A Novel Bone Marrow Stimulation Technique Augmented by Administration of Ultrapurified Alginate Gel Enhances Osteochondral Repair in a Rabbit Model

Alginate Use in Orthopedics and Peripheral Nerve Repair: A Systematic Review

The use of alginate, a derivative of seaweed, has been proposed for multiple orthopedic indications. We aimed to review the current use of alginate in orthopedics and to focus on the future applications of alginate for peripheral nerve repair. A comprehensive literature search was performed to identify biomechanical, laboratory, animal, and human studies where alginate has been utilized for orthopedic or nerve repair indications. A systematic review of orthopedic indications was conducted for safety and efficacy, and a specific focus was placed on alginate for use in peripheral nerve repair and reconstruction. Thirty-two studies were identified. Alginate has a strong history and safety profile for usage in orthopedic surgery. Its primary usage has been for the repair of articular cartilage, although it has also been used for disc regeneration of the lumbar spine and for cushioning joints in osteoarthritis. The primary indication in peripheral nerve repair is to create an environment that encourages Schwann cell migration and repair in nerve injuries while blocking fibrotic scar tissue formation by inhibiting the activity of fibroblasts. Alginate hydrogel may serve as a potential conduit for nerve regeneration in nerve injuries with small to medium-sized gaps.

Depletion of b-series ganglioside prevents limb length discrepancy after growth plate injury

INTRODUCTION

Growth plate damage in long bones often results in progressive skeletal growth imbalance and deformity, leading to significant physical problems. Gangliosides, key glycosphingolipids in cartilage, are notably abundant in articular cartilage and regulate chondrocyte homeostasis. This suggests their significant roles in regulating growth plate cartilage repair.

METHODS

Chondrocytes from 3 to 5 day-old C57BL/6 mice underwent glycoblotting and mass spectrometry. Based on the results of the glycoblotting analysis, we employed GD3 synthase knockout mice (GD3-/-), which lack b-series gangliosides. In 3-week-old mice, physeal injuries were induced in the left tibiae, with right tibiae sham operated. Tibiae were analyzed at 5 weeks postoperatively for length and micro-CT for growth plate height and bone volume at injury sites. Tibial shortening ratio and bone mineral density were measured by micro-CT.

RESULTS

Glycoblotting analysis indicated that b-series gangliosides were the most prevalent in physeal chondrocytes among ganglioside series. At 3 weeks, GD3-/- exhibited reduced tibial shortening (14.7 ± 0.2 mm) compared to WT (15.0 ± 0.1 mm, P = 0.03). By 5 weeks, the tibial lengths in GD3-/- (16.0 ± 0.4 mm) closely aligned with sham-operated lengths (P = 0.70). Micro-CT showed delayed physeal bridge formation in GD3-/-, with bone volume measuring 168.9 ± 5.8 HU at 3 weeks (WT: 180.2 ± 3.2 HU, P = 0.09), but normalizing by 5 weeks.

CONCLUSION

This study highlights that GD3 synthase knockout mice inhibit physeal bridge formation after growth plate injury, proposing a new non-invasive approach for treating skeletal growth disorders.

Single-step ultra-purified alginate gel implantation in patients with knee chondral defects

Aims

Implantation of ultra-purified alginate (UPAL) gel is safe and effective in animal osteochondral defect models. This study aimed to examine the applicability of UPAL gel implantation to acellular therapy in humans with cartilage injury.

Methods

A total of 12 patients (12 knees) with symptomatic, post-traumatic, full-thickness cartilage lesions (1.0 to 4.0 cm2) were included in this study. UPAL gel was implanted into chondral defects after performing bone marrow stimulation technique, and assessed for up to three years postoperatively. The primary outcomes were the feasibility and safety of the procedure. The secondary outcomes were self-assessed clinical scores, arthroscopic scores, tissue biopsies, and MRI-based estimations.

