Transfection of the IHH gene into rabbit BMSCs in a simulated microgravity environment promotes chondrogenic differentiation and inhibits cartilage aging

Revolutionizing osteoarthritis treatment: How mesenchymal stem cells hold the key

Osteoarthritis (OA) is a multifaceted disease characterized by imbalances in extracellular matrix metabolism, chondrocyte and synoviocyte senescence, as well as inflammatory responses mediated by macrophages. Although there have been notable advancements in pharmacological and surgical interventions, achieving complete remission of OA remains a formidable challenge, oftentimes accompanied by significant side effects. Mesenchymal stem cells (MSCs) have emerged as a promising avenue for OA treatment, given their ability to differentiate into chondrocytes and facilitate cartilage repair, thereby mitigating the impact of an inflammatory microenvironment induced by macrophages. This comprehensive review aims to provide a concise overview of the diverse roles played by MSCs in the treatment of OA, while elucidating the underlying mechanisms behind these contributions. Specifically, the roles include: (a) Promotion of chondrocyte and synoviocyte regeneration; (b) Inhibition of extracellular matrix degradation; (c) Attenuating the macrophage-induced inflammatory microenvironment; (d) Alleviation of pain. Understanding the multifaceted roles played by MSCs in OA treatment is paramount for developing novel therapeutic strategies. By harnessing the regenerative potential and immunomodulatory properties of MSCs, it may be possible to devise more effective and safer approaches for managing OA. Further research and clinical studies are warranted to optimize the utilization of MSCs and realize their full potential in the field of OA therapeutics.

3D biofabrication and space: A 'far-fetched dream' or a 'forthcoming reality'?

The long duration space missions across the Low Earth Orbit (LEO) often expose the voyagers to an abrupt zero gravity influence. The severe extraterrestrial cosmic radiation directly causes a plethora of moderate to chronic healthcare crises. The only feasible solution to manage critical injuries on board is surgical interventions or immediate return to Earth. This led the group of space medicine practitioners to adopt principles from tissue engineering and develop human tissue equivalents as an immediate regenerative therapy on board. The current review explicitly demonstrates the constructive application of different tissue-engineered equivalents matured under the available ground-based microgravity simulation facilities. Further, it elucidates how augmenting the superiority of biomaterial-based 3D bioprinting technology can enhance their clinical applicability. Additionally, the regulatory role of weightlessness condition on the underlying cellular signaling pathways governing tissue morphogenesis has been critically discussed. This information will provide future directions on how 3D biofabrication can be used as a plausible tool for healing on-flight chronic health emergencies. Thus, in our review, we aimed to precisely debate whether 3D biofabrication is deployed to cater to on-flight healthcare anomalies or space-like conditions are being utilized for generating 3D bioprinted human tissue constructs for efficient drug screening and regenerative therapy.

In situ self-assembled organoid for osteochondral tissue regeneration with dual functional units

The regeneration of hierarchical osteochondral units is challenging due to difficulties in inducing spatial, directional and controllable differentiation of mesenchymal stem cells (MSCs) into cartilage and bone compartments. Emerging organoid technology offers new opportunities for osteochondral regeneration. In this study, we developed gelatin-based microcryogels customized using hyaluronic acid (HA) and hydroxyapatite (HYP), respectively for inducing cartilage and bone regeneration (denoted as CH-Microcryogels and OS-Microcryogels) through in vivo self-assembly into osteochondral organoids. The customized microcryogels showed good cytocompatibility and induced chondrogenic and osteogenic differentiation of MSCs, while also demonstrating the ability to self-assemble into osteochondral organoids with no delamination in the biphasic cartilage-bone structure. Analysis by mRNA-seq showed that CH-Microcryogels promoted chondrogenic differentiation and inhibited inflammation, while OS-Microcryogels facilitated osteogenic differentiation and suppressed the immune response, by regulating specific signaling pathways. Finally, the in vivo engraftment of pre-differentiated customized microcryogels into canine osteochondral defects resulted in the spontaneous assembly of an osteochondral unit, inducing simultaneous regeneration of both articular cartilage and subchondral bone. In conclusion, this novel approach for generating self-assembling osteochondral organoids utilizing tailor-made microcryogels presents a highly promising avenue for advancing the field of tissue engineering.

