Progenitor and stem cells for bone and cartilage regeneration

The Current State of Osteoarthritis Treatment Options Using Stem Cells for Regenerative Therapy: A Review

Articular cartilage has very low metabolic activity. While minor injuries may be spontaneously repaired within the joint by chondrocytes, there is very little chance of a severely impaired joint regenerating itself when damaged. Therefore, any significant joint injury has little chance of spontaneously healing without some type of therapy. This article is a review that will examine the causes of osteoarthritis, both acute and chronic, and how it may be treated using traditional methods as well as with the latest stem cell technology. The latest regenerative therapy is discussed, including the use and potential risks of mesenchymal stem cells for tissue regeneration and implantation. Applications are then discussed for the treatment of OA in humans after using canine animal models. Since the most successful research models of OA were dogs, the first applications for treatment were veterinary. However, the treatment options have now advanced to the point where patients suffering from osteoarthritis may be treated with this technology. A survey of the literature was performed in order to determine the current state of stem cell technology being used in the treatment of osteoarthritis. Then, the stem cell technology was compared with traditional treatment options.

Case Report: Unable to Jump Like a Kangaroo Due to Myositis Ossificans Circumscripta

A male 10-year-old captive red kangaroo (Macropus rufus) was presented with a chronic progressive pelvic limb lameness and reluctance to jump. The general examination revealed a palpable induration of the lumbar epaxial muscles. Magnetic resonance imaging performed under general anesthesia revealed bilateral almost symmetric, well-circumscribed mass lesions in superficial erector spinae muscles. The lesions had irregular to multilobulated appearance with hyper-, hypo-, and isointense areas in T2- and T1-weighted (w) sequences without contrast enhancement. On computed tomography, a peripheral rim of mineralization was apparent. Histopathological analysis of a muscle biopsy showed osseous trabeculae with rare clusters of chondrocytes indicating metaplasia of muscle tissue to bone. No indications of inflammation or malignancy were visible. The clinical, histopathological, and imaging workup of this case was consistent with myositis ossificans circumscripta. This disorder is particularly well-known among human professional athletes such as basketball players, where excessive, chronic-repetitive force or blunt trauma causes microtrauma to the musculature. Metaplasia of muscle tissue due to abnormal regeneration processes causes heterotopic ossification. The kangaroo's clinical signs improved with cyto-reductive surgery, cage rest, weight reduction, and meloxicam without further relapse.

Establishing a deeper understanding of the osteogenic differentiation of monolayer cultured human pluripotent stem cells using novel and detailed analyses

Background

Derivation of osteoblast-like cells from human pluripotent stem cells (hPSCs) is a popular topic in bone tissue engineering. Although many improvements have been achieved, the low induction efficiency because of spontaneous differentiation hampers their applications. To solve this problem, a detailed understanding of the osteogenic differentiation process of hPSCs is urgently needed.

Methods

Monolayer cultured human embryonic stem cells and human-induced pluripotent stem cells were differentiated in commonly applied serum-containing osteogenic medium for 35 days. In addition to traditional assays such as cell viability detection, reverse transcription-polymerase chain reaction, immunofluorescence, and alizarin red staining, we also applied studies of cell counting, cell telomerase activity, and flow cytometry as essential indicators to analyse the cell type changes in each week.

Results

The population of differentiated cells was quite heterogeneous throughout the 35 days of induction. Then, cell telomerase activity and cell cycle analyses have value in evaluating the cell type and tumourigenicity of the obtained cells. Finally, a dynamic map was made to integrate the analysis of these results during osteogenic differentiation of hPSCs, and the cell types at defined stages were concluded.

Conclusions

Our results lay the foundation to improve the in vitro osteogenic differentiation efficiency of hPSCs by supplementing with functional compounds at the desired stage, and then establishing a stepwise induction system in the future.

Enhanced Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells in Ossification of the Posterior Longitudinal Ligament Through Activation of the BMP2-Smad1/5/8 Pathway

Ossification of the posterior longitudinal ligament (OPLL) is characterized by ectopic OPLL. To date, the specific molecular pathogenesis of OPLL has not been clearly elucidated. In this study, bone marrow-derived mesenchymal stem cells obtained from healthy donors (HD-MSCs) and patients with OPLL (OPLL-MSCs) were cultured in osteogenic differentiation medium for 21 days. The osteogenic differentiation capacity was determined by alizarin red S (ARS) and alkaline phosphatase (ALP) assays. Gene expression levels of osteoblastic markers were measured by quantitative reverse transcription-polymerase chain reaction. Protein levels of related genes and the activation of related signaling pathways were measured by western blotting. LDN193189 was used to inhibit the Smad1/5/8 pathway, and small interfering RNA was used to regulate BMP2 expression. Our results showed that the OPLL-MSCs had stronger ARS staining and ALP activity and higher expression of RUNX2, Osterix, and OCN than the HD-MSCs. During osteogenic differentiation, the Smad1/5/8 pathway was overactivated in the OPLL-MSCs, and LDN193189 inhibition reversed the enhanced osteogenic ability of these cells. Besides, BMP2 was upregulated in the OPLL-MSCs. After BMP2 knockdown, the abnormal osteogenic differentiation of OPLL-MSCs was rescued. Thus, abnormal activation of the BMP2-Smad1/5/8 pathway induces enhanced osteogenic differentiation of OPLL-MSCs compared with HD-MSCs. These findings reveal a mechanism of pathological osteogenesis in OPLL and provide a new perspective on inhibiting pathological osteogenesis by regulating BMP2.

