Adult mesenchymal stem cells: biological properties, characteristics, and applications in maxillofacial surgery

The applications of 3D printing in wound healing: the external delivery of stem cells and antibiosis

As the global number of chronic wound patients rises, the financial burden and social pressure on patients increase daily. Stem cells have emerged as promising tissue engineering seed cells due to their enriched sources, multidirectional differentiation ability, and high proliferation rate. However, delivering them in vitro for the treatment of skin injury is still challenging. In addition, bacteria from the wound site and the environment can significantly impact wound healing. In the last decade, 3D bioprinting has dramatically enriched cell delivery systems. The produced scaffolds by this technique can be precisely localized within cells and perform antibacterial actions. In this review, we summarized the 3D bioprinting-based external delivery of stem cells and their antibiosis to improve wound healing.

Dynamic transcriptome changes during osteogenic differentiation of bone marrow-derived mesenchymal stem cells isolated from chicken

Osteoblasts are indispensable for skeletal growth and maintenance. Bone marrow-derived mesenchymal stem cells (BMSCs) are useful in studying osteogenesis. In this study, BMSCs isolated from White Leghorns were differentiated into osteoblasts in vitro. Cells induced for -1, 0, 1, 11, and 22 d were used for transcriptomic analyses using the HISAT2-Stringtie-DESeq2 pipeline. Weighted correlation network analysis was processed to investigate significant modules, including differentially expressed genes (DEGs), correlated with osteogenic differentiation. Gene ontology and pathway enrichment analyses of DEGs were performed to elucidate the mechanisms of osteoblast differentiation. A total of 534, 1,144, 1,077, and 337 DEGs were identified between cells induced for -1 and 0, 0 and 1, 1 and 11, and 11 and 22 d, respectively (|log2FC| > 1.0, FDR <0.05). DEGs were mainly enriched in pathways related to cell proliferation in the early stage of osteogenic differentiation and pathways, such as the TGF-β signaling pathway, in the middle and late stages of osteogenic differentiation. A protein–protein interaction network of the 87 DEGs in the MEturquoise module within top 5-%-degree value was built utilizing the STRING database. This study is the first to elucidate the transcriptomic changes in the osteogenic differentiation of BMSCs isolated from White Leghorns at different times. Our results provide insight into the dynamic transcriptome changes during BMSC differentiation into osteoblasts in chicken.

Clinical Application of Stem Cell Therapy in Reconstructing Maxillary Cleft Alveolar Bone Defects: A Systematic Review of Randomized Clinical Trials

An alveolar cleft is the most common congenital bone defect. This systematic review aimed to investigate the use of stem cells for alveolar cleft repair and summarize the outcomes of clinical research studies. The electronic databases PubMed, Scopus, Web of Sciences, and Google Scholar were utilized to search the literature for relevant studies after administering specific inclusion and exclusion criteria. The search included articles that were published from 2011 to 2021 and specific keywords were used in the databases. The search was completed by two independent reviewers following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.Only four studies satisfied both the inclusion and exclusion criteria and were included in this systematic review. These studies investigated different aspects of bone reconstruction in the maxillary alveolar bone by stem cells, including cell types, clinical applications, biomaterial scaffolds, and follow-up period. The accumulated evidence in this systematic review is limited and insufficient to support the role of stem cell use in bone regeneration of maxillary alveolar bone defects. The outcome of using stem cells was studied only in 57 subjects from the four included studies. Although the noninvasive methods of isolating stem cells make them attractive resources for bone regeneration, more research is required in order to standardize and investigate stem cell therapy. This should be done beforehand in adults in less invasive procedures such as bone defect repair in dentistry prior to considering this type of therapy in this vulnerable patient population.

MSCs Become Collagen-Type I Producing Cells with Different Phenotype in Allogeneic and Syngeneic Bone Marrow Transplantation

Mesenchymal stem cells (MSCs) have been widely used in therapeutic applications for many decades. However, more and more evidence suggests that factors such as the site of origin and pre-implantation treatment have a crucial impact on the result. This study investigates the role of freshly isolated MSCs in the lacrimal gland after allogeneic transplantation. For this purpose, MSCs from transgenic GFP mice were isolated and transplanted into allogeneic and syngeneic recipients. While the syngeneic MSCs maintained a spherical shape, allogeneic MSCs engrafted into the tissue as spindle-shaped cells in the interstitial stroma. Furthermore, the MSCs produced collagen type I in more than 85% to 95% of the detected GFP+ MSCs in the recipients of both models, supposedly contributing to pathogenic fibrosis in allogeneic recipients compared to syngeneic models. These findings indicate that allogeneic MSCs act completely differently from syngeneic MSCs, highlighting the importance of understanding the exact mechanisms behind MSCs.

Comparison of bone regenerative capacity of donor-matched human adipose-derived and bone marrow mesenchymal stem cells

Adipose-derived stem cells (ASC) have been used as an alternative to bone marrow mesenchymal stem cells (BMSC) for bone tissue engineering. However, the efficacy of ASC in bone regeneration in comparison with BMSC remains debatable, since inconsistent results have been reported. Comparing ASC with BMSC obtained from different individuals might contribute to this inconsistency in results. Therefore, this study aimed to compare the bone regenerative capacity of donor-matched human ASC and BMSC seeded onto poly(l-lactide-co-ε-caprolactone) scaffolds using calvarial bone defects in nude rats. First, donor-matched ASC and BMSC were seeded onto the co-polymer scaffolds to evaluate their in vitro osteogenic differentiation. Seeded scaffolds and scaffolds without cells (control) were then implanted in calvarial defects in nude rats. The expression of osteogenesis-related genes was examined after 4 weeks. Cellular activity was investigated after 4 and 12 weeks. Bone formation was evaluated radiographically and histologically after 4, 12, and 24 weeks. In vitro, ASC and BMSC demonstrated mineralization. However, BMSC showed higher alkaline phosphatase activity than ASC. In vivo, human osteogenesis–related genes Runx2 and collagen type I were expressed in defects with scaffold/cells. Defects with scaffold/BMSC had higher cellular activity than defects with scaffold/ASC. Moreover, bone formation in defects with scaffold/BMSC was greater than in defects with scaffold/ASC, especially at the early time-point. These results suggest that although ASC have the potential to regenerate bone, the rate of bone regeneration with ASC may be slower than with BMSC. Accordingly, BMSC are more suitable for bone regenerative applications.

Efficacy of autologous stem cells for bone regeneration during endosseous dental implants insertion - A systematic review of human studies

Availability of adequate quantity and quality of bone is prerequisite for longevity and survival of endosseous dental implants. Most of the clinicians face with the problem of lack of bone due to long-standing edentulism during this treatment modality. Conventional therapies with the use of various types of bone grafts and membranes have provided clinicians with unpredictable and compromised results. Cell-based therapies utilizing undifferentiated cells, that have the potential to differentiate into various cell types including osteoblastic lineages, have demonstrated through various previously conducted in-vitro and animal studies, a successful formation of bone in a predictable manner. Thus the main objective of this review was to evaluate the effectiveness of these therapies when applied on human subjects. A search was carried out in MEDLINE (via PubMed) and Cochrane CENTRAL databases for completed randomized and non-randomised clinical trials utilizing stem cell-based therapies with histologic and radiographic analysis written in English up to January 2019. This search of the literature yielded 10 studies meeting the inclusion and exclusion criteria. In all these studies, stem cells were primarily used to achieve bone augmentation during insertion of endosseous dental implants. Results of these therapies conducted on human subjects have shown a positive impact on bone regeneration, in particular, therapies utilizing bone marrow and adipose tissue derived stem cells. But the clinicians need to examine the efficacy, safety, feasibility of these therapies while treating large size defects or planning for shorter healing period and early loading of dental implants.

