Fate of donor bone marrow cells in medial collateral ligament after simulated autologous transplantation

Achilles Tendinopathy Pathogenesis and Management: A Narrative Review

The Achilles tendon is the thickest and strongest tendon of the human body, and it is frequently injured during sports activity. The incidence of Achilles tendon pathologies has increased over recent decades, especially in the last few years, because of increased sports participation among the general population and due to the diffusion of competitive sports at a high level. Tendinopathies are common in athletes and in middle-aged overweight patients. The term "tendinopathy" refers to a condition characterised clinically by pain and swelling, with functional limitations of tendon and nearby structures, and consequently to chronic failure of healing response process. Tendinopathies can produce marked morbidity, and at present, scientifically validated management modalities are limited. Despite the constantly increasing interest and number of studies about Achilles tendinopathy (AT), there is still not a consensual point of view on which is the best treatment, and its management is still controversial. AT can be treated conservatively primarily, with acceptable results and clinical outcomes. When this approach fails, surgery should be considered. Several surgical procedures have been described for both conditions with a relatively high rate of success with few complications and the decision for treatment in patients with AT should be tailored on patient's needs and level of activity. The aim of this article is to give insights about the pathogenesis and most used and recent treatment options for AT.

Mesenchymal Stem Cells for Enhanced Healing of the Medial Collateral Ligament of the Knee