Advancements in scaffold for treating ligament injuries; in vitro evaluation

Tendon/ligament (T/L) injuries are a worldwide health problem that affects millions of people annually. Due to the characteristics of tendons, the natural rehabilitation of their injuries is a very complex and lengthy process. Surgical treatment of a T/L injury frequently necessitates using autologous or allogeneic grafts or synthetic materials. Nonetheless, these alternatives have limitations in terms of mechanical properties and histocompatibility, and they do not permit the restoration of the original biological function of the tissue, which can negatively impact the patient's quality of life. It is crucial to find biological materials that possess the necessary properties for the successful surgical treatment of tissues and organs. In recent years, the in vitro regeneration of tissues and organs from stem cells has emerged as a promising approach for preparing autologous tissue and organs, and cell culture scaffolds play a critical role in this process. However, the biological traits and serviceability of different materials used for cell culture scaffolds vary significantly, which can impact the properties of the cultured tissues. Therefore, this review aims to analyze the differences in the biological properties and suitability of various materials based on scaffold characteristics such as cell compatibility, degradability, textile technologies, fiber arrangement, pore size, and porosity. This comprehensive analysis provides valuable insights to aid in the selection of appropriate scaffolds for in vitro tissue and organ culture.

Additively manufactured polyethylene terephthalate scaffolds for scapholunate interosseous ligament reconstruction

The regeneration of the ruptured scapholunate interosseous ligament (SLIL) represents a clinical challenge. Here, we propose the use of a Bone-Ligament-Bone (BLB) 3D-printed polyethylene terephthalate (PET) scaffold for achieving mechanical stabilisation of the scaphoid and lunate following SLIL rupture. The BLB scaffold featured two bone compartments bridged by aligned fibres (ligament compartment) mimicking the architecture of the native tissue. The scaffold presented tensile stiffness in the range of 260 ± 38 N/mm and ultimate load of 113 ± 13 N, which would support physiological loading. A finite element analysis (FEA), using inverse finite element analysis (iFEA) for material property identification, showed an adequate fit between simulation and experimental data. The scaffold was then biofunctionalized using two different methods: injected with a Gelatin Methacryloyl solution containing human mesenchymal stem cell spheroids (hMSC) or seeded with tendon-derived stem cells (TDSC) and placed in a bioreactor to undergo cyclic deformation. The first approach demonstrated high cell viability, as cells migrated out of the spheroid and colonised the interstitial space of the scaffold. These cells adopted an elongated morphology suggesting the internal architecture of the scaffold exerted topographical guidance. The second method demonstrated the high resilience of the scaffold to cyclic deformation and the secretion of a fibroblastic related protein was enhanced by the mechanical stimulation. This process promoted the expression of relevant proteins, such as Tenomodulin (TNMD), indicating mechanical stimulation may enhance cell differentiation and be useful prior to surgical implantation. In conclusion, the PET scaffold presented several promising characteristics for the immediate mechanical stabilisation of disassociated scaphoid and lunate and, in the longer-term, the regeneration of the ruptured SLIL.

Insulin-Functionalized Bioactive Fiber Matrices with Bone Marrow-Derived Stem Cells in Rat Achilles Tendon Regeneration

Approximately half of annual musculoskeletal injuries in the US involve tendon tears. The naturally hypocellular and hypovascular tendon environment makes tendons injury-prone and heal slowly. Tendon tissue engineering strategies often use biomimetic scaffolds combined with bioactive factors and/or cells to enhance healing. FDA-approved growth factors to promote tendon healing are lacking, which highlights the need for safe and effective bioactive factors. Our previous work evaluated insulin as a bioactive factor and identified an optimal dose to promote in vitro mesenchymal stem cell survival, division, and tenogenesis. The present work evaluates the ability of insulin-functionalized electrospun nanofiber matrices with or without mesenchymal stem cells to enhance tendon repair in a rat Achilles injury model. Electrospun nanofiber matrices were functionalized with insulin, cultured with or without mesenchymal stem cells, and sutured to transected Achilles tendons in rats. We analyzed rat tendons 4 and 8 weeks after surgery for the tendon morphology, collagen production, and mechanical properties. Bioactive insulin-functionalized fiber matrices with mesenchymal stem cells resulted in significantly increased collagen I and III at 4 and 8 weeks postsurgery. Additionally, these matrices supported highly aligned collagen fibrils in the regenerated tendon tissue at 8 weeks. However, treatment- and control-regenerated tissues had similar tensile properties at 8 weeks, which were less than that of the native Achilles tendon. Our preliminary results establish the benefits of insulin-functionalized fiber matrices in promoting higher levels of collagen synthesis and alignment needed for functional recovery of tendon repair.