Bone regeneration in rabbit calvarial defects using PRGF and adipose-derived stem cells: histomorphometrical analysis

Aim: The aim of this study was to evaluate the osteogenic potential of adipose-derived stem cells (ADSCs) and to assess the influence of plasma rich in growth factors (PRGF) on bone regeneration using ADSCs. Materials & methods: Bone defects were randomly allocated to the five treatment modalities: spontaneous healing, natural bovine bone mineral (BBM), BBM loaded with PRGF, BBM loaded with ADSCs and BBM loaded with a combination of ADSCs and PRGF. Results: The PRGF significantly enhanced the biomaterial-to-bone contact. Defects treated with ADSCs and PRGF or a combination of both showed the greatest bone regeneration. Conclusion: Combining PRGF and ADSCs boosts the bone graft regenerative potential at the earliest period of healing.

Enhanced efficiency in isolation and expansion of hAMSCs via dual enzyme digestion and micro-carrier

A two-stage method of obtaining viable human amniotic stem cells (hAMSCs) in large-scale is described. First, human amniotic stem cells are isolated via dual enzyme (collagenase II and DNAase I) digestion. Next, relying on a culture of the cells from porous chitosan-based microspheres in vitro, high purity hAMSCs are obtained in large-scale. Dual enzymatic (collagenase II and DNase I) digestion provides a primary cell culture and first subculture with a lower contamination rate, higher purity and a larger number of isolated cells. The obtained hAMSCs were seeded onto chitosan microspheres (CM), gelatin-chitosan microspheres (GCM) and collagen-chitosan microspheres (CCM) to produce large numbers of hAMSCs for clinical trials. Growth activity measurement and differentiation essays of hAMSCs were realized. Within 2 weeks of culturing, GCMs achieved over 1.28 ± 0.06 × 107 hAMSCs whereas CCMs and CMs achieved 7.86 ± 0.11 × 106 and 1.98 ± 0.86 × 106 respectively within this time. In conclusion, hAMSCs showed excellent attachment and viability on GCM-chitosan microspheres, matching the hAMSCs' normal culture medium. Therefore, dual enzyme (collagenase II and DNAase I) digestion may be a more useful isolation process and culture of hAMSCs on porous GCM in vitro as an ideal environment for the large-scale expansion of highly functional hAMSCs for eventual use in stem cell-based therapy.

Is There a Noninvasive Source of MSCs Isolated with GMP Methods with Better Osteogenic Potential?

BACKGROUND

A new trend in the treatment for alveolar clefts in patients with cleft lip and palate involves the use of bone tissue engineering strategies to reduce or eliminate the morbidity associated with autologous bone grafting. The use of mesenchymal stem cells-autologous cells obtained from tissues such as bone marrow and fat-combined with various biomaterials has been proposed as a viable option for use in cleft patients. However, invasive procedures are necessary to obtain the mesenchymal stem cells from these two sources. To eliminate donor site morbidity, noninvasive stem cell sources such as the umbilical cord, orbicularis oris muscle, and deciduous dental pulp have been studied for use in alveolar cleft bone tissue engineering. In this study, we evaluate the osteogenic potential of these various stem cell types.

METHODS

Ten cellular strains obtained from each different source (umbilical cord, orbicularis oris muscle, or deciduous dental pulp) were induced to osteogenic differentiation in vitro, and the bone matrix deposition of each primary culture was quantified. To evaluate whether greater osteogenic potential of the established mesenchymal stem cell strains was associated with an increase in the expression profile of neural crest genes, real-time qPCR was performed on the following genes: SRY-box 9, SRY-box 10, nerve growth factor receptor, transcription factor AP-2 alpha, and paired box 3.

RESULTS

The mesenchymal stem cells obtained from deciduous dental pulp and orbicularis oris muscle demonstrated increased osteogenic potential with significantly more extracellular bone matrix deposition when compared to primary cultures obtained from the umbilical cord after twenty-one days in culture (p = 0.007 and p = 0.005, respectively). The paired box 3 gene was more highly expressed in the MSCs obtained from deciduous dental pulp and orbicularis oris muscle than in those obtained from the umbilical cord.

CONCLUSION

These results suggest that deciduous dental pulp and orbicularis oris muscle stem cells demonstrate superior osteogenic differentiation potential relative to umbilical cord-derived stem cells and that this increased potential is related to their neural crest origins. Based on these observations, and the distinct translational advantage of incorporating stem cells from noninvasive tissue sources into tissue engineering protocols, greater study of these specific cell lines in the setting of alveolar cleft repair is indicated.

Ultrastructure Morphological Characterization of Different Passages of Rat Dental Follicle Stem Cells at In vitro Culture

Introduction:

Stem cells play important roles in tissue renewal and repair. Tissue-derived stem cells have been demonstrated for their applications in tissue engineering and regenerative medicine. Expansion of primary stem cells isolated from tissues to a large quantity through in vitro culture is needed for application of the stem cells. However, it is known that tissue stem cells commonly reduce or lose their stemness properties during in vitro culture. In this study, we assessed ultrastructural changes of rat dental follicle stem cells (DFSCs) during in vitro culture. It is our attempt to explain the loss of stemness properties in cultured tissue-stem cells at the ultrastructural level.

Method:

DFSCs was isolated from first molars of Sprague Dawley rat pups and cultured in medium consisting of alpha-MEM plus 20% FBS. Cells were passaged at 1 to 3 ratio at 90% confluence, and collected at passages 3, 6, 7 and 9 for assessment of ultrastructure morphology by transmission electron microscopy.

Results:

Of the four passages (3, 6, 7, and 9) examined, dilated rough endoplasmic reticulum (RER) was abundant in Passage 3 but less so in Passages 6, 7, and 9. The dilated RER contained lipid in Passages 3, 7, and 9. The mono- and polyribosomes in Passages 3 and 6 were located between the mitochondria and the RER. Mono- and polyribosomes were abundant in Passage 7, although mainly monoribosomes were present in Passage 9. Membrane-bound glycogen granules were in vacuoles bulging off the cells in Passage 3. Some glycogen granules were grouped in the periphery of a stem cell in Passage 9. Nuclei shapes were irregular and mainly euchromatic in Passages 6, 7, and 9. The mitochondria were dark and scarce in Passage 9; irregular, small, and dark in Passage 7; and small and rounded in Passage 6, and they were spread in the cytoplasm away from the nucleus in Passage 3. Cell contacts were seen in Passages 6, 7, and 9. The ultrastructure morphology of the examined DFScs was not very different from the morphology criteria of the undifferentiated cells. Large vacuoles in Passage 3 were mainly at the periphery of the cell, with the small vacuoles in the cell center. Small vacuoles were scattered in the cell center of Passage 6 and the larger ones were observed at the cell's periphery.