MECHANOBIOLOGICAL APPROACHES FOR STIMULATING CHONDROGENESIS OF STEM CELLS

Chondrogenesis is the process of differentiation of stem cells into mature chondrocytes. Such a process consists of chemical, functional, and structural changes which are initiated and mediated by the host environment of the cells. To date, the mechanobiology of chondrogenesis has not been fully elucidated. Hence, experimental activity is focused on recreating specific environmental conditions for stimulating chondrogenesis, and to look for a mechanistic interpretation of the mechanobiological response of cells in the cartilaginous tissues. There are a large number of studies on the topic that vary considerably in their experimental protocols used for providing environmental cues to cells for differentiation, making generalizable conclusions difficult to ascertain. The main objective of this contribution is to review the mechanobiological stimulation of stem cell chondrogenesis and methodological approaches utilized to date to promote chondrogenesis of stem cells in-vitro. In-vivo models will also be explored, but this area is currently limited. An overview of the experimental approaches used by different research groups may help the development of unified testing methods that could be used to overcome existing knowledge gaps, leading to an accelerated translation of experimental findings to clinical practice.

Altered Expression of the Hedgehog Pathway Proteins BMP2, BMP4, SHH, and IHH Involved in Knee Cartilage Damage of Patients With Osteoarthritis and Kashin-Beck Disease

OBJECTIVE

To investigate the expression of Hedgehog (HH) signaling pathway proteins in knee articular cartilage from Kashin-Beck disease (KBD) and osteoarthritis (OA) patients.

METHODS

Knee articular cartilage samples were collected from normal (N), OA, and KBD adults (aged 38-60 years) and divided into 3 groups with 6 subjects in each group. The localization of the HH pathway proteins bone morphogenetic protein 2 (BMP2), bone morphogenetic protein 4 (BMP4), Sonic hedgehog (SHH), and Indian hedgehog (IHH) was observed with the microscope after immunohistochemical (IHC) staining. Positive staining cell rates of each proteins were compared.

RESULTS

The strongest stainings of all proteins were observed in the middle zones of all 3 groups. The positive staining rates of BMP4 and IHH were significantly lower in the OA and KBD groups than those in the N group in all 3 zones. The positive staining rates of BMP2 and SHH tend to be lower in the OA and KBD groups than those in the N group in the deep zone, while higher in the OA and KBD groups than those in the N group in superficial and middle zones.

CONCLUSIONS

Altered expression of the HH pathway proteins BMP2, BMP4, SHH, and IHH was found in OA and KBD articular cartilage. There seemed to be a compensatory effect between SHH and IHH in cartilage damage. Further studies on the pathogenesis of OA and KBD may be carried out from these aspects in the future.

Implication of Mesenchymal Stem Cells and Their Derivates for Osteochondral Regeneration

Healing of articular cartilage defects presents a challenging issue, due to its regenerative shortcomings. Lacking vascularity and innervation of cartilage and low proliferative potential of chondrocytes are the main reasons for the limited healing potential of articular cartilage. Traditional reparative approaches are limited in their efficiency, hence there is a demand for novel reparative treatments. Mesenchymal stromal cells, preferred for clinical uses, can be readily derived from various sources and have been proven to have a therapeutic effect on cartilage and subchondral bone. Therefore, mesenchymal stromal cells, their derivates, and scaffolds have been utilized in research targeting osteochondral regeneration. The present review aims to comprehensively outline and discuss literature considering this topic published within last 5 years.

Spaceflight and simulated microgravity suppresses macrophage development via altered RAS/ERK/NFκB and metabolic pathways

Spaceflight-associated immune system weakening ultimately limits the ability of humans to expand their presence beyond the earth's orbit. A mechanistic study of microgravity-regulated immune cell function is necessary to overcome this challenge. Here, we demonstrate that both spaceflight (real) and simulated microgravity significantly reduce macrophage differentiation, decrease macrophage quantity and functional polarization, and lead to metabolic reprogramming, as demonstrated by changes in gene expression profiles. Moreover, we identified RAS/ERK/NFκB as a major microgravity-regulated pathway. Exogenous ERK and NFκB activators significantly counteracted the effect of microgravity on macrophage differentiation. In addition, microgravity also affects the p53 pathway, which we verified by RT-qPCR and Western blot. Collectively, our data reveal a new mechanism for the effects of microgravity on macrophage development and provide potential molecular targets for the prevention or treatment of macrophage differentiation deficiency in spaceflight.

