-SMS related to the core genes for the development of OA. LZ-SMS has a putative role in regulating inflammatory circumstance through influencing the MAPK signaling pathway.

Conclusion

Our study elucidated a protective effect of HA-gel ​+ ​LZ-SMS in mitigating cartilage degradation and putative interaction with targets and signaling pathway for the development of traumatic OA.

The translational potential of this article

Our results provide a biological rationale for the use of LZ-SMS as a potential candidate for OA treatment.

The emerging role of lncRNAs in chondrocytes from osteoarthritis patients

Long non-coding RNAs (lncRNAs) play important roles in many physiological and pathological processes, including osteoarthritis (OA). Recent studies have demonstrated that lncRNAs are involved in the pathogenesis of OA by affecting various essential cellular features of chondrocytes, such as proliferation, apoptosis, inflammation, and degradation of the extracellular matrix (ECM). However, there are only a limited number of studies in this area, indicating that the role of lncRNAs in OA may have been overlooked. The aim of this literature review is to summarize the versatile roles and molecular mechanisms of lncRNAs in chondrocytes involved in OA. At the end of this article, the function of the lncRNA HOX transcript antisense RNA (HOTAIR) in chondrocytes in OA is highlighted. Because lncRNAs affect proliferation, apoptosis, inflammatory responses, and ECM degradation by chondrocytes in OA, they may serve as potential biomarkers or therapeutic targets for the diagnosis or treatment of OA. The specific role and related mechanisms of lncRNAs in OA warrants further investigation.

Decellularized adipose matrix provides an inductive microenvironment for stem cells in tissue regeneration

Stem cells play a key role in tissue regeneration due to their self-renewal and multidirectional differentiation, which are continuously regulated by signals from the extracellular matrix (ECM) microenvironment. Therefore, the unique biological and physical characteristics of the ECM are important determinants of stem cell behavior. Although the acellular ECM of specific tissues and organs (such as the skin, heart, cartilage, and lung) can mimic the natural microenvironment required for stem cell differentiation, the lack of donor sources restricts their development. With the rapid development of adipose tissue engineering, decellularized adipose matrix (DAM) has attracted much attention due to its wide range of sources and good regeneration capacity. Protocols for DAM preparation involve various physical, chemical, and biological methods. Different combinations of these methods may have different impacts on the structure and composition of DAM, which in turn interfere with the growth and differentiation of stem cells. This is a narrative review about DAM. We summarize the methods for decellularizing and sterilizing adipose tissue, and the impact of these methods on the biological and physical properties of DAM. In addition, we also analyze the application of different forms of DAM with or without stem cells in tissue regeneration (such as adipose tissue), repair (such as wounds, cartilage, bone, and nerves), in vitro bionic systems, clinical trials, and other disease research.

Positive Feedback Loop LINC00511/miR-150-5p/SP1 Modulates Chondrocyte Apoptosis and Proliferation in Osteoarthritis

Osteoarthritis (OA) acts as the most common type of degenerative joint disease. Long noncoding RNA (lncRNA) has been identified to regulate the apoptosis and proliferation of chondrocyte. However, the deepgoing mechanism involved in the regulation is still unclear. This research aims to investigate the role and molecular mechanism by which lncRNA LINC00511 regulates the OA biology. Functionally, the functional experiments found that LINC00511 expression was upregulated in the IL-1β-stimulated chondrocyte (ATDC5). Knockdown of LINC00511 facilitated proliferation, and repressed the apoptosis and extracellular matrix (ECM) synthesis of chondrocyte. Mechanically, LINC00511 functioned as sponge of miR-150-5p and then interacted with the 3'-UTR of transcription factor (SP1). In turn, transcription factor SP1 bound with the promoter region of LINC00511 and thus upregulated LINC00511 expression. In conclusion, our findings highlight the function and prognostic value of LINC00511/miR-150-5p/SP1 feedback loop in OA and extend the importance of lncRNA epigenetics in OA biology.

