The in vivo origin of bone‐producing osteoblasts is not fully defined. Skeletal stem cells, a population of mesenchymal stem cells resident in the bone marrow compartment, are thought to act as ...osteoprogenitors during growth and adulthood. Quiescent bone lining cells (BLCs) have been suggested as a population capable of activation into mature osteoblasts. These cells were defined by location and their morphology and studies addressing their significance have been hampered by their inaccessibility, and lack of markers that would allow for their identification and tracing. Using lineage tracing models, we have observed labeled osteoblasts at time points extending beyond the reported lifespan for this cell type, suggesting continuous reactivation of BLCs. BLCs also make a major contribution to bone formation after osteoblast ablation, which includes the ability to proliferate. In contrast, mesenchymal progenitors labeled by Gremlin1 or alpha smooth muscle actin do not contribute to bone formation in this setting. BLC activation is inhibited by glucocorticoids, which represent a well‐established cause of osteoporosis. BLCs express cell surface markers characteristic of mesenchymal stem/progenitors that are largely absent in osteoblasts including Sca1 and Leptin Receptor. BLCs also show different gene expression profiles to osteoblasts, including elevated expression of Mmp13, and osteoclast regulators RANKL and macrophage colony stimulating factor, and retain osteogenic potential upon transplantation. Our findings provide evidence that bone lining cells represent a major source of osteoblasts during adulthood. Stem Cells 2016;34:2930–2942
•Physically crosslinked chitosan-HAp hydrogel was prepared by NaHCO3.•In situ apatite synthesis in chitosan ensured application of low NaHCO3 quantity.•The gelation time of chitosan-HAp/NaHCO3 system ...is approximately 4min.•Cells encapsulated within chitosan-HAp/NaHCO3 show high viability.
The development of bioactive injectable system as cell carrier with minimal impact on viability of encapsulated cells represents a great challenge. In the present work, we propose a new pH-responsive chitosan-hydroxyapatite-based hydrogel with sodium bicarbonate (NaHCO3) as the gelling agent. The in situ synthesis of hydroxyapatite phase has resulted in stable composite suspension and final homogeneous hydrogel. The application of sodium bicarbonate has allowed non-cytotoxic fast gelation of chitosan-hydroxyapatite within 4min, and without excess of sodium ions concentration. Rheological properties of crosslinked hydrogel have demonstrated possible behaviour as ‘strong physical hydrogel’. The live dead staining has confirmed good viability and dispersion, as well as proliferation of encapsulated cells by the culture time. Presented preliminary results show good potential of chitosan-hydroxyapatite/NaHCO3 as a cell carrier, whose impact on the cell differentiation need to be confirmed by encapsulation of other cell phenotypes.
Presently there is no clear evidence for the ability of mature osteogenic lineage cells to dedifferentiate. In order to identify and trace mature osteogenic lineage cells, we have utilized transgenic ...mouse models in which the dentin matrix protein 1 (Dmp1) promoter drives expression of GFP (active marker) or Cre recombinase (historic label) in preosteocytes/osteocytes. In long bone chip outgrowth cultures, in which cells on the bone surface were enzymatically removed, cells with previous activity of the Dmp1 promoter migrated onto plastic and down-regulated Dmp1-GFP expression. Dmp1Cre-labeled cells from these cultures had the potential to re-differentiate into the osteogenic lineage, while the negative population showed evidence of adipogenesis. We observed numerous Dmp1Cre-labeled osteoblasts on the surface of bone chips following their in vivo transplantation. Our data indicate that cells embedded in bone matrix are motile, and once given access to the extra bony milieu will migrate out of their lacunae. This population of cells is phenotypically and functionally heterogeneous in vitro. Once the preosteocytes/osteocytes leave lacunae, they can dedifferentiate, potentially providing an additional source of functional osteoblasts.
Abstract Heterotopic ossification (HO) is a pathological process where bone forms in connective tissues such as skeletal muscle. Previous studies have suggested that muscle-resident non-myogenic ...mesenchymal progenitors are the likely source of osteoblasts and chondrocytes in HO. However, the previously identified markers of muscle-resident osteoprogenitors label up to half the osteoblasts within heterotopic lesions, suggesting other cell populations are involved. We have identified alpha smooth muscle actin (αSMA) as a marker of osteoprogenitor cells in bone and periodontium, and of osteo-chondro progenitors in the periosteum during fracture healing. We therefore utilized a lineage tracing approach to evaluate whether αSMACreERT2 identifies osteoprogenitors in the muscle. We show that in the muscle, αSMACreERT2 labels both perivascular cells, and satellite cells. αSMACre-labeled cells undergo osteogenic differentiation in vitro and form osteoblasts and chondrocytes in BMP2-induced HO in vivo. In contrast, Pax7CreERT2-labeled muscle satellite cells were restricted to myogenic differentiation in vitro, and rarely contributed to HO in vivo. Our data indicate that αSMACreERT2 labels a large proportion of osteoprogenitors in skeletal muscle, and therefore represents another marker of muscle-resident cells with osteogenic potential under HO-inducing stimulus. In contrast, muscle satellite cells make minimal contribution to bone formation in vivo.