The effects of oyster shell/alpha-calcium sulfate hemihydrate/platelet-rich plasma/bone mesenchymal stem cells bioengineering scaffold on rat critical-sized calvarial defects

Engineering scaffolds combining natural biomineral and artificially synthesized material hold promising potential for bone tissue regeneration. We fabricated a bioengineering scaffold, oyster shell (OS) and alpha-calcium sulfate hemihydrate (α-CSH) as scaffold, platelet-rich plasma (PRP) as provider of growth factors and bone mesenchymal stem cells (BMSCs) as seed cells, and determined it could be applied as a new type of bone graft substitutes by rat calvarial defects repairing experiment in vitro and in vivo. SEM showed that the mean diameter of the pores was about 150 μm with a range of 50-200 μm, and scaffold's porosity was ~27.4% by Archimedes' Principle. In vitro, Scaffold + BMSCs + PRP group presented a higher ALP activity compared with other groups by ELISA (P < 0.05). But the expression of OC was not detectable on day 4 or 8. The MTT assay showed that the relative cell number of BMSCs+PRP group increased significantly (P < 0.05). In vivo, the smallest defect area of skull and highest volume of regenerated new bone were observed in Scaffold + PRP + BMSCs group by X-ray and Micro-CT analysis (P < 0.05). And the similar results also were observed in HE and Masson staining. The immunohistochemistry staining for osteogenic marker proteins ALP and OC showed that the most obvious positive staining was observed in Scaffold + PRP + BMSCs group (P < 0.05). The expression of inflammatory markers IL-6 and TNF-α was the lowest in control group (P < 0.05). In conclusion, a bioengineering scaffold based on OS, created by simply combining α-CSH and PRP and implanting with BMSCs, could be clinically useful and has marked advantages as a targeted, off-the-shelf, cell-loaded treatment option for the bone healing of critical-size calvarial defects.

Bone Repair and Regenerative Biomaterials: Towards Recapitulating the Microenvironment

Biomaterials and tissue engineering scaffolds play a central role to repair bone defects. Although ceramic derivatives have been historically used to repair bone, hybrid materials have emerged as viable alternatives. The rationale for hybrid bone biomaterials is to recapitulate the native bone composition to which these materials are intended to replace. In addition to the mechanical and dimensional stability, bone repair scaffolds are needed to provide suitable microenvironments for cells. Therefore, scaffolds serve more than a mere structural template suggesting a need for better and interactive biomaterials. In this review article, we aim to provide a summary of the current materials used in bone tissue engineering. Due to the ever-increasing scientific publications on this topic, this review cannot be exhaustive; however, we attempted to provide readers with the latest advance without being redundant. Furthermore, every attempt is made to ensure that seminal works and significant research findings are included, with minimal bias. After a concise review of crystalline calcium phosphates and non-crystalline bioactive glasses, the remaining sections of the manuscript are focused on organic-inorganic hybrid materials.

Mummy Material Can Promote Differentiation of Adipose Derived Stem Cells into Osteoblast through Enhancement of Bone Specific Transcription Factors Expression

Purpose: Application of Mummy material for treatment of different diseases such as bone fracture, cutaneous wounds and joint inflammation has been advised since hundred years ago in Persian traditional medicine. Due to the claims of indigenous people and advice of traditional medicine for application of this material in healing of bone fractures, this study has been designed to evaluate whether Mummy material can promote the differentiation of mesenchymal stem cells into osteoblasts and enhance the expression of bone specific genes and proteins.

Methods: Adipose derived stem cells (ASCs) at fourth cell passage were divided into control, osteogenesis group (received osteogenic medium), Mummy group (received Mummy at concentration of 500 µg/ml). ASCs in the fourth group were treated with both osteogenic medium and Mummy (500µg/ml). Cells in all groups were harvested on days 7, 14 and 21 days for further evaluation through Real time RT-PCR, Von kossa staining, Immunocytochemistry and flowcytometery.

Results: Treatment of ASCs with Mummy at concentration of 500µg/ml promotes the expression level of Osteocalcin, RUNX-2 and β1-integrin genes in different time points but that of the Osterix did not changed. Furthermore the expression of Osteocalcin protein enhanced significantly in ASCs treated with Mummy detected by Immunocytochemistry and flowcytometery technique compared to the control groups. The results of this study also showed that treatment of ASCs with Mummy resulted in formation of mineral deposits which was evaluated by Von Kossa staining method.

Conclusion: Obtained data from this study reveals that Mummy is a potent enhancer for differentiation of ASCs into osteoblasts in in vitro system, probably through increasing the level of bone specific genes and proteins.

Standardization and quality assessment for clinical grade mesenchymal stem cells from human adipose tissue

Background

Mesenchymal stem cells have immense potential in stem cell-based therapies, however there is a pre-requisite to develop a curative cell dose. Adipose tissue-derived mesenchymal stem cells are promising mainly due to their potential abundance, immunomodulatory effect and remarkable differentiation potential. Nevertheless, senescence may develop during their in vitro expansion due to the incidence of genetic instability. Hence, it is important to attain an ideal balance between mesenchymal stem cell growth, quality and genetic integrity before their clinical use.

Methods

Stromal vascular fraction was obtained from omentum tissue of patients undergoing liposuction procedures for morbid obesity. This study standardized a closed system protocol which can be utilized for clinical grade stem cell derivation. Stages of cell growth and characterization of human adipose tissue-derived mesenchymal stem cells were also assessed along with the chromosomal stability in these in vitro cultures.

Results

Human adipose tissue-derived mesenchymal stem cells maintained their spindle-shaped morphology and were able to proliferate and renew, confirming their suitability for in vitro cultivation and generate clinical grade mesenchymal stem cells. Immunophenotyping indicates that the cells expressed cluster of differentiation (CD)73/CD90/CD105, mesenchymal stem-cell markers, while lacked CD34/CD45/ Human Leukocyte antigen-antigen D related (HLA-DR) expression (hematopoietic cell markers). A cell cycle study demonstrated growth kinetics under in vitro culture conditions. Human adipose tissue derived mesenchymal stem cells expressed normal cell karyotype by chromosomal G-banding indicating their genetic stability at Passage 5. Mesenchymal stem cells also demonstrated trilineage differentiation.

Conclusions

Availability of adipose tissue in abundance is a major advantage for clinical applications. Furthermore, detailed characterization of human adipose tissue-derived mesenchymal stem cells, their genomic stability and differentiation potential from stromal vascular fraction of human adipose tissue would help assist in tissue regeneration and repair.