TL1A/TNFR2 Axis Enhances Immunoregulatory Effects of Bone Marrow Derived Mesenchymal Stem Cell by Indian Hedgehog Signaling Pathway

Background and Objectives

The immunomodulatory potential of mesenchymal stem cells (MSCs) can be regulated by a variety of molecules, especially cytokines. The inflammatory cytokine, TNF-like ligand 1A (TL1A), has been reported as an inflammation stimulator in-multiple autoimmune diseases. Here, we studied the effects of TL1A/TNF-receptor 2 (TNFR2) pathway on the therapeutic potency of bone marrow-derived MSCs (BMSCs).

Methods and Results

BMSCs, fibroblast-like synoviocytes (FLSs), and H9 and jurkat human T lymphocytes were used in this study. BMSCs paracrine activities, differentiation, proliferation, and migration were investigated after stimulation with TL1A, and intervened with anti-TNFR2. Additionally, the effects of TL1A on BMSCs therapeutic potency were evaluated by treating RA-FLSs, and H9 and jurkat T cells with TL1A-stimulated BMSCs conditioned medium (CM). Indian hedgehog (IHH) involvement was determined by gene silencing and treatment by recombinant IHH (rIHH). TL1A induced BMSCs stemness-related genes, COX-2, IL-6, IDO, TGF-β and HGF through TNFR2. Also, TL1A corrected biased differentiation and increased proliferation, and migration through TNFR2. Meanwhile, CM of TL1A-stimulated BMSCs decreased the inflammatory markers of RA-FLSs and T cells. Moreover, TL1A-stimulated BMSCs experienced IHH up-regulation coupled with NF-κB and STAT3 signaling up-regulation, while p53 and oxidative stress were down-regulated. Furthermore, treatment of BMSCs by rIHH increased their anti-inflammatory effects. More importantly, knockdown of IHH decreased the ability of TL1A-stimulated BMSCs to alleviating the inflammation in RA-FLSs and T cells.

Conclusions

This study reports the effects of TL1A/TNFR2 pathway on the biological behaviors and therapeutic potency of BMSCs through IHH. These findings could introduce novel procedures to increase the stemness of MSCs in cellular therapy.

Synergistic effects of Indian hedgehog and sonic hedgehog on chondrogenesis during cartilage repair

Sonic hedgehog (Shh) and Indian hedgehog (Ihh) have been shown to control the induction of early cartilaginous differentiation. However, it is unclear whether Ihh and Shh exert synergistic effects on chondrogenesis during articular cartilage repair. Herein, we investigate the effects of chondrogenesis of bone-derived mesenchymal stem cells (BMSCs) following co-transfection with Shh and Ihh via adenoviral vectors in vitro and in vivo. A rotary cell culture system (RCCS) and Cytodex 3 microcarriers were used to create a stereoscopic dynamic environment for cell culture. In the RCCS environment, BMSCs co-transfected with Ihh and Shh displayed stronger chondrogenic differentiation and chondrogenesis than BMSCs transfected with Ihh or Shh alone, and exhibited higher expression levels of Sox 9, ACAN and collagen II, stronger toluidine blue and collagen II immunohistochemical staining. After transplanted into the osteochondral defect at 8 weeks, Ihh/Shh co-transfected BMSCs showed a significantly better cartilage repair than BMSCs transfected with Ihh or Shh alone. Ihh and Shh have synergistic effects on the induction of chondrogenic differentiation and chondrogenesis under a microgravity environment, and help to repair damaged cartilage and reverse subchondral defects during the early stages.

Exosomes derived from umbilical cord mesenchymal stem cells in mechanical environment show improved osteochondral activity via upregulation of LncRNA H19

Background

Exosomes derived from stem cells have been demonstrated to be good candidates for the treatment of osteochondral injury. Our previous studies have demonstrated that mechanical stimulation could be crucial for the secretion of exosomes derived from umbilical cord mesenchymal stem cells (U-MSCs). Therefore, we explore whether mechanical stimulation caused by a rotary cell culture system (RCCS) has a beneficial effect on exosome yield and biological function.

Methods

U-MSCs were subjected to an RCCS at different rotational speeds and exosomes were characterised by transmission electron microscopy, nanoparticle tracking analysis and western blotting. small-interfering RNAs of Rab27a (siRNA-Rab27a) was used to reduce exosome production. Quantitative real-time PCR (qRT-PCR) was used to detect the expression of mechanically sensitive long non-coding RNA H19 (LncRNA H19). The effects of exosomes on chondrocyte proliferation were examined using cell counting kit-8 (CCK-8), toluidine blue staining and a series of related genes. Annexin V-FITC and PI (V-FITC/PI) flow cytometry was used to detect the effect of exosomes on the inhibition of chondrocyte apoptosis. Macroscopic evaluation, MRI quantification and immunohistochemical staining were conducted to investigate the in vivo effects of exosomal LncRNA H19 through SD rat cartilage defect models.

