Multipotent mesenchymal stromal cell sheet therapy for bisphosphonate-related osteonecrosis of the jaw in a rat model

Functional aligned mesenchymal stem cell sheets fabricated using micropatterned thermo-responsive cell culture surfaces

Mesenchymal stem cells (MSCs) are frequently applied for cell transplantation and regenerative therapy because they secrete diverse therapeutic cytokines that prompt immuno-stimulatory and tissue repair processes. Furthermore, cultured MSC sheets exhibit enhanced cytokine secretion compared to their MSC suspensions, and represent a durable, versatile format for tissue engineering as singular, multi-layered, or multi-cell type sandwiched, transplantable constructs. Tissue engineered implants with various cellular orientations have been reported. In this study, patterned, temperature-responsive culture surfaces were used to prepare oriented MSC sheets. Patterned culture surfaces were fabricated by grafting polyacrylamide (PAAm) onto commercial poly(N-isopropylacrylamide) (PNIPAAm)-modified plastic via photopolymerization using a stripe-patterned photomask. Patterned surfaces were characterized using x-ray photoelectron spectroscopy, fluorescently labelled fibronectin and albumin adsorption assays, wetting (contact angle) measurements, atomic force microscopy, and scanning electron microscopy. Striped grafted patterns of PAAm were fabricated on the PNIPAAm-coated culture substrates, and PAAm polymerized within the PNIPAAm overlayer. Cell-aligned MSC sheets were then produced from MSC culture on this patterned surface, secreting higher amounts of therapeutic cytokines (vascular endothelial growth factor, hepatocyte growth factor, and transforming growth factor-β) than non-aligned MSC control sheets. In addition, aligned MSC sheets maintained enhanced cell multi-potent differentiation capabilities. New, aligned MSC sheets might exhibit improved functional properties for cell sheet transplant therapies.

Recent Stem-Cell-Based and Stem-Cell-Free Possibilities for the Therapeutic Management of the Osteonecrosis of the Jaw

Osteonecrosis of the jaw (ONJ), including the maxilla and mandible, is considered a challenging therapeutic problem, mainly due to the lack of understanding of its pathogenesis. It is well known that ONJ is a severe side effect caused by certain medications used to treat bone metastasis and osteoporosis, such as bisphosphonates, which inhibit bone resorption. Other therapeutics with similar side effects are, for instance, receptor activators of nuclear factor kappa-B ligand (RANK-L) inhibitor (denosumab), tyrosine kinase inhibitors (sunitinib), and antiangiogenics (bevacizumab). The conservative or surgical treatment of these medication-related osteonecroses of the jaw (MRONJs) is generally effortful and still not entirely effective. Therefore, the research seeks alternative treatment options like tissue engineering and stem cell therapy, which predominantly represent mesenchymal stem cells (MSCs) and their derivatives, such as extracellular vesicles. Moreover, it was published that novel stem cell therapy could even prevent the onset of MRONJ. On the other hand, the administration of stem cells may also be accompanied by some other health risks, such as an increased chance of cancer metastasis occurrence in cancer patients. The current review paper summarizes the most recent progress in stem-cell-based and stem-cell-free treatment options for the ONJ. Similarly, we discuss this novel approach's future perspectives and possible obstacles.

Novel standardized method for inducing medication-related osteonecrosis of the jaw in rats and precise quantitative assessment of pathological outcomes

Medication-related osteonecrosis of the jaw (MRONJ) is a serious complication of antiresorptive therapies, characterized by delayed healing, bone necrosis, and infection following dental procedures. Progress in the understanding of its pathophysiology has been hindered by the lack of standardized animal models. Existing models involving first molar or multiple molar extractions disrupt anatomic landmarks and face technical challenges, such as retained root fragments and inconsistent surgical procedures, which reduce reproducibility. To address these limitations, we developed a novel rat MRONJ model using maxillary second molar extraction combined with standardized palatal gingiva resection. By preserving the adjacent first and third molars, anatomic landmarks were retained, enabling precise and reproducible evaluations. The modified extraction technique incorporating wedge insertion improved the success rate and minimized root fractures. Notably, our findings revealed that suppressed bone metabolism in the MRONJ model inhibited natural tooth movement observed in the control group, highlighting a unique pathologic hallmark of MRONJ. The model effectively reproduced MRONJ-specific features, including persistent bone exposure, impaired bone healing, necrotic bone formation, and inflammation. Three-dimensional micro-computed tomography and histologic analyses provided robust and quantitative assessments of bone pathology. By integrating anatomic standardization and precise quantitative assessments, this model addresses the key limitations of previous approaches. It also provides a reliable platform for investigating the pathogenesis of MRONJ and for assessing preventive and therapeutic strategies. This approach contributes to translational research and holds promise for improving clinical outcomes.

MicroRNA-21-5p profile in the alveolar bone following tooth extraction in medication-related osteonecrosis of the jaw rat model

Objective

This study aimed to compare microRNA-21-5p expressions at the extraction wound in the maxillary bones of rats with medication-related osteonecrosis of the jaw (MRONJ) and normal rats at different time points.

Materials and methods

In total, 18 female, 8-week-old Sprague-Dawley rats were randomly assigned to the experimental group (n = 9) and the control group (n = 9). To establish MRONJ in the right maxillary first molar area in the experimental group, zoledronate (66 µg/kg) and dexamethasone (5 mg/kg) were administered intraperitoneally every other day for 2 weeks before tooth extraction. Normal saline was administered in the control group. After tooth extraction, the drugs were continuously administered until the experimental endpoints, namely 1, 14, and 28 days post-tooth extraction. At each endpoint, three rats from each group were euthanized. The maxilla bones at the wound area were harvested. A real-time polymerase chain reaction (RT-PCR) was performed to compare the expression levels of miRNA-21-5p at each time point between the MRONJ group and the control group.

Results

From their gross appearance, the rats that received zoledronate and dexamethasone developed MRONJ as demonstrated by non-healing wounds and exposed bone at 14 and 28 days post-extraction in contrast to the controls. The RT-PCR showed that the expression levels of miRNA-21-5p were relatively higher in the MRONJ rats compared to the control rats at day 14 and then the difference was lower at day 28 post-tooth extraction.

Conclusion

The findings indicated that the microRNA-21-5p expression levels varied during the socket healing process in the MRONJ rats, reaching a peak at 2 weeks after tooth extraction.

Exploring mesenchymal stem cells homing mechanisms and improvement strategies

Mesenchymal stem cells (MSCs) are multipotent cells with high self-renewal and multilineage differentiation abilities, playing an important role in tissue healing. Recent advancements in stem cell-based technologies have offered new and promising therapeutic options in regenerative medicine. Upon tissue damage, MSCs are immediately mobilized from the bone marrow and move to the injury site via blood circulation. Notably, allogenically transplanted MSCs can also home to the damaged tissue site. Therefore, MSCs hold great therapeutic potential for curing various diseases. However, one major obstacle to this approach is attracting MSCs specifically to the injury site following systemic administration. In this review, we describe the molecular pathways governing the homing mechanism of MSCs and various strategies for improving this process, including targeted stem cell administration, target tissue modification, in vitro priming, cell surface engineering, genetic modifications, and magnetic guidance. These strategies are crucial for directing MSCs precisely to the injury site and, consequently, enhancing their migration and local tissue repair properties. Specifically, our review provides a guide to improving the therapeutic efficacy of clinical applications of MSCs through optimized in vivo administration and homing capacities.

Revolutionizing bone defect healing: the power of mesenchymal stem cells as seeds

Bone defects can arise from trauma or pathological factors, resulting in compromised bone integrity and the loss or absence of bone tissue. As we are all aware, repairing bone defects is a core problem in bone tissue engineering. While minor bone defects can self-repair if the periosteum remains intact and normal osteogenesis occurs, significant defects or conditions such as congenital osteogenesis imperfecta present substantial challenges to self-healing. As research on mesenchymal stem cell (MSC) advances, new fields of application have emerged; however, their application in orthopedics remains one of the most established and clinically valuable directions. This review aims to provide a comprehensive overview of the research progress regarding MSCs in the treatment of diverse bone defects. MSCs, as multipotent stem cells, offer significant advantages due to their immunomodulatory properties and ability to undergo osteogenic differentiation. The review will encompass the characteristics of MSCs within the osteogenic microenvironment and summarize the research progress of MSCs in different types of bone defects, ranging from their fundamental characteristics and animal studies to clinical applications.