Cell density, dimethylsulfoxide concentration and needle gauge affect hydrogel-induced bone marrow mesenchymal stromal cell viability

Mesenchymal stromal cells (MSCs) have shown potential therapeutic benefits for a range of medical disorders and continue to be a focus of intense scientific investigation. Transplantation of MSCs into injured tissue can improve wound healing, tissue regeneration and functional recovery. However, implanted cells rapidly lose their viability or fail to integrate into host tissue. Hydrogel-seeded bone marrow (BM)-MSCs offer improved viability in response to mechanical forces caused by syringe needles, cell density and dimethylsulfoxide (DMSO) concentration, which in turn, will help to clarify which factors are important for enhancing biomaterial-induced cell transplantation efficiency and provide much needed guidance for clinical trials. In this study, under the control of cell density (<2 × 107 cells/mL) and final DMSO concentration (<0.5%), hydrogel-induced BM-MSC viability remained >82% following syringe needle passage by 25- or 27-gauge needles, providing improved cell therapeutic approaches for regenerative medicine.

Biofabrication and Bone Tissue Regeneration: Cell Source, Approaches, and Challenges

The growing occurrence of bone disorders and the increase in aging population have resulted in the need for more effective therapies to meet this request. Bone tissue engineering strategies, by combining biomaterials, cells, and signaling factors, are seen as alternatives to conventional bone grafts for repairing or rebuilding bone defects. Indeed, skeletal tissue engineering has not yet achieved full translation into clinical practice because of several challenges. Bone biofabrication by additive manufacturing techniques may represent a possible solution, with its intrinsic capability for accuracy, reproducibility, and customization of scaffolds as well as cell and signaling molecule delivery. This review examines the existing research in bone biofabrication and the appropriate cells and factors selection for successful bone regeneration as well as limitations affecting these approaches. Challenges that need to be tackled with the highest priority are the obtainment of appropriate vascularized scaffolds with an accurate spatiotemporal biochemical and mechanical stimuli release, in order to improve osseointegration as well as osteogenesis.

Imbalance Between Bone Morphogenetic Protein 2 and Noggin Induces Abnormal Osteogenic Differentiation of Mesenchymal Stem Cells in Ankylosing Spondylitis

OBJECTIVE

To study the osteogenic differentiation capacity of bone marrow-derived mesenchymal stem cells (BM-MSCs) from patients with ankylosing spondylitis (AS) and to investigate the mechanisms of abnormal osteogenic differentiation of BM-MSCs in AS.

METHODS

BM-MSCs from healthy donors (HD-MSCs) and patients with AS (AS-MSCs) were cultured in osteogenic differentiation medium for 0-21 days, after which their osteogenic differentiation capacity was determined using alizarin red S and alkaline phosphatase assays. Gene expression levels of osteoblastic markers and related cytokines were detected by high-throughput quantitative reverse transcription-polymerase chain reaction. Enzyme-linked immunosorbent assay was performed to detect protein levels of bone morphogenetic protein 2 (BMP-2) and Noggin in the cell culture supernatant. The activation of Smad1/5/8 and MAPK signaling pathways was measured by Western blotting. The balance between BMP-2 and Noggin expression was regulated using lentiviruses encoding short hairpin RNA and exogenous Noggin, respectively, which enabled evaluation of how this balance affected osteogenic differentiation of AS-MSCs.

RESULTS

AS-MSCs outperformed HD-MSCs in osteogenic differentiation capacity. During osteogenic differentiation, AS-MSCs secreted more BMP-2 but less Noggin, accompanied by an overactivation of Smad1/5/8 and ERK-1/2. When the Noggin concentration was increased or BMP-2 expression was inhibited, the abnormal osteogenic differentiation of AS-MSCs was rectified. In addition, the balance between BMP-2 and Noggin secretion was restored.

CONCLUSION

The results of this study demonstrate that an imbalance between BMP-2 and Noggin secretion induces abnormal osteogenic differentiation of AS-MSCs. These findings reveal a mechanism of pathologic osteogenesis in AS and provide a new perspective on inhibiting pathologic osteogenesis by regulating the balance between BMP-2 and Noggin.

Biofabrication of bone tissue: approaches, challenges and translation for bone regeneration

The rising incidence of bone disorders has resulted in the need for more effective therapies to meet this demand, exacerbated by an increasing ageing population. Bone tissue engineering is seen as a means of developing alternatives to conventional bone grafts for repairing or reconstructing bone defects by combining biomaterials, cells and signalling factors. However, skeletal tissue engineering has not yet achieved full translation into clinical practice as a consequence of several challenges. The use of additive manufacturing techniques for bone biofabrication is seen as a potential solution, with its inherent capability for reproducibility, accuracy and customisation of scaffolds as well as cell and signalling factor delivery. This review highlights the current research in bone biofabrication, the necessary factors for successful bone biofabrication, in addition to the current limitations affecting biofabrication, some of which are a consequence of the limitations of the additive manufacturing technology itself.

The tumor suppressor BTG1 is expressed in the developing digits and regulates skeletogenic differentiation of limb mesodermal progenitors in high density cultures

In the developing limb, differentiation of skeletal progenitors towards distinct connective tissues of the digits is correlated with the establishment of well-defined domains of Btg1 gene expression. Zones of high expression of Btg1 include the earliest digit blastemas, the condensing mesoderm at the tip of the growing digits, the peritendinous mesenchyme, and the chondrocytes around the developing interphalangeal joints. Gain- and loss-of function experiments in micromass cultures of skeletal progenitors reveal a negative influence of Btg1 in cartilage differentiation accompanied by up-regulation of Ccn1, Scleraxis and PTHrP. Previous studies have assigned a role to these factors in the aggregation of progenitors in the digit tips (Ccn1), in the differentiation of tendon blastemas (Scleraxis) and repressing hypertrophic cartilage differentiation (PTHrP). Overexpression of Btg1 up-regulates the expression of retinoic acid and thyroid hormone receptors, but, different from other systems, the influence of BTG1 in connective tissue differentiation appears to be independent of retinoic acid and thyroid hormone signaling.