The effect of melt electrospun writing fiber orientation onto cellular organization and mechanical properties for application in Anterior Cruciate Ligament tissue engineering

The effect of melt electrospun writing fiber arrangement on cellular behavior has not yet been thoroughly investigated. Cellular orientation is particularly important in the context of ligament tissue engineering for orthopedic applications whereby a high degree of cell alignment is present in the native tissue. The aim of this study was to investigate the response of human mesenchymal stem cells (hMSC) to three different patterned porous polycaprolactone scaffolds (aligned, crimped and random) fabricated by melt electrospinning writing, resulting in 20 μm diameter electrospun fibers. Cell orientation was investigated over 4 weeks in vitro and it was demonstrated that the aligned pattern was capable of orientating the hMSCs towards the main direction of the fibers and this feature was maintained over the entire culture period whereas the orientation was rapidly lost in the crimped pattern. In order to fabricate a functional scaffold for ligament tissue engineering, the scaffolds were rolled in three bundles, subsequently braided and combined with a bone compartment (consisting of a melt electrospun scaffold seeded with osteogenically induced hMSCs) for the development of a Bone-Ligament-Bone (BLB) construct. The mechanical properties of non-cellularized and cellularized BLB constructs were assessed under both quasi-static and cyclic conditions. This revealed that the in vitro maturation significantly softened the BLB constructs and that the mechanical properties were several fold lower than those of native tissue. The cyclic testing demonstrated that the presence of cell sheets resulted in increased resilience and elasticity, even though the global mechanical properties were decreased for the in vitro matured constructs (regardless of the pattern). In conclusion, we demonstrated that melt electrospinning writing fiber organization can induce spontaneous cell alignment and that large cellularized BLB constructs with complex geometry can achieve mechanical resilience under cyclic stretching.

Supporting Cell-Based Tendon Therapy: Effect of PDGF-BB and Ascorbic Acid on Rabbit Achilles Tenocytes in Vitro

Cell-based tendon therapies with tenocytes as a cell source need effective tenocyte in vitro expansion before application for tendinopathies and tendon injuries. Supplementation of tenocyte culture with biomolecules that can boost proliferation and matrix synthesis is one viable option for supporting cell expansion. In this in vitro study, the impacts of ascorbic acid or PDGF-BB supplementation on rabbit Achilles tenocyte culture were studied. Namely, cell proliferation, changes in gene expression of several ECM and tendon markers (collagen I, collagen III, fibronectin, aggrecan, biglycan, decorin, ki67, tenascin-C, tenomodulin, Mohawk, α-SMA, MMP-2, MMP-9, TIMP1, and TIMP2) and ECM deposition (collagen I and fibronectin) were assessed. Ascorbic acid and PDGF-BB enhanced tenocyte proliferation, while ascorbic acid significantly accelerated the deposition of collagen I. Both biomolecules led to different changes in the gene expression profile of the cultured tenocytes, where upregulation of collagen I, Mohawk, decorin, MMP-2, and TIMP-2 was observed with ascorbic acid, while these markers were downregulated by PDGF-BB supplementation. Vice versa, there was an upregulation of fibronectin, biglycan and tenascin-C by PDGF-BB supplementation, while ascorbic acid led to a downregulation of these markers. However, both biomolecules are promising candidates for improving and accelerating the in vitro expansion of tenocytes, which is vital for various tendon tissue engineering approaches or cell-based tendon therapy.