Conclusions:

We observed the following ultrastructural changes: decreases of fine cell cytoplasmic processes, dilated cytoplasmic vacuoles, cytoplasmic pinocytotic vesicles, and nuclear heterochromatin with increasing cell passage number. Conversely, mean ratios of lipid globules, nuclear euchromatin, irregular nuclear shape, and cell contact between cells were increased with passage number. The observations may suggest an increase in committed cells among the population after long-term culture of DFSCs.

The Pluripotent Microvascular Pericytes Are the Adult Stem Cells Even in the Testis

The pericytes of the testis are part of the omnipresent population of pericytes in the vertebrate body and are the only true pluripotent adult stem cells able to produce structures typical for the tree primitive germ layers: ectoderm, mesoderm, and endoderm. They originate very early in the embryogenesis from the pluripotent epiblast. The pericytes become disseminated through the whole vertebrate organism by the growing and differentiating blood vessels where they remain in specialized periendothelial vascular niches as resting pluripotent adult stem cells for tissue generation, maintenance, repair, and regeneration. The pericytes are also the ancestors of the perivascular multipotent stromal cells (MSCs). The variable appearance of the pericytes and their progeny reflects the plasticity under the influence of their own epigenetic and the local environmental factors of the host organ. In the testis the pericytes are the ancestors of the neuroendocrine Leydig cells. After activation the pericytes start to proliferate, migrate, and build transit-amplifying cells that transdifferentiate into multipotent stromal cells. These represent progenitors for a number of different cell types in an organ. Finally, it becomes evident that the pericytes are a brilliant achievement of the biological nature aiming to supply every organ with an omnipresent population of pluripotent adult stem cells. Their fascinating features are prerequisites for future therapy concepts supporting cell systems of organs.

Evaluation of the Possible Synergic Regenerative Effects of Platelet-Rich Plasma and Hydroxyapatite/Zirconia in the Rabbit Mandible Defect Model

BACKGROUND

Platelet-rich plasma (PRP) and bioceramics such as hydroxyapatite (HA) and zirconium oxide (ZrO₂) are used to reconstruct mandibular defects. We sought to determine the synergistic effects of HA/ZrO₂ and PRP and compare their osteogenic activity.

METHODS

ZrO₂ scaffolds were constructed by the slurry method and were then coated with HA and impregnated by PRP/heparan sulfate (HS). Bilateral mandibular defects were created in 26 male rabbits. In 20 rabbits, the left defects were treated with HA/ZrO₂/PRP (Group 1) and the corresponding right defects were filled with HA/ZrO₂ (Group 2). The 6 remaining models were treated with PRP gels at both sides (Group 3). The osteoconductivity of HA/ZrO₂/PRP was compared with that of HA/ZrO₂ or PRP by radiological and histological methods after the follow-up period, at weeks 2, 6 and 8. The statistical analyses were performed by ANOVA and LSD using SPSS, version 16.0, for Windows (P<0.05).

RESULTS

After 2 weeks, the percentage of the surface occupied by bone was significantly higher in the HA/ZrO₂/PRP-treated defects than in the PRP-treated defects (P=0.007). Osteoblast and osteocyte counts were higher significantly in the PRP-treated group (P=0.032); however, the cells had not started matrix formation on a large scale and just small islands of osteoid with trapped osteocytes were observed. In the long term, the regenerative potential of all the scaffolds was the same.

CONCLUSION

HA/ZrO₂ showed a superior osteoconductive capacity over PRP in the short term; however, they showed no long-term synergic effects.

Applications of stem cells in orthodontics and dentofacial orthopedics: Current trends and future perspectives

A simple overview of daily orthodontic practice involves use of brackets, wires and elastomeric modules. However, investigating the underlying effect of orthodontic forces shows various molecular and cellular changes. Also, orthodontics is in close relation with dentofacial orthopedics which involves bone regeneration. In this review current and future applications of stem cells (SCs) in orthodontics and dentofacial orthopedics have been discussed. For craniofacial anomalies, SCs have been applied to regenerate hard tissue (such as treatment of alveolar cleft) and soft tissue (such as treatment of hemifacial macrosomia). Several attempts have been done to reconstruct impaired temporomandibular joint. Also, SCs with or without bone scaffolds and growth factors have been used to regenerate bone following distraction osteogenesis of mandibular bone or maxillary expansion. Current evidence shows that SCs also have potential to be used to regenerate infrabony alveolar defects and move the teeth into regenerated areas. Future application of SCs in orthodontics could involve accelerating tooth movement, regenerating resorbed roots and expanding tooth movement limitations. However, evidence supporting these roles is weak and further studies are required to evaluate the possibility of these ideas.

Adipose-derived and bone marrow mesenchymal stem cells: a donor-matched comparison

Background

Adipose-derived stem cells (ASCs) have been introduced as an alternative to bone marrow mesenchymal stem cells (BMSCs) for cell-based therapy. However, different studies comparing ASCs and BMSCs have shown conflicting results. In fact, harvesting ASCs and BMSCs from different individuals might influence the results, making comparison difficult. Therefore, this study aimed to characterize donor-matched ASCs and BMSCs in order to investigate proliferation, differentiation potential and possible effects of donor variation on these mesenchymal stem cells (MSCs).

Methods

Human bone marrow and adipose tissue samples were obtained from nine donors aged 8–14. ASCs and BMSCs were isolated and characterized based on expression of surface markers using flow cytometry. The proliferation up to 21 days was investigated. Multi-lineage differentiation was induced using osteogenic, chondrogenic and adipogenic differentiation media. Alkaline phosphatase (ALP) activity was monitored and collagen type I formation was evaluated by immunofluorescence staining. In vitro multi-potency was studied using tissue-specific stains and lineage-specific gene expression. In addition, the osteogenic lineage was evaluated at protein level.

Results

Isolated ASCs and BMSCs from all donors demonstrated morphologic and immunophenotypic characteristics of MSCs, with expression of MSCs markers and negative expression of hematopoietic markers. Unlike BMSCs, ASCs showed high expression of CD49d and low expression of Stro-1. In general, ASCs showed significantly higher proliferation and adipogenic capacity with more lipid vesicle formation and expression of the adipogenesis-related genes than BMSCs. In contrast, BMSCs showed significantly higher osteogenic and chondrogenic capacity compared to ASCs. BMSCs had earlier and higher ALP activity, calcium deposition, and expression of the osteogenesis- and chondrogenesis-related genes and the osteogenesis-related protein osteopontin. Proliferation and differentiation capacity of ASCs and BMSCs varied significantly among the donors.

Conclusions

ASCs and BMSCs showed tissue-specific differentiation abilities, but with significant variation between donors. The similarities and differences in the properties of ASCs and BMSCs should be taken into consideration when planning stem cell-based therapy.