Delayed minimally invasive injection of allogenic bone marrow stromal cell sheets regenerates large bone defects in an ovine preclinical animal model

Cell-based tissue engineering approaches are promising strategies in the field of regenerative medicine. However, the mode of cell delivery is still a concern and needs to be significantly improved. Scaffolds and/or matrices loaded with cells are often transplanted into a bone defect immediately after the defect has been created. At this point, the nutrient and oxygen supply is low and the inflammatory cascade is incited, thus creating a highly unfavorable microenvironment for transplanted cells to survive and participate in the regeneration process. We therefore developed a unique treatment concept using the delayed injection of allogenic bone marrow stromal cell (BMSC) sheets to regenerate a critical-sized tibial defect in sheep to study the effect of the cells' regeneration potential when introduced at a postinflammatory stage. Minimally invasive percutaneous injection of allogenic BMSCs into biodegradable composite scaffolds 4 weeks after the defect surgery led to significantly improved bone regeneration compared with preseeded scaffold/cell constructs and scaffold-only groups. Biomechanical testing and microcomputed tomography showed comparable results to the clinical reference standard (i.e., an autologous bone graft). To our knowledge, we are the first to show in a validated preclinical large animal model that delayed allogenic cell transplantation can provide applicable clinical treatment alternatives for challenging bone defects in the future.

MicroRNAs are potential prognostic and therapeutic targets in diabetic osteoarthritis

Osteoarthritis is an aging-related degenerative disease that severely influences the elders' life quality. However, there have been few clinical approaches available until now. Currently, more knowledge of the pathology of osteoarthritis has been illustrated. Especially, diabetes can be the only predictor of osteoarthritis. Due to its outstanding characteristics, MicroRNA has been considered as an efficient target in treating diseases. In this review, we will discuss a new insight focusing on the roles of microRNA in the progression of osteoarthritis-induced by diabetes, especially type II diabetes mellitus.

Continuous hypoxia regulates the osteogenic potential of mesenchymal stem cells in a time-dependent manner

The effects of hypoxia on the osteogenic potential of mesenchymal stem cells (MSCs) have been previously reported. From these studies, possible factors affecting the association between hypoxia and the osteogenic differentiation of MSCs have been suggested, including hypoxia severity, cell origin and methods of induction. The effect of the duration of hypoxia, however, remains poorly understood. The aim of the present study was to investigate the effect of continuous hypoxia on the induced osteogenesis of MSCs. Rat MSCs were isolated and cultured in vitro. Once the cells had been cultured to passage three, they were switched to 1% oxygen and cultured either with or without osteogenic medium, while cells in the control groups were cultured under normoxia in corresponding conditions. Four osteogenic differentiation biomarkers, runt-related transcription factor 2, osteopontin, osteocalcin and alkaline phosphatase, were analyzed by quantitative polymerase chain reaction and western blotting at defined intervals throughout the culture period. In addition, Alizarin Red staining was used to assess changes in mineralization. The results showed that 1% hypoxia was able to enhance and accelerate the osteogenic ability of the MSCs during the initial phases of differentiation, and the protein expression of certain associated biomarkers was upregulated. However, continuous hypoxia was shown to impair osteogenesis in the latter stages of differentiation. These findings suggest that hypoxia can regulate the osteogenesis of MSCs in a time-dependent manner.

Basic science and clinical application of stem cells in veterinary medicine

Stem cells play an important role in veterinary medicine in different ways. Currently several stem cell therapies for animal patients are being developed and some, like the treatment of equine tendinopathies with mesenchymal stem cells (MSCs), have already successfully entered the market. Moreover, animal models are widely used to study the properties and potential of stem cells for possible future applications in human medicine. Therefore, in the young and emerging field of stem cell research, human and veterinary medicine are intrinsically tied to one another. Many of the pioneering innovations in the field of stem cell research are achieved by cooperating teams of human and veterinary medical scientists.Embryonic stem (ES) cell research, for instance, is mainly performed in animals. Key feature of ES cells is their potential to contribute to any tissue type of the body (Reed and Johnson, J Cell Physiol 215:329-336, 2008). ES cells are capable of self-renewal and thus have the inherent potential for exceptionally prolonged culture (up to 1-2 years). So far, ES cells have been recovered and maintained from non-human primate, mouse (Fortier, Vet Surg 34:415-423, 2005) and horse blastocysts (Guest and Allen, Stem Cells Dev 16:789-796, 2007). In addition, bovine ES cells have been grown in primary culture and there are several reports of ES cells derived from mink, rat, rabbit, chicken and pigs (Fortier, Vet Surg 34:415-423, 2005). However, clinical applications of ES cells are not possible yet, due to their in vivo teratogenic degeneration. The potential to form a teratoma consisting of tissues from all three germ lines even serves as a definitive in vivo test for ES cells.Stem cells obtained from any postnatal organism are defined as adult stem cells. Adult haematopoietic and MSCs, which can easily be recovered from extra embryonic or adult tissues, possess a more limited plasticity than their embryonic counterparts (Reed and Johnson, J Cell Physiol 215:329-336, 2008). It is believed that these stem cells serve as cell source to maintain tissue and organ mass during normal cell turnover in adult individuals. Therefore, the focus of attention in veterinary science is currently drawn to adult stem cells and their potential in regenerative medicine. Also experience gained from the treatment of animal patients provides valuable information for human medicine and serves as precursor to future stem cell use in human medicine.Compared to human medicine, haematopoietic stem cells only play a minor role in veterinary medicine because medical conditions requiring myeloablative chemotherapy followed by haematopoietic stem cell induced recovery of the immune system are relatively rare and usually not being treated for monetary as well as animal welfare reasons.In contrast, regenerative medicine utilising MSCs for the treatment of acute injuries as well as chronic disorders is gradually turning into clinical routine. Therefore, MSCs from either extra embryonic or adult tissues are in the focus of attention in veterinary medicine and research. Hence the purpose of this chapter is to offer an overview on basic science and clinical application of MSCs in veterinary medicine.