miR-17-5p and miR-19b-3p prevent osteoarthritis progression by targeting EZH2

Osteoarthritis (OA) is a joint disease caused by a variety of factors, including aging, obesity and trauma. MicroRNAs (miRNAs) have been reported to be crucial regulators during OA progression. The present study aimed to investigate the role of miR-17-5p and miR-19b-3p during OA development. Interleukin (IL)-1β-treated chondrocytes were used to mimic OA in vitro. The expression levels of miR-17-5p and enhancer of zeste homolog 2 (EZH2) were measured in cartilage tissues and chondrocytes using reverse transcription-quantitative PCR or western blotting. Apoptosis was assessed by flow cytometry. The protein expression levels of extracellular matrix (ECM)-associated genes were detected by western blotting. The binding sites between miR-17-5p or miR-19b-3p and EZH2 were predicted using the MicroT-CDS online database and verified using dual-luciferase reporter and RIP assays. miR-17-5p expression was downregulated, whereas EZH2 expression was upregulated in OA cartilage tissues and IL-1β-induced chondrocytes compared with that in the control tissues and cells. miR-17-5p mimics inhibited IL-1β-induced apoptosis and ECM degradation in chondrocytes. EZH2 was the target of miR-17-5p and miR-19b-3p in chondrocytes, and enhanced apoptosis and ECM degradation in IL-1β-stimulated chondrocytes. Rescue experiments revealed that miR-17-5p or miR-19b-3p mimic-induced inhibition of OA progression was reversed by EZH2 overexpression. In conclusion, miR-17-5p and miR-19b-3p inhibited OA progression by targeting EZH2, which may serve as a potential therapeutic target for OA.

Evaluation of a Cell-Free Collagen Type I-Based Scaffold for Articular Cartilage Regeneration in an Orthotopic Rat Model

The management of chondral defects represents a big challenge because of the limited self-healing capacity of cartilage. Many approaches in this field obtained partial satisfactory results. Cartilage tissue engineering, combining innovative scaffolds and stem cells from different sources, emerges as a promising strategy for cartilage regeneration. The aim of this study was to evaluate the capability of a cell-free collagen I-based scaffold to promote cartilaginous repair after orthotopic implantation in vivo. Articular cartilage lesions (ACL) were created at the femoropatellar groove in rat knees and cell free collagen I-based scaffolds (S) were then implanted into right knee defect for the ACL-S group. No scaffold was implanted for the ACL group. At 4-, 8- and 16-weeks post-transplantation, degrees of cartilage repair were evaluated by morphological, histochemical and gene expression analyses. Histological analysis shows the formation of fibrous tissue, at 4-weeks replaced by a tissue resembling the calcified one at 16-weeks in the ACL group. In the ACL-S group, progressive replacement of the scaffold with the newly formed cartilage-like tissue is shown, as confirmed by Alcian Blue staining. Immunohistochemical and quantitative real-time PCR (qRT-PCR) analyses display the expression of typical cartilage markers, such as collagen type I and II (ColI and ColII), Aggrecan and Sox9. The results of this study display that the collagen I-based scaffold is highly biocompatible and able to recruit host cells from the surrounding joint tissues to promote cartilaginous repair of articular defects, suggesting its use as a potential approach for cartilage tissue regeneration.

miR‑10a‑5p inhibits osteogenic differentiation of bone marrow‑derived mesenchymal stem cells