Application of mesenchymal stromal cell sheets to prevent medication-related osteonecrosis of the jaw with titanium implants in rats

Medication-related osteonecrosis of the jaw (MRONJ) is an intractable adverse event. Dental implants are one of the triggering factors of MRONJ, and implant therapy with low MRONJ risk is required. This study aimed to investigate a rat model of MRONJ induced by extraoral placement of titanium materials and the use of mesenchymal stromal cell (MSCs) sheets to prevent MRONJ. Eight-week-old male rats were administered zoledronate and dexamethasone thrice weekly until killing. A week after drug initiation, a titanium screw and a plate were placed on the left buccal side of the mandible. Allogeneic bone marrow-derived MSC sheets were co-grafted with the titanium plates in the MSC sheet ( +) group. Six weeks after titanium placement, the rats were killed, and their excised mandibular bones were subjected to micro-computed tomography (CT) analysis. Histological analysis was performed after the titanium implants were removed. Empty lacunae visualized on hematoxylin and eosin staining were used as evidence of bone necrosis. Bone necrosis was reduced in the MSC sheet ( +) group. Tartrate-resistant acid phosphatase (TRAP) staining revealed a decreased number of TRAP-positive cells in areas with a large number of empty lacunae in the MSC sheet (-) group. Micro-CT analyses demonstrated that the bone volume fraction (BV/TV) was not significantly different between the MSC sheet (-) and ( +) groups. We conclude that MRONJ can be triggered by a titanium placement in rats, and grafting of allogeneic MSC sheets has the potential to prevent MRONJ.

Rodents as an animal model for studying tooth extraction-related medication-related osteonecrosis of the jaw: assessment of outcomes

OBJECTIVE

To assess the outcomes of several rodent animal models for studying tooth extraction-related medication-related osteonecrosis of the jaw (MRONJ).

DESIGN

After a search of the databases, 2004 articles were located, and 118 corroborated the inclusion factors (in vivo studies in rodents evaluating tooth extraction as a risk factor for the development of MRONJ).

RESULTS

Numerous studies attempting to establish an optimal protocol to induce MRONJ were found. Zoledronic acid (ZA) was the most used drug, followed by alendronate (ALN). Even when ZA did not lead to the development of MRONJ, its effect compromised the homeostasis of the bone and soft tissue. The association of other risk factors (dexamethasone, diabetes, and tooth-related inflammatory dental disease) besides tooth extraction also played a role in the development of MRONJ. In addition, studies demonstrated a relationship between cumulative dose and MRONJ.

CONCLUSIONS

Both ZA and ALN can lead to MRONJ in rodents when equivalent human doses (in osteoporosis or cancer treatment) are used. Local oral risk factors and tooth-related inflammatory dental disease increase the incidence of MRONJ in a tooth extraction-related rodent model.

bFGF-releasing biodegradable nanoparticles for effectively engrafting transplanted hepatocyte sheet

Hepatic tissue engineering has been applied for the treatment of intractable liver diseases, and hepatocyte sheets are promising for this purpose. However, hepatocyte sheets have poor survival after transplantation because of their high metabolic activity. In this study, we aimed to develop basic fibroblast growth factor (bFGF)-releasing nanoparticles to prolong the survival of hepatocyte sheets after transplantation. The nanoparticles were prepared by electrospraying a bFGF-dispersed poly(D,l-lactide-co-glycolide) emulsion. bFGF-loaded PLGA nanoparticles can be developed by optimizing the applied electrospray voltage and the oil:water ratio of the emulsion. The prepared nanoparticles exhibited prompt release at the initial duration and continuous gradual release at the subsequent duration. Hepatocyte sheet engraftment was evaluated by transplanting hepatocyte sheets containing the prepared nanoparticles into rats. The hepatocyte sheets with the prepared nanoparticles exhibited longer survival than those without the bFGF nanoparticles or solution owing to the local and continuous release of bFGF from the nanoparticles and the subsequent enhanced angiogenesis at the transplantation site. These results indicated that the prepared bFGF-releasing nanoparticles can enhance the efficiency of hepatocyte sheet transplantation. The developed bFGF-releasing nanoparticles would be useful for the transplantation of cellular tissue with post-transplantation survival challenges.

Umbilical cord-derived mesenchymal stem cell sheets transplanted subcutaneously enhance cell retention and survival more than dissociated stem cell injections

BACKGROUND

Human umbilical cord-derived mesenchymal stem cell (hUC-MSC) sheets have recently attracted attention as an alternative approach to injected cell suspensions for stem cell therapy. However, cell engraftment and cytokine expression levels between hUC-MSC sheets and their cell suspensions in vivo have not yet been compared. This study compares hUC-MSC in vivo engraftment efficacy and cytokine expression for both hUC-MSC sheets and cell suspensions.

METHODS

hUC-MSC sheets were prepared using temperature-responsive cell culture; two types of hUC-MSC suspensions were prepared, either by enzymatic treatment (trypsin) or by enzyme-free temperature reduction using temperature-responsive cell cultureware. hUC-MSC sheets and suspensions were transplanted subcutaneously into ICR mice through subcutaneous surgical placement and intravenous injection, respectively. hUC-MSC sheet engraftment after subcutaneous surgical transplantation was investigated by in vivo imaging while intravenously injected cell suspensions were analyzing using in vitro organ imaging. Cytokine levels in both transplant site tissues and blood were quantified by enzyme-linked immunosorbent assay.

RESULTS

After subcutaneous transplant, hUC-MSC sheets exhibited longer engraftment duration than hUC-MSC suspensions. This was attributed to extracellular matrix (ECM) and cell-cell junctions retained in sheets but enzymatically altered in suspensions. hUC-MSC suspensions harvested using enzyme-free temperature reduction exhibited relatively long engraftment duration after intravenous injection compared to suspensions prepared using trypsin, as enzyme-free harvest preserved cellular ECM. High HGF and TGF-β1 levels were observed in sheet-transplanted sites compared to hUC-MSC suspension sites. However, no differences in human cytokine levels in murine blood were detected, indicating that hUC-MSC sheets might exert local paracrine rather than endocrine effects.

CONCLUSIONS

hUC-MSC sheet transplantation could be a more effective cell therapeutic approach due to enhanced engraftment and secretion of therapeutic cytokines over injected hUC-MSC suspensions.

Exosomes Derived from Adipose Tissue-Derived Mesenchymal Stromal Cells Prevent Medication-Related Osteonecrosis of the Jaw through IL-1RA

Medication-related osteonecrosis of the jaw (MRONJ) is a severe disease with unclear pathogenesis. Adipose tissue-derived mesenchymal stromal cells (MSC(AT)s) serve as a special source for cell therapy. Herein, we explored whether exosomes (Exo) derived from MSC(AT)s promote primary gingival wound healing and prevent MRONJ. An MRONJ mice model was constructed using zoledronate (Zol) administration and tooth extraction. Exosomes were collected from the conditioned medium (CM) of MSC(AT)s (MSC(AT)s-Exo) and locally administered into the tooth sockets. Interleukin-1 receptor antagonist (IL-1RA)-siRNA was used to knock down the expression of IL-1RA in MSC(AT)s-Exo. Clinical observations, micro-computed tomography (microCT), and histological analysis were used to evaluate the therapeutic effects in vivo. In addition, the effect of exosomes on the biological behavior of human gingival fibroblasts (HGFs) was evaluated in vitro. MSC(AT)s-Exo accelerated primary gingival wound healing and bone regeneration in tooth sockets and prevented MRONJ. Moreover, MSC(AT)s-Exo increased IL-1RA expression and decreased interleukin-1 beta (IL-1β) and tumor necrosis factor-α (TNF-α) expression in the gingival tissue. The sequent rescue assay showed that the effects of preventing MRONJ in vivo and improving the migration and collagen synthesis abilities of zoledronate-affected HGFs in vitro were partially impaired in the IL-1RA-deficient exosome group. Our results indicated that MSC(AT)s-Exo might prevent the onset of MRONJ via an IL-1RA-mediated anti-inflammatory effect in the gingiva wound and improve the migration and collagen synthesis abilities of HGFs.

Application of mesenchymal stem cell sheet for regeneration of craniomaxillofacial bone defects

Bone defects are among the most common damages in human medicine. Due to limitations and challenges in the area of bone healing, the research field has turned into a hot topic discipline with direct clinical outcomes. Among several available modalities, scaffold-free cell sheet technology has opened novel avenues to yield efficient osteogenesis. It is suggested that the intact matrix secreted from cells can provide a unique microenvironment for the acceleration of osteoangiogenesis. To the best of our knowledge, cell sheet technology (CST) has been investigated in terms of several skeletal defects with promising outcomes. Here, we highlighted some recent advances associated with the application of CST for the recovery of craniomaxillofacial (CMF) in various preclinical settings. The regenerative properties of both single-layer and multilayer CST were assessed regarding fabrication methods and applications. It has been indicated that different forms of cell sheets are available for CMF engineering like those used for other hard tissues. By tackling current challenges, CST is touted as an effective and alternative therapeutic option for CMF bone regeneration.