Adapted chondrogenic differentiation of human mesenchymal stem cells via controlled release of TGF-β1 from poly(ethylene oxide)-terephtalate/poly(butylene terepthalate) multiblock scaffolds

Controlled release of TGF-β1 from scaffolds is an attractive mechanism to modulate the chondrogenesis of human bone marrow mesenchymal stem cells (hBMSCs) that repopulate articular cartilage defects. Here, we evaluated the ability of porous scaffolds composed of poly(ethylene oxide)-terephtalate and poly(butylene terepthalate) (PEOT/PBT) to release bioactive TGF-β1 for chondrogenesis of hBMSCs in a pellet culture model. Chondroinduction was compared with that promoted by direct addition of the recombinant factor to the culture medium. The data show a controlled release of TGF-β1 from scaffolds for at least 21 days in vitro, with ∼10% of TGF-β1 released during this period. The delivered TGF-β1 was bioactive, as confirmed by successful chondrogenic differentiation of hBMSCs monitored by morphological, histological, immunohistochemical, biochemical, and real-time reverse transcription polymerase chain reaction analyses. Third, semiquantitative histological evaluations revealed a similar pattern of chondrogenesis compared with the positive controls. Importantly, TGF-β1-loaded scaffolds allowed for a ∼700-fold upregulation of type-II collagen mRNA compared to when pellets were maintained in the presence of the soluble TGF-β1, reflected also in the highest score of immunoreactivity to type-II collagen, not significantly different from the positive controls. Likewise, aggrecan mRNA was ∼200-fold upregulated. Interestingly, most (>94%) of the glycosaminoglycan produced remaining associated with the pellets. Analysis of hypertrophic events showed no significant difference in the average total hypertrophy score compared with the positive controls. These results demonstrate the suitability of controlled TGF-β1 release from biocompatible scaffolds to promote hBMSC chondrogenesis at a physical distance and in the absence of soluble TGF-β1.

Double-chamber rotating bioreactor for dynamic perfusion cell seeding of large-segment tracheal allografts: comparison to conventional static methods

Tracheal transplantation with a long-segment recellularized tracheal allograft has previously been performed without the need for immunosuppressive therapy. Recipients' mesenchymal stromal cells (MSC) and tracheal epithelial cells (TEC) were harvested, cultured, expanded, and seeded on a donor trachea within a bioreactor. Prior techniques used for cellular seeding have involved only static-seeding methods. Here, we describe a novel bioreactor for recellularization of long-segment tracheae. Tracheae were recellularized with epithelial cells on the luminal surface and bone marrow-derived MSC on the external surface. We used dynamic perfusion seeding for both cell types and demonstrate an increase in both cellular counts and homogeneity scores compared with traditional methods. Despite these improvements, orthotopic transplantation of these scaffolds revealed no labeled cells at postoperative day 3 and lack of re-epithelialization within the first 2 weeks. The animals in this study had postoperative respiratory distress and tracheal collapse that was incompatible with life.

Implementing tissue engineering and regenerative medicine solutions in medical implants

BACKGROUND

Surgical implants are widely used in the medical field but their long-term performance is limited due to failure of integration with tissues. This manuscript describes very well-known problems associated with implants and discusses novel solutions used in tissue engineering and regenerative medicine that can be implemented in this uncommonly discussed medical area.

SOURCES OF DATA

General and medical literature describing modifications of medical and surgical implants, biofunctionalization, tissue engineering and regenerative medicine.

AREAS OF AGREEMENT

Procedures for surgical implantation have grown substantially in the last few decades and provided improved quality of life for patients, regardless of area of implantation and device type and purpose.

AREAS OF CONTROVERSY

In general, implants fail because of lack of long-term integration with the surrounding tissues. Implant manufacturers have not addressed implant failure from the point of view of biointegration. In addition, some medical practitioners are inclined to treat implant failure by using anti-infection methods to prevent bacterial adhesion. However, both approaches are conceptually limited, as discussed in this manuscript.

GROWING POINTS

Implantation in the future will not be limited to medically needed procedures but also to a growing number of cosmetic body transformation procedures, which may include perceived 'improved implant functions' over natural tissues or organs. An additional trend is that implant procedures are being progressively performed in younger individuals.

AREAS TIMELY FOR DEVELOPING RESEARCH

Current implants generally do not allow the physician to have controlled long-term access to internal tissues in contact with the implants, for example to release specific compounds when medically needed to the problem area.

Regenerative medicine: implications for craniofacial surgery

Craniofacial reconstruction of cases with complex anatomy challenges surgeons. The recently emerging field of tissue engineering and regenerative medicine has resulted in a variety of novel therapeutic concepts particularly in the craniofacial area. However, researchers still face significant problems when translating scientific concepts from the bench to the bedside. Reconstruction procedures depend on sustainability, aesthetic outcome, and functionality. Tissue engineering approaches yield powerful tools for long-term satisfying results enabling customized reconstruction and supporting natural healing processes. In conclusion, further advances of tissue-engineered reconstruction need multidisciplinary research to create complex tissue structures and make satisfactory outcomes clinically achievable for most patients. This review highlights clinical advances in the field and gives an overview about current scientific concepts.

Bone regeneration with a combination of nanocrystalline hydroxyapatite silica gel, platelet-rich growth factor, and mesenchymal stem cells: a histologic study in rabbit calvaria

OBJECTIVE

This study aimed to assess NanoBone as a carrier construct for mesenchymal stem cells (MSCs) and platelet-rich growth factor (PRGF).

STUDY DESIGN

In the calvarial bone of 8 mature New Zealand White male rabbits, four 8-mm defects were created. Each defect received one of the following treatments: Group 1, 0.2 mg Nano-hydroxyapatite (HA) granule + 2 mL culture medium; Group 2, 0.2 mg Nano-HA + 1 mL autologous PRGF + 2 mL acellular culture medium; Group 3, 0.2 mg Nano-HA + 2 mL culture medium containing 100,000 autogenous MSCs; Group 4, 0.2 mg Nano-HA + 2 mL culture medium containing 100,000 autogenous MSCs + 1 mL autologous PRGF.