Results

No obvious adverse events related to UPAL gel implantation were observed. Self-assessed clinical scores, including pain, symptoms, activities of daily living, sports activity, and quality of life, were improved significantly at three years after surgery. Defect filling was confirmed using second-look arthroscopy at 72 weeks. Significantly improved MRI scores were observed from 12 to 144 weeks postoperatively. Histological examination of biopsy specimens obtained at 72 weeks after implantation revealed an extracellular matrix rich in glycosaminoglycan and type II collagen in the reparative tissue. Histological assessment yielded a mean overall International Cartilage Regeneration & Joint Preservation Society II score of 69.1 points (SD 10.4; 50 to 80).

Conclusion

This study provides evidence supporting the safety of acellular UPAL gel implantation in facilitating cartilage repair. Despite being a single-arm study, it demonstrated the efficacy of UPAL gel implantation, suggesting it is an easy-to-use, one-step method of cartilage tissue repair circumventing the need to harvest donor cells.

Alginate hydrogels: A potential tissue engineering intervention for intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is a major cause of low back pain and disability, affecting millions of people worldwide. Current treatments for IVD degeneration are limited to invasive surgery or pain management. Recently, there has been increasing interest in the use of biomaterials, such as alginate hydrogels, for the treatment of IVD degeneration. Alginate hydrogels are an example of such a biomaterial that is biocompatible and can be tailored to mimic the native extracellular matrix of the IVD. Derived from alginate, a naturally derived polysaccharide from brown seaweed that can be transformed into a gelatinous solution, alginate hydrogels are emerging in the field of tissue engineering. They can be used to deliver therapeutic agents, such as growth factors or cells, to the site of injury, providing a localized and sustained release that may enhance treatment outcomes. This paper provides an overview on the use of alginate hydrogels for the treatment of IVD degeneration. We discuss the properties of alginate hydrogels and their potential applications for IVD regeneration, including the mechanism against IVD degeneration. We also highlight the research outcomes to date along with the challenges and limitations of using alginate hydrogels for IVD regeneration, including their mechanical properties, biocompatibility, and surgical compatibility. Overall, this review paper aims to provide a comprehensive overview of the current research on alginate hydrogels for IVD degeneration and to identify future directions for research in this area.

Injection of Ultra-Purified Stem Cells with Sodium Alginate Reduces Discogenic Pain in a Rat Model

Intervertebral disc (IVD) degeneration is a major cause of low back pain. However, treatments directly approaching the etiology of IVD degeneration and discogenic pain are not yet established. We previously demonstrated that intradiscal implantation of cell-free bioresorbable ultra-purified alginate (UPAL) gel promotes tissue repair and reduces discogenic pain, and a combination of ultra-purified, Good Manufacturing Practice (GMP)-compliant, human bone marrow mesenchymal stem cells (rapidly expanding clones; RECs), and the UPAL gel increasingly enhanced IVD regeneration in animal models. This study investigated the therapeutic efficacy of injecting a mixture of REC and UPAL non-gelling solution for discogenic pain and IVD regeneration in a rat caudal nucleus pulposus punch model. REC and UPAL mixture and UPAL alone suppressed not only the expression of TNF-α, IL-6, and TrkA (p < 0.01, respectively), but also IVD degeneration and nociceptive behavior compared to punching alone (p < 0.01, respectively). Furthermore, REC and UPAL mixture suppressed these expression levels and nociceptive behavior compared to UPAL alone (p < 0.01, respectively). These results suggest that this minimally invasive treatment strategy with a single injection may be applied to treat discogenic pain and as a regenerative therapy.

Mesenchymal Stem Cell Extracellular Vesicles as Adjuvant to Bone Marrow Stimulation in Chondral Defect Repair in a Minipig Model

OBJECTIVE

This study evaluated the effects of mesenchymal stem cell-extracellular vesicles (MSC-EVs) on chondrocyte proliferation in vitro and on cartilage repair in vivo following bone marrow stimulation (BMS) of focal chondral defects of the knee.

METHODS

Six adult Göttingen minipigs received 2 chondral defects in each knee. The pigs were randomized to treatment with either BMS combined with MSC-EVs or BMS combined with phosphate-buffered saline (PBS). Intraarticular injections MSC-EVs or PBS were performed immediately after closure of the surgical incisions, and at 2 and 4 weeks postoperatively. Repair was evaluated after 6 months with gross examination, histology, histomorphometry, immunohistochemistry, and micro-computed tomography (µCT) analysis of the trabecular bone beneath the defect.