Rapid and effective preparation of clonal bone marrow-derived mesenchymal stem/stromal cell sheets to reduce renal fibrosis

Allogeneic "off-the-shelf" mesenchymal stem/stromal cell (MSC) therapy requires scalable, quality-controlled cell manufacturing and distribution systems to provide clinical-grade products using cryogenic cell banking. However, previous studies report impaired cell function associated with administering freeze-thawed MSCs as single cell suspensions, potentially compromising reliable therapeutic efficacy. Using long-term culture-adapted clinical-grade clonal human bone marrow MSCs (cBMSCs) in this study, we engineered cBMSC sheets in 24 h to provide rapid preparation. We then sought to determine the influence of cBMSC freeze-thawing on both in vitro production of pro-regenerative factors and in vivo ability to reduce renal fibrosis in a rat model compared to freshly harvested cBMSCs. Sheets from freeze-thawed cBMSCs sheets exhibited comparable in vitro protein production and gene expression of pro-regenerative factors [e.g., hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), and interleukin 10 (IL-10)] to freshly harvested cBMSC sheets. Additionally, freeze-thawed cBMSC sheets successfully suppressed renal fibrosis in vivo in an established rat ischemia-reperfusion injury model. Despite previous studies reporting that freeze-thawed MSCs exhibit impaired cell functions compared to fresh MSC single cell suspensions, cell sheets engineered from freeze-thawed cBMSCs do not exhibit impaired cell functions, supporting critical steps toward future clinical translation of cBMSC-based kidney disease treatment.

Therapeutic Effect of Benidipine on Medication-Related Osteonecrosis of the Jaw

Medication-related osteonecrosis of the jaw (MRONJ) is an intractable disease that is typically observed in patients with osteoporosis or tumors that have been treated with either bisphosphonate (BP) or antiangiogenic medicine. The mechanism of MRONJ pathogenesis remains unclear, and no effective definitive treatment modalities have been reported to date. Previous reports have indicated that a single injection of benidipine, an antihypertensive calcium channel blocker, in the vicinity of a tooth extraction socket promotes wound healing in healthy rats. The present study was conducted to elucidate the possibility of using benidipine to promote the healing of MRONJ-like lesions. In this study, benidipine was administered near the site of MRONJ symptom onset in a model rat, which was then sacrificed two weeks after benidipine injection, and analyzed using histological sections and CT images. The analysis showed that in the benidipine groups, necrotic bone was reduced, and soft tissue continuity was recovered. Furthermore, the distance between epithelial edges, length of necrotic bone exposed in the oral cavity, necrotic bone area, and necrotic bone ratio were significantly smaller in the benidipine group. These results suggest that a single injection of benidipine in the vicinity of MRONJ-like lesions can promote osteonecrotic extraction socket healing.

Human Mesenchymal Stem Cell Sheets Improve Uterine Incision Repair in a Rodent Hysterotomy Model

OBJECTIVE

The study aimed to assess the feasibility of creating and transplanting human umbilical cord mesenchymal stem cell sheets applied to a rat model of hysterotomy, and additionally to determine benefits of human umbilical cord mesenchymal stem cell sheet transplantation in reducing uterine fibrosis and scarring.

STUDY DESIGN

Human umbilical cord mesenchymal stem cell sheets are generated by culturing human umbilical cord mesenchymal stem cells on thermo-responsive cell culture plates. The temperature-sensitive property of these culture dishes facilitates normal cell culture in a thin contiguous layer and allows for reliable recovery of intact stem cell sheets without use of destructive proteolytic enzymes.We developed a rat hysterotomy model using nude rats. The rat uterus has two distinct horns: one horn provided a control/untreated scarring site, while the second horn was the cell sheet transplantation site.On day 14 following surgery, complete uteri were harvested and subjected to histologic evaluations of all hysterotomy sites.

RESULTS

The stem cell sheet culture process yielded human umbilical cord mesenchymal stem cell sheets with surface area of approximately 1 cm².Mean myometrial thickness in the cell sheet-transplanted group was 274 μm compared with 191 μm in the control group (p = 0.02). Mean fibrotic surface area in the human umbilical cord mesenchymal stem cell sheet-transplanted group was 95,861 μm² compared with 129,185 μm² in the control group. Compared with control horn sites, cell sheet-transplanted horns exhibited significantly smaller fibrotic-to-normal myometrium ratios (0.18 vs. 0.27, respectively, p = 0.029). Mean number of fibroblasts in cell sheet-transplanted horns was significantly smaller than the control horns (483 vs. 716/mm², respectively, p = 0.001).

CONCLUSION

Human umbilical cord mesenchymal stem cell sheet transplantation is feasible in a rat model of hysterotomy. Furthermore, use of stem cell sheets reduces fibroblast infiltration and uterine scar fibrotic tissue formation during hysterotomy healing, potentially mitigating risks of uterine scar formation.

KEY POINTS

· Stem cell sheet transplanted to hysterotomy promotes myometrial regeneration and reduced fibrotic tissue formation.. · This study demonstrates the feasibility of using human umbilical cord mesenchymal stem cell sheets..

Novel Cell Therapy Using Mesenchymal Stromal Cell Sheets for Medication-Related Osteonecrosis of the Jaw

Despite medication-related osteonecrosis of the jaw (MRONJ) being first reported in 2003, the optimal treatment and prevention modalities for MRONJ are not clear. As a result, dentistry, oral surgery, and departments involved in the treatment of cancer and bone diseases are struggling with the management of MRONJ. Several cases of MRONJ cannot be managed by conventional treatment strategies recommended in various position papers. Therefore, studies have been conducted to investigate the efficacy of novel therapies for MRONJ. However, the optimal treatment is unknown. Several cell therapies including autologous cell transplantation have been reported for MRONJ. Although the efficacy of cell therapy for MRONJ has been demonstrated, large, statistically accurate clinical trials are lacking. We have been investigating the efficacy of MRONJ treatment using mesenchymal stromal cell (MSC) sheets since 2013 and confirmed its efficacy through various experiments, wherein MSC sheets were transplanted in model rats and beagle dogs with MRONJ-like lesions. Based on these results, we are planning to conduct a clinical trial of MRONJ therapy using periodontal ligament-derived MSC sheets.

Preclinical models of medication-related osteonecrosis of the jaw (MRONJ)

Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe adverse event affecting patients with cancer and patients with osteoporosis who have been treated with powerful antiresorptives (pARs) or angiogenesis inhibitors (AgIs). pARs, including nitrogen-containing bisphosphonates (N-BPs; e.g., zoledronic acid, alendronate) and anti-RANKL antibodies (e.g., denosumab), are used to manage bone metastases in patients with cancer or to prevent fragility fractures in patients with osteoporosis. Though significant advances have been made in understanding MRONJ, its pathophysiology is still not fully elucidated. Multiple species have been used in preclinical MRONJ research, including the rat, mouse, rice rat, rabbit, dog, sheep, and pig. Animal research has contributed immensely to advancing the MRONJ field, particularly, but not limited to, in developing models and investigating risk factors that were first observed in humans. MRONJ models have been developed using clinically relevant doses of systemic risk factors, like N-BPs, anti-RANKL antibodies, or AgIs. Specific local oral risk factors first noted in humans, including tooth extraction and inflammatory dental disease (e.g., periodontitis, periapical infection, etc.), were then added. Research in rodents, particularly the rat, and, to some extent, the mouse, across multiple laboratories, has contributed to establishing multiple relevant and complementary preclinical models. Models in larger species produced accurate clinical and histopathologic outcomes suggesting a potential role for confirming specific crucial findings from rodent research. We view the current state of animal models for MRONJ as good. The rodent models are now reliable enough to produce large numbers of MRONJ cases that could be applied in experiments testing treatment modalities. The course of MRONJ, including stage 0 MRONJ, is characterized well enough that basic studies of the molecular or enzyme-level findings in different MRONJ stages are possible. This review provides a current overview of the existing models of MRONJ, their more significant features and findings, and important instances of their application in preclinical research.

Thermally-modulated cell separation columns using a thermoresponsive block copolymer brush as a packing material for the purification of mesenchymal stem cells

Cell therapy using mesenchymal stem cells (MSCs) is used as effective regenerative treatment. Cell therapy requires effective cell separation without cell modification and cellular activity reduction. In this study, we developed a temperature-modulated mesenchymal stem cell separation column. A temperature-responsive cationic block copolymer, poly(N,N-dimethylaminopropylacrylamide)-b-poly(N-isopropylacrylamide)(PDMAPAAm-b-PNIPAAm) brush with various cationic copolymer compositions, was grafted onto silica beads via two-step atom transfer radical polymerization. Using the packed beads, the elution behavior of the MSCs was observed. At 37 °C, the MSCs were adsorbed onto the column via both hydrophobic and electrostatic interactions with the PNIPAAm and PDMAPAAm segments of the copolymer brush, respectively. By reducing the temperature to 4 °C, the adsorbed MSCs were eluted from the column by reducing the hydrophobic and electrostatic interactions attributed to the hydration and extension of the PNIPAAm segment of the block copolymer brush. From the temperature-modulated adsorption and elution behavior of MSCs, a suitable DMAPAAm composition of the block copolymer brush was determined. Using the column, a mixture of MSC and BM-CD34⁺ cells was separated by simply changing the column temperature. The column was used to purify the MSCs, with purities of 78.2%, via a temperature change from 37 °C to 4 °C. Additionally, the cellular activity of the MSCs was retained throughout the column separation step. Overall, the obtained results show that the developed column is useful for MSC separation without cell modification and cellular activity reduction.