The use of human bone marrow mesenchymal stem cells (hBMSCs) as a tissue engineering application for individuals affected by osteoporosis and other types of bone loss diseases has been well studied in recent years. The osteogenic differentiation of hBMSCs can be regulated by a number of cues. MicroRNAs (miRNAs/miRs) serve as the key regulators of various biological processes; however, to the best of our knowledge, no information exists with regards to the specific modulatory effects of miR-10a-5p on osteogenic differentiation of hBMSCs. The aim of the present study was to investigate the relationship between hBMSCs and miR-10a-5p and, ultimately, to determine how miR-10a-5p affects the osteogenic differentiation process of hBMSCs in vitro and in vivo. The hBMSCs used in the present study were transfected with mirVana™ miRNA inhibitors and mimics, and transfection efficiency was assessed by fluorescence microscopy and reverse transcription-quantitative PCR (RT-qPCR). Viability of hBMSCs following transfection was analyzed using a Cell Counting Kit-8 assay. The mRNA expression levels of specific osteoblast markers, including alkaline phosphatase (ALP) and runt-related transcription factor 2 (RUNX2) were measured using RT-qPCR and western blot analysis. New bone formation was evaluated by Goldner's trichrome staining and micro-CT analysis in vivo. No significant difference in cell viability was observed among the different groups 24 h post-transfection. Overexpression of miR-10a-5p inhibited the expression of osteoblast makers in hBMSCs, whereas inhibition of miR-10a-5p upregulated the expression of ALP and RUNX2 in vitro. Furthermore, miR-10a-5p acted as a suppressor during the process of new bone formation in vivo. In conclusion, the findings of the present study suggested that miR-10a-5p served as a negative regulatory factor during osteoblast differentiation of hBMSCs and may be utilized in a treatment approach for bone repair in osteogenic-related diseases.

New Insights on Mechanical Stimulation of Mesenchymal Stem Cells for Cartilage Regeneration

Successful tissue regeneration therapies require further understanding of the environment in which the cells are destined to be set. The aim is to structure approaches that aspire to a holistic view of biological systems and to scientific reliability. Mesenchymal stem cells represent a valuable resource for cartilage tissue engineering, due to their chondrogenic differentiation capacity. Promoting chondrogenesis, not only by growth factors but also by exogenous enhancers such as biomechanics, represents a technical enhancement. Tribological evaluation of the articular joint has demonstrated how mechanical stimuli play a pivotal role in cartilage repair and participate in the homeostasis of this tissue. Loading stresses, physiologically experienced by chondrocytes, can upregulate the production of proteins like glycosaminoglycan or collagen, fundamental for articular wellness, as well as promote and preserve cell viability. Therefore, there is a rising interest in the development of bioreactor devices that impose compression, shear stress, and hydrostatic pressure on stem cells. This strategy aims to mimic chondrogenesis and overcome complications like hypertrophic phenotyping and inappropriate mechanical features. This review will analyze the dynamics inside the joint, the natural stimuli experienced by the chondrocytes, and how the biomechanical stimuli can be applied to a stem cell culture in order to induce chondrogenesis.

Investigating lubricin and known cartilage-based biomarkers of osteoarthritis

Introduction: Osteoarthritis (OA) is a degenerative disease which primarily affects hyaline cartilage, leading to pain, stiffness and loss of mobility of the entire articulation. Diagnosis is commonly based on symptoms and radiographs, but there is a growing interest in detecting novel biomarkers, in serum, urine and synovial fluid, which can be predictors of disease onset and progression.Areas covered: This review provides an overview of the main biomarkers currently used in OA clinical practice, with a focus on lubricin, a surface glycoprotein secreted in the synovial fluid that lubricates the cartilage and reduces the coefficient of friction within the joint. Key findings of the last years are presented throughout the article.Expert opinion: Analysis of biomarkers might suggest personalized protocols of treatment, guide the classification of OA phenotypes, contribute to precision medicine, avoid further unnecessary exams, facilitate drug discovery or refine treatment guidelines. For all these reasons, the investigation of novel cartilage-based biomarker of osteoarthritis needs to be promoted and improved.