Encapsulation of mesenchymal stem cells in chitosan/β-glycerophosphate hydrogel for seeding on a novel calcium phosphate cement scaffold

Due to its moldability, biocompatibility, osteoconductivity and resorbability, calcium phosphate cement (CPC) is a highly promising scaffold material for orthopedic applications. However, pH changes and ionic activity during the CPC setting reaction may adversely affect cells seeded directly on CPC. Moreover, a lack of macropores in CPC limits ingrowth of new bone. The objectives of this study were to prepare macroporous CPC scaffolds via porogen leaching, using mannitol crystals as the porogen and to evaluate the in vitro proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs) encapsulated in chitosan/β-glycerophosphate (C/GP) hydrogel prior to exposure to the novel CPC scaffold. MSCs were found to be adhered to the surfaces of CPC macropores via scanning electron microscopy. The viability and osteogenic differentiation of MSCs in C/GP hydrogel with or without exposure to CPC constructs containing mannitol crystals indicated that coating with C/GP hydrogel protected the cells during cement mixing and setting. In conclusion, novel, macroporous CPC scaffolds were prepared, and our data indicate that a hydrogel encapsulation-based strategy can be used to protect cells during scaffold formation. Thus, the MSC-laden CPC scaffolds show promise for the delivery of stem cells to promote bone regeneration.

Efficacy of stem cells on the healing of peri-implant defects: systematic review of preclinical studies

This systematic review considers the evidence from animal studies evaluating the effectiveness of mesenchymal stem cells (MSC) in the treatment of intraoral peri-implant defects. MEDLINE, EMBASE, and LILACS databases were searched for quantitative preclinical controlled animal model studies that evaluated the effect of MSC on bone healing at intraoral peri-implant bone defects. The primary outcome was the amount of (re-)osseointegration reported as bone-to-implant contact in the defect area. The systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement guidelines. Ten studies met the inclusion criteria. Only one study induced peri-implant inflammation to produce peri-implant bone defects. In all others, defects were surgically created at implant installation. Differences in defect morphology were identified among the studies. Both xenogenous and autogenous MSC were used to treat peri-implant defects. These included bone marrow-derived MSC, periodontal ligament-derived MSC, umbilical cord MSC, bone marrow-derived mononuclear cells, and peripheral blood mononuclear cells. Meta-analysis was not possible because of heterogeneities in study designs. Nonetheless, in most studies, local MSC implantation was not associated with adverse effects and had a positive effect on bone healing around peri-implant defects. Combination of MSC with membranes and bioactive factors appears to provide improved treatment outcomes. In large animal models, intraoral use of MSC may provide beneficial effects on bone healing within peri-implant defects. The various degrees of success of MSC in peri-implant bone healing are likely to be related to the use of cells from various populations, tissues, and donor species. However, human safety and efficacy must be demonstrated before its clinical use can be considered.

Evaluation of the role of autogenous bone-marrow-derived mesenchymal stem cell transplantation for the repair of mandibular bone defects in rabbits

The repair of craniofacial bony defects by traditional grafting techniques requires substantial time and effort, with associated morbidity. Tissue engineering has therefore become a novel approach targeting application for bone regeneration. This study used the rabbit model for radiographic and histological evaluation of bone bioengineering for mandibular defects reconstruction using only β-tricalcium phosphate (β-TCP) and, when loaded with autogenous; bone marrow-derived undifferentiated mesenchymal stem cells (BM-MSCs). Critical-sized defects (10 × 15 mm) were created unilaterally in the mandibular body region of each rabbit (n = 16), to be filled with the BM-MSCs/β-TCP constructs for the study group (group I) (n1 = 8) and with scaffold devoid of cells for the control group (group II) (n2 = 8). Two rabbits from each group were sacrificed after healing periods of 2, 4, 12, and 24 weeks. The results revealed that the BM-MSCs endowed β-TCP scaffold with a better and more rapid bone regenerating potential: since the first evaluation period of 2 weeks, the regenerated bone tissue in group I was more mature, denser and homogeneously distributed. From these findings we could infer that the bone regeneration process was jump-started within the study group cases, which led to better quality of regenerated bone.

Stem cells: Sources, and regenerative therapies in dental research and practice

Stem cells are considered to be among the principle scientific breakthroughs of the twentieth century for the future of medicine, and considered to be an important weapon to fight against diseases, particularly those that have resisted the efforts of science for a long time. Human dental tissues have limited potentials to regenerate but the discovery of dental stem cells have developed new and surprising scenario in regenerative dentistry. Stem cell treatments are one example of the possibility using adult cells sourced from patients’ own bodies’ means that it can be expected that in the near future such treatments may become routine at dental practices. The hope is that it will become possible to regenerate bone and dental tissues including the periodontal ligament, dental pulp and enamel, and that the creation of new teeth may also become feasible. In view of this possibility of achieving restoration with regenerative medicine, it can be considered that a new era of dentistry is beginning. Thus the aim of this review is to give dental professionals a brief overview of different stem cells sources and the latest findings and their implications for improving oral health and treating certain conditions of the human mouth and face.

Transplantation of stem cells from human exfoliated deciduous teeth for bone regeneration in the dog mandibular defect

AIM: To investigate the effect of stem cells from human exfoliated deciduous teeth (SHED) transplanted for bone regeneration in the dog mandibular defect.

METHODS: In this prospective comparative study, SHEDs had been isolated 5 years ago from human exfoliated deciduous teeth. The undifferentiated stem cells were seeded into mandibular bone through-and-through defects of 4 dogs. Similar defects in control group were filled with cell-free collagen scaffold. After 12 wk, biopsies were taken and morphometric analysis was performed. The percentage of new bone formation and foreign body reaction were measured in each case. The data were subject to statistical analysis using the Mann-Whitney U and Kruskalwalis statistical tests. Differences at P < 0.05 was considered as significant level.

RESULTS: There were no significant differences between control and SHED-seeded groups in connective tissue (P = 0.248), woven bone (P = 0.248) and compact bone (P = 0.082). There were not any side effects in transplanted SHED group such as teratoma or malignancy and abnormalities in this period.

CONCLUSION: SHEDs which had been isolated and characterized 5 years ago and stored with cryopreservation banking were capable of proliferation and osteogenesis after 5 years, and no immune response was observed after three months of seeded SHEDs.

Mesenchymal stem cells for chronic wounds therapy

Wound healing is a complex process that involves interaction of soluble mediators, extracellular matrix and infiltrating blood cells. Chronic and non-healing skin defects contribute significantly to morbidity and mortality of many patients. Recently, despite the current medical progress, the chronic and non-healing wounds still represent a serious medical problem. In many cases, conventional therapeutic approaches, such as dermal substitutes and growth factor therapy failed and do not produce the expected results, patients are exposed to a high risk of infection, sepsis or amputation. For that reason clinicians and researchers are forced to searching for alternative methods to induce healing process which may result into complete wound closure. Mesenchymal stem cells (MSCs) represent a unique tool of tissue engineering and regenerative medicine and a promising therapeutic strategy. Due to their unique biological properties, MSCs seem to be the perspective modality method for these patients. Many preclinical and clinical studies suggest the possibility of using these cells in tissue regeneration, healing acute and chronic wounds and scar remodelling. The objective of the present review is to summarize the current information and preclinical data about MSCs, their biological characteristics and mode of action during regenerative and healing processes, as well as their clinical application in chronic wounds treatment.