Results

RCCS significantly promoted exosome production at 36 rpm/min within 196 h. Mechanical stimulation was able to increase the expression level of exosomes. The exosomal LncRNA H19 was found to promote chondrocyte proliferation and matrix synthesis and inhibit apoptosis in vitro. Chondral regeneration activity was lost in LncRNA H19-defective exosomes. The injection of exosomal LncRNA H19 in vivo resulted in improved macroscopic assessment, MRI quantification and histological analysis. Moreover, exosomal LncRNA H19 was able to relieve pain levels during the early stages of cartilage repair in an animal experiment.

Conclusion

Our findings confirmed that mechanical stimulation can enhance exosome yield as well as biological function for the repair of cartilage defects. The underlying mechanism may be related to the high expression of LncRNA H19 in exosomes. The translational potential of this article: This study provides a theoretical support of optimizing exosome production. It advances the yield of mesenchymal stem cell exosome and facilitate the clinical application to repair of osteochondral damage.

Indian Hedgehog regulates senescence in bone marrow-derived mesenchymal stem cell through modulation of ROS/mTOR/4EBP1, p70S6K1/2 pathway

Premature senescence of bone marrow-derived mesenchymal stem cells (BMSC) remains a major concern for their application clinically. Hedgehog signaling has been reported to regulate aging-associated markers and MSC skewed differentiation. Indian Hedgehog (IHH) is a ligand of Hedgehog intracellular pathway considered as an inducer in chondrogenesis of human BMSC. However, the role of IHH in the aging of BMSC is still unclear. This study explored the role IHH in the senescence of BMSC obtained from human samples and senescent mice. Isolated BMSC were transfected with IHH siRNA or incubated with exogenous IHH protein and the mechanisms of aging and differentiation investigated. Moreover, the interactions between IHH, and mammalian target of rapamycin (mTOR) and reactive oxygen species (ROS) were evaluated using the corresponding inhibitors and antioxidants. BMSC transfected with IHH siRNA showed characteristics of senescence-associated features including increased senescence-associated β-galactosidase activity (SA-β-gal), induction of cell cycle inhibitors (p53/p16), development of senescence-associated secretory phenotype (SASP), activation of ROS and mTOR pathways as well as the promotion of skewed differentiation. Interestingly, BMSC treatment with IHH protein reversed the senescence markers and corrected biased differentiation. Moreover, IHH shortage-induced senescence signs were compromised after mTOR and ROS inhibition. Our findings presented anti-aging activity for IHH in BMSC through down-regulation of ROS/mTOR pathways. This discovery might contribute to increasing the therapeutic, immunomodulatory and regenerative potency of BMSC and introduce a novel remedy in the management of aging-related diseases.

Exosomes produced from 3D cultures of umbilical cord mesenchymal stem cells in a hollow-fiber bioreactor show improved osteochondral regeneration activity

Animal and clinical studies have shown that mesenchymal stem cells (MSCs) play an important role in cartilage repair. The therapeutic effect of mesenchymal stem cells based therapies has been increasingly demonstrated to exosome-mediated paracrine secretion. Here, we investigated the cellular processes and mechanism of exosomes produced by conventional 2D culture (2D-Exos) and exosomes produced from 3D culture (3D-Exos) of umbilical MSCs (U-MSCs) in a hollow-fiber bioreactor for the treatment of cartilage repair. We found that the yield of 3D-Exos was 7.5-fold higher than that of 2D-Exos. The in vitro experiments indicated that both 2D-Exos and 3D-Exos can stimulate chondrocyte proliferation, migration, and matrix synthesis, and inhibit apoptosis, with 3D-Exos exerting a stronger effect than 2D-Exos. This effect was partly attributed to the activation of transforming growth factor beta 1 and Smad2/3 signaling. The injection of 2D-Exos and 3D-Exos showed enhanced gross appearance and attenuated cartilage defect; however, 3D-Exos showed a superior therapeutic effect than 2D-Exos. In summary, our study provides novel insights into the chondroprotective effects of exosomes produced from 3D culture of U-MSCs in a hollow-fiber bioreactor. Because of its promising biological function and high yield, 3D-Exos may become a promising therapeutic method for the treatment of cartilage defects.