Cycloastragenol as an Exogenous Enhancer of Chondrogenic Differentiation of Human Adipose-Derived Mesenchymal Stem Cells. A Morphological Study

Stem cell therapy and tissue engineering represent a promising approach for cartilage regeneration. However, they present limits in terms of mechanical properties and premature de-differentiation of engineered cartilage. Cycloastragenol (CAG), a triterpenoid saponin compound and a hydrolysis product of the main ingredient in Astragalus membranaceous, has been explored for cartilage regeneration. The aim of this study was to investigate CAG’s ability to promote cell proliferation, maintain cells in their stable active phenotype, and support the production of cartilaginous extracellular matrix (ECM) in human adipose-derived mesenchymal stem cells (hAMSCs) in up to 28 days of three-dimensional (3D) chondrogenic culture. The hAMSC pellets were cultured in chondrogenic medium (CM) and in CM supplemented with CAG (CAG–CM) for 7, 14, 21, and 28 days. At each time-point, the pellets were harvested for histological (hematoxylin and eosin (H&E)), histochemical (Alcian-Blue) and immunohistochemical analysis (Type I, II, and X collagen, aggrecan, SOX9, lubricin). After excluding CAG’s cytotoxicity (MTT Assay), improved cell condensation, higher glycosaminoglycans (sGAG) content, and increased cell proliferation have been detected in CAG–CM pellets until 28 days of culture. Overall, CAG improved the chondrogenic differentiation of hAMSCs, maintaining stable the active chondrocyte phenotype in up to 28 days of 3D in vitro chondrogenic culture. It is proposed that CAG might have a beneficial impact on cartilage regeneration approaches.

Mechanical stimulation promotes the proliferation and the cartilage phenotype of mesenchymal stem cells and chondrocytes co-cultured in vitro

Mesenchymal stem cells and chondrocytes are an important source of the cells for cartilage tissue engineering. Therefore, the culture and expansion methods of these cells need to be improved to overcome the aging of chondrocytes and induced chondrogenic differentiation of mesenchymal stem cells. The aim of this study was to expand the cells for cartilage tissue engineering by combining the advantages of growing cells in co-culture and under a mechanically-stimulated environment. Rabbit chondrocytes and co-cultured cells (bone mesenchymal stem cells and chondrocytes) were subjected to cyclic sinusoidal dynamic tensile mechanical stimulationusing the FX-4000 tension system. Chondrocyte proliferation was assayed by flow cytometry and CFSE labeling. The cell cartilage phenotype was determined by detecting GAG, collagen II and TGF-β1 protein expression by ELISA and the Col2α1, TGF-β1 and Sox9 gene expression by RT-PCR. The results show that the co-culture improved both the proliferation ability of chondrocytes and the cartilage phenotype of co-cultured cells. A proper cyclic sinusoidal dynamic tensile mechanical stimulation improved the proliferation ability and cartilage phenotype of chondrocytes and co-cultured cells. These results suggest that the co-culture of mesenchymal stem cells with chondrocytes and proper mechanical stimulation may be an appropriate way to rapidly expand the cells that have an improved cartilage phenotype for cartilage tissue engineering.

Functional Biomolecule Delivery Systems and Bioengineering in Cartilage Regeneration

Osteoarthritis (OA) is a common degenerative disease which involves articular cartilage, and leads to total joint disability in the advanced stages. Due to its avascular and aneural nature, damaged cartilage cannot regenerate itself. Stem cell therapy and tissue engineering represent a promising route in OA therapy, in which cooperation of mesenchymal stem cells (MSCs) and three-dimensional (3D) scaffolds contribute to cartilage regeneration. However, this approach still presents some limits such as poor mechanical properties of the engineered cartilage. The natural dynamic environment of the tissue repair process involves a collaboration of several signals expressed in the biological system in response to injury. For this reason, tissue engineering involving exogenous "influencers" such as mechanostimulation and functional biomolecule delivery systems (BDS), represent a promising innovative approach to improve the regeneration process. BDS provide a controlled release of biomolecules able to interact between them and with the injured tissue. Nano-dimensional BDS is the future hope for the design of personalized scaffolds, able to overcome the delivery problems. MSC-derived extracellular vesicles (EVs) represent an attractive alternative to BDS, due to their innate targeting abilities, immunomodulatory potential and biocompatibility. Future advances in cartilage regeneration should focus on multidisciplinary strategies such as modular assembly strategies, EVs, nanotechnology, 3D biomaterials, BDS, mechanobiology aimed at constructing the functional scaffolds for actively targeted biomolecule delivery. The aim of this review is to run through the different approaches adopted for cartilage regeneration, with a special focus on biomaterials, BDS and EVs explored in terms of their delivery potential, healing capabilities and mechanical features.