Biologic and mechanical aspects of tendon fibrosis after injury and repair

Tendon injuries of the hand that require surgical repair often heal with excess scarring and adhesions to adjacent tissues. This can compromise the natural gliding mechanics of the flexor tendons in particular, which operate within a fibro-osseous tunnel system similar to a set of pulleys. Even combining the finest suture repair techniques with optimal hand therapy protocols cannot ensure predictable restoration of hand function in these cases. To date, the majority of research regarding tendon injuries has revolved around the mechanical aspects of the surgical repair (i.e. suture techniques) and postoperative rehabilitation. The central principles of treatment gleaned from this literature include using a combination of core and epitendinous sutures during repair and initiating motion early on in hand therapy to improve tensile strength and limit adhesion formation. However, it is likely that the best clinical solution will utilize optimal biological modulation of the healing response in addition to these core strategies and, recently, the research in this area has expanded considerably. While there are no proven additive biological agents that can be used in clinical practice currently, in this review, we analyze the recent literature surrounding cytokine modulation, gene and cell-based therapies, and tissue engineering, which may ultimately lead to improved clinical outcomes following tendon injury in the future.

Spheroid formation and modulation of tenocyte-specific gene expression under simulated microgravity

Background

For tendon tissue engineering, tenocyte-seeded scaffolds are a promising approach. Under conventional 2D culture however, tenocytes show rapid senescene and phenotype loss. We hypothesized that phenotype loss could be counteracted by simulated microgravity conditions.

Methods

Human tenocytes were exposed to microgravity for 9 days on a Random Positioning Machine (RPM). Formation of 3D-structures (spheroids) was observed under light microscopy, gene expression was measured by real-time PCR. Cells under conventional 2D-culture served as control group.

Results

Simulated microgravity reached a value of as low as 0.003g. Spheroid formation was observed after 4 days, and spheroids showed stable existance to the end of the observation period. After 9 days, spheroids showed a significantly higher gene expression of collagen 1 (Col1A1) compared to adherent cells under microgravity (4.4x, p=0.04) and compared to the control group (5.6x, p=0.02). Gene expression of collagen 3 (COL3A1) was significantly increased in spheroids compared to the control group (2.3x, p=0.03). Gene expressions of the extracellular matrix genes Tenascin C und Fibronectin (TNC and FN) were increased in adherent cells under microgravity compared to the 1g-control group, not reaching statistical significance (p=0.1 and p=0.3). For the gene expression of vimentin, no significant alteration was observed both in the adherent cells and in the spheroids compared to the 1g control group. Gene expression of the tenocyte-specific transcription factor scleraxis (SCX) was significantly increased in spheroids compared to the control group (3.7x, p=0.03).

Conclusion

Simulated microgravity could counteract tenocyte senescence in vitro and serve as a promising model for scaffold-free 3D cell culturing and tissue engineering.

Level of evidence

V (laboratory study).

Combining electrospinning and cell sheet technology for the development of a multiscale tissue engineered ligament construct (TELC)

Ligament tissue rupture is a common sport injury. Although current treatment modalities can achieve appropriate reconstruction of the damaged ligament, they present significant drawbacks, mostly related to reduced tissue availability and pain associated with tissue harvesting. Stem cell based tissue regeneration combined with electrospun scaffolds represents a novel treatment method for torn ligaments. In this study, a low fiber density polycaprolactone (PCL) electrospun mesh and sheep mesenchymal stem cells (sMSCs) were used to develop tissue engineered ligament construct (TELC) in vitro. The assembly of the TELC was based on the spontaneous capacity of the cells to organize themselves into a cell sheet once seeded onto the electrospun mesh. The cell sheet matured over 4 weeks and strongly integrated with the low fiber density electrospun mesh which was subsequently processed into a ligament-like bundle and braided with two other bundles to develop the final construct. Live/dead assay revealed that the handling of the construct through the various phases of assembly did not cause significant difference in viability compared to the control. Mechanical evaluation demonstrated that the incorporation of the cell sheet into the braided construct resulted in significantly modifying the mechanical behavior. A stress/displacement J-curve was observed for the TELC that was similar to native ligament, whereas this particular feature was not observed in the non-cellularized specimens. The regenerative potential of the TELC was evaluated ectopically in immunocompromized rats, compared to non cellularized electrospun fiber mesh and this demonstrated that the TELC was well colonized by host cells and that a significant remodelling of the implanted construct was observed. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 399-409, 2018.

Mesenchymal stem cells for tendon healing: what is on the horizon?