RESULT

Histomorphometric analysis at 6 and 12 weeks demonstrated significantly higher bone formation in group 4 (29.45% and 44.55%, respectively) (P < .05). Bone formation in groups 1, 2, and 3 were as follows: 11.35% and 32.53%, 29.10% and 39.74%, and 25.82% and 39.11%, respectively.

CONCLUSIONS

NanoBone with MSCs and PRGF seems to be an effective combination for bone regeneration in a rabbit calvaria model.

Craniomaxillofacial reconstruction using allotransplantation and tissue engineering: challenges, opportunities, and potential synergy

The face is composed of an intricate underlying bony/cartilaginous framework that supports muscle, secretory organs, and sophisticated skin/subcutaneous structures. These components are attached through numerous ligaments and interact dynamically with a vast neurovascular network. The most sophisticated autologous reconstructive techniques, utilizing composite free-tissue flaps, are often inadequate to restore extensive maxillofacial defects. Massive craniomaxillofacial (CMF) defects resulting from trauma, oncologic resection, or congenital deformity present a unique challenge to reconstructive surgeons. Therefore, recent advances in craniofacial surgery and immunotherapy spurred the innovation of composite tissue allotransplantation (CTA), which permits reconstruction with tissue composed of all necessary components. However, CMF allotransplantation carries with it side effects of lifelong immunosuppression. Furthermore, the donor skeletal framework may not provide an ideal match, resulting in less than ideal occlusion and soft-tissue anthropometrics. An alternative to transplantation, tissue engineering, has provided hope for regenerating missing tissue and avoiding the need for immunosuppression. Many tissue subtypes, including bone and cartilage, have been successfully created, with sparse reports of clinical application. Tissue-engineered composite tissue required for complete CMF reconstruction continues to elude development, with vascular supply and tissue interactions posing the largest remaining obstacles. We report herein the current status and limitations of CTA and tissue engineering. Furthermore, we describe for the first time our vision of hybridization of CTA and engineering, utilizing the strengths of each strategy.

Stem cell-mediated osteogenesis: therapeutic potential for bone tissue engineering

Intervertebral disc degeneration often requires bony spinal fusion for long-term relief. Current arthrodesis procedures use bone grafts from autogenous bone, allogenic backed bone, or synthetic materials. Autogenous bone grafts can result in donor site morbidity and pain at the donor site, while allogenic backed bone and synthetic materials have variable effectiveness. Given these limitations, researchers have focused on new treatments that will allow for safe and successful bone repair and regeneration. Mesenchymal stem cells have received attention for their ability to differentiate into osteoblasts, cells that synthesize new bone. With the recent advances in scaffold and biomaterial technology as well as stem cell manipulation and transplantation, stem cells and their scaffolds are uniquely positioned to bring about significant improvements in the treatment and outcomes of spinal fusion and other injuries.

Musculoskeletal tissue engineering by endogenous stem/progenitor cells

From its inception, tissue engineering has had three tenets: cells, biomaterial scaffolds and signaling molecules. Among the triad, cells are the center piece, because cells are the building blocks of tissues. For decades, cell therapies have focused on the procurement, manipulation and delivery of healthy cells for the treatment of diseases or trauma. Given the complexity and potential high cost of cell delivery, there is recent and surging interest to orchestrate endogenous cells for tissue regeneration. Biomaterial scaffolds are vital for many but not all, tissue-engineering applications and serve to accommodate or promote multiple cellular functions. Signaling molecules can be produced by transplanted cells or endogenous cells, or delivered specifically to regulate cell functions. This review highlights recent work in tissue engineering and cell therapies, with a focus on harnessing the capacity of endogenous cells as an alternative or adjunctive approach for tissue regeneration.

Evaluation of bone marrow-derived mesenchymal stem cells after cryopreservation and hypothermic storage in clinically safe medium

Achievements in tissue engineering using mesenchymal stem cells (MSC) demand a clinically acceptable "off-the-shelf" cell therapy product. Efficacy of cryopreservation of human bone marrow-derived MSC in clinically safe, animal product-free medium containing 2%, 5%, and 10% dimethyl sulfoxide (DMSO) was evaluated by measuring cell recovery, viability, apoptosis, proliferation rate, expression of a broad panel of MSC markers, and osteogenic differentiation. Rate-controlled freezing in CryoStor media was performed in a programmable cell freezer. About 95% of frozen cells were recovered as live cells after freezing in CryoStor solutions with 5% and 10% DMSO followed by storage in liquid nitrogen for 1 month. Cell recovery after 5 months storage was 72% and 80% for 5% and 10% DMSO, respectively. Measurements of caspase 3 activity demonstrated that 15.5% and 12.8% of cells after 1 month and 18.3% and 12.9% of cells after 5 months storage in 5% and 10% DMSO, respectively, were apoptotic. Proliferation of MSC recovered after cryopreservation was measured during 2 weeks post-plating. Proliferation rate was not compromised and was even enhanced. Cryopreservation did not alter expression of MSC markers. Quantitative analysis of alkaline phosphatase (ALP) activity, ALP surface expression and Ca⁺⁺ deposition in previously cryopreserved MSC and then differentiated for 3 weeks in osteogenic medium demonstrated the same degree of osteogenic differentiation as in unfrozen parallel cultures. Cell viability and functional parameters were analyzed in MSC after short-term storage at 4°C in HypoThermosol-FRS solution, also free of animal products. Hypothermic storage for 2 and 4 days resulted in about 100% and 85% cell recovery, respectively, less than 10% of apoptotic cells, and normal proliferation, marker expression, and osteogenic potential. Overall, our results demonstrate that human MSC could be successfully cryopreserved for banking and clinical applications and delivered to the bedside in clinically safe protective reagents.