Adipose derived mesenchymal stem cells alleviated osteoarthritis and chondrocyte apoptosis through autophagy inducing

OBJECTIVE

We aim to explore the effect of adipose derived mesenchymal stem cells (ADMSCs) on a knee osteoarthritis rat model and analyze how ADMSCs affect chondrocyte apoptosis.

MATERIALS AND METHODS

A surgically induced rat knee osteoarthritis (OA) model was constructed. ADMSCs were engrafted into the right knee cavity. Hematoxylin and eosin (H&E), Masson, and Safranin O were used to compare the histopathology of synovial membrane and cartilage. Immunohistochemical (IHC) was used to measure MMP-13, Collagen 2 (Col-2), Caspase-3 (Cas-3), PARP, p62, LC3b, DDR-2, FGFR-1, Wnt, P-AKT/AKT, p-CAMKII/CAMKII, and p-Smad1/Smad1 expression in the articular cartilage. qPCR and Western blot analysis were used to detect mRNA and protein levels of markers in chondrocytes. TUNEL and Annexin-V were used to assess apoptosis.

RESULTS

Histological analysis showed that ADMSCs alleviated the deterioration of cartilage and osteoarthritis. ADMSCs coculture increase the expression of Col2 and Sox-9, while down regulated MMP-13 in IL-1β stimulated chondrocytes. ADMSCs decreased proinflammatory cytokines IL-1β, IL-6, and TNF-α. ADMSCs enhanced the viability of IL-1β stimulated chondrocytes. ADMSC attenuated chondrocyte apoptosis. The pretreatment of 3-methyladenine (3-MA) reversed the reduction of Caspase-3 caused by ADMSCs, showing that the antiapoptotic effect was associated with autophagy inducing. ADMSCs significantly reduced the expression of FGFR-1, DDR-2, and Wnt in IL-1β stimulated chondrocytes. ADMSCs reduced the ratio of p-Smad1/Smad1 and p-CAMK II/CAMKII, and increased the ratio of p-AKT/AKT.

CONCLUSIONS

ADMSCs treatment alleviate osteoarthritis in rat OA models. AMDSCs reduced the secretion of proinflammatory cytokines and protected against apoptosis through autophagy inducing. ADMSCs' function could be related to multiple signaling pathway.

Brain-derived neurotrophic factor modified human umbilical cord mesenchymal stem cells-derived cholinergic-like neurons improve spatial learning and memory ability in Alzheimer's disease rats

Alzheimer's disease (AD) is an age-related neurodegenerative disease and the most common type of dementia. Although it is still incurable, stem cell replacement therapy provides new hope for AD. Human umbilical cord mesenchymal stem cells (hUC-MSCs) have multiple differentiation potentials, which can differentiate into cholinergic-like neurons and promote the release of acetylcholine. Brain-derived neurotrophic factor (BDNF) can also promote neurogenesis and synaptic formation, reduce oxidative stress and cell death. Therefore, we investigated the therapeutic effects of BDNF modified hUC-MSCs-derived cholinergic-like neurons in AD rats in this study. To make AD models, 1 μl beta amyloid (Aβ)_1-42 was injected into the right hippocampus of the rats. After two weeks, the hUC-MSCs-derived cholinergic-like neurons null cells or overexpressing BDNF cells delivered by lentiviralvectors were slowly injected into the right hippocampus of the AD rats. After 8 weeks of transplantation, Morris water maze test, Western blotting, Immunohistochemistry, Immunofluorescence assay and TdT mediated dUTP Nick End Labeling (TUNEL) detection were performed. Transplantation of BDNF modified hUC-MSCs-derived cholinergic-like neurons significantly improved spatial learning and memory abilities in the AD rats, increased the release of acetylcholine and ChAT expression in the hippocampus, enhanced the activation of astrocytes and microglia, reduced the expression of Aβ and recombinant human beta-site APP-cleaving enzyme1 (BACE1), inhibited neuronal apoptosis, and promoted neurogenesis. Our results demonstrate that BDNF modified hUC-MSCs-derived cholinergic-like neurons might be a promising therapeutic strategy for AD.