Tendon injuries are a noteworthy morbidity but at present there are few effective scientifically proven treatments. In recent decades, a number of new strategies including tissue engineering with mesenchymal stem cells (MSCs) have been proposed to enhance tendon healing. Although MSCs are an interesting and promising approach, many questions regarding their use in tendon repair remain unanswered. This descriptive overview of the literature of the last decade explores the in vivo studies on tendon healing, in small and large animal models, which used MSCs harvested from different tissues, and the state of the art in clinical applications. It was observed that there are still doubts about the optimum amount of MSCs to use and their source and the type of scaffolds to deliver the cells. Thus, further studies are needed to determine the best protocol for MSC use in tendon healing. Copyright © 2016 John Wiley & Sons, Ltd.

IN VITRO AND IN VIVO DEGRADATION OF A TWISTED SILK FIBROIN–POLY(LACTIC-CO-GLYCOLIC ACID) FIBER COMPOSITE ROPE-LIKE SCAFFOLD AND CHANGES IN ITS MECHANICAL PROPERTIES

Natural silk fibroin fiber is slowly degraded, which makes it difficult to be replaced quickly by regenerating tissues of tissue engineering. We used poly(lactic-co-glycolic acid) (PLGA, lactic acid:glycolic acid [Formula: see text] 10:90) fibers to adjust the overall degradation rate of the scaffolds. This study fabricated a three-strand helical composite rope-like scaffold from silk fibroin and PLGA fibers (silk fibroin:PLGA [Formula: see text] 36:64) using a twisting method. In vitro and in vivo degradation experiments were performed over 16 weeks. Results suggest that the in vitro and in vivo degradation tendencies of the scaffold were similar, with mass loss lagging behind mechanical property loss. The speed of degradation in vivo was faster than that in vitro. Mechanical property loss of the scaffold was fast during the first three weeks, when mass loss was slow. Mass loss rate accelerated from weeks 3 to 8. The mass and mechanical properties were relatively stable from 8 to 16 weeks. After 16 weeks of degradation, the scaffold still had considerably strong mechanical properties. The scaffold showed a reasonable and suitable degradation speed with good histocompatibility for ligament tissue engineering.

Rolled knitted scaffolds based on PLA-pluronic copolymers for anterior cruciate ligament reinforcement: A step by step conception

The aim of this study was to prepare a new knitted scaffold from PLA-Pluronic block copolymers for anterior cruciate ligament reconstruction. The impact of sterilization methods (beta-ray and gamma-ray sterilization) on copolymers was first evaluated in order to take into account the possible damages due to the sterilization process. Beta-ray radiation did not significantly change mechanical properties in contrast to gamma-ray sterilization. It was shown that ACL cells proliferate onto these copolymers, demonstrating their cytocompatibility. Thirdly, in order to study the influence of shaping on mechanical properties, several shapes were created with copolymers yarns: braids, ropes and linear or rolled knitted scaffolds. The rolled knitted scaffold presented interesting mechanical characteristics, similar to native anterior cruciate ligament (ACL) with a 67 MPa Young's Modulus and a stress at failure of 22.5 MPa. These findings suggest that this three dimensional rolled knitted scaffold meet the mechanical properties of ligament tissues and could be suitable as a scaffold for ligament reconstruction. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 735-743, 2017.

Principles of tendon reconstruction following complex trauma of the upper limb

Reconstruction of tendons following complex trauma to the upper limb presents unique clinical and research challenges. In this article, the authors review the principles guiding preoperative assessment, surgical reconstruction, and postoperative rehabilitation and management of the upper extremity. Tissue engineering approaches to address tissue shortages for tendon reconstruction are also discussed.

[Use of tissue engineering in the reconstruction of flexor tendon injuries of the hand]

In his literary analysis, the author describes a novel method applied in the reconstruction of flexor tendon injuries of the hand. This procedure is named tissue engineering, and it is examined mainly under experimental circumstances. After definition of the method and descriptions of literary preliminaries the author discusses the healing process of the normal tendon tissue, then development of the scaffold, an important step of tissue engineering is described. After these topics the introduction of the pluripotent mesenchymal stem cells into the scaffold, and proliferation of these cells and development of the sliding systems are presented. The mechanical resisting ability of the formed tendon tissue is also discussed. Finally, the author concludes that as long as results of experimental research cannot be successfully applied into clinical practice, well-tried tendon reconstruction operations and high quality postoperative rehabilitation are needed.