Novel therapies using cell sheets engineered from allogeneic mesenchymal stem/stromal cells

Mesenchymal stem/stromal cells (MSCs) have long been recognized to help regenerate tissues, by exploiting their intrinsic potentials for differentiation and secretion of therapeutic paracrine factors together with feasibility for cell banking. These unique MSC properties are attractive to provide effective new cell-based therapies for unmet medical needs. Currently, the infusion of suspended MSCs is accepted as a promising therapy to treat systemic inflammatory diseases. However, low cell engraftment/retention in target organs and off-target entrapment using conventional cell infusion must be improved to provide reliable localized disease treatments. Cell sheet technology offers an alternative: three-dimensional (3D) tissue-like structures can be harvested from culture using mild temperature reduction, and transplanted directly onto target tissue sites without suturing, yielding stable cell engraftment and prolonged cell retention in situ without off-target losses. Engineered MSC sheets directly address two major cell therapy strategies based on their therapeutic benefits: (1) tissue replacements based on mult-ilineage differentiation capacities, focusing on cartilage regeneration in this review, and (2) enhancement of tissue recovery via paracrine signaling, employing their various secreted cytokines to promote neovascularization. MSCs also have production benefits as a promising allogeneic cell source by exploiting their reliable proliferative capacity to facilitate expansion and sustainable cell banking for off-the-shelf therapies. This article reviews the advantages of both MSCs as allogeneic cell sources in contrast with autologous cell sources, and allogeneic MSC sheets engineered on thermo-responsive cell dishes as determined in basic studies and clinical achievements, indicating promise to provide robust new cell therapies to future patients.

Therapeutic effect of fluvastatin on medication-related osteonecrosis of the jaw

BACKGROUND

Refractory jaw osteonecrosis that occurs in osteoporotic or cancer patients treated with bisphosphonates is called medication-related osteonecrosis of the jaw but its underlying mechanism is unclear. Statins, therapeutic agents for dyslipidemia, lower blood low-density lipoprotein cholesterol. Fluvastatin promotes the healing of tooth extraction sockets and reduces the risk of developing medication-related osteonecrosis of the jaw-like lesions. We used a rat model to investigate whether injecting fluvastatin at extraction sites promoted the healing of medication-related osteonecrosis of the jaw-like lesions.

METHODS

Upper first molars of rats administered zoledronate and dexamethasone for 2 weeks were extracted. Two weeks after tooth extraction, rats with medication-related osteonecrosis of the jaw-like lesions (bone exposure) were included in this study. A single injection of fluvastatin was administered in the vicinity of the medication-related osteonecrosis of the jaw-like onset site in rats.

RESULTS

The distance between the edges of the epithelia, the length of the necrotic bone exposed toward the oral cavity, the area of the necrotic bone, and the necrotic bone ratio were significantly smaller in the fluvastatin-administered group compared with the saline group. A single application of fluvastatin near the site of medication-related osteonecrosis of the jaw onset showed a tendency to close the epithelium, reduce necrotic bone, and form new bone, even when symptoms had already developed.

CONCLUSION

This study suggests that a single topical administration of fluvastatin may be a novel treatment for medication-related osteonecrosis of the jaw.

Effect of Human Umbilical Cord Matrix-Derived Mesenchymal Stem Cells on Bisphosphonate-Related Osteonecrosis of the Jaw

BACKGROUND

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a severe sequela caused by bisphosphonates (BPs), which are widely used to treat osteoporosis or other malignancies. However, the mechanism underlying BRONJ remains unclear. Recently, human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) have been studied for treatment of diverse diseases and injuries. This study aimed to investigate the therapeutic effects of hUC-MSCs in BRONJ.

METHODS

The therapeutic effects of hUC-MSCs were examined in rat bone marrow (rBM)-derived cells using cell viability, colony-forming, and real-time PCR assays and FACS for analyzing essential proinflammatory and bone regeneration markers in vitro. To demonstrate the in vivo therapeutic and adverse effects of transfused hUC-MSCs, micro-CT, H&E staining, IHC (Angiogenesis marker gene expression) staining, and parathyroid hormone (PTH)/calcium assay were conducted in a BRONJ-induced animal model.

RESULTS

BP-induced cytotoxicity and inflammation in rBM-derived cells decreased, after co-culture with hUC-MSCs. The expression levels of bone regeneration markers (RUNX2, OSX, and BMP-2) significantly increased in BP-treated rBM-derived cells, after co-culture with hUC-MSCs. The BP-induced abnormal shift in RANKL/OPG expression ratio in rBM-derived cells was normalized by hUC-MSCs. Consistent with these in vitro results, transfused hUC-MSCs markedly decreased BRONJ and significantly healed injured mucosa in the BRONJ-induced animal model. The animals exhibited serious destruction of the kidney structure and increases in serum PTH and calcium levels, which were significantly normalized by hUC-MSC transfusion.

CONCLUSION

hUC-MSCs exerted therapeutic effects on BRONJ in vitro and in vivo through their anti-cytotoxicity, anti-inflammatory activity and ability to recover bone regeneration.

Periosteal Tissue Engineering: Current Developments and Perspectives

Periosteum, a highly vascularized bilayer connective tissue membrane plays an indispensable role in the repair and regeneration of bone defects. It is involved in blood supply and delivery of progenitor cells and bioactive molecules in the defect area. However, sources of natural periosteum are limited, therefore, there is a need to develop tissue-engineered periosteum (TEP) mimicking the composition, structure, and function of natural periosteum. This review explores TEP construction strategies from the following perspectives: i) different materials for constructing TEP scaffolds; ii) mechanical properties and surface topography in TEP; iii) cell-based strategies for TEP construction; and iv) TEP combined with growth factors. In addition, current challenges and future perspectives for development of TEP are discussed.

Preventive effect of tetrahedral framework nucleic acids on bisphosphonate-related osteonecrosis of the jaw

Zoledronic acid (ZA) is a bisphosphonate (BP) drug that has been widely used in clinical treatments as a potent bone resorption inhibitor. In recent years, an increasing number of cases of bisphosphonate-associated osteonecrosis of the jaw (BRONJ) have been reported. This is a severe maxillofacial complication characterized clinically by bone exposure, necrosis, pain, and halitosis. Its pathogenesis is still not clear, and there is no effective clinical treatment known. Therefore, prevention of BRONJ is especially important. To provide a new research direction for the treatment of BRONJ, this study used a new tetrahedral framework nucleic acid (TFNA), which can antagonize the inhibitory effect of ZA on the differentiation and maturation of osteoclasts (OCs). In vivo and in vitro experiments showed that TFNAs at a specific concentration exhibited no cytotoxicity and could reverse the inhibition of ZA on OC differentiation and maturation, effectively inhibiting the formation of BRONJ.

Adipose-Derived Stem Cells Promote Bone Coupling in Bisphosphonate-Related Osteonecrosis of the Jaw by TGF-β1

This study aimed to investigate molecularly targeted therapy to revive bone remodeling and prevent BRONJ by local adipose-derived stem cells (ADSCs) transplantation. Clinical samples of BRONJ and healthy jawbones were used to examine the bone coupling-related cells and TGF-β1 expression. Bone coupling-related cells and TGF-β1 expression were also assessed in BRONJ-like animal model to confirm the results in clinical samples. ADSCs were locally administered in vivo and the therapeutic effects were evaluated by gross observation, radiological imaging, and histological examination. Furthermore, ADSCs-conditioned medium (ADSCs-CM) and neutralizing antibody were applied to assess the effects of ADSCs-derived TGF-β1 on restoring bone coupling in vivo. Osteoclast formation and resorption assays were performed to evaluate the effects of ADSCs-derived TGF-β1 on ZA-treated pre-osteoclasts. Cell migration was performed to assess the effects of ADSCs-derived TGF-β1 on patients’ bone marrow stem cells (BMSCs). The number of osteoclasts, Runx2-positive bone-lining cells (BLCs) and TGF-β1 expression were decreased in BRONJ and animal model jaw bone samples. These reductions were significantly rescued and necrotic jawbone healing was effectively promoted by local ADSCs administration in BRONJ-like animal models. Mechanistically, ADSCs-CM mainly contributed to promoting bone coupling, while TGF-β1 neutralizing antibody in the conditioned medium inhibited these effects. Besides, osteoclastogenesis and patients’ BMSCs migration were also rescued by ADSCs-derived TGF-β1. Furthermore, bone resorption-released bone matrix TGF-β1, together with ADSCs-derived TGF-β1, synergistically contributed to rescuing BMSCs migration. Collectively, ADSCs promoted bone healing of BRONJ by TGF-β1-activated osteoclastogenesis and BMSCs migration capacities.