Sonic hedgehog promotes chondrogenesis of rabbit bone marrow stem cells in a rotary cell culture system

BACKGROUND

Sonic hedgehog (Shh) is an important signalling protein involved in the induction of early cartilaginous differentiation. Herein, we demonstrate that Shh markedly induces chondrogenesis of rabbit bone marrow stromal cells (BMSCs) under microgravity conditions, and promotes cartilage regeneration.

RESULTS

In the rotary cell culture system (RCCS), chondrogenic differentiation was revealed by stronger Toluidine Blue and collagen II immunohistochemical staining in the Shh transfection group, and chondroinductive activity of Shh was equivalent to that of TGF-β. Western blotting and qRT-PCR analysis results verified the stronger expression of Sox9, aggrecan (ACAN), and collagen II in rabbit BMSCs treated with Shh or TGF-β in a microgravity environment. Low levels of chondrogenic hypertrophy, osteogenesis, and adipogenesis-related factors were detected in all groups. After transplantation in vivo, histological analysis revealed a significant improvement in cartilage and subchondral repair in the Shh transfection group.

CONCLUSIONS

These results suggested that Shh signalling promoted chondrogenesis in rabbit BMSCs under microgravity conditions equivalent to TGF-β, and improved the early stages of the repair of cartilage and subchondral defects. Furthermore, RCCS provided a dynamic culture microenvironment conducive for cell proliferation, aggregation and differentiation.

Cyclic tensile strain promotes chondrogenesis of bone marrow-derived mesenchymal stem cells by increasing miR-365 expression

AIMS

The chondrogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) is critical for cartilage regeneration. Tissues constructed from BMSCs through cartilage tissue engineering still exhibit some histological, morphological, and biomechanical differences from normal cartilage tissues. Cyclic tensile strain (CTS) can increase chondrogenic gene expression and reduce hypertrophic gene expression in chondrocytes. miR-365 has been identified as a mechanoresponsive microRNA and is an important regulator of both chondrocyte hypertrophy and differentiation. Therefore, we hypothesized that CTS may promote the chondrogenesis of BMSCs by upregulating the expression of miR-365.

METHODS

BMSCs were subjected to CTS to investigate the effects and mechanism on chondrogenesis. An Agilent miRNA microarray was used to profile miRNAs in the CTS-treated BMSCs and 3D-cultured control BMSCs. miR-365 was shown to interact with HDAC4 mRNA through a luciferase reporter assay. An animal cartilage defect model was constructed and different groups of BMSCs were implanted to investigate their in vivo effect.

KEY FINDINGS

CTS promoted BMSC chondrogenesis. miR-365 was significantly upregulated in CTS-treated cells and played an important role in CTS-mediated chondrogenesis. Luciferase assays showed that HDAC4 is a direct target of miR-365. An in vivo study showed that CTS treatment and miR-365 overexpression could promote cartilage regeneration from BMSCs.

SIGNIFICANCE

CTS can promote the expression of miR-365, a crucial mechanosensitive microRNA involved in the chondrogenesis of BMSCs, which directly inhibits the expression of HDAC4, in turn, enhancing the chondrogenesis of BMSCs.

Chondrogenic differentiation of bone marrow-derived mesenchymal stem cells following transfection with Indian hedgehog and sonic hedgehog using a rotary cell culture system

Background

Indian hedgehog (IHH) and Sonic hedgehog (SHH) are important regulators of chondrogenesis. However, activation of IHH and SHH also promotes chondrocyte hypertrophy and ossification during chondrogenesis. The aims of this study were to investigate the effect of microgravity on IHH- and SHH-induced chondrogenic differentiation and to elucidate the role of microgravity in this process.

Methods

Adenovirus plasmids encoding the rabbit IHH gene and SHH genes were constructed in vitro and transfected into rabbit bone marrow-derived mesenchymal stem cells (BMSCs). A rotary cell culture system (RCCS), in which a dynamic three-dimensional culture system combines the mechanical environment with a three-dimensional culture surface, was used for cell culture and differentiation. During the induction of differentiation, expression levels of cartilage-related and cartilage hypertrophy-related genes and proteins were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting, respectively. Toluidine blue and collagen II immunohistochemical staining and annexin V-Cy3 staining were used to indicate investigate cartilage matrix synthesis and hypertrophic hypertrophy, respectively, on day 21 after induction of differentiation.

