Synergistic effect of recombinant human bone morphogenic protein-7 and osteogenic differentiation medium on human bone-marrow-derived mesenchymal stem cells in vitro

Extracellular derivatives for bone metabolism

BACKGROUND

Bone metabolism can maintain the normal homeostasis and function of bone tissue. Once the bone metabolism balance is broken, it will cause osteoporosis, osteoarthritis, bone defects, bone tumors, or other bone diseases. However, such orthopedic diseases still have many limitations in clinical treatment, such as drug restrictions, drug tolerance, drug side effects, and implant rejection.

AIM OF REVIEW

In complex bone therapy and bone regeneration, extracellular derivatives have become a promising research focus to solve the problems of bone metabolic diseases. These derivatives, which include components such as extracellular matrix, growth factors, and extracellular vesicles, have significant therapeutic potential. It has the advantages of good biocompatibility, low immune response, and dynamic demand for bone tissue. The purpose of this review is to provide a comprehensive perspective on extracellular derivatives for bone metabolism and elucidate the intrinsic properties and versatility of extracellular derivatives. Further discussion of them as innovative advanced orthopedic materials for improving the effectiveness of bone therapy and regeneration processes.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this review, we first listed the types and functions of three extracellular derivatives. Then, we discussed the effects of extracellular derivatives of different cell sources on bone metabolism. Subsequently, we collected applications of extracellular derivatives in the treatment of bone metabolic diseases and summarized the advantages and challenges of extracellular derivatives in clinical applications. Finally, we prospected the extracellular derivatives in novel orthopedic materials and clinical applications. We hope that the comprehensive understanding of extracellular derivatives in bone metabolism will provide new solutions to bone diseases.

Concentrated Bone Marrow Aspirate Injection for Hallux Sesamoid Disorders

Concentrated bone marrow aspirate (CBMA) offers an alternative to sesamoid resection in end stage sesamoid pathology. CBMA potentiates the anti-inflammatory effect, stimulates local tissue regeneration and osteogenesis, when injected into bone. The purpose of this study is to evaluate the functional outcomes in a cohort of athletes following CBMA injection for the treatment of hallux sesamoid disorders. A retrospective case series of consecutive patients treated with CBMA injection for hallux sesamoid disorders were identified. Radiographs, Foot and Ankle Outcome Scores (FAOS), and Visual Analogue Scale (VAS) score were collected pre- and postinjections. Descriptive statistics were presented as the mean and standard deviation for continuous variables and frequency as percentages for categorical variables. Fifteen consecutive patients with were included with a mean follow-up time of 20.1 (range 12-34) months. Significant improvement in all scoring subscales of the FAOS and VAS score was noted preinjection compared to final follow-up postinjection (p < .001). Eight of 11 patients that were involved in sports prior to the CBMA injection returned to play, with 7 successfully returning to preinjury level status. Three patients required further treatment (20%). The case series suggests that CBMA injection is a safe and effective treatment option for hallux sesamoid disorders with a high rate of return to play.

Role of microRNA-335 carried by bone marrow mesenchymal stem cells-derived extracellular vesicles in bone fracture recovery

Mesenchymal stem cells (MSCs) have the potential to reduce healing time and treat nonunion in fracture patients. In this study, bone marrow MSCs-derived extracellular vesicles (B-EVs) were firstly extracted and identified. CD9-/- and normal mice were enrolled for the establishment of fracture models and then injected with B-EVs. Osteoblast differentiation and fracture recovery were estimated. The levels of osteoblast-related genes were detected, and differentially expressed microRNAs (miRs) in B-EVs-treated normal fracture mice were screened and verified. The downstream mechanisms of miR were predicted and assessed. The loss-of functions of miR-335 in B-EV and gain-of-functions of VapB were performed in animal and cell experiments to evaluate their roles in bone fracture. Collectively, B-EVs promoted bone fracture recovery and osteoblast differentiation by releasing miR-335. miR-335 downregulation in B-EVs impaired B-EV functions in fracture recovery and osteoblast differentiation. miR-335 could target VapB, and VapB overexpression reversed the effects of B-EVs on osteoblast differentiation. B-EV treatment activated the Wnt/β-catenin pathway in fracture mice and osteoblasts-like cells. Taken together, the study suggested that B-EVs carry miR-335 to promote bone fracture recovery via VapB and the Wnt/β-catenin pathway. This study may offer insights into bone fracture treatment.