Modulation of human mesenchymal stem cell function in a three-dimensional matrix promotes attenuation of adverse remodelling after myocardial infarction

The application of tissue engineering (TE) practices for cell delivery offers a unique approach to cellular cardiomyoplasty. We hypothesized that human mesenchymal stem cells (hMSCs) applied to the heart in a collagen matrix would outperform the same cells grown in a monolayer and directly injected for cardiac cell replacement after myocardial infarction in a rat model. When hMSC patches were transplanted to infarcted hearts, several measures for left ventricle (LV) remodelling and function were improved, including fractional area change, wall thickness, -dP/dt and LV end-diastolic pressure. Neovessel formation throughout the LV infarct wall after hMSC patch treatment increased by 37% when compared to direct injection of hMSCs. This observation was correlated with increased secretion of angiogenic factors, with accompanying evidence that these factors enhanced vessel formation (30% increase) and endothelial cell growth (48% increase) in vitro. These observations may explain the in vivo observations of increased vessel formation and improved cardiac function with patch-mediated cell delivery. Although culture of hMSC in collagen patches enhanced angiogenic responses, there was no effect on cell potency or viability. Therefore, hMSCs delivered as a cardiac patch showed benefits above those derived from monolayers and directly injected. hMSCs cultured and delivered within TE constructs may represent a good option to maximize the effects of cellular cardiomyoplasty.

Cell therapy in bone healing disorders

In addition to osteosynthetic stabilizing techniques and autologous bone transplantations, so-called orthobiologics play an increasing role in the treatment of bone healing disorders. Besides the use of various growth factors, more and more new data suggest that cell-based therapies promote local bone regeneration. For ethical and biological reasons, clinical application of progenitor cells on the musculoskeletal system is limited to autologous, postpartum stem cells. Intraoperative one-step treatment with autologous progenitor cells, in particular, delivered promising results in preliminary clinical studies. This article provides an overview of the rationale for, and characteristics of the clinical application of cell-based therapy to treat osseous defects based on a review of existing literature and our own experience with more than 100 patients. Most clinical trials report successful bone regeneration after the application of mixed cell populations from bone marrow. The autologous application of human bone marrow cells which are not expanded ex vivo has medico-legal advantages. However, there is a lack of prospective randomized studies including controls for cell therapy for bone defects. Autologous bone marrow cell therapy seems to be a promising treatment option which may reduce the amount of bone grafting in future.

Laser-induced regeneration of cartilage

Laser radiation provides a means to control the fields of temperature and thermo mechanical stress, mass transfer, and modification of fine structure of the cartilage matrix. The aim of this outlook paper is to review physical and biological aspects of laser-induced regeneration of cartilage and to discuss the possibilities and prospects of its clinical applications. The problems and the pathways of tissue regeneration, the types and features of cartilage will be introduced first. Then we will review various actual and prospective approaches for cartilage repair; consider possible mechanisms of laser-induced regeneration. Finally, we present the results in laser regeneration of joints and spine disks cartilages and discuss some future applications of lasers in regenerative medicine.

Current trends in mesenchymal stem cell application in bone augmentation: a review of the literature

PURPOSE

The literature regarding mesenchymal stem cell (MSC)-based bone reconstruction techniques are sparse and no comprehensive review of current methods has been performed. The aim of this article was to provide a discussion of clinical and experimental reports of MSC application in the reconstruction of bony defects in live models.

MATERIALS AND METHODS

This search was executed using the PubMed database with various combinations of related keywords. Currently published English-language studies that had applied MSCs as a part of their treatment protocol for reconstruction of bony defects in rat, rabbit, dog, and human models were reviewed. The included studies had reported substantiation that the applied cells were of MSC origin as a part of the study design. Publications inclusive to February 1, 2010 were evaluated. Of review of 187 found abstracts and full texts, 25 articles met the inclusion criteria.

RESULT

Based on this review, tremendous differences exist among investigators for the application of MSCs in bone augmentation procedures. These differences include not only species uniqueness but also a plethora of other variances, such as stem cell source, defect sites and sizes, carriers and constructs, use of additional growth factors, measured parameters, and methods of data collection.

CONCLUSION

Because of the multitude of protocols, range of parameters, and data in the current English-language literature, this review did not reach any significant conclusion as to the "most predictable" model in stem cell reconstruction. However, it does "shed light" on the need for additional collaborated studies using similar homogenous designs and data analysis in advancing the science of bone reconstruction using MSCs.

Adipose-derived stromal cell transplantation for treatment of stress urinary incontinence

We aimed to investigate the application of adipose-derived stromal cells in the treatment of stress urinary incontinence (SUI). Animal models of stress urinary incontinence were established with Sprague-Dawley female rats by complete cutting of the pudendal nerve. Rat adipose-derived stromal cells were isolated, cultured and successfully transplanted into animal models. Effects of stem cell transplantation were evaluated through urodynamic testing and morphologic changes of the urethra and surrounding tissues before and after transplantation. Main urodynamic outcome measures were measured. Intra-bladder pressure and leak point pressure were measured during filling phase. Morphologic examinations were performed. Transplantation of adipose-derived stem cells significantly strengthened local urethral muscle layers and significantly improved the morphology and function of sphincters. Urodynamic testing showed significant improvements in maximum bladder capacity, abdominal leak point pressure, maximum urethral closure pressure, and functional urethral length. Morphologic changes and significant improvement in urination control were consistent over time. It was concluded that periurethral injection of adipose-derived stromal cells improves function of the striated urethral sphincter, resulting in therapeutic effects on SUI. Reconstruction of the pelvic floor through transplantation of adipose-derived cells is a minimally invasive and effective treatment for SUI.

Gene therapy for the regeneration of bone

Gene transfer technologies offer the prospect of enhancing bone regeneration by delivering osteogenic gene products locally to osseous defects. In most cases the gene product will be a protein, which will be synthesized endogenously within and around the lesion in a sustained fashion. It will have undergone authentic post-translational processing and lack the alterations that occur when recombinant proteins are synthesized in bioreactors and stored. Several different ex vivo and in vivo gene delivery strategies have been developed for this purpose, using viral and non-viral vectors. Proof of principle has been established in small animal models using a variety of different transgenes, including those encoding morphogens, growth factors, angiogenic factors, and transcription factors. A small number of studies demonstrate efficacy in large animal models. Developing these promising findings into clinical trials will be a long process, constrained by economic, regulatory and practical considerations. Nevertheless, the overall climate for gene therapy is improving, permitting optimism that applications in bone regeneration will eventually become available.