Weft-knitted silk-poly(lactide-co-glycolide) mesh scaffold combined with collagen matrix and seeded with mesenchymal stem cells for rabbit Achilles tendon repair

Natural silk fibroin fiber scaffolds have excellent mechanical properties, but degrade slowly. In this study, we used poly(lactide-co-glycolide) (PLGA, 10:90) fibers to adjust the overall degradation rate of the scaffolds and filled them with collagen to reserve space for cell growth. Silk fibroin-PLGA (36:64) mesh scaffolds were prepared using weft-knitting, filled with type I collagen, and incubated with rabbit autologous bone marrow-derived mesenchymal stem cells (MSCs). These scaffold-cells composites were implanted into rabbit Achilles tendon defects. At 16 weeks after implantation, morphological and histological observations showed formation of tendon-like tissues that expressed type I collagen mRNA and a uniformly dense distribution of collagen fibers. The maximum load of the regenerated Achilles tendon was 58.32% of normal Achilles tendon, which was significantly higher than control group without MSCs. These findings suggest that it is feasible to construct tissue engineered tendon using weft-knitted silk fibroin-PLGA fiber mesh/collagen matrix seeded with MSCs for rabbit Achilles tendon defect repair.

Organic electrode coatings for next-generation neural interfaces

Traditional neuronal interfaces utilize metallic electrodes which in recent years have reached a plateau in terms of the ability to provide safe stimulation at high resolution or rather with high densities of microelectrodes with improved spatial selectivity. To achieve higher resolution it has become clear that reducing the size of electrodes is required to enable higher electrode counts from the implant device. The limitations of interfacing electrodes including low charge injection limits, mechanical mismatch and foreign body response can be addressed through the use of organic electrode coatings which typically provide a softer, more roughened surface to enable both improved charge transfer and lower mechanical mismatch with neural tissue. Coating electrodes with conductive polymers or carbon nanotubes offers a substantial increase in charge transfer area compared to conventional platinum electrodes. These organic conductors provide safe electrical stimulation of tissue while avoiding undesirable chemical reactions and cell damage. However, the mechanical properties of conductive polymers are not ideal, as they are quite brittle. Hydrogel polymers present a versatile coating option for electrodes as they can be chemically modified to provide a soft and conductive scaffold. However, the in vivo chronic inflammatory response of these conductive hydrogels remains unknown. A more recent approach proposes tissue engineering the electrode interface through the use of encapsulated neurons within hydrogel coatings. This approach may provide a method for activating tissue at the cellular scale, however, several technological challenges must be addressed to demonstrate feasibility of this innovative idea. The review focuses on the various organic coatings which have been investigated to improve neural interface electrodes.

History and performance of implant materials applied as peritendinous antiadhesives

Peritendinous fibrotic adhesions after tendon surgery are still a problem up-to-date. Approaches to overcome or at least minimize adhesion formation include implantation of barrier materials, application of lubricants or combinations of materials and functionalized drugs that are controllably released and support the healing tendon to glide and achieve the full range of motion after regeneration. Although a huge amount of different materials have been experimentally tested, the optimal strategy with respect to material and method has not yet been determined. In this review, we present a historical overview of physical barriers as well as liquid agents that have been used in order to prevent peritendinous adhesion formation. The materials are divided according to their first publication into two time frames; before and after 1980. There is no claim to include all materials tested neither will the "best" material be chosen; however, we present several materials that were experimentally tested in different animal trials as well as in clinical trials in contrast to other materials that were only tested once and disappeared from the assortment of anti-adhesives; which as such is a valuable information about its applicability for this purpose.

Tissue engineering in flexor tendon surgery: current state and future advances

Tissue engineering of flexor tendons addresses a challenge often faced by hand surgeons: the restoration of function and improvement of healing with a limited supply of donor tendons. Creating an engineered tendon construct is dependent upon understanding the normal healing mechanisms of the tendon and tendon sheath. The production of a tendon construct includes: creating a three-dimensional scaffold; seeding cells within the scaffold; encouraging cellular growth within the scaffold while maintaining a gliding surface; and finally ensuring mechanical strength. An effective construct incorporates these factors in its design, with the ultimate goal of creating tendon substitutes that are readily available to the reconstructive hand surgeon.