Small Extracellular Vesicles Derived from Adipose Tissue Prevent Bisphosphonate-Related Osteonecrosis of the Jaw by Promoting Angiogenesis

Purpose

There is no definitive treatment for bisphosphonate-related osteonecrosis of the jaw (BRONJ). Small extracellular vesicles derived from adipose tissue (sEV-AT) have been proved efficient at promoting tissue regeneration. The aim of this study was to evaluate the effects of sEV-AT administration on BRONJ-like lesions in rats.

Methods

Zoledronate (Zol) and dexamethasone (Dex) were subcutaneously administered to create a BRONJ rat model. Rats were randomly divided into three groups: 1) Control; 2) Zol+Dex; 3) sEV-AT. The maxillary left first molars were extracted two weeks after the first administration. In the sEV-AT group, sEV-AT were given intravenously every three days right after tooth extraction. We preformed occlusal view images, microcomputed tomography (µCT) and histological analysis to measure the regeneration of osseous and soft tissue in extraction sockets. Human umbilical vein endothelial cells (HUVECs) were isolated and cultured with endothelial cell medium (ECM). HUVECs were then divided into three groups: 1) Control: ECM; 2) Zol: ECM+Zol; 3) sEV-AT: ECM+Zol+sEV-AT. We evaluated the proliferation, tube formation and migration of HUVECs in each group.

Results

Rats treated with Zol+Dex showed BRONJ-like lesions including open wounds, necrotic bones, empty osteocyte lacunae and reduced osteoclasts. sEV-AT administration reduced BRONJ-like lesions by promoting soft tissue healing. µCT results showed that bone volume in extraction sockets in the sEV-AT group was larger than the Zol+Dex group. Histological analysis showed less necrotic bones and empty osteocyte lacunae in the sEV-AT group compared to the Zol+Dex group. Histological analysis also showed more osteoclasts, collagen fibers and blood vessels in the sEV-AT group compared to the Zol+Dex group. Furthermore, sEV-AT enhanced the proliferation, migration and tube formation of HUVECs which were inhibited by Zol.

Conclusion

Our findings indicate that sEV-AT prevent BRONJ in rats. Angiogenesis promotion contributes to the prevention of BRONJ.

Mesenchymal stem cells in the treatment of osteonecrosis of the jaw

Medication-related osteonecrosis of the jaw (MRONJ) has recently associated to the increase in antiresorptive and anti-angiogenic drugs prescriptions in the treatment of oncologic and osteoporotic patients. The physiopathogenesis of MRONJ remains unclear and available treatments are unsatisfactory. Newer pharmacological treatments have shown good results, but are not curative and could have major side effects. At the same time as pharmacological treatments, mesenchymal stem cells (MSCs) have emerged as a promising therapeutic modality for tissue regeneration and repair. MSCs are multipotential non-hematopoietic progenitor cells capable to differentiating into multiple lineages of the mesenchyme. Bone marrow MSCs can differentiate into osteogenic cells and display immunological properties and secrete paracrine anti-inflammatory factors in damaged tissues. The immunomodulatory, reparative, and anti-inflammatory properties of bone marrow MSCs have been tested in a variety of animal models of MRONJ and applied in specific clinical settings. The aim of this review is to discuss critically the immunogenicity and immunomodulatory properties of MSCs, both in vitro and in vivo, the possible underlying mechanisms of their effects, and their potential clinical use as modulators of immune responses in MRONJ, and to identify clinical safety and recommendations for future research.

The progress of medication-related osteonecrosis of the jaw with conservative initial treatment: A 12-year retrospective study of 129 patients

This retrospective study aimed to examine the course and prognosis of medication-related osteonecrosis of the jaw (MRONJ) initially treated conservatively and the effects of various factors affecting treatment outcomes. We evaluated 129 patients with MRONJ between January 2008 and December 2018 at a university hospital. The factors examined included sex, age, stage of MRONJ (1-3), type of bone modifying agents (bisphosphonate or denosumab), primary disease (osteoporosis or malignant tumor), medical history (diabetes and rheumatoid arthritis), use of corticosteroids, the trigger of MRONJ (teeth extraction or others), and separation of sequestrum, using logistic regression analysis. Patients with MRONJ were treated conservatively as the initial treatment in accordance with the position paper of the American Association of Oral and Maxillofacial Surgeons. Of the 129 patients, 59 (45.7%) were cured, and the condition of 70 (54.3%) remained unchanged or worsened. The overall cure rates at 12, 36, and 60 months were 25.8%, 50.8%, and 72.4% respectively. The cure rate of stage 1 was lower than that of stages 2 and 3 at 80 months. In multivariate analysis, it was found that 37 (64.9%) of 57 patients with osteoporosis as a primary disease were cured (odds ratio [OR], 7.7; 95% confidence interval [CI], 2.4-24.4). In addition, 40 (69.0%) of 58 patients with separation of sequestrum were cured (OR, 8.9; 95% CI, 3.4-23.5). The cure rate was significantly higher in patients with osteoporosis than in those with cancer when the treatment outcomes of primary disease were compared using the Kaplan-Meier method (p < 0.01). It was also significantly higher in patients who had separation of sequestrum than in those who did not (p < 0.05). Our results suggest that primary disease and separation of sequestrum were associated with favorable outcomes in patients with MRONJ initially treated conservatively. MRONJ had a poor prognosis with conventional treatment carried according to the stage of the disease. This was especially prominent when conservative treatment was employed for mild cases.

The Application of a Bone Marrow Mesenchymal Stem Cell Membrane in the Vascularization of a Decellularized Tracheal Scaffold

Airway stenosis is a common problem in the neonatal intensive care unit (NICU) and pediatric intensive care unit (PICU). A tissue-engineered trachea is a new therapeutic method and a research hotspot. Successful vascularization is the key to the application of a tissue-engineered trachea. However, successful vascularization studies lack a complete description. In this study, it was assumed that rabbit bone marrow mesenchymal stem cells were obtained and induced by ascorbic acid to detect the tissue structure, ultrastructure, and gene expression of the extracellular matrix. A vascular endothelial cell culture medium was added in vitro to induce the vascularization of the stem cell sheet (SCS), and the immunohistochemistry and gene expression of vascular endothelial cell markers were detected. At the same time, vascular growth-related factors were added and detected during SCS construction. After the SCS and decellularized tracheal (DT) were constructed, a tetrandrine allograft was performed to observe its vascularization potential. We established the architecture and identified rabbit bone marrow mesenchymal stem cell membranes by 14 days of ascorbic acid, studied the role of a vascularized membrane in inducing bone marrow mesenchymal stem cells by in vitro ascorbic acid, and assessed the role of combining the stem cell membranes and noncellular tracheal scaffolds in vivo. Fourteen experiments confirmed that cell membranes promote angiogenesis at gene level. The results of 21-day in vitro experiments showed that the composite tissue-engineered trachea had strong angiogenesis. In vivo experiments show that a composite tissue-engineered trachea has strong potential for angiogenesis. It promotes the understanding of diseases of airway stenosis and tissue-engineered tracheal regeneration in newborns and small infants.

PDGF-BB exhibited therapeutic effects on rat model of bisphosphonate-related osteonecrosis of the jaw by enhancing angiogenesis and osteogenesis

The mechanism and effective treatment of bisphosphonate-related osteonecrosis of the jaw (BRONJ) are still uncertain. Our previous study revealed that zoledronate (ZOL) preferentially inhibited osteoclasts formation and platelet-derived growth factor-BB (PDGF-BB) secretion, causing suppression of angiogenesis and osteogenesis in vitro. The present study aimed to elucidate whether PDGF-BB had therapeutic effects on rat model of BRONJ by enhancing angiogenesis and angiogenesis. Firstly, rat model of BRONJ was established by ZOL and dexamethasone administration, followed by teeth extraction. The occurrence of BRONJ was confirmed and detected dead bone formation by maxillae examination, micro-CT scan and HE staining (10/10). Compared to control rats (0/10), both angiogenesis and mature bone formation were suppressed in BRONJ-like rats, evidenced by enzyme-linked immunosorbent assay (ELISA) for VEGF (P < 0.01), immunohistochemistry of CD31 (P < 0.05) and OCN (P < 0.01). Moreover, in the early stage of bone healing, the number of preosteoclasts (P < 0.001) and PDGF-BB secretion (P < 0.05) were significantly decreased in bisphosphonates-treated rats, along with the declined numbers of microvessels (P < 0.05) and osteoblasts (P < 0.05). In vitro study, CCK8 assay, alizarin red S staining and western blot assay showed that mandible-derived bone marrow mesenchymal stem cells (BMMSCs) in BRONJ-like rats presented suppressed functions of proliferation, osteogenesis and angiogenesis. Interestingly, recombinant PDGF-BB was able to rescue the impaired functions of BMMSCs derived from BRONJ-like rats at more than 10 ng/ml. Then fibrin sealant with or without recombinant PDGF-BB were tamped into the socket after debridement in BRONJ rats. After 8 weeks, fibrin sealant containing PDGF-BB showed significant therapeutic effects on BRONJ-like rats (bone healing: 8/10 vs 3/10, P < 0.05) with enhancing microvessels and mature bone formation. Our study suggested that the inhibition of angiogenesis and osteogenesis, the potential mechanisms of BRONJ, might partly result from suppression of PDGF-BB secretion in the early stage of bone healing. PDGF-BB local treatment after debridement might avail the healing of BRONJ by increasing angiogenesis and osteogenesis.