Bombyx mori derived scaffolds and their use in cartilage regeneration: a systematic review

For the last two decades, silk has been extensively used as scaffolds in tissue engineering because of its remarkable properties. Unfortunately, the aneural property of cartilage limits its regenerative potential which can be achieved using tissue engineering approach. A lot of research has been published searching for the optimization of silk fibroin (SF) and its blends in order to get the best cartilage mimicking properties. However, according to our best knowledge, there is no systematic review available regarding the use of Bombyx mori derived biomaterials limited to cartilage related studies. This systematic review highlights the in vitro and in vivo work done for the past 7 years on structural and functional properties of B. mori derived biomaterials together with different parameters for cartilage regeneration. PubMed database was searched focusing on in vitro and in vivo studies using the search thread "silk fibroin" and "cartilage". A total of 40 articles met the inclusion criteria. All the articles were deeply studied for cell types, scaffold types and animal models used along with study design and results. Five types of cells were used for in vitro while seven types of cells were used for in vivo studies. Three types of animal models were used for scaffold implantation purpose. Moreover, different types of scaffolds either seeded with cells or supplemented with various factors were explored and discussed in detail. Results suggest the suitability of silk as a better biomaterial because of its cartilage mimicking properties.

Non-apoptotic Caspase regulation of stem cell properties

The evolutionarily conserved family of proteins called caspases are the main factors mediating the orchestrated programme of cell suicide known as apoptosis. Since this protein family was associated with this essential biological function, the majority of scientific efforts were focused towards understanding their molecular activation and function during cell death. However, an emerging body of evidence has highlighted a repertoire of non-lethal roles within a large variety of cell types, including stem cells. Here we intend to provide a comprehensive overview of the key role of caspases as regulators of stem cell properties. Finally, we briefly discuss the possible pathological consequences of caspase malfunction in stem cells, and the therapeutic potential of caspase regulation applied to this context.

Using the interplay of magnetic guidance and controlled TGF-β release from protein-based nanocapsules to stimulate chondrogenesis

Introduction

Stimulating the proliferation and differentiation of chondrocytes for the regeneration of articular cartilage is a promising strategy, but it is currently ineffective. Although both physical stimulation and growth factors play important roles in cartilage repair, their interplay remains unclear and requires further investigation. In this study, we aimed to clarify their contribution using a magnetic drug carrier that not only can deliver growth factors but also provide an external stimulation to cells in the two-dimensional environment.

Materials and methods

We developed a nanocapsule (transforming growth factor-β1 [TGF-β1]-loaded magnetic amphiphilic gelatin nanocapsules [MAGNCs]; TGF-β1@MAGNCs) composed of hexanoic-anhydride-grafted gelatin and iron oxide nanoparticles to provide a combination treatment of TGF-β1 and magnetically induced physical stimuli. With the expression of Arg-Gly-Asp peptide in the gelatin, the TGF-β1@MAGNCs have an inherent affinity for chondrogenic ATDC5 cells.

Results

In the absence of TGF-β1, ATDC5 cells treated with a magnetic field show significantly upregulated Col2a1 expression. Moreover, TGF-β1 slowly released from biodegradable TGF-β1@ MAGNCs further improves the differentiation with increased expression of Col2a1 and Aggrecan.

Conclusion

Our study shows the time-dependent interplay of physical stimuli and growth factors on chondrogenic regeneration, and demonstrates the promising use of TGF-β1@MAGNCs for articular cartilage repair.