Adult Stem Cells and Diseases of Aging

Preservation of adult stem cells pools is critical for maintaining tissue homeostasis into old age. Exhaustion of adult stem cell pools as a result of deranged metabolic signaling, premature senescence as a response to oncogenic insults to the somatic genome, and other causes contribute to tissue degeneration with age. Both progeria, an extreme example of early-onset aging, and heritable longevity have provided avenues to study regulation of the aging program and its impact on adult stem cell compartments. In this review, we discuss recent findings concerning the effects of aging on stem cells, contributions of stem cells to age-related pathologies, examples of signaling pathways at work in these processes, and lessons about cellular aging gleaned from the development and refinement of cellular reprogramming technologies. We highlight emerging therapeutic approaches to manipulation of key signaling pathways corrupting or exhausting adult stem cells, as well as other approaches targeted at maintaining robust stem cell pools to extend not only lifespan but healthspan.

Influence of Autologus Adipose Derived Stem Cells and PRP on Regeneration of Dehiscence-Type Defects in Alveolar Bone: A Comparative Histochemical and Histomorphometric Study in Dogs

BACKGROUND AND OBJECTIVES

Autogenous bone grafts is considered to be the best choice for reconstructive surgery. Adipose Derived Stromal Cells (ASCs) represents a promising tool for new clinical concepts in supporting cellular therapy. The goal of our study was to investigate bone regeneration following application of autologous ASCs with or without Platelet-Rich Plasma (PRP) at dehiscence-type defects in alveolar bone in dogs.

METHODS AND RESULTS

Standardized buccal dehiscence defects (4× 3×3 mm) were surgically created in eighteen dogs, the defects were grafted with either ASCs -PRP, ASCs alone, or without grafting material. Three months later; a bone core was harvested from grafted and non grafted sites for histological, histochemical and histomorphometric assessment. There was no evidence of inflammation or adverse tissue reaction with either treatment. Defects grafted with ASCs-PRP showed a significantly higher result (p≤ 0.05), with a mean area % of spongy bone and compact bone of (64.96±5.37 and 837.62±24.95), compared to ASCs alone (47.65±1.43 and 661.92±12.65) and without grafting (33.55± 1.74 and 290.85±7.27) respectively. The area % of lamellated bone increased significantly reaching its highest level in group A followed by group B. Also a significant increase in area % of neutral mucopolysaccharides and calcified reactivity of Masson|s Trichrome stain in groups A and B compared to group C was obtained.

CONCLUSIONS

Our results suggest that, the addition of PRP to ASCs enhances bone formation after 3 months and may be clinically effective in accelerating postsurgical healing in both periodontal and maxillofacial surgical applications.

Reprogramming of mesenchymal stem cells derived from iPSCs seeded on biofunctionalized calcium phosphate scaffold for bone engineering

Human induced pluripotent stem cell-derived mesenchymal stem cells (iPSC-MSCs) are a promising choice of patient-specific stem cells with superior capability of cell expansion. There has been no report on bone morphogenic protein 2 (BMP2) gene modification of iPSC-MSCs for bone tissue engineering. The objectives of this study were to: (1) genetically modify iPSC-MSCs for BMP2 delivery; and (2) to seed BMP2 gene-modified iPSC-MSCs on calcium phosphate cement (CPC) immobilized with RGD for bone tissue engineering. iPSC-MSCs were infected with green fluorescence protein (GFP-iPSC-MSCs), or BMP2 lentivirus (BMP2-iPSC-MSCs). High levels of GFP expression were detected and more than 68% of GFP-iPSC-MSCs were GFP positive. BMP2-iPSC-MSCs expressed higher BMP2 levels than iPSC-MSCs in quantitative RT-PCR and ELISA assays (p < 0.05). BMP2-iPSC-MSCs did not compromise growth kinetics and cell cycle stages compared to iPSC-MSCs. After 14 d in osteogenic medium, ALP activity of BMP2-iPSC-MSCs was 1.8 times that of iPSC-MSCs (p < 0.05), indicating that BMP2 gene transduction of iPSC-MSCs enhanced osteogenic differentiation. BMP2-iPSC-MSCs were seeded on CPC scaffold biofunctionalized with RGD (RGD-CPC). BMP2-iPSC-MSCs attached well on RGD-CPC. At 14 d, COL1A1 expression of BMP2-iPSC-MSCs was 1.9 times that of iPSC-MSCs. OC expression of BMP2-iPSC-MSCs was 2.3 times that of iPSC-MSCs. Bone matrix mineralization by BMP2-iPSC-MSCs was 1.8 times that of iPSC-MSCs at 21 d. In conclusion, iPSC-MSCs seeded on CPC were suitable for bone tissue engineering. BMP2 gene-modified iPSC-MSCs on RGD-CPC underwent osteogenic differentiation, and the overexpression of BMP2 in iPSC-MSCs enhanced differentiation and bone mineral production on RGD-CPC. BMP2-iPSC-MSC seeding on RGD-CPC scaffold is promising to enhance bone regeneration efficacy.

Adult stem cells derived from skeletal muscle — biology and potential

Skeletal muscle contains at least two distinct populations of adult stem cells — satellite cells and multipotent muscle-derived stem cells. Monopotential satellite cells are located under the basal lamina of muscle fibers. They are capable of giving rise only to cells of myogenic lineage, which play an important role in the processes of muscle regeneration. Multipotent muscle-derived stem cells are considered to be predecessors of the satellite cells. Under proper conditions, both in vitro and in vivo, they undergo myogenic, cardiogenic, chondrogenic, osteogenic and adipogenic differentiation. The main purpose of the present article is to summarize current information about adult stem cells derived from skeletal muscle, and to discuss their isolation and in vitro expansion techniques, biological properties, as well as their potential for regenerative medicine.

Great promise of tissue-resident adult stem/progenitor cells in transplantation and cancer therapies

Recent progress in tissue-resident adult stem/progenitor cell research has inspired great interest because these immature cells from your own body can act as potential, easily accessible cell sources for cell transplantation in regenerative medicine and cancer therapies. The use of adult stem/progenitor cells endowed with a high self-renewal ability and multilineage differentiation potential, which are able to regenerate all the mature cells in the tissues from their origin, offers great promise in replacing non-functioning or lost cells and regenerating diseased and damaged tissues. The presence of a small subpopulation of adult stem/progenitor cells in most tissues and organs provides the possibility of stimulating their in vivo differentiation, or of using their ex vivo expanded progenies for cell-replacement and gene therapies with multiple applications in humans without a high-risk of graft rejection and major side effects. Among the diseases that could be treated by adult stem cell-based therapies are hematopoietic and immune disorders, multiple degenerative disorders such as Parkinson's and Alzheimer's diseases, Types 1 and 2 diabetes mellitus as well as skin, eye, liver, lung, tooth and cardiovascular disorders. In addition, a combination of the current cancer treatments with an adjuvant treatment consisting of an autologous or allogeneic adult stem/progenitor cell transplantation also represents a promising strategy for treating and even curing diverse aggressive, metastatic, recurrent and lethal cancers. In this chapter, we reviewed the most recent advancements on the characterization of phenotypic and functional properties of adult stem/progenitor cell types found in bone marrow, heart, brain and other tissues and discussed their therapeutic implications in the stem cell-based transplantation therapy.