The effect of polystyrene sodium sulfonate grafting on polyethylene terephthalate artificial ligaments on in vitro mineralisation and in vivo bone tissue integration

This study investigates the impact of polystyrene sodium sulfonate (PolyNaSS) grafting onto the osseo-integration of a polyethylene terephthalate artificial ligament (Ligament Advanced Reinforcement System, LARS™) used for Anterior Cruciate Ligament (ACL). The performance of grafted and non-grafted ligaments was assessed in vitro by culturing human osteoblasts under osteogenic induction and this demonstrated that the surface modification was capable of up-regulating the secretion of ALP and induced higher level of mineralisation as measured 6 weeks post-seeding by Micro-Computed Tomography. Grafted and non-grafted LARS™ were subsequently implanted in an ovine model for ACL reconstruction and the ligament-to-bone interface was evaluated by histology and biomechanical testings 3 and 12 months post-implantation. The grafted ligaments exhibited more frequent direct ligament-to-bone contact and bone formation in the core of the ligament at the later time point than the non-grafted specimens, the grafting also significantly reduced the fibrous encapsulation of the ligament 12 months post-implantation. However, this improved osseo-integration was not translated into a significant increase in the biomechanical pull-out loads. These results provide evidences that PolyNaSS grafting improved the osseo-integration of the artificial ligament within the bone tunnels. This might positively influence the outcome of the surgical reconstructions, as higher ligament stability is believed to limit micro-movement and therefore permits earlier and enhanced healing.

Electrospinning and crosslinking of low-molecular-weight poly(trimethylene carbonate-co-(L)-lactide) as an elastomeric scaffold for vascular engineering

The growth of suitable tissue to replace natural blood vessels requires a degradable scaffold material that is processable into porous structures with appropriate mechanical and cell growth properties. This study investigates the fabrication of degradable, crosslinkable prepolymers of l-lactide-co-trimethylene carbonate into porous scaffolds by electrospinning. After crosslinking by γ-radiation, dimensionally stable scaffolds were obtained with up to 56% trimethylene carbonate incorporation. The fibrous mats showed Young's moduli closely matching human arteries (0.4-0.8MPa). Repeated cyclic extension yielded negligible change in mechanical properties, demonstrating the potential for use under dynamic physiological conditions. The scaffolds remained elastic and resilient at 30% strain after 84days of degradation in phosphate buffer, while the modulus and ultimate stress and strain progressively decreased. The electrospun mats are mechanically superior to solid films of the same materials. In vitro, human mesenchymal stem cells adhered to and readily proliferated on the three-dimensional fiber network, demonstrating that these polymers may find use in growing artificial blood vessels in vivo.

Biomimetic poly(lactide) based fibrous scaffolds for ligament tissue engineering

The aim of this study was to fabricate a fibrous scaffold that closely resembled the micro-structural architecture and mechanical properties of collagen fibres found in the anterior cruciate ligament (ACL). To achieve this aim, fibrous scaffolds were made by electrospinning L-lactide based polymers. L-Lactide was chosen primarily due to its demonstrated biocompatibility, biodegradability and high modulus. The electrospun fibres were collected in tension on a rotating wire mandrel. Upon treating these fibres in a heated aqueous environment, they possessed a crimp-like pattern having a wavelength and amplitude similar to that of native ACL collagen. Of the polymer fibre scaffolds studied, those made from poly(L-lactide-co-D,L-lactide) PLDLA exhibited the highest modulus and were also the most resilient to in vitro hydrolytic degradation, undergoing a slight decrease in modulus compared to the other polymeric fibres over a 6 month period. Bovine fibroblasts seeded on the wavy, crimp-like PLDLA fibres attached, proliferated and deposited extracellular matrix (ECM) molecules on the surface of the fibrous scaffold. In addition, the deposited ECM exhibited bundle formation that resembled the fascicles found in native ACL. These findings demonstrate the importance of replicating the geometric microenvironment in developing effective tissue engineering scaffolds.