RESULTS

Defects treated with MSC-EVs had more bone in the cartilage defect area than the PBS-treated defects (7.9% vs. 1.5%, P = 0.02). Less than 1% of the repair tissue in both groups was hyaline cartilage. International Cartilage and Joint Preservation Society II histological scoring showed that defects treated with MSC-EVs scored lower on "matrix staining" (20.8 vs. 50.0, P = 0.03), "cell morphology" (35.4 vs. 53.8, P = 0.04), and "overall assessment" (30.8 vs. 52.9, P = 0.03). Consistently, defects treated with MSC-EVs had lower collagen II and higher collagen I areal deposition. Defects treated with MSC-EVs had subchondral bone with significantly higher tissue mineral densities than PBS-treated defects (860 mg HA/cm3 vs. 838 mg HA/cm3, P = 0.02).

CONCLUSION

Intraarticular injections of MSC-EVs in conjunction with BMS led to osseous ingrowth that impaired optimal cartilage repair, while enhancing subchondral bone healing.

Acellular Cartilage Repair Technique Based on Ultrapurified Alginate Gel Implantation for Advanced Capitellar Osteochondritis Dissecans

Background:

One of the most important limitations of osteochondral autograft transplant is the adverse effect on donor sites in the knee. Ultrapurified alginate (UPAL) gel is a novel biomaterial that enhances hyaline-like cartilage repair for articular defects. To avoid the need for knee cartilage autografting when treating osteochondritis dissecans (OCD) of the capitellum, we developed a surgical procedure involving a bone marrow stimulation technique (BMST) augmented by implantation of UPAL gel.

Hypothesis:

BMST augmented by UPAL gel implantation improves the cartilage repair capacity and provides satisfactory clinical outcomes in OCD of the capitellum.

Study Design:

Case series; Level of evidence, 4.

Methods:

A total of 5 athletes with advanced capitellar OCD in the dominant elbow underwent BMST augmented by implantation of UPAL gel. The osteochondral defects were filled with UPAL gel after BMST. At a mean follow-up of 97 weeks, all patients were evaluated clinically and radiographically.

Results:

At final follow-up, all 5 patients had returned to competitive-level sports, and 4 patients were free from elbow pain. The mean Timmerman-Andrews score significantly improved from 100 to 194 points. Radiographically, all patients exhibited graft incorporation and a normal contour of the subchondral cortex. Magnetic resonance imaging showed that the preoperative heterogeneity of the lesion had disappeared, and the signal intensity had returned to normal. Arthroscopic examinations consistently exhibited improvement in the International Cartilage Regeneration and Joint Preservation Society (ICRS) grade of lesions from 3 or 4 to 1 or 2 in 4 patients at 85 weeks postoperatively. Histologic analysis of biopsy specimens revealed an average total ICRS Visual Assessment Scale II histologic score of 1060.

Conclusion:

The acellular cartilage repair technique using UPAL gel for advanced capitellar OCD provided satisfactory clinical and radiographic results. The present results suggest that this novel technique is a useful, minimally invasive approach for treating cartilaginous lesions in athletes.

Ultra-purified alginate gel implantation decreases inflammatory cytokine levels, prevents intervertebral disc degeneration, and reduces acute pain after discectomy

Lumbar intervertebral disc (IVD) herniation causes severe low back pain (LBP), which results in substantial financial and emotional strains. Despite the effectiveness of discectomy, there is no existing treatment for post-operative LBP induced by progressive IVD degeneration. Two key factors of LBP are intradiscal inflammation, indicated by tumour necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), and sensory nerve ingrowth into the inner layer of the annulus fibrosus, triggered by nerve growth factor/high-affinity tyrosine kinase A (TrkA) signalling. In an animal models of discectomy, the bioresorbable ultra-purified alginate (UPAL) gel with an extremely low-toxicity has been effective in acellular tissue repair. We aimed to investigate whether UPAL gel can alleviate LBP using a rat nucleus pulposus (NP) punch model and a rabbit NP aspirate model. In both models, we assessed TNF-α and IL-6 production and TrkA expression within the IVD by immunohistochemistry. Further, histological analysis and behavioural nociception assay were conducted in the rat model. UPAL gel implantation suppressed TNF-α and IL-6 production, downregulated TrkA expression, inhibited IVD degeneration, and reduced nociceptive behaviour. Our results suggest the potential of UPAL gel implantation as an innovative treatment for IVD herniation by reducing LBP and preventing IVD degeneration after discectomy.