Medical researchers are ethically and legally required to inform participants and get written permission before enrolling them into a human research project ("Informed Consent"). Accordingly, ...information and consent represent a complex procedure, and the participant concerned "must receive comprehensible oral and written information" (Swiss legislation: Human Research Act (HRA) Art. 16). A triangle of stakeholders is involved in the procedure: ethics committees that review and approve research projects and "Informed Consent" (IC) documents, medical researchers who produce the documents and discuss enrolment with patients, and patients who have to be informed comprehensibly. From a linguistic point of view, the question arises as to which perceptions of comprehensibility form the basis of the IC process and how shared language can be established considering the complex relationship between these stakeholders. This contribution presents findings from two perspectives (ethics committees and researchers) while considering the needs of all three stakeholders. Firstly, the conceptualisation of comprehensibility among three ethic committees is presented, and steps toward harmonisation are outlined. Secondly, limitations of how researchers conduct oral IC information are analysed, and the measures that were implemented to improve patient information are discussed. A transdisciplinary approach is key in establishing these solutions because they do not stem from linguistic analysis alone but have been developed in close collaboration with members of ethics committees and medical researchers. Thus, the project shows how the expertise of applied linguistics in cooperation with practitioners can deliver an important impact in both academic analysis and optimisation of professional procedures.
This contribution addresses obstacles to comprehensibility of specialized vocabulary within informed consent information for laypeople and digital means of overcoming those obstacles. In specific, it ...is shown that basic concepts of research in information texts represent particular obstacles to comprehensibility. These basic concepts are highly frequent in information texts regarding participation in human research, and a lack of prior knowledge about these concepts can hardly be established textually. As a solution, this contribution focuses on a rarely considered part of expert-layperson communication: the layperson's use of specialized vocabulary. The layperson's use of specialized vocabulary is introduced as a distinct variable and compared to the expert's use. An analysis of interactions in internet forums shows that laypeople have their own practices in using specialized vocabulary. To make information texts more comprehensible, we argue for replacing expert specialized vocabulary in favor of those variables that are closer to laypersons' everyday life. Finally, we present a digital dictionary of specialized variables that aims to show both expert and layperson variables of specialized vocabulary and to make them productive for information practice.
Purpose
The aim of this study is to examine the capacity of muscle tissue preserved on hamstring tendons forming candy-stripe grafts in order to improve tendon to bone ingrowth and ligamentization. ...We hypothesized that muscle tissue does possess a stem cell population that could enhance the healing process of the ACL graft when preserved on the tendons.
Methods
Human samples from gracilis and semitendinosus muscles were collected during ACL surgery from ten patients and from these tissue samples human muscle-derived stem cells and tendon-derived stem cells were isolated and propagated. Both stem cell populations were in-vitro differentiated into osteogenic lineage. Alkaline phosphatase activity was determined at days zero and 14 of the osteogenic induction and von Kossa staining to assess mineralization of the cultures. Total RNA was collected from osteoblast cultures and real time quantitative PCR was performed. Western-blot for osteocalcin and collagen type I followed protein isolation. Immunofluorescence double labeling of pericytes in muscle and tendon tissue was performed.
Results
Mesenchymal stem cells from muscle and tendon tissue were isolated and expanded in cell culture. More time was needed to grow the tendon derived culture compared to muscle derived culture. Muscle derived stem cells exhibited more alkaline phosphatase actvity compared to tendon derived stem cells, whereas tendon derived stem cells formed more mineralized nodules after 14 days of osteoinduction. Muscle derived stem cells exhibited higher expression levels of bone sialoprotein, and tendon derived stem cells showed higher expression of dental-matrix-protein 1 and osteocalcin. Immunofluorescent staining against pericytes indicated that they are more abundant in muscle tissue.
Conclusions
These results indicate that muscle tissue is a better source of stem cells than tendon tissue. Achievement of this study is proof that there is vast innate capacity of muscle tissue for enhancement of bone-tendon integration and ligamentization of ACL hamstring grafts and consequently muscle tissue should not be treated as waste after harvesting.