The tissue engineering of articular cartilage: cells, scaffolds and stimulating factors

Damage or loss of articular cartilage as a consequence of congenital anomaly, degenerative joint disease or injury leads to progressive debilitation, which has a negative impact on the quality of life of affected individuals in all age groups. Classical surgical techniques for hyaline cartilage reparation are frequently insufficient and in many cases it is not possible to obtain the expected results. For this reason, researchers and surgeons are forced to find a method to induce complete cartilage repair. Recently, the advent of tissue engineering has provided alternative possibilities for the treatment of these patients by application of cell-based therapy (e.g. chondrocytes and adult stem cells) combined with synthetic substitutes of the extracellular matrix and bioactive factors to prepare functional replacement of hyaline cartilage. This communication is aimed at a brief review of the current status of cartilage tissue engineering and recent advances in the field.

Tissue engineering for bone production- stem cells, gene therapy and scaffolds

A bone graft has been the gold standard treatment for repairing bone defects. However, due to bone grafts associated donor site morbidity several alternative bone substitutes options have been made available but with their added expense and limited osteoinductive properties they are not ideal. Therefore, research has begun in tissue engineering to investigate stem cells, which are one of the body’s own mechanisms used to repair bone. Stem cells are clonogenic undifferentiated cells capable of self-renewal. Readily available from numerous of sources stem cells have the potential to differentiate in osteoblasts and chrondrocytes showing capability to repair both bone and cartilage. The known immunologic properties of stem cells further enhance their therapeutic appeal. Stem cells have shown to be excellent carriers for gene transfer having the capability to be transduced. Gene transfer could enable growth factors and bone morphogentic proteins to enhance bone repair. Stem cells are implanted onto scaffolds, which are structures capable of supporting tissue formation by allowing cell migration, proliferation and differentiation. Research aims to produce scaffolds that deliver and retain cells, allow for cell attachment has adequate biodegradability, biocompatibility and non-immunogenicity. However, having tried and testing numerous materials including synthetic and natural products research into the perfect scaffold product continues. This review aims to explain how stem cells were discovered, the techniques used to isolate stem cells, identify and manipulate them down different cell lineages and discuss the research into using stem cells to reconstruct bone using genetic modification and scaffolds.

Guided bone regeneration in pig calvarial bone defects using autologous mesenchymal stem/progenitor cells - a comparison of different tissue sources

Due to donor side morbidity and the absence of osteogenic properties in bone substitutes, there is a growing need for an alternative to traditional bone grafting within the scope of tissue engineering. This animal study was conducted to compare the in vivo osteogenic potential of adipose-derived (AD), periosteum-derived (PD) and bone marrow-derived (BM) mesenchymal stem/progenitor cells (MSC). Autologous mesenchymal stem/progenitor cells of named tissue origin were induced into osteogenic differentiation following in vitro cell expansion. Ex vivo cultivated cells were seeded on a collagen scaffold and subsequently added to freshly created monocortical calvarial bone defects in 21 domestic pigs. Pure collagen scaffold served as a control defect. The animals were sacrificed at specific time points and de novo bone formation was quantitatively analyzed by histomorphometry. Bone volume/total defect volume (BV/TV) and the mineralization rate of newly formed bone were compared among the groups. In the early stages of wound healing, up to 30 days, the test defects did not show better bone regeneration than those in the control defect, but the bone healing process in the test defects was accelerated in the later stage compared to those in the control defect. All the test defects showed complete osseous healing after 90 days compared to those in the control defect. During the observation period, no significant differences in BV/TV and mineralization of newly formed bone among the test defects were observed. Irrespective of the tissue sources of MSC, the speed and pattern of osseous healing after cell transplantations into monocortical bone defects were comparable. Our results indicate that the efficiency of autologous AD-MSC, PD-MSC and BM-MSC transplantation following ex vivo cell expansion is not significantly different for the guided regeneration of bone defects.

Human bone marrow stem cell-encapsulating calcium phosphate scaffolds for bone repair

Due to its injectability and excellent osteoconductivity, calcium phosphate cement (CPC) is highly promising for orthopedic applications. However, a literature search revealed no report on human bone marrow mesenchymal stem cell (hBMSC) encapsulation in CPC for bone tissue engineering. The aim of this study was to encapsulate hBMSCs in alginate hydrogel beads and then incorporate them into CPC, CPC-chitosan and CPC-chitosan-fiber scaffolds. Chitosan and degradable fibers were used to mechanically reinforce the scaffolds. After 21 days, that the percentage of live cells and the cell density of hBMSCs inside CPC-based constructs matched those in alginate without CPC, indicating that the CPC setting reaction did not harm the hBMSCs. Alkaline phosphate activity increased by 8-fold after 14 days. Mineral staining, scanning electron microscopy and X-ray diffraction confirmed that apatitic mineral was deposited by the cells. The amount of hBMSC-synthesized mineral in CPC-chitosan-fiber matched that in CPC without chitosan and fibers. Hence, adding chitosan and fibers, which reinforced the CPC, did not compromise hBMSC osteodifferentiation and mineral synthesis. In conclusion, hBMSCs were encapsulated in CPC and CPC-chitosan-fiber scaffolds for the first time. The encapsulated cells remained viable, osteodifferentiated and synthesized bone minerals. These self-setting, hBMSC-encapsulating CPC-based constructs may be promising for bone tissue engineering applications.

Culture human mesenchymal stem cells with calcium phosphate cement scaffolds for bone repair

Because of its moldability and excellent osteoconductivity, calcium phosphate cement (CPC) is highly promising for craniofacial and orthopedic applications. The objectives of this study were to investigate the response of human mesenchymal stem cells (hMSCs) to a high-strength CPC-chitosan scaffold and to examine cell proliferation and osteogenic differentiation. hMSCs were seeded onto CPC-chitosan composite, CPC control, and tissue culture polystyrene (TCPS). Alkaline phosphatase activity (ALP) and mineralization of hMSCs were measured. CPC-chitosan had a flexural strength (mean + or - SD; n = 5) of (19.5 + or - 1.4) MPa, higher than (8.0 + or - 1.4) MPa of CPC control (p < 0.05). The percentage of live hMSCs on CPC-chitosan was (90.5 + or - 1.3)% at 8 days, matching (90.7 + or - 3.8)% of CPC control (p > 0.1). The CPC-chitosan surface area covered by the attached hMSCs increased from (51 + or - 11)% at 1 day to (90 + or - 4)% at 8 days (p < 0.05), matching those of CPC control (p > 0.1). Hence, the CPC strength was significantly increased via chitosan without compromising the hMSC response. At 8 days, there was a significant increase in ALP of cells in osteogenic media (10.99 + or - 0.93) [(mM pNpp/min)/(microg DNA)] versus control media (3.62 + or - 0.40) (p < 0.05). hMSCs in osteogenic media exhibited greater mineralization area of (47.5 + or - 19.7)% compared with (6.1 + or - 2.3)% in control medium on TCPS (p < 0.05). In conclusion, hMSCs showed excellent attachment and viability on the strong and tough CPC-chitosan scaffold, matching the hMSC response on CPC control. hMSCs were successfully differentiated down the osteogenic lineage. Hence, the strong, in situ hardening CPC-chitosan scaffold may be useful as a moderate load-bearing vehicle to deliver hMSCs for maxillofacial and orthopedic bone tissue engineering.

Alveolar bone regeneration by transplantation of periodontal ligament stem cells and bone marrow stem cells in a canine peri-implant defect model: a pilot study

BACKGROUND

The present study was undertaken to evaluate the potential of periodontal ligament stem cells (PDLSCs) and bone marrow SCs (BMSCs) on alveolar bone regeneration in a canine peri-implant defect model.