Results

In this study, IHH and SHH were shown to be equipotent inducers of chondrogenesis in rabbit BMSCs, as evidenced by strong staining for proteoglycans and collagen II, and increased expression of mRNAs and proteins associated with chondrogenesis in an RCCS environment. More importantly, chondrogenic hypertrophy and aging were effectively inhibited in the RCCS environment. In addition, levels of cartilage-related markers in the IHH and SHH transfection groups were initially increased and later decreased in the traditional two-dimensional environment, while cartilage hypertrophy-related factors revealed higher mRNA expression levels during induction.

Conclusions

In summary, microgravity significantly promoted chondrogenic differentiation of BMSCs induced by IHH and SHH and attenuated chondrogenic hypertrophy and aging during chondrogenesis. Furthermore, exogenous IHH and SHH had the same effect on chondrogenic differentiation of BMSCs in the RCCS environment. This study provides further evidence of chondrogenic induction of BMSCs in vitro via IHH and SHH gene delivery.

Electronic supplementary material

The online version of this article (10.1186/s11658-019-0144-2) contains supplementary material, which is available to authorized users.

Sequential Zonal Chondrogenic Differentiation of Mesenchymal Stem Cells in Cartilage Matrices

IMPACT STATEMENT

The higher regenerative capacity of fetal articular cartilage compared with the adult is rooted in differences in cell density and matrix composition. We hypothesized that the zonal organization of articular cartilage can be engineered by encapsulation of mesenchymal stem cells in a single superficial zone-like matrix followed by sequential addition of zone-specific growth factors within the matrix, similar to the process of fetal cartilage development. The results demonstrate that the zonal organization of articular cartilage can potentially be regenerated using an injectable, monolayer cell-laden hydrogel with sequential release of growth factors.

Cartilage oligomeric matrix protein improves in vivo cartilage regeneration and compression modulus by enhancing matrix assembly and synthesis

Cartilage oligomeric matrix protein (COMP), an abundant cartilage extracellular matrix protein, plays an important role in mesenchymal chondrogenesis. To test our hypothesis that COMP could promote tissue engineering cartilage regeneration as well as improve cartilaginous mechanical properties, COMP gene transfected rabbit bone marrow mesenchymal stem cells (BMSCs) were used for chondrogenic differentiation in vitro and were implanted with biphasic scaffolds into osteochondral defects of New Zealand white rabbit trochlear grooves for cartilage regeneration in vivo. In vitro, over expressed COMP could enhance the chondrogenic differentiation and ECM secretion of BMSCs. After euthanasia at 12 weeks post implantation, macroscopic observation, histological staining, mechanical tests and micro-CT were performed for the assessment of repaired cartilage. Overexpression of COMP leads to more newly formed hyaline cartilage and significantly improved mechanical property. These results demonstrated the significant role of COMP in the cartilage regeneration in vivo and offered inspiring advantage of COMP in the application of tissue engineering.

Osteoblast-oriented differentiation of BMSCs by co-culturing with composite scaffolds constructed using silicon-substituted calcium phosphate, autogenous fine particulate bone powder and alginate in vitro

Autogenous bone graft is the best for spinal fusion in clinics, however, lacking sources, bleeding and infection are limited its practice. Seeking alternative materials are urgent for orthopaedic surgeon. Here, we evaluated osteoblast-oriented differentiation of rabbit BMSCs by co-culturing with composite scaffolds constructed using silicon-substituted-CaP-fine particulate bone powder-alginate. Using CCk8-kit, biocompatibility was evaluated by testing BMSCs proliferation; morphology and survival of osteoblasts within scaffolds were observed using EM and HE staining; growth factors and related genes were detected using RT-PCR. HE staining showed spindle-shaped BMSCs after the 3rd passage; EM data showed that uneven surface and longitudinal section were observed with scattered distribution of 5-100 mm interspaces, which leave enough space for BMSCs adhesion and growth. Interestingly, at 14-day culture with HE staining, osteocytes within the scaffolds grew well with regular shape and integrate structure. RT-PCR results showed that expression levels of BMP2, TGF-b and COL-I, ALP, OPN were increased significantly and time-dependently. Collectively, all mentioned effects were more obvious in co-culture BMSCs with scaffolds than those with other components. Immunohistochemistry showed that positive OPN expression was detected at 7-day co-culturing BMSCs with scaffold, rather than other situations. These results suggest that composite scaffolds constructed with Si-CaP-fine particulate bone powder-alginate have a certain degree of biocompatibility and bioactivity to promote osteoblast-oriented BMSCs differentiation.