Insulin-Like Growth Factor-1 as a Possible Alternative to Bone Morphogenetic Protein-7 to Induce Osteogenic Differentiation of Human Mesenchymal Stem Cells in Vitro

Growth factors and mesenchymal stem cells (MSC) support consolidation of bone defects. Bone Morphogenetic Protein-7 (BMP-7) has been used clinically and experimentally, but the outcomes remain controversial. Increased systemic expression of Insulin-like Growth Factor-1 (IGF-1) significantly correlates with successful regeneration of bone healing disorders, making IGF-1 a promising alternative to BMP-7. There is no experimental data comparing the osteoinductive potential of IGF-1 and BMP-7. Therefore, in this study, the influence of IGF-1 and BMP-7 in different concentrations on the osteogenic differentiation of two human MSC-subtypes, isolated from reaming debris (RMSC) and iliac crest bone marrow (BMSC) has been assessed. A more sensitive reaction of BMSC towards stimulation with IGF-1 in concentrations of 400–800 ng/mL was found, leading to a significantly higher degree of osteogenic differentiation compared to stimulation with BMP-7. RMSC react more sensitively to stimulation with BMP-7 compared to BMSC. Lower concentrations of IGF-1 were necessary to significantly increase osteogenic differentiation of RMSC and BMSC compared to BMP-7. Therefore, IGF-1 should be considered as a valuable option to improve osteogenic differentiation of MSC and merits further experimental consideration. The MSC subtype and method of differentiation factor application also have to be considered, as they affect the outcome of osteogenic differentiation.

Bioinspired Design of Polycaprolactone Composite Nanofibers as Artificial Bone Extracellular Matrix for Bone Regeneration Application

The design and development of functional biomimetic systems for programmed stem cell response is a field of topical interest. To mimic bone extracellular matrix, we present an innovative strategy for constructing drug-loaded composite nanofibrous scaffolds in this study, which could integrate multiple cues from calcium phosphate mineral, bioactive molecule, and highly ordered fiber topography for the control of stem cell fate. Briefly, inspired by mussel adhesion mechanism, a polydopamine (pDA)-templated nanohydroxyapatite (tHA) was synthesized and then surface-functionalized with bone morphogenetic protein-7-derived peptides via catechol chemistry. Afterward, the resulting peptide-loaded tHA (tHA/pep) particles were blended with polycaprolactone (PCL) solution to fabricate electrospun hybrid nanofibers with random and aligned orientation. Our research demonstrated that the bioactivity of grafted peptides was retained in composite nanofibers. Compared to controls, PCL-tHA/pep composite nanofibers showed improved cytocompatibility. Moreover, the incorporated tHA/pep particles in nanofibers could further facilitate osteogenic differentiation potential of human mesenchymal stem cells (hMSCs). More importantly, the aligned PCL-tHA/pep composite nanofibers showed more osteogenic activity than did randomly oriented counterparts, even under nonosteoinductive conditions, indicating excellent performance of biomimetic design in cell fate decision. After in vivo implantation, the PCL-tHA/pep composite nanofibers with highly ordered structure could significantly promote the regeneration of lamellar-like bones in a rat calvarial critical-sized defect. Accordingly, the presented strategy in our work could be applied for a wide range of potential applications in not only bone regeneration application but also pharmaceutical science.

Bone formation of human mesenchymal stem cells harvested from reaming debris is stimulated by low-dose bone morphogenetic protein-7 application in vivo

Stimulation of mesenchymal stem cells (MSC) by bone morphogenetic protein-7 (BMP-7) leads to superior bone formation in vitro. In this in vivo-study we evaluated the use of BMP-7 in combination with MSC isolated from reaming debris (RIA-MSC) and iliac crest bone marrow (BMSC) with micro-computed tomography (mCT)-analysis. β-Tricalciumphosphate scaffolds coated with BMSC and RIA-MSC were stimulated with three different BMP-7-concentrations and implanted ectopically in severe combined immunodeficiency (SCID) mice. Our results demonstrate that RIA-MSC show a higher osteogenic potential in vivo compared to BMSC. Ossification increased in direct correlation with the BMP-7-dose applied, however low-dose-stimulation by BMP-7 was more effective for RIA-MSC.