METHODS

Four adult, male beagle dogs were used in this study. Autologous BMSCs from the iliac crests and PDLSCs from extracted teeth were cultured. Three months after extraction, BMSC- and PDLSC-loaded hydroxyapatite/beta-tricalcium phosphate (HA/TCP) (test groups) and cell-free HA/TCP (control group) were implanted in three rectangular, saddle-like peri-implant defects, respectively. The left side of the mandible was initially prepared, and after 8 weeks, the right side was also prepared. The animals were sacrificed after an 8-week healing period. Undecalcified ground sections were prepared. New bone formation and bone-to-implant contact (BIC) were measured histomorphometrically. BMSCs and PDLSCs were fluorescently labeled and traced.

RESULTS

Alveolar bone regeneration in surgically created peri-implant saddle-like defects was more effective in test groups than the control group. The BMSC group had the highest new bone formation (34.99% and 40.17% at healing times of 8 and 16 weeks, respectively) followed by the PDLSC group (31.90% and 36.51%) and control group (23.13% and 28.36%), respectively. Test groups exhibited a significantly higher new bone formation than the control group at 8 weeks, but the same was true for only the BMSC group at 16 weeks (P <0.05). Fluorescently labeled cells were identified adjacent to HA/TCP carriers and, partly, near connective tissues and osteoids.

CONCLUSION

This study demonstrated the feasibility of using stem cell-mediated bone regeneration to treat peri-implant defects.

Engineering anatomically shaped human bone grafts

The ability to engineer anatomically correct pieces of viable and functional human bone would have tremendous potential for bone reconstructions after congenital defects, cancer resections, and trauma. We report that clinically sized, anatomically shaped, viable human bone grafts can be engineered by using human mesenchymal stem cells (hMSCs) and a "biomimetic" scaffold-bioreactor system. We selected the temporomandibular joint (TMJ) condylar bone as our tissue model, because of its clinical importance and the challenges associated with its complex shape. Anatomically shaped scaffolds were generated from fully decellularized trabecular bone by using digitized clinical images, seeded with hMSCs, and cultured with interstitial flow of culture medium. A bioreactor with a chamber in the exact shape of a human TMJ was designed for controllable perfusion throughout the engineered construct. By 5 weeks of cultivation, tissue growth was evidenced by the formation of confluent layers of lamellar bone (by scanning electron microscopy), markedly increased volume of mineralized matrix (by quantitative microcomputer tomography), and the formation of osteoids (histologically). Within bone grafts of this size and complexity cells were fully viable at a physiologic density, likely an important factor of graft function. Moreover, the density and architecture of bone matrix correlated with the intensity and pattern of the interstitial flow, as determined in experimental and modeling studies. This approach has potential to overcome a critical hurdle-in vitro cultivation of viable bone grafts of complex geometries-to provide patient-specific bone grafts for craniofacial and orthopedic reconstructions.

Tissue engineered bone grafts: biological requirements, tissue culture and clinical relevance

The tremendous need for bone tissue in numerous clinical situations and the limited availability of suitable bone grafts are driving the development of tissue engineering approaches to bone repair. In order to engineer viable bone grafts, one needs to understand the mechanisms of native bone development and fracture healing, as these processes should ideally guide the selection of optimal conditions for tissue culture and implantation. Engineered bone grafts have been shown to have capacity for osteogenesis, osteoconduction, osteoinduction and osteointegration - functional connection between the host bone and the graft. Cells from various anatomical sources in conjunction with scaffolds and osteogenic factors have been shown to form bone tissue in vitro. The use of bioreactor systems to culture cells on scaffolds before implantation further improved the quality of the resulting bone grafts. Animal studies confirmed the capability of engineered grafts to form bone and integrate with the host tissues. However, the vascularization of bone remains one of the hurdles that need to be overcome if clinically sized, fully viable bone grafts are to be engineered and implanted. We discuss here the biological guidelines for tissue engineering of bone, the bioreactor cultivation of human mesenchymal stem cells on three-dimensional scaffolds, and the need for vascularization and functional integration of bone grafts following implantation.

Effect of initial cell seeding density on early osteogenic signal expression of rat bone marrow stromal cells cultured on cross-linked poly(propylene fumarate) disks

The intercellular signaling mechanisms among a transplanted cell population are largely determined by the cell population itself as well as the surrounding environment. Changes in cell-to-cell paracrine signaling distance can be obtained by altering cell density, and signal expression of growth factors can be enhanced by auto/paracrine signal transduction. To examine these relationships, we investigated the effect of cell seeding density on viability, proliferation, differentiation, and the endogenous osteogenic signal expression among rat bone marrow stromal cells (BMSCs) cultured on a 2D disk. Rat BMSCs were isolated from rats and then cultured for 8 days on biodegradable poly(propylene fumarate) disks with three different seeding densities (0.06, 0.15, and 0.30 million cells/disk). At days 1, 4, and 8, viability by live/dead fluorescent staining, DNA amount, osteogenic differentiation by alkaline phosphatase and osteocalcin mRNA expression, calcium deposition, and osteogenic growth factor mRNA expression were assayed. Osteogenic signal expression was evaluated using quantitative reverse transcriptase-polymerase chain reaction, and signals of interest include bone morphogenetic protein-2, transforming growth factor-β(1), fibroblast growth factor-2, and platelet-derived growth factor-A. The results from this study demonstrate that rat BMSCs were viable over 8 days without being affected by cell density and that both cell proliferation rate and early osteogenic differentiation were stimulated by lower cell seeding density. Most importantly, this study has demonstrated for the first time that the temporal gene expression profiles of endogenous growth factors can be controlled by altering the initial cell seeding density on poly(propylene fumarate) disks. Therefore, our results suggest that changes in the paracrine signal distance by altering cell seeding density may be a useful strategy to optimize the cell-biomaterial construct microenvironments to enhance the osteogenic signal expression.

Biomaterial technology for tissue engineering applications

Tissue engineering is a newly emerging biomedical technology and methodology to assist and accelerate the regeneration and repairing of defective and damaged tissues based on the natural healing potentials of patients themselves. For the new therapeutic strategy, it is indispensable to provide cells with a local environment that enhances and regulates their proliferation and differentiation for cell-based tissue regeneration. Biomaterial technology plays an important role in the creation of this cell environment. For example, the biomaterial scaffolds and the drug delivery system (DDS) of biosignalling molecules have been investigated to enhance the proliferation and differentiation of cell potential for tissue regeneration. In addition, the scaffold and DDS technologies contribute to develop the basic research of stem cell biology and medicine as well as obtain a large number of cells with a high quality for cell transplantation therapy. A technology to genetically engineer cells for their functional manipulation is also useful for cell research and therapy. Several examples of tissue engineering applications with the cell scaffold and DDS of growth factors and genes are introduced to emphasize the significance of biomaterial technology in new therapeutic and research fields.