Adipose-derived stem-cell-implanted poly(ϵ-caprolactone)/chitosan scaffold improves bladder regeneration in a rat model

AIM

The study investigated the feasibility of seeding adipose-derived stem cells (ASCs) onto a poly(ϵ-caprolactone)/chitosan (PCL/CS) scaffold for bladder reconstruction using a rat model of bladder augmentation.

MATERIALS & METHODS

In the experimental group, the autologous ASCs were seeded onto the PCL/CS scaffold for bladder augmentation. An unseeded scaffold was used for bladder augmentation as control group. The sham group was also set.

RESULT

8 weeks after implantation, more densely smooth muscles were detected in the experimental group with a larger bladder capacity and more intensive blood vessels. Immunofluorescence staining demonstrated that some of the smooth muscle cells were transdifferentiated from the ASCs.

CONCLUSION

Our findings indicated that ASC-seeded PCL/CS may be a potential scaffold for bladder tissue engineering.

Platelet-rich plasma enhances the proliferation of human adipose stem cells through multiple signaling pathways

BACKGROUND

Platelet-rich plasma (PRP) is an autologous blood product that contains a high concentration of several growth factors. Platelet-derived growth factor (PDGF)-BB is a potential mitogen for human adipose-derived stem cells (hASCs). PRP stimulates proliferation of hASCs; however, the signaling pathways activated by PRP remain unclear.

METHODS

hASCs were cultured with or without PRP or PDGF-BB, and proliferation was assessed. hASCs were also treated with PRP or PDGF-BB with or without imatinib, which is a PDGF receptor tyrosine kinase inhibitor, or sorafenib, which is a multikinase inhibitor. Inhibition of cell proliferation was examined using anti-PDGF antibody (Abcam, Cambridge, UK), by cell counting. We assessed the effects of inhibitors of various protein kinases such as ERK1/2, JNK, p38, and Akt on the proliferation of hASCs.

RESULTS

The proliferation was remarkably promoted in cells treated with either 1% PRP or 10 ng/ml PDGF-BB, and both imatinib and sorafenib inhibited this proliferation. Anti-PDGF antibody (0.5 and 2 μg/ml) significantly decreased the proliferation of hASCs compared with control. PRP-mediated hASC proliferation was blocked by inhibitors of ERK1/2, Akt, and JNK, but not by an inhibitor of p38.

CONCLUSIONS

PRP promotes hASC proliferation, and PDGF-BB in PRP plays a major role in inducing the proliferation of hASCs. PRP promotes hASC proliferation via ERK1/2, PI3K/Akt, and JNK signaling pathways.

Autophagy is required for human umbilical cord mesenchymal stem cells to improve spatial working memory in APP/PS1 transgenic mouse model

Background

Recent studies have shown that autophagy plays a central role in mesenchymal stem cells (MSCs), and many studies have shown that human umbilical cord MSCs (huMSCs) can treat Alzheimer’s disease (AD) through a variety of mechanisms. However, no studies have looked at the effects of autophagy on neuroprotective function of huMSCs in the AD mouse model. Thus, in this study we investigated whether inhibition of autophagy could weaken or block the function of huMSCs through in vitro and in vivo experiments.

Methods

In vitro we examined huMSC migration and neuronal differentiation by inhibiting or activating autophagy; in vivo autophagy of huMSCs was inhibited by knocking down Beclin 1, and these huMSCs were transplanted into the APP/PS1 transgenic mouse. A series of related indicators were detected by T-maze task, electrophysiological experiments, immunofluorescence staining, enzyme-linked immunosorbent assay (ELISA), and Western blotting.

Results

We demonstrated that regulation of autophagy can affect huMSC migration and their neuronal differentiation. Moreover, inhibition of autophagy in huMSCs could not realize neuroprotective effects via anti-apoptosis or promoting neurogenesis and synapse formation compared with those of control huMSCs.

Conclusions

These findings indicate that autophagy is required for huMSCs to maintain their function and improve cognition impairment in APP/PS1 transgenic mice.