Reduced immunomodulation potential of bone marrow-derived mesenchymal stem cells induced CCR4+CCR6+ Th/Treg cell subset imbalance in ankylosing spondylitis

INTRODUCTION

Ankylosing spondylitis (AS) is a chronic autoimmune disease, and the precise pathogenesis is largely unknown at present. Bone marrow-derived mesenchymal stem cells (BMSCs) with immunosuppressive and anti-inflammatory potential and Th17/Treg cells with a reciprocal relationship regulated by BMSCs have been reported to be involved in some autoimmune disorders. Here we studied the biological and immunological characteristics of BMSCs, the frequency and phenotype of CCR4+CCR6+ Th/Treg cells and their interaction in vitro in AS.

METHODS

The biological and immunomodulation characteristics of BMSCs were examined by induced multiple-differentiation and two-way mixed peripheral blood mononuclear cell (PBMC) reactions or after stimulation with phytohemagglutinin, respectively. The interactions of BMSCs and PBMCs were detected with a direct-contact co-culturing system. CCR4+CCR6+ Th/Treg cells and surface markers of BMSCs were assayed using flow cytometry.

RESULTS

The AS-BMSCs at active stage showed normal proliferation, cell viability, surface markers and multiple differentiation characteristics, but significantly reduced immunomodulation potential (decreased 68 ± 14%); the frequencies of Treg and Fox-P3+ cells in AS-PBMCs decreased, while CCR4+CCR6+ Th cells increased, compared with healthy donors. Moreover, the AS-BMSCs induced imbalance in the ratio of CCR4+CCR6+ Th/Treg cells by reducing Treg/PBMCs and increasing CCR4+CCR6+ Th/PBMCs, and also reduced Fox-P3+ cells when co-cultured with PBMCs. Correlation analysis showed that the immunomodulation potential of BMSCs has significant negative correlations with the ratio of CCR4+CCR6+ Th to Treg cells in peripheral blood.

CONCLUSIONS

The immunomodulation potential of BMSCs is reduced and the ratio of CCR4+CCR6+ Th/Treg cells is imbalanced in AS. The BMSCs with reduced immunomodulation potential may play a novel role in AS pathogenesis by inducing CCR4+CCR6+ Th/Treg cell imbalance.

The influence of scaffold architecture on chondrocyte distribution and behavior in matrix-associated chondrocyte transplantation grafts

Scaffold architecture and composition are important parameters in cartilage tissue engineering. In this in vitro study, we compared the morphology of four different cell-graft systems applied in clinical cartilage regeneration and analyzed the cell distribution (DAPI nuclei staining) and cell-scaffold interaction (SEM, TEM). Our investigations revealed major differences in cell distribution related to scaffold density, pore size and architecture. Material composition influenced the quantity of autogenous matrix used for cellular adhesion. Cell bonding was further influenced by the geometry of the scaffold subunits. On scaffolds with widely spaced fibers and a thickness less than the cell diameter, chondrocytes surrounded the scaffold fibers with cell extensions. On those fibers, chondrocytes were spherical, suggesting a differentiated phenotype. Fiber sizes smaller than chondrocyte size, and widely spaced, are therefore beneficial in terms of improved adhesion by cell shape adaptation. They also support the differentiated stage of chondrocytes by preventing the fibroblast-like and polygonal cell shape, at least briefly.

Osteoblasts in bone tissue engineering

Osteoblasts are integral to the development, growth, function, repair and maintenance of bone. The osteoblast forms organic, non-mineralized bone matrix and is involved in complex interactions with a variety of factors, mediators and cell types. Degeneration, pathology, and trauma cause disruption and destruction of the normal skeletal environment and may lead to bone loss.

There is a rise in active populations involved in trauma, elderly patients with fragility fractures and an overall increase in primary, revision and reconstructive bone and joint surgery. Despite the rapid evolution of implant technologies and bone grafting techniques, there is still a great demand for novel bone replacement strategies.

Bone tissue engineering is the state of the art science with the potential to regenerate bone with natural form and function. This review presents the biology of osteoblasts and their current applications in bone tissue engineering biotechnologies and role in stem cell, bioactive factor, recombinant signalling molecule and gene therapy research.

Engipore acts on human bone marrow stem cells

OBJECTIVES

Porous HA scaffolds are promising materials for tissue engineering because they offer a tridimensional support and serve as template for cell proliferation and at last tissue formation. Engipore provide a natural 3D scaffold with organic fibrous material in bone. However, how this material alters osteoblast activity to promote bone formation is poorly understood.

MATERIALS AND METHODS

To study how Engipore can induce osteoblast differentiation in mesenchymal stem cells, the expression levels of bone related genes and mesenchymal stem cells marker were analyzed.

RESULTS

Engipore causes a significant induction of osteoblast transcriptional factors like SP7 and RUNX2 and of the bone-related gene osteocalcin (BGLAP). The expression of CD105 was not significantly changed in stem cells treated with Engipore with respect to untreated cells, while SSP1 (osteopontin) was significantly down expressed thus reducing osteoclast activity.

CONCLUSIONS

The obtained results can be relevant to better understand the molecular mechanism of bone regeneration.

Concerted stimuli regulating osteo-chondral differentiation from stem cells: phenotype acquisition regulated by microRNAs

Bone and cartilage are being generated de novo through concerted actions of a plethora of signals. These act on stem cells (SCs) recruited for lineage-specific differentiation, with cellular phenotypes representing various functions throughout their life span. The signals are rendered by hormones and growth factors (GFs) and mechanical forces ensuring proper modelling and remodelling of bone and cartilage, due to indigenous and programmed metabolism in SCs, osteoblasts, chondrocytes, as well as osteoclasts and other cell types (eg T helper cells).This review focuses on the concerted action of such signals, as well as the regulatory and/or stabilizing control circuits rendered by a class of small RNAs, designated microRNAs. The impact on cell functions evoked by transcription factors (TFs) via various signalling molecules, also encompassing mechanical stimulation, will be discussed featuring microRNAs as important members of an integrative system. The present approach to cell differentiation in vitro may vastly influence cell engineering for in vivo tissue repair.