To assess whether an adenoviral vector carrying the bone morphogenetic protein genes (Ad.BMP-2) can transduce human muscle tissue and direct it toward osteogenic differentiation within one hour.
This ...in vitro study, performed at the Department of Molecular Biology, Faculty of Science, Zagreb from 2012 to 2017, used human muscle tissue samples collected during anterior cruciate ligament reconstructions performed in St Catherine Hospital, Zabok. Samples from 28 patients were transduced with adenoviral vector carrying firefly luciferase cDNA (Ad.luc) by using different doses and times of transduction, and with addition of positive ions for transduction enhancement. The optimized protocol was further tested on muscle samples from three new patients, which were transduced with Ad.BMP-2. Released bone morphogenetic protein 2 (BMP-2) levels in osteogenic medium were measured every three days during a period of 21 days. Expression of osteogenic markers was measured at day 14 and 21. After 21 days of cultivation, muscle tissue was immunohistochemically stained for collagen type I detection (COL-I).
The new transduction protocol was established using 108 plaque-forming units (P<0.001) as an optimal dose of adenoviral vector and 30 minutes (P<0.001) as an optimal contact time. Positive ions did not enhance transduction. Samples transduced with Ad.BMP-2 according to the optimized protocol showed enhanced expression of osteogenic markers (P<0.050), BMP-2 (P<0.001), and COL I.
This study confirms that Ad.BMP-2 can transduce human muscle tissue and direct it toward osteogenic differentiation within 30 minutes.
Sun or therapy-related ultraviolet B (UVB) irradiation induces different cell death modalities such as apoptosis, necrosis/necroptosis and autophagy. Understanding of mechanisms implicated in ...regulation and execution of cell death program is imperative for prevention and treatment of skin diseases. An essential component of death-inducing complex is Fas-associated protein with death domain (FADD), involved in conduction of death signals of different death modalities. The purpose of this study was to enlighten the role of FADD in the selection of cell death mode after narrow-band UVB (NB-UVB) irradiation using specific cell death inhibitors (carbobenzoxy-valyl-alanyl-aspartyl-O-methyl- fluoromethylketone (zVAD-fmk), Necrostatin-1 and 3-Methyladenine) and FADD-deficient (FADD−/−) mouse embryonic fibroblasts (MEFs) and their wild type (wt) counterparts. The results imply that lack of FADD sensitized MEFs to induction of receptor–interacting protein 1 (RIPK1)-dependent apoptosis by the generation of reactive oxygen species (ROS), but without activation of the proteins p53, Bax and Bcl-2 as well as without the enrolment of calpain-2. Autophagy was established as a contributing factor to NB-UVB-induced death execution. By contrast, wt cells triggered intrinsic apoptotic pathway that was resistant to the inhibition by zVAD-fmk and Necrostatin-1 pointing to the mechanism overcoming the cell survival. These findings support the role of FADD in prevention of autophagy-dependent apoptosis.
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•UVB triggers RIPK1-dependent apoptosis in FADD-deficient mouse embryonic fibroblasts.•RIPK1-dependent apoptosis involves generation of reactive oxygen species•RIPK1-dependent apoptosis does not depend on p53, Bax, Bcl-2 and calpain-2.•Autophagy is a contributing factor to RIPK1-depenedent apoptosis.•FADD acts as negative regulator of autophagy.
Determine the levels of expression of pluripotency genes OCT-4 and SOX-2 before and after osteogenic differentiation of human mesenchymal stem cells (hMSCs).
Human MSCs were derived from the bone ...marrow and differentiated into osteoblasts. The analyses were performed on days 0 and 14 of the cell culture. In vitro differentiation was evaluated due to bone markers - alkaline phosphatase (AP) activity and the messenger RNA (mRNA) expression of AP and bone sialoprotein (BSP). The OCT-4 and SOX-2 expression was evaluated at mRNA level by real-time qPCR and at protein level by immunocytochemistry.
In vitro cultures on day 14 showed an increase in AP activity and upregulation of AP and BSP gene expression. OCT-4 and SOX-2 in undifferentiated hMSCs on day 0 is detectable and very low compared to tumor cell lines as a positive control. Immunocytochemistry detected OCT-4 in the cell nuclei prior (day 0) and post differentiation (day 14). On the same time points, cultures were negative for SOX-2 protein.
Messenger RNA for pluripotency markers OCT-4 and SOX-2 isolated from hMSCs was less present, while OCT-4 protein was detected in cell nuclei prior and post differentiation into osteoblast lineage.
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