Heidelberg-mCT-Analyzer: a novel method for standardized microcomputed-tomography-guided evaluation of scaffold properties in bone and tissue research

Bone tissue engineering and bone scaffold development represent two challenging fields in orthopaedic research. Micro-computed tomography (mCT) allows non-invasive measurement of these scaffolds' properties in vivo. However, the lack of standardized mCT analysis protocols and, therefore, the protocols' user-dependency make interpretation of the reported results difficult. To overcome these issues in scaffold research, we introduce the Heidelberg-mCT-Analyzer. For evaluation of our technique, we built 10 bone-inducing scaffolds, which underwent mCT acquisition before ectopic implantation (T0) in mice, and at explantation eight weeks thereafter (T1). The scaffolds' three-dimensional reconstructions were automatically segmented using fuzzy clustering with fully automatic level-setting. The scaffold itself and its pores were then evaluated for T0 and T1. Analysing the scaffolds' characteristic parameter set with our quantification method showed bone formation over time. We were able to demonstrate that our algorithm obtained the same results for basic scaffold parameters (e.g. scaffold volume, pore number and pore volume) as other established analysis methods. Furthermore, our algorithm was able to analyse more complex parameters, such as pore size range, tissue mineral density and scaffold surface. Our imaging and post-processing strategy enables standardized and user-independent analysis of scaffold properties, and therefore is able to improve the quantitative evaluations of scaffold-associated bone tissue-engineering projects.

3D brown adipogenesis to create "Brown-Fat-in-Microstrands"

The ability of brown adipocytes (fat cells) to dissipate energy as heat shows great promise for the treatment of obesity and other metabolic disorders. Employing pluripotent stem cells, with an emphasis on directed differentiation, may overcome many issues currently associated with primary fat cell cultures. In addition, three-dimensional (3D) cell culture systems are needed to better understand the role of brown adipocytes in energy balance and treating obesity. To address this need, we created 3D "Brown-Fat-in-Microstrands" by microfluidic synthesis of alginate hydrogel microstrands that encapsulated cells and directly induced cell differentiation into brown adipocytes, using mouse embryonic stem cells (ESCs) as a model of pluripotent stem cells, and brown preadipocytes as a positive control. Brown adipocyte differentiation within microstrands was confirmed by immunocytochemistry and qPCR analysis of the expression of the brown adipocyte-defining marker uncoupling protein 1 (UCP1), as well as other general adipocyte markers. Cells within microstrands were responsive to a β-adrenergic agonist with an increase in gene expression of thermogenic UCP1, indicating that these "Brown-Fat-in-Microstrands" are functional. The ability to create "Brown-Fat-in-Microstrands" from pluripotent stem cells opens up a new arena to understanding brown adipogenesis and its implications in obesity and metabolic disorders.

Bone marrow derived stem cells in joint and bone diseases: a concise review

Stem cells have huge applications in the field of tissue engineering and regenerative medicine. Their use is currently not restricted to the life-threatening diseases but also extended to disorders involving the structural tissues, which may not jeopardize the patients' life, but certainly influence their quality of life. In fact, a particularly popular line of research is represented by the regeneration of bone and cartilage tissues to treat various orthopaedic disorders. Most of these pioneering research lines that aim to create new treatments for diseases that currently have limited therapies are still in the bench of the researchers. However, in recent years, several clinical trials have been started with satisfactory and encouraging results. This article aims to review the concept of stem cells and their characterization in terms of site of residence, differentiation potential and therapeutic prospective. In fact, while only the bone marrow was initially considered as a "reservoir" of this cell population, later, adipose tissue and muscle tissue have provided a considerable amount of cells available for multiple differentiation. In reality, recently, the so-called "stem cell niche" was identified as the perivascular space, recognizing these cells as almost ubiquitous. In the field of bone and joint diseases, their potential to differentiate into multiple cell lines makes their application ideally immediate through three main modalities: (1) cells selected by withdrawal from bone marrow, subsequent culture in the laboratory, and ultimately transplant at the site of injury; (2) bone marrow aspirate, concentrated and directly implanted into the injury site; (3) systemic mobilization of stem cells and other bone marrow precursors by the use of growth factors. The use of this cell population in joint and bone disease will be addressed and discussed, analysing both the clinical outcomes but also the basic research background, which has justified their use for the treatment of bone, cartilage and meniscus tissues.