Transplantation of fetal liver tissue coated by ultra-purified alginate gel over liver improves hepatic function in the cirrhosis rat model

In this study, we used a new coating agent, that is, ultra-purified alginate gel (UPAL), for fetal liver tissue transplantation. This study aims to compare the effect of UPAL with the effect of other coating agents on improving the effect of fetal liver tissue transplantation in a liver cirrhosis rat model. Prior to the transplantation of wild-type ED14 fetal liver tissues, various coating agents were separately applied on the liver surface of rats with cirrhosis. Then, we compared the engraftment area, engraftment rate and liver function level of these rats. As a result, coating the liver surface of a cirrhosis rat with UPAL obtained the best effect in terms of engraftment area and engraftment rate of the transplanted liver tissue and in the recovery of liver function compared with control group. Therefore, UPAL coating may serve as a novel strategy for liver organoid transplantation.

Therapeutic effects and adaptive limits of an acellular technique by ultrapurified alginate (UPAL) gel implantation in canine osteochondral defect models

Background

The aim of this study was to clarify the objective therapeutic effects of an acellular technique by ultrapurified alginate (UPAL) gel implantation in canine osteochondral defect models.

Methods

Two osteochondral defects (diameters: 3.0 and 5.0 mm) were created on each patellar groove in both knees of 10 dogs. Defects were divided into four groups (n = 10 each): Group 1, untreated 3.0-mm defect; Group 2, 3.0-mm defect with UPAL gel; Group 3, untreated 5.0-mm defect; and Group 4, 5.0-mm defect with UPAL gel. All surgical procedures were performed by individuals unfamiliar with the technique at an independent institution. Articular surfaces were evaluated grossly and histologically at 27 weeks after operation.

Results

UPAL gel-treated osteochondral defects showed significantly improved gross appearance in Group 4 and histological appearance in Groups 2 and 4. Reparative tissues in the 3.0-mm defect with UPAL gel were replaced by hyaline-like cartilage tissue. The 5.0-mm defects with UPAL gel were mostly covered with fibrocartilaginous tissue, whereas UPAL gel-untreated defects mostly remained uncovered by any tissue.

Conclusions

Although an acellular technique using UPAL gel implantation significantly enhanced osteochondral repair in canines, reparative tissues of the large defect with alginate gel comprised of fibrocartilaginous tissue. This surgical technique is effective, especially for small cartilage injuries. Further improvements are required before clinical application in cases of severe osteochondral defects in humans.

CCL21/CCR7 axis regulating juvenile cartilage repair can enhance cartilage healing in adults

Juvenile tissue healing is capable of extensive scarless healing that is distinct from the scar-forming process of the adult healing response. Although many growth factors can be found in the juvenile healing process, the molecular mechanisms of juvenile tissue healing are poorly understood. Here we show that juvenile mice deficient in the chemokine receptor CCR7 exhibit diminished large-scale healing potential, whereas CCR7-depleted adult mice undergo normal scar-forming healing similar to wild type mice. In addition, the CCR7 ligand CCL21 was transiently expressed around damaged cartilage in juvenile mice, whereas it is rarely expressed in adults. Notably, exogenous CCL21 administration to adults decreased scar-forming healing and enhanced hyaline-cartilage repair in rabbit osteochondral defects. Our data indicate that the CCL21/CCR7 axis may play a role in the molecular control mechanism of juvenile cartilage repair, raising the possibility that agents modulating the production of CCL21 in vivo can improve the quality of cartilage repair in adults. Such a strategy may prevent post-traumatic arthritis by mimicking the self-repair in juvenile individuals.