Exploring the application of stem cells in tendon repair and regeneration

PURPOSE

To conduct a systematic review of the current evidence for the effects of stem cells on tendon healing in preclinical studies and human studies.

METHODS

A systematic search of the PubMed, CINAHL (Cumulative Index to Nursing and Allied Health Literature), Cochrane, and Embase databases was performed for stem cells and tendons with their associated terminology. Data validity was assessed, and data were collected on the outcomes of trials.

RESULTS

A total of 27 preclinical studies and 5 clinical studies met the inclusion criteria. Preclinical studies have shown that stem cells are able to survive and differentiate into tendon cells when placed into a new tendon environment, leading to regeneration and biomechanical benefit to the tendon. Studies have been reported showing that stem cell therapy can be enhanced by molecular signaling adjunct, mechanical stimulation of cells, and the use of augmentation delivery devices. Studies have also shown alternatives to the standard method of bone marrow-derived mesenchymal stem cell therapy. Of the 5 human studies, only 1 was a randomized controlled trial, which showed that skin-derived tendon cells had a greater clinical benefit than autologous plasma. One cohort study showed the benefit of stem cells in rotator cuff tears and another in lateral epicondylitis. Two of the human studies showed how stem cells were successfully extracted from the humerus and, when tagged with insulin, became tendon cells.

CONCLUSIONS

The current evidence shows that stem cells can have a positive effect on tendon healing. This is most likely because stem cells have regeneration potential, producing tissue that is similar to the preinjury state, but the results can be variable. The use of adjuncts such as molecular signaling, mechanical stimulation, and augmentation devices can potentially enhance stem cell therapy. Initial clinical trials are promising, with adjuncts for stem cell therapy in development.

Engaging stem cells for customized tendon regeneration

The need for a consistent therapeutic approach to tendon injury repair is long overdue. Patients with tendon microtears or full ruptures are eligible for a wide range of invasive and non invasive interventions, often subjectively decided by the physician. Surgery produces the best outcomes, and while studies have been conducted to optimize graft constructs and to track outcomes, the data from these studies have been inconclusive on the whole. What has been established is a clear understanding of healthy tendon architecture and the inherent process of healing. With this knowledge, tissue regeneration efforts have achieved immense progress in scaffold design, cell line selection, and, more recently, the appropriate use of cytokines and growth factors. This paper evaluates the plasticity of bone-marrow-derived stem cells and the elasticity of recently developed biomaterials towards tendon regeneration efforts. Mesenchymal stem cells (MSCs), hematopoietic progenitor cells, and poly(1,8-octanediol co-citrate) scaffolds (POC) are discussed in the context of established grafting strategies. With POC scaffolds to cradle the growth of MSCs and hematopoietic progenitor cells, developing a fibroelastic network guided by cytokines and growth factors may contribute towards consistent graft constructs, enhanced functionality, and better patient outcomes.

Elaboration and characterization of nanoliposome made of soya; rapeseed and salmon lecithins: application to cell culture

Health benefits of unsaturated fatty acids have been demonstrated over the last decades. Nanotechnology provided new process to produce particles such as liposomes and nanoliposomes made of pure phospholipids. These techniques are already used in pharmaceutics to augment the bioavailability and the bioefficiency of drugs. The aim of this paper is to characterize and evaluate the potential of nanoliposomes made of three lecithins (soya, rapeseed and salmon) on cell culture in order to use them in the future as drug delivery systems for tissue engineering. We began to measure, with zetasizer, the radius size of liposomes particles which are 125.5, 136.7 and 130.3 nm respectively for rapeseed, soya and salmon lecithin. Simultaneously, solutions observed by TEM demonstrated the particles were made much of liposomes than droplet (emulsion). Finally, we found that the solutions of lecithins were enough stable over 5 days at 37 °C to be used in culture medium. We investigated the effect of soya, rapeseed and salmon lecithin liposome from 2mg/mL to 5.2 μg/mL on metabolic activity and cell proliferation on rat bone marrow stem cells (rBMSC) during 14 days. The results showed that the three lecithins (soya, rapeseed and salmon) improve cell proliferation at different concentration.