In Vitro Cytological Responses against Laser Photobiomodulation for Periodontal Regeneration

Periodontal disease is a chronic inflammatory disease caused by periodontal bacteria. Recently, periodontal phototherapy, treatment using various types of lasers, has attracted attention. Photobiomodulation, the biological effect of low-power laser irradiation, has been widely studied. Although many types of lasers are applied in periodontal phototherapy, molecular biological effects of laser irradiation on cells in periodontal tissues are unclear. Here, we have summarized the molecular biological effects of diode, Nd:YAG, Er:YAG, Er,Cr:YSGG, and CO₂ lasers irradiation on cells in periodontal tissues. Photobiomodulation by laser irradiation enhanced cell proliferation and calcification in osteoblasts with altering gene expression. Positive effects were observed in fibroblasts on the proliferation, migration, and secretion of chemokines/cytokines. Laser irradiation suppressed gene expression related to inflammation in osteoblasts, fibroblasts, human periodontal ligament cells (hPDLCs), and endothelial cells. Furthermore, recent studies have revealed that laser irradiation affects cell differentiation in hPDLCs and stem cells. Additionally, some studies have also investigated the effects of laser irradiation on endothelial cells, cementoblasts, epithelial cells, osteoclasts, and osteocytes. The appropriate irradiation power was different for each laser apparatus and targeted cells. Thus, through this review, we tried to shed light on basic research that would ultimately lead to clinical application of periodontal phototherapy in the future.

Mesenchymal stromal cells for osteonecrosis

Osteonecrosis (ON) is an acquired debilitating skeletal disorder, which is caused by a multitude of traumatic and non-traumatic etiological factors. Vascular damage, mechanical stress and increased intraosseous pressure have been discussed as contributors to ON. The optimal treatment of ON remains to be determined, since the current gold standard, core decompression, is insufficiently effective. Specific properties of mesenchymal stromal cells (MSCs) provide the rationale for their assessment in advanced stages of ON: Osteoinductive potential has been demonstrated and MSC preparations of suitable quality for use as medicinal products have been developed. Here we review the scant information on the use of allogeneic or autologous MSCs in advanced ON as well as potentially supportive data from pre-clinical studies with autologous bone marrow mononuclear cells (auto BM-MNCs), which have been studied quite extensively and the presumed therapeutic effect of which was attributed to the rare MSCs contained in these cell products. Outcomes in clinical trials with MSCs and auto-BM-MNCs remain preliminary and non-definitive, at best promising, with respect to their pharmacological effect. Clearly, though, the application of any of these cell therapies was technically feasible and safe in that it was associated with low complication rates. The heterogeneity of cell type and source, study protocols, cell manufacturing, cell properties, cell doses and surgical techniques might contribute to inconsistent results.

The effect of melatonin on prevention of bisphosphonate-related osteonecrosis of the jaw: an animal study in rats

Objectives

Melatonin induces human stem cells, converts pre-osteoblasts to mature osteoblasts, and reduces the duration of this transition. However, melatonin itself prevents activation of osteoclasts. Here, we evaluate the role of melatonin in prevention of bisphosphonate-related osteonecrosis of the jaw.

Materials and Methods

In this experimental-interventional study, 30 rats were evaluated in 3 groups. The first and second groups received saline and zoledronic acid, respectively, for 4 weeks and the third group received 4 weeks of zoledronic acid and 3 weeks of melatonin simultaneously. First-right-maxillary-molar extraction was performed for all animals, which were sacrificed after 4 weeks of recovery. The extraction sockets were examined histologically for the presence of osteonecrosis, number of osteoclasts and fibroblasts, severity of inflammation, and vascularization. Data were analyzed by chi-square, one-way ANOVA, Tukey, Kruskal–Wallis and Fisher’s exact statistical tests (α=0.05).

Results

Osteonecrosis was observed in 20%, 90%, and 70% of the first, second and third groups, respectively (P=0.008). The lowest number of osteoclasts and fibroblasts was seen in the third group.

Conclusion

Melatonin may effectively prevent some undesirable side effects of bisphosphonates. However, further studies are required to confirm the results of this study.

Mesenchymal Stem Cell Therapy for Oral Inflammatory Diseases: Research Progress and Future Perspectives

Mesenchymal stem cell (MSC) therapy for clinical diseases associated with inflammation and tissue damage has become a progressive treatment strategy. MSCs have unique biological functions, such as homing, immune regulation, and differentiation capabilities, which provide the prerequisites for the treatment of clinical diseases. Oral diseases are often associated with abnormal immune regulation and epithelial tissue damage. In this review, we summarize previous studies that use MSC therapy to treat various oral inflammatory diseases, including oral ulceration, allergic diseases, chemo/radiotherapy-induced oral mucositis, periodontitis, osteonecrosis of the jaw, Sjögren's syndrome (SS), among other similar diseases. We highlight MSC treatment as a promising approach in the management of oral inflammatory diseases, and discuss the obstacles that remain and must be overcome for MSC treatment to thrive in the future.

Amniotic Stem Cells Cultured on Thermoresponsive Polymers Allow Obtaining a Full Cell Sheet

Amniotic stem cells promote adhesion and migration of epithelial cells. Obtaining a full sheet containing amniotic stem cells seems to be the best solution for the treatment of burn wounds. The main advantage of this method is obtaining a full sheet of cells by lowering the temperature below the transition temperature, which does not affect extracellular matrix. The purpose of this work was to produce a skin substitute-a full sheet consisting of amniotic mesenchymal stem cells-and compare with well-known fibroblast sheet. Amniotic membrane cells revealed better tendency to full sheet detachment than fibroblasts. Confluence after 24 hours was always higher on polymer-coated dishes than on normal polypropylene dishes. Also viability was higher than on the control culture dish, while the number of apoptotic cells was always highest on polypropylene (control). Ile-Lys-Val-ala-Val (IKVAV) 0.28 addition to poly (poly [ethylene glycol] ethyl methacrylate) (PTEGMA) caused best cell confluence and highest percentage of cells in mitosis phase of cell cycle, but also worst cell detachment was observed in both cell types on PTEGMA IKVAV 0.28. Viability of cells transferred in cell sheet form onto a new culture dish was higher than when detached as suspension enzymatically. Additionally, percentage of apoptotic cells transferred in cell sheet form onto a new culture dish was always lower than when detached as suspension enzymatically. Culturing of PTEGMA, PTEGMA IKVAV 0.28 and PTEGMA IKVAV 0.14 have a stimulating effect on number of cells in mitosis in amniotic cell culture even after cell sheet transfer onto a new dish, whereas such effect with fibroblast was not observed.

Endothelial progenitors increase vascularization and improve fibroblasts function that prevent medication-related osteonecrosis of the jaw

OBJECTIVES

In a previous rat model, MRONJ occurrence was 50%. Our aim was to investigate the potential of endothelial progenitor cells (EPCs) to improve fibroblasts function and prevent MRONJ.

METHODS

Human gingival fibroblasts were cultured with EPC-conditioned media (EPC-CM); endothelial growth media (EGM-2) or DMEM followed by incubation with 10 µM zoledronic (ZOL) and dexamethasone (DEX). Cell proliferation and migration were assessed by XTT and scratch wound healing assays. In vivo, ten Lewis rats were treated weekly with ZOL and DEX for 11 weeks. After a week, EPCs or EGM-2 were injected to the gingiva around the molars. At 3 weeks, bilateral molars were extracted. After 8 weeks, wound healing was assessed, and serum VEGF and blood vessels were quantified.

RESULTS

ZOL/DEX significantly reduced fibroblasts proliferation and wound healing. Treatment with EPC-CM before ZOL/DEX improved cell proliferation, and scratch healing (p = .007, p = .023). In vivo, local EPC injection before tooth extraction increased serum VEGF (p = .01) and soft tissue vascularization (p = .05). Normal healing was similar (80%) in EPCs and EGM-2 groups.

CONCLUSION

EPC rescued fibroblasts from the cytotoxic effect of ZOL/DEX and elevated serum VEGF and vessel density that might reduce MRONJ occurrence to 20% compared to 50% in a similar model.

Preventive effect of fluvastatin on the development of medication-related osteonecrosis of the jaw

Medication-related osteonecrosis of the jaw (MRONJ) occurs in patients undergoing oral surgery while medicated with bisphosphonate, denosumab or anti-angiogenic agents. We employed a MRONJ-like rat model to investigate whether injecting fluvastatin at extraction sites prevents MRONJ-like lesion. A MRONJ-like model was created by treating rats with zoledronate and dexamethasone, extracting teeth, and immediately injecting fluvastatin at the extraction site. The experimental group comprised three subgroups treated with low (0.1 mg/kg; FS-L), medium (1.0 mg/kg; FS-M) and high concentrations (10 mg/kg; FS-H) of fluvastatin. Necrotic bone exposure was significantly lower in the FS-M (p = 0.028) and FS-H (p = 0.041) groups than in the MRONJ group. The distance between the edges of the epithelial surfaces was significantly shorter in the FS-M (p = 0.042) and FS-H (p = 0.041) groups. The area of necrotic bone and the necrotic bone ratio were significantly smaller in the FS-H group (p = 0.041 and p = 0.042 respectively). Bone volume fraction calculated on μ-CT images was significantly larger in the FS-H group than in the MRONJ group (p = 0.021). Our findings suggest that a single local injection of fluvastatin following tooth extraction can potentially reduce the chance of developing MRONJ-like lesion in rats.

Allogeneic adipose-derived mesenchymal stem cell sheet that produces neurological improvement with angiogenesis and neurogenesis in a rat stroke model

OBJECTIVE

Stem cell therapy is a promising strategy for the treatment of severe cerebral ischemia. However, targeting sufficient grafted cells to the affected area remains challenging. Choosing an adequate transplantation method for the CNS appears crucial for this therapy to become a clinical reality. The authors used a scaffold-free cell sheet as a translational intervention. This method involves the use of cell sheet layers and allows the transplantation of a large number of cells, locally and noninvasively. The authors evaluated the effectiveness of allogeneic adipose tissue-derived mesenchymal stem cell sheets in a rat model of stroke.

METHODS

The animals, subjected to middle cerebral artery occlusion, were randomly divided in two groups: one in which a cell sheet was transplanted and the other in which a vehicle was used (n = 10/group). Over a period of 14 days after transplantation, the animals' behavior was evaluated, after which brain tissue samples were removed and fixed, and the extent of angiogenesis and infarct areas was evaluated histologically.

RESULTS

Compared to the vehicle group, in the cell sheet group functional angiogenesis and neurogenesis were significantly increased, which resulted in behavioral improvement. Transplanted cells were identified within newly formed perivascular walls as pericytes, a proportion of which were functional. Newly formed blood vessels were found within the cell sheet that had anastomosed to the cerebral blood vessels in the host.

CONCLUSIONS

The transplantation approach described here is expected to provide not only a paracrine effect but also a direct cell effect resulting in cell replacement that protects the damaged neurovascular unit. The behavioral improvement seen with this transplantation approach provides the basis for further research on cell sheet-based regenerative treatment as a translational treatment for patients with stroke.

Thermoresponsive polymers and their biomedical application in tissue engineering - a review

Thermoresponsive polymers hold great potential in the biomedical field, since they enable the fabrication of cell sheets, in situ drug delivery and 3D-printing under physiological conditions. In this review we provide an overview of several thermoresponsive polymers and their application, with focus on poly(N-isopropylacrylamide)-surfaces for cell sheet engineering. Basic knowledge of important processes like protein adsorption on surfaces and cell adhesion is provided. For different thermoresponsive polymers, namely PNIPAm, Pluronics, elastin-like polypeptides (ELP) and poly(N-vinylcaprolactam) (PNVCL), synthesis and basic chemical and physical properties have been described and the mechanism of their thermoresponsive behavior highlighted. Fabrication methods of thermoresponsive surfaces have been discussed, focusing on PNIPAm, and describing several methods in detail. The latter part of this review is dedicated to the application of the thermoresponsive polymers and with regard to cell sheet engineering, the process of temperature-dependent cell sheet detachment is explained. We provide insight into several applications of PNIPAm surfaces in cell sheet engineering. For Pluronics, ELP and PNVCL we show their application in the field of drug delivery and tissue engineering. We conclude, that research of thermoresponsive polymers has made big progress in recent years, especially for PNIPAm since the 1990s. However, manifold research possibilities, e.g. in surface fabrication and 3D-printing and further translational applications are conceivable in near future.

Endothelial Progenitor Cells inhibit jaw osteonecrosis in a rat model: A major adverse effect of bisphosphonate therapy

Medication-related osteonecrosis of the jaw (MRONJ) is a serious adverse effect of antiresorptive and antiangiogenic therapies. MRONJ is identified by chronic wounds in the oral mucosa associated with exposed necrotic bone. We hypothesized that zoledronic acid (ZOL) impairs keratinocyte and fibroblast function and reduces soft tissue vascularization; therefore, treating MRONJ with proangiogenic cells may benefit MRONJ patients. The effect of ZOL and dexamethasone (DEX) on gingival fibroblasts and keratinocytes was investigated. In-vitro, ZOL inhibited fibroblast and keratinocyte proliferation, delaying scratch healing. In-vivo, exposed bone was detected at tooth extraction sites, mainly in ZOL(+)/DEX(+) rats; and was associated with significantly decreased soft tissue vascularization, serum-VEGF, and tissue-VEGF. Local injection of early and late endothelial progenitor cells (EPCs) healed 13 of 14 MRONJ lesions compared with 2/7 lesions in the mesenchymal stem cells, and 2/6, in culture-medium group. The EPCs reduced necrotic bone area, increased serum and tissue VEGF levels. EPCs engraftment was minimal, suggesting their paracrine role in MRONJ healing. The EPC-conditioned medium improved scratch healing of keratinocytes and fibroblasts via VEGF pathway and elevated mRNA of VEGFA and collagen1A1. In conclusion, a novel MRONJ treatment with EPCs, increased vascularization and improved epithelial and fibroblast functions as well as cured the lesion.

Characteristic differences of cell sheets composed of mesenchymal stem cells with different tissue origins

INTRODUCTION

Stem cell therapy with mesenchymal stem cells (MSCs) has been widely used in many clinical trials, and therapy with MSC sheets shows promise for patients. However, there are few reports characterizing MSC sheets. In the present study, the properties of MSC sheets derived from bone marrow, adipose tissue, and umbilical cord were evaluated.

METHODS

Cell sheets were fabricated with MSCs from different tissue origins in temperature-responsive cell culture dishes with and without pre-coating of fetal bovine serum (FBS). MSC adhesion behavior in the culture dish was observed. Secretion of cytokines related to cell proliferation and immune regulation from MSC sheets was investigated by ELISA. The adhesion properties of the MSC sheets were investigated by time-lapse microscopy.

RESULTS

Different cell adhesion and proliferation rates in temperature-responsive cell culture dishes were observed among the three types of MSCs. FBS pre-coating of the dishes enhanced cell attachment and proliferation in all cell types. Harvested cell sheets showed high attachment capacity to tissue culture polystyrene dish surfaces.

CONCLUSIONS

MSC sheets can be fabricated from MSCs from different tissue origins using temperature-responsive cell culture dishes. The fabricated MSC sheets could be useful in cell transplantation therapies by choosing appropriate types of MSCs that secrete therapeutic cytokines for the targeted diseases.

Rat Mesenchymal Stromal Cell Sheets Suppress Renal Fibrosis via Microvascular Protection

Renal fibrosis is one of the largest global health care problems, and microvascular (MV) injury is important in the development of progressive fibrosis. Although conventional cell therapy suppresses kidney injury via the role of vasoprotective cytokines, the effects are limited due to low retention of administered cells. We recently described that transplantation of hepatocyte growth factor (HGF)‐transgenic mesothelial cell sheets showed a remarkable cell survival and strong therapeutic effects in a rat renal fibrosis model. Due to the translational hurdles of transgenic cells, we here applied this technique for allogeneic transplantation using rat bone marrow mesenchymal stromal cells (MSCs). MSC sheets were transplanted onto the kidney surface of a rat renal ischemia–reperfusion‐injury model and the effects were compared between those in untreated rats and those receiving intravenous (IV) administration of the cells. We found that donor‐cell survival was superior in the cell sheet group relative to the IV group, and that the cell sheets secreted HGF and vascular endothelial growth factor (VEGF) up to day 14. Transplantation of cell sheets increased the expression of activated HGF/VEGF receptors in the kidney. There was no evidence of migration of transplanted cells into the kidney parenchyma. Additionally, the cell sheets significantly suppressed renal dysfunction, MV injury, and fibrosis as compared with that observed in the untreated and IV groups. Furthermore, we demonstrated that the MSC sheet protected MV density in the whole kidney according to three‐dimensional microcomputed tomography. In conclusion, MSC sheets strongly prevented renal fibrosis via MV protection, suggesting that this strategy represents a potential novel therapy for various kidney diseases. stem cells translational medicine2019;8:1330&1341

Rat bone marrow mesenchymal stromal cell sheets were transplanted onto the kidney surface. In ischemia–reperfusion‐injury, microvascular density loss caused by endothelial injury resulted in progressive renal fibrosis. Mesenchymal stromal cell sheets remained long‐term on the kidney surface and protected the microvasculature, which resulted in suppression of progressive fibrosis. The therapeutic effects were partially explained by the role of hepatocyte growth factor/vascular endothelial growth factor secreted from mesenchymal stromal cell sheets.

Bisphosphonate-related osteonecrosis. Application of adipose-derived stem cells in an experimental murine model

Background

Bisphosphonate-related osteonecrosis of the jaw is a pathological condition without effective established treatment and preventive strategies. The aim of this study was to analyse the effect of adipose-derived stem cells (ASC) in an experimental murine model of osteonecrosis.

Material and Methods

38 Wistar rats were injected intraperitoneally with zoledronic acid. After treatment, upper jaw molars were extracted. The animals were randomly assigned to one of two groups. In the control group, saline solution was applied over the alveolar sockets after the tooth extractions. In the treatment group, ASCs were applied instead of saline solution. The control and treatment groups were subdivided based on the time of euthanasia. A clinical and histological analysis was performed.

Results

The presence of osteonecrosis in alveolar bone was observed in a similar distribution in both groups. In the ASC-treated group, new bone formation was greater than in controls.

Conclusions

In this study, application of ASCs showed greater new bone formation in an osteonecrosis-like murine model. Previous inhibited post-extraction bone remodelling could be reactivated, and these findings appeared to be secondary to implantation of ASCs.

Key words:Osteonecrosis; bisphosphonates, Mesenchymal stem cells (MSC), adipose-derived stem cells (ASCs), zoledronic acid.

Synthetic Calcium Phosphate Ceramics as a Potential Treatment for Bisphosphonate-Related Osteonecrosis of the Jaw

(1) Background: Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is one of the most often seen side effects in patients treated with nitrogen-containing bisphosphonates (BPs), a post-surgical non-healing wound condition. Since calcium phosphate (CP) compounds are able to adsorb zoledronate (ZOL) when used as a drug delivery vehicle, we aimed to verify if these ceramics might have a potential protective effect for soft tissues surrounding surgical osseous wounds. (2) Methods: The chemical reaction between ZOL and CP compounds was evaluated through ultraviolet-visible spectroscopy and elemental analysis. A primary culture of human gingival fibroblasts (HGF) was established as a model to evaluate the cytotoxicity of the association of ZOL (5–500 μM) and of ZOL/biphasic calcium phosphates (BCP). Metabolic activity, cell viability, types of cell death, the cell cycle through, and the migration ability of human gingival fibroblasts were evaluated. (3) Results: ZOL was adsorbed by biphasic calcium phosphate compounds in an aqueous solution. The HGF were sensitive to ZOL toxicity; nevertheless, ZOL/BCP showed a significant protective effect regarding metabolic activity, cell viability, and cell migration. (4) Conclusions: BCP interaction with ZOL reduces or abolishes its toxicity in HGF. This finding represents a potential solution for BRONJ in the case of patients undergoing therapy with ZOL.

Allogeneic multipotent mesenchymal stromal cell sheet transplantation promotes healthy healing of wounds caused by zoledronate and dexamethasone in canine mandibular bones

INTRODUCTION

Many cases of bisphosphonate-related osteonecrosis of the jaw (BRONJ), which is an intractable disease, have been reported. Although a general intravenous injection of multipotent mesenchymal stromal cells (MSCs) may be effective for treating BRONJ, it has some severe problems. Therefore, our aim was to develop a treatment of locally administered MSCs. In this study, we investigated the effect of MSC sheet transplantation in the mandibular bone healing in beagle dogs, which were administered zoledronate and dexamethasone.

METHODS

MSCs isolated from subcutaneous fat were seeded onto temperature-responsive culture dishes to produce MSC sheets. Zoledronate and dexamethasone were administered to beagle dogs. Then, the parts of mandibular cortical bones were removed, and MSC sheets were transplanted to cover those bone defects (MSC sheet transplant side) or not (Control side). The specimens were evaluated in micro CT, histology, and immunohistochemistry.

RESULTS

Four weeks after surgery, redness and swellings were observed in the mucosal wounds of the control sides of 2 of 3 dogs. In contrast, the mucosal wounds of the MSC sheet transplant sides of all dogs completely healed. Histological images showed some free sequestrums and many bacterial colonies, and Immunohistological analysis showed some cathepsin K-positive multinuclear cells detached from jaw bone surfaces in the control sides.

CONCLUSIONS

MSC sheet transplantation promotes healthy healing of wounds caused by zoledronate and dexamethasone in canine mandibular bones. And the injured canine mandibular bones administered zoledronate and dexamethasone showed BRONJ-like findings.

Mesenchymal Stromal Cell Homing: Mechanisms and Strategies for Improvement

Mesenchymal stromal cells (MSCs) have been widely investigated for their therapeutic potential in regenerative medicine, owing to their ability to home damaged tissue and serve as a reservoir of growth factors and regenerative molecules. As such, clinical applications of MSCs are reliant on these cells successfully migrating to the desired tissue following their administration. Unfortunately, MSC homing is inefficient, with only a small percentage of cells reaching the target tissue following systemic administration. This attrition represents a major bottleneck in realizing the full therapeutic potential of MSC-based therapies. Accordingly, a variety of strategies have been employed in the hope of improving this process. Here, we review the molecular mechanisms underlying MSC homing, based on a multistep model involving (1) initial tethering by selectins, (2) activation by cytokines, (3) arrest by integrins, (4) diapedesis or transmigration using matrix remodelers, and (5) extravascular migration toward chemokine gradients. We then review the various strategies that have been investigated for improving MSC homing, including genetic modification, cell surface engineering, in vitro priming of MSCs, and in particular, ultrasound techniques, which have recently gained significant interest. Contextualizing these strategies within the multistep homing model emphasizes that our ability to optimize this process hinges on our understanding of its molecular mechanisms. Moving forward, it is only with a combined effort of basic biology and translational work that the potential of MSC-based therapies can be realized.

Effects of zoledronic acid and dexamethasone on early phases of socket healing after tooth extraction in rats: A preliminary macroscopic and microscopic quantitative study

Background

The exact pathogenesis of medication-related osteonecrosis of the jaw (MRONJ) is still unknown. The aim of this paper was to investigate the effects of zoledronic acid and dexamethasone on the early phases of socket healing in rats subjected to tooth extractions.

Material and Methods

Thirty male Sprague-Dawley rats were divided into 2 groups: pharmacologically treated group (T, n=20) and non-pharmacologically treated group (C, n=10). T group rats received 0.1 mg/Kg of zoledronic acid (ZOL) and 1 mg/Kg of dexamethasone (DEX) three times a week for 10 consecutive weeks. C group rats were infused with vehicle. After 9 weeks from the first infusion, first maxillary molars were extracted in each of the rats. Quantitative macroscopic and microscopic analysis was performed to evaluate socket healing 8 days after extraction.

Results

Pharmacologically treated rats showed significant inhibition of bone remodeling. Connective tissue/alveolar bone ratio, osteoclast number and woven bone deposition were significantly reduced in group T compared to group C. Conversely, the proportion of necrotic bone was higher in group T compared to group C (0.8% and 0.3%, respectively. P=0.031). ZOL plus DEX do not cause gross effects on socket healing at a macroscopic level.

Conclusions

Our findings confirmed that exposure to ZOL plus DEX impairs alveolar wound repair. Inhibition of osteoclastic resorption of socket walls after tooth extraction and the inability to dispose of the necrotic bone may be considered the initial steps of MRONJ onset.

Key words:Medication-related osteonecrosis of the jaw, zoledronic acid, dexamethasone, tooth extraction, rat.

Microfiber-Reinforced Composite Hydrogels Loaded with Rat Adipose-Derived Stem Cells and BMP-2 for the Treatment of Medication-Related Osteonecrosis of the Jaw in a Rat Model

Severe adverse reactions of bisphosphonates and anti-resorptive or anti-angiogenic medications, termed medication-related osteonecrosis of the jaw (MRONJ), have been reported. MRONJ are difficult to completely cure and could cause great pain to patients. Recent studies have shown that mesenchymal stem cell (MSC) therapies are effective for treating MRONJ, but the method of intravenous injection is unstable and increases the risk of producing tumors. In the present study, low-acyl gellan gum (LAGG) hydrogels were modified with hemicellulose polysaccharide microfibers (PMs) to improve the performance of supporting three-dimensional (3D) cell growth. LAGG-PM composite hydrogels were found to be nontoxic to rat adipose-derived stem cells (rADSCs) in vitro. The hydrogels also promoted the secretion of angiogenic factors, induced osteoclastogenesis by conditioned medium, and supported osteogenic marker expression after the addition of human bone morphogenetic protein-2 (BMP-2). Due to its injectability, the LAGG-PM composite hydrogel incorporated with rADSCs and BMP-2 could be applied into the MRONJ lesion site, which promoted mucosal recovery, bone tissue reconstruction, and osteoclastogenesis. This study confirms the potential applications of LAGG-PM composite hydrogels as 3D cell culture platforms and delivery vehicles for the treatment of MRONJ in a rat model.