Effects of Ultra-Purified Alginate Gel Implantation on Meniscal Defects in Rabbits

BACKGROUND

Many tissue-engineered methods for meniscal repair have been studied, but their utility remains unclear.

HYPOTHESIS

Implantation of low-endotoxin, ultra-purified alginate (UPAL) gel without cells could induce fibrocartilage regeneration on meniscal defects in rabbits.

STUDY DESIGN

Controlled laboratory study.

METHODS

Forty-two mature Japanese White rabbits were divided into 2 groups of 21 animals each. In each animal, a cylindrical defect measuring 2 mm in diameter was created with a biopsy punch on the anterior horn of the medial meniscus. In the control group, no treatment was applied on the left medial meniscal defect. In the UPAL gel group, the right medial meniscal defect was injected with the UPAL gel and gelated by a CaCl₂ solution. Samples were evaluated at 3, 6, and 12 weeks postoperatively. For biomechanical evaluation, 6 additional samples from intact animals were used for comparison.

RESULTS

The macroscopic score was significantly greater in the UPAL gel group than in the control group at 3 weeks (mean ± SE: 5.6 ± 0.82 vs 3.4 ± 0.83, P = .010), 6 weeks (5.9 ± 0.72 vs 2.5 ± 0.75, P = .026), and 12 weeks (5.2 ± 1.21 vs 1.0 ± 0.63, P = .020). The histological score was significantly greater in the UPAL group than in the control group at 3 weeks (2.1 ± 0.31 vs 1.2 ± 0.25, P = .029) and 12 weeks (2.2 ± 0.55 vs 0.3 ± 0.21, P = .016). The mean stiffness of the reparative tissue in the UPAL gel group was significantly greater than that in the control group at 6 weeks (24.325 ± 3.920 N/mm vs 8.723 ± 1.190 N/mm, P = .006) and at 12 weeks (27.804 ± 6.169 N/mm vs not applicable [because of rupture]).

CONCLUSION

The UPAL gel enhanced the spontaneous repair of fibrocartilage tissues in a cylindrical meniscal defect in rabbits.

CLINICAL RELEVANCE

These results imply that the acellular UPAL gel may improve the repair of traumatic meniscal injuries.

Chondrogenic differentiation of mouse induced pluripotent stem cells using the three-dimensional culture with ultra-purified alginate gel

As articular cartilages have rarely healed by themselves because of their characteristics of avascularity and low cell density, surgical intervention is ideal for patients with cartilaginous injuries. Because of structural characteristics of the cartilage tissue, a three-dimensional culture of stem cells in biomaterials is a favorable system on cartilage tissue engineering. Induced pluripotent stem cells (iPSCs) are a new cell source in cartilage tissue engineering for its characteristics of self-renewal capability and pluripotency. However, the optimal cultivation condition for chondrogenesis of iPSCs is still unknown. Here we show that a novel chondrogenic differentiation method of iPSCs using the combination of three-dimensional cultivation in ultra-purified alginate gel (UPAL gel) and multi-step differentiation via mesenchymal stem cell-like cells (iPS-MSCs) could efficiently and specifically differentiate iPSCs into chondrocytes. The iPS-MSCs in UPAL gel culture sequentially enhanced the expression of chondrogenic marker without the upregulation of that of osteogenic and adipogenic marker and histologically showed homogeneous chondrogenic extracellular matrix formation. Our results suggest that the pluripotency of iPSCs can be controlled when iPSCs are differentiated into iPS-MSCs before embedding in UPAL gel. These results lead to the establishment of an efficient three-dimensional system to engineer artificial cartilage tissue from iPSCs for cartilage regeneration. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1086-1093, 2019.

Osteochondral Autograft Transplantation Technique Augmented by an Ultrapurified Alginate Gel Enhances Osteochondral Repair in a Rabbit Model

BACKGROUND

One of the most important limitations of osteochondral autograft transplantation (OAT) is the adverse effect on donor sites in the knee. To decrease the number and/or size of osteochondral defects, we devised a method with biomaterial implantation after OAT.