In vitro adipose tissue engineering using an electrospun nanofibrous scaffold

Electrospun 3-dimensional nanofibrous scaffolds share morphologic similarities to collagen fibrils, and promote favorable biologic responses of seeded cells. In this study, we have fabricated a 3-dimensional nanofibrous scaffold made of poly L-lactic acid, and examined its ability to support and maintain the adipogenic differentiation of human bone marrow-derived mesenchymal stem cells in vitro. After a 21-day incubation, oil red O staining of constructs treated with adipogenic supplements revealed positive adipose-like staining, compared with lack of staining in untreated cultures. Semi-quantitative RT-PCR analysis of human bone marrow-derived mesenchymal stem cells cultured in adipogenic medium revealed highly elevated levels of adipogenesis-associated genes (1797-fold for lipoprotein lipase, and 5.6-fold for peroxisome proliferator-activated receptor gamma). Immunofluorescence staining of cellular constructs in adipogenic culture media showed the presence of lipoprotein lipase vesicles, a characteristic feature of adipose tissue. These results suggest that the poly L-lactic acid-based nanofibrous scaffold is a promising candidate for adult stem cell-based engineering of adipose tissue.

Mesenchymal stem cell proliferation and differentiation on an injectable calcium phosphate-chitosan composite scaffold

Calcium phosphate cement (CPC) can be molded or injected to form a scaffold in situ, has excellent osteoconductivity, and can be resorbed and replaced by new bone. However, its low strength limits CPC to non-stress-bearing repairs. Chitosan could be used to reinforce CPC, but mesenchymal stem cell (MSC) interactions with CPC-chitosan scaffold have not been examined. The objective of this study was to investigate MSC proliferation and osteogenic differentiation on high-strength CPC-chitosan scaffold. MSCs were harvested from rat bone marrow. At CPC powder/liquid (P/L) mass ratio of 2, flexural strength (mean+/-sd; n=5) was (10.0+/-1.1) MPa for CPC-chitosan, higher than (3.7+/-0.6) MPa for CPC (p<0.05). At P/L of 3, strength was (15.7+/-1.7)MPa for CPC-chitosan, higher than (10.2+/-1.8)MPa for CPC (p<0.05). Percentage of live MSCs attaching to scaffolds increased from 85% at 1 day to 99% at 14 days. There were (180+/-37) cells/mm(2) on scaffold at 1 day; cells proliferated to (1808+/-317) cells/mm(2) at 14 days. SEM showed MSCs with healthy spreading and anchored on nano-apatite crystals via cytoplasmic processes. Alkaline phosphatase activity (ALP) was (557+/-171) (pNPP mM/min)/(microg DNA) for MSCs on CPC-chitosan, higher than (159+/-47) on CPC (p<0.05). Both were higher than (35+/-32) of baseline ALP for undifferentiated MSCs on tissue-culture plastic (p<0.05). In summary, CPC-chitosan scaffold had higher strength than CPC. MSC proliferation on CPC-chitosan matched that of the FDA-approved CPC control. MSCs on the scaffolds differentiated down the osteogenic lineage and expressed high levels of bone marker ALP. Hence, the stronger CPC-chitosan scaffold may be useful for stem cell-based bone regeneration in moderate load-bearing maxillofacial and orthopedic applications.

Effect of mesenchymal stem cells and platelet-rich plasma on the healing of standardized bone defects in the alveolar ridge: a comparative histomorphometric study in minipigs

PURPOSE

The purpose of this study was to test the effect of the combination of mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP) incorporated into a fluorohydroxyapatite (FHA) scaffold on bone regeneration in cylindrical defects in the edentulous mandibular ridge of minipigs.

MATERIALS AND METHODS

Two mandibular premolar teeth were extracted bilaterally in 8 adult minipigs. After 2 months, 4 standardized defects of 3.5 mm diameter and 8 mm depth were created in each root site. The defects were randomly grafted with autogenous mandibular bone, FHA alone, PRP-FHA, or MSCs-PRP-FHA. A resorbable collagen membrane was placed over the defect area and the flaps were sutured. The animals were sacrificed 3 months later and biopsy samples were taken from the defect sites for histologic and histomorphometric assessment.

RESULTS

There was no evidence of inflammation or adverse tissue reaction with either treatment. MSCs-PRP-FHA-treated sites showed new vital bone between residual grafting particles. PRP-FHA- and FHA-treated sites showed residual particles in a background of marrow soft tissue with a moderate quantity of newly formed bone. Autogenous bone (46.97%) and MSCs-PRP-FHA (45.28%) produced a significantly higher amount of vital bone than PRP-FHA (37.95%), or FHA alone (36.03%). Further, the MSCs-PRP-FHA-treated defects showed a significantly higher percentage of contact between graft particles and newly formed bone compared with PRP-FHA and FHA group (59.23% vs 48.37% and 46.43%, respectively).

CONCLUSIONS

Our results suggest that, in this animal model, the addition of MSCs to PRP-FHA enhances bone formation after 3 months.

Novel approach to engineer implantable nasal alar cartilage employing marrow precursor cell sheet and biodegradable scaffold

PURPOSE

Repair of nasal and auricular malformation remains an obstacle for clinicians because of poor regenerative capacity of cartilage and limitation of donor sites. In the current study, we developed a novel approach to regenerate implantable nasal alar cartilage by using marrow precursor cell (MPC) sheet and biodegradable scaffold of polylactic acid-polyglycolic acid copolymer (PLGA).

MATERIALS AND METHODS

Rabbit MPCs were expanded and induced by transforming growth factor-beta to improve chondrocyte phenotype. MPC sheets were obtained by continuous culture and used to wrap PLGA scaffold in the shape of the human nasal alar. The constructs were incubated in a spinner flask for 4 weeks, and cartilage formation was investigated by gross inspection and histological examination. The constructs were then implanted subcutaneously into a nude mouse. Specimens were harvested and analyzed 4 weeks after implantation.

RESULTS

The results showed that cartilaginous tissue formed and PLGA absorbed during in vitro incubation. Histological analysis showed engineered cartilage consisted of evenly spaced lacunae embedded in a matrix rich in proteoglycans, and kept the initial shape of the nasal alar. Based on this "MPC sheet combining polymer strategy," implantable nasal alar could be successfully regenerated.

CONCLUSION

This strategy has the advantage of high cell transplantation efficiency and great potential for clinical application.

Recent progress on tissue-resident adult stem cell biology and their therapeutic implications

Recent progress in the field of the stem cell research has given new hopes to treat and even cure diverse degenerative disorders and incurable diseases in human. Particularly, the identification of a rare population of adult stem cells in the most tissues/organs in human has emerged as an attractive source of multipotent stem/progenitor cells for cell replacement-based therapies and tissue engineering in regenerative medicine. The tissue-resident adult stem/progenitor cells offer the possibility to stimulate their in vivo differentiation or to use their ex vivo expanded progenies for cell replacement-based therapies with multiple applications in human. Among the human diseases that could be treated by the stem cell-based therapies, there are hematopoietic and immune disorders, multiple degenerative disorders, such as Parkinson's and Alzheimer's diseases, type 1 or 2 diabetes mellitus as well as eye, liver, lung, skin and cardiovascular disorders and aggressive and metastatic cancers. In addition, the genetically-modified adult stem/progenitor cells could also be used as delivery system for expressing the therapeutic molecules in specific damaged areas of different tissues. Recent advances in cancer stem/progenitor cell research also offer the possibility to targeting these undifferentiated and malignant cells that provide critical functions in cancer initiation and progression and disease relapse for treating the patients diagnosed with the advanced and metastatic cancers which remain incurable in the clinics with the current therapies.