The human umbilical cord stem cells improve the viability of OA degenerated chondrocytes

Osteoarthritis (OA) affects a large number of patients; however, human umbilical cord stem cells exhibit therapeutic potential for treating OA. The aim of the present study was to explore the interaction between human umbilical cord stem cells and degenerated chondrocytes, and the therapeutic potential of human umbilical cord stem cells on degenerated chondrocytes. Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) were harvested from human umbilical cords, and flow cytometry was used to analyze the surface antigen markers, in addition, chondrogenic, osteogenic and adipogenic differentiation on the cells was investigated. OA cells at P3 were cocultured with hUC-MSCs in a separated co-culture system, and reverse transcription-polymerase chain reaction and western blot were used to evaluate the mRNA, and protein expression of collagen type II (Col2), SRY-box 9 (sox-9) and aggrecan. The level of inflammatory cytokines, tumor necrosis factor-α, interleukin (IL)-1β, IL-6, IL-10, were analyzed by ELISA in the supernatant. hUC-MSCs grow in a fibroblastic shape with stable proliferation. hUC-MSCs expressed cluster of differentiation 44 (CD44), CD73, CD90, CD105; while did not express CD34, CD45, CD106, CD133. After multi-induction, hUC-MSCs were able to differatiate into adipogenic, osteogenic and chondrogenic lineage. hUC-MSCs inhibited the expression of matrix metalloproteinase-13, collagen type X α1 chain and cyclooxygenase-2 in OA chondrocytes, and enhanced the proliferation of OA chondrocytes, while OA chondrocytes stimulated the production of Col2, sox-9 and aggrecan and promoted hUC-MSCs differentiate into chondrocytes. Flow cytometry analysis demonstrated hUC-MSCs have a predominant expression of stem cell markers, while the hematopoietic and endothelial markers were absent. Osteogenic, chondrogenic and adipogenic differentiation was observed in certain induction conditions. hUC-MSCs improved the proliferation of OA chondrocytes and downregulated the expression of inflammatory cytokines, while OA chondrocytes promoted MSCs to differentiate into chondrocytes. Taken together, the co-culture of hUC-MSCs and OA chondrocytes may provide a therapeutic potential in OA treatment.

The effects of knee immobilization on marrow adipocyte hyperplasia and hypertrophy at the proximal rat tibia epiphysis

Marrow adipose deposition is observed during aging and in association with extended periods of immobility. The objective of this study was to determine the contribution of adipocyte hypertrophy and hyperplasia to bone marrow fat deposition induced by immobilization of the rat knee joint for 2, 4, 16 or 32 weeks. Histomorphometric analyses compared immobilized to sham-operated proximal tibia from age and gender matched rats to assess the contribution of aging and duration of immobilization on the number and size of marrow adipocytes. Results indicated that marrow adipose tissue increased with the duration of immobilization and was significant larger at 16 weeks compared to the sham-operated group (0.09956±0.13276mm² vs 0.01990±0.01100mm², p=0.047). The marrow adipose tissue was characterized by hyperplasia of adipocytes with a smaller average size after 2 and 4 weeks of immobilization (at 2 weeks hyperplasia: 68.86±33.62 vs 43.57±24.47 adipocytes/mm², p=0.048; at 4 weeks hypotrophy: 0.00036±0.00019 vs 0.00046±0.00023mm², p=0.027), and by adipocyte hypertrophy after 16 weeks of immobilization (0.00083±0.00049 vs 0.00046±0.00028mm², p=0.027) compared to sham-operated. Both immobilized and sham-operated groups showed marrow adipose conversion with age; immobilized (p=0.008; sham: p=0.003). Overall, fat deposition in the bone marrow of the proximal rat tibia epiphysis and induced by knee joint immobilization was characterized by hyperplasia of small adipocytes in the early phase and by adipocyte hypertrophy in the later phase. Mediators of marrow fat deposition after immobilization and preventive countermeasures need to be investigated.