Exogenously added BMP-6, BMP-7 and VEGF may not enhance the osteogenic differentiation of human adipose stem cells

In the present study bone morphogenetic protein (BMP)-6 alone or in synergy with BMP-7 and vascular endothelial growth factor (VEGF) were tested with human adipose stem cells (hASCs) seeded on cell culture plastic or 3D bioactive glass. Osteogenic medium (OM) was used as a positive control for osteogenic differentiation. The same growth factor groups were also tested combined with OM. None of the growth factor treatments could enhance the osteogenic differentiation of hASCs in 3D- or 2D-culture compared to control or OM. In 3D-culture OM promoted significantly total collagen production, whereas in 2D-culture OM induced high total ALP activity and mineralization compared to control and growth factors groups, but also high cell proliferation. In this study, hASCs did not respond to exogenously added growth although various parameters of the study set-up may have affected these findings contradictory to the previous literature.

Role of mesenchymal stem cells in bone regeneration and fracture repair: a review

Mesenchymal stem cells (MSCs) are non-haematopoietic stromal stem cells that have many sources, such as bone marrow, periosteum, vessel walls, adipose, muscle, tendon, peripheral circulation, umbilical cord blood, skin and dental tissues. They are capable of self-replication and of differentiating into, and contributing to the regeneration of, mesenchymal tissues, such as bone, cartilage, ligament, tendon, muscle and adipose tissue. The homing of MSCs may play an important role in the repair of bone fractures. As a composite material, the formation and growth of bone tissue is a complex process, including molecular, cell and biochemical metabolic changes. The recruitment of factors with an adequate number of MSCs and the micro-environment around the fracture are effective for fracture repair. Several studies have investigated the functional expression of various chemokine receptors, trophic factors and adhesion molecules in human MSCs. Many external factors affect MSC homing. MSCs have been used as seed cells in building tissue-engineered bone grafts. Scaffolds seeded with MSCs are most often used in tissue engineering and include biotic and abiotic materials. This knowledge provides a platform for the development of novel therapies for bone regeneration with endogenous MSCs.

Injectable thermosensitive chitosan/β-glycerophosphate/collagen hydrogel maintains the plasticity of skeletal muscle satellite cells and supports their in vivo viability

A cell carrier plays an important role in the maintenance, growth and engraftment of specific cells aimed for defined therapeutic uses in many tissue engineering strategies. A suitable microenvironment for the cells allows for the maximum efficacy of the hybrid device. We have prepared an injectable thermosensitive chitosan/β-glycerophosphate/collagen (C/GP/Co) gel and investigated its potential application as a support for the culture of skeletal muscle satellite cells (SMSCs). A cell viability assay was used to evaluate the in vitro cytocompatibility of the gel. Cell growth was assessed by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and histological analysis. The influence of the C/GP/Co gel on the plasticity of SMSCs seeded at the surface of the gel was assessed by induction of the myogenic, osteogenic and adipogenic differentiation. C/GP/Co gel provided the appropriate environment for the culture of SMSCs in vitro. In addition, the C/GP/Co gel supported SMSC plasticity. In vivo testing of the SMSC-seeded gel was investigated by subcutaneous injection into the dorsum of nude mice. Cell viability was assessed both by in vivo imaging and histological examination of the explants. In conclusion, C/GP/Co hydrogel is a cytocompatible carrier for the in vivo delivery of SMSCs and supportive for SMSC plasticity. Thus, this gel has potential applications in tissue engineering and regenerative medicine.

Post injury changes in the properties of mesenchymal stem cells derived from human anterior cruciate ligaments

PURPOSE

The anterior cruciate ligament (ACL) rarely heals spontaneously after rupture. Mesenchymal stem cells (MSCs) contribute to healing in various tissues, therefore, they may also have a key role in healing after ACL rupture. The purpose of this study was to investigate the properties of MSCs in ruptured ACLs.

METHODS

Human ACL samples were harvested from patients undergoing primary ACL reconstruction, and samples were classified by the number of days post rupture (phase I<21 days; phase II 21–56 days; phase III 57–139 days phase IV≥140 days). We evaluated the characteristics of MSCs, such as colony-forming capacity, differentiation potential and cell-surface markers.

RESULTS

There was a tendency for high colony-forming capacity during phases I and II, which tended to decrease in phase III. Chondrogenic, adipogenic and osteogenic differentiation potential was maintained until phase II but decreased in phase III. Most surface-epitope expression was consistent from phase I to III: positive for CD44, CD73, CD90 and CD105; negative for CD11b, CD19, CD34, CD45 and human leukocyte antigen-D-related (HLA-DR). The presence of these surface markers proved the existence of MSCs in ruptured ACL tissue.

CONCLUSIONS

Our results suggest that colony-forming and differentiation potential decrease over time. It is important to consider changes in properties of MSCs and use ACL tissue in the acute phase of rupture when biological manipulation is required.