HYPOTHESIS

OAT augmented by ultrapurified alginate (UPAL) gel enhances cartilage repair capacity.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seventy-five osteochondral defects in rabbits were divided into 3 groups: osteochondral defects with OAT alone, defects with OAT augmented by UPAL gel (combined group), and defects without intervention as controls. Macroscopic and histological evaluations of the reparative tissues were performed at 4 and 12 weeks postoperatively. Histological evaluation of graft cartilage degradation was also performed. To evaluate the effects of UPAL gel on graft healing, repaired bone volumes and osseointegration of the graft were evaluated. Collagen orientation and the mechanical properties of the reparative tissue and graft cartilage were also evaluated qualitatively.

RESULTS

The macroscopic and histological evaluations of the combined group were significantly superior to the other groups at 12 weeks postoperatively. Regarding degenerative change of the graft, the histological scores of the combined group were significantly higher than those of the OAT-alone group. The values of repaired subchondral bone volumes and osseointegration of the graft were almost identical in both groups. Collagen orientation and the mechanical properties of the reparative tissue and graft cartilage were significantly better in the combined group than in the other groups.

CONCLUSION

Administration of UPAL gel in OAT enhanced cartilage repair and protected graft cartilage without inhibiting subchondral bone repair and graft survival.

CLINICAL RELEVANCE

OAT augmented by UPAL gel decreases the number and/or size of osteochondral grafts, minimizing the risk of donor site morbidity. This combination technique has the potential to improve clinical outcomes and expand the surgical indications for OAT.

An acellular bioresorbable ultra-purified alginate gel promotes intervertebral disc repair: A preclinical proof-of-concept study

Background

The current surgical procedure of choice for lumbar intervertebral disc (IVD) herniation is discectomy. However, defects within IVD produced upon discectomy may impair tissue healing and predispose patients to subsequent IVD degeneration. This study aimed to investigate whether the use of an acellular bioresorbable ultra-purified alginate (UPAL) gel implantation system is safe and effective as a reparative therapeutic strategy after lumbar discectomy.

Methods

Human IVD cells were cultured in a three-dimensional system in UPAL gel. In addition, lumbar spines of sheep were used for mechanical analysis. Finally, the gel was implanted into IVD after discectomy in rabbits and sheep in vivo.

Findings

The UPAL gel was biocompatible with human IVD cells and promoted extracellular matrix production after discectomy, demonstrating sufficient biomechanical characteristics without material protrusion.

Interpretation

The present results indicate the safety and efficacy of UPAL gels in a large animal model and suggest that these gels represent a novel therapeutic strategy after discectomy in cases of lumbar IVD herniation.

Fund

Grant-in-Aid for the Ministry of Education, Culture, Sports, Science, and Technology of Japan, Japan Agency for Medical Research and Development, and the Mochida Pharmaceutical Co., Ltd.

Bone Marrow Stimulation Technique Augmented by an Ultrapurified Alginate Gel Enhances Cartilage Repair in a Canine Model

BACKGROUND

The optimal treatment for a medium- or large-sized cartilage lesion is still controversial. Since an ultrapurified alginate (UPAL) gel enhances cartilage repair in animal models, this material is expected to improve the efficacy of the current treatment strategies for cartilage lesions.

HYPOTHESIS

The bone marrow stimulation technique (BMST) augmented by UPAL gel can induce hyaline-like cartilage repair.

STUDY DESIGN

Controlled laboratory study.

METHODS

Two cylindrical osteochondral defects were created in the patellar groove of 27 beagle dogs. A total of 108 defects were divided into 3 groups: defects without intervention (control group), defects with the BMST (microfracture group), and defects with the BMST augmented by implantation of UPAL gel (combined group). At 27 weeks postoperatively, macroscopic and histological evaluations, micro-computed tomography assessment, and mechanical testing were performed for each reparative tissue.

RESULTS

The defects in the combined group were almost fully covered with translucent reparative tissues, which consisted of hyaline-like cartilage with well-organized collagen structures. The macroscopic score was significantly better in the combined group than in the control group ( P < .05). The histological scores in the combined group were significantly better than those in the control group ( P < .01) and microfracture group ( P < .05). Although the repaired subchondral bone volumes were not influenced by UPAL gel augmentation, the mechanical properties of the combined group were significantly better than those of the microfracture group ( P < .05).

CONCLUSION

The BMST augmented by UPAL gel elicited hyaline-like cartilage repair that had characteristics of rich glycosaminoglycan and matrix immunostained by type II collagen antibody in a canine osteochondral defect model. The present results suggest that the current technique has the potential to be one of the autologous matrix-induced chondrogenesis techniques of the future and to expand the operative indications for the BMST without loss of its technical simplicity.

CLINICAL RELEVANCE

The data support the clinical reality of 1-step minimally invasive cartilage-reparative medicine with UPAL gel without harvesting donor cells.

In Vivo Articular Cartilage Regeneration Using Human Dental Pulp Stem Cells Cultured in an Alginate Scaffold: A Preliminary Study

Osteoarthritis is an inflammatory disease in which all joint-related elements, articular cartilage in particular, are affected. The poor regeneration capacity of this tissue together with the lack of pharmacological treatment has led to the development of regenerative medicine methodologies including microfracture and autologous chondrocyte implantation (ACI). The effectiveness of ACI has been shown in vitro and in vivo, but the use of other cell types, including bone marrow and adipose-derived mesenchymal stem cells, is necessary because of the poor proliferation rate of isolated articular chondrocytes. In this investigation, we assessed the chondrogenic ability of human dental pulp stem cells (hDPSCs) to regenerate cartilage in vitro and in vivo. hDPSCs and primary isolated rabbit chondrocytes were cultured in chondrogenic culture medium and found to express collagen II and aggrecan. Both cell types were cultured in 3% alginate hydrogels and implanted in a rabbit model of cartilage damage. Three months after surgery, significant cartilage regeneration was observed, particularly in the animals implanted with hDPSCs. Although the results presented here are preliminary, they suggest that hDPSCs may be useful for regeneration of articular cartilage.

Numerical Simulation of Mass Transfer and Three-Dimensional Fabrication of Tissue-Engineered Cartilages Based on Chitosan/Gelatin Hybrid Hydrogel Scaffold in a Rotating Bioreactor

Cartilage tissue engineering is believed to provide effective cartilage repair post-injuries or diseases. Biomedical materials play a key role in achieving successful culture and fabrication of cartilage. The physical properties of a chitosan/gelatin hybrid hydrogel scaffold make it an ideal cartilage biomimetic material. In this study, a chitosan/gelatin hybrid hydrogel was chosen to fabricate a tissue-engineered cartilage in vitro by inoculating human adipose-derived stem cells (ADSCs) at both dynamic and traditional static culture conditions. A bioreactor that provides a dynamic culture condition has received greater applications in tissue engineering due to its optimal mass transfer efficiency and its ability to simulate an equivalent physical environment compared to human body. In this study, prior to cell-scaffold fabrication experiment, mathematical simulations were confirmed with a mass transfer of glucose and TGF-β2 both in rotating wall vessel bioreactor (RWVB) and static culture conditions in early stage of culture via computational fluid dynamic (CFD) method. To further investigate the feasibility of the mass transfer efficiency of the bioreactor, this RWVB was adopted to fabricate three-dimensional cell-hydrogel cartilage constructs in a dynamic environment. The results showed that the mass transfer efficiency of RWVB was faster in achieving a final equilibrium compared to culture in static culture conditions. ADSCs culturing in RWVB expanded three times more compared to that in static condition over 10 days. Induced cell cultivation in a dynamic RWVB showed extensive expression of extracellular matrix, while the cell distribution was found much more uniformly distributing with full infiltration of extracellular matrix inside the porous scaffold. The increased mass transfer efficiency of glucose and TGF-β2 from RWVB promoted cellular proliferation and chondrogenic differentiation of ADSCs inside chitosan/gelatin hybrid hydrogel scaffolds. The improved mass transfer also accelerated a dynamic fabrication of cell-hydrogel constructs, providing an alternative method in tissue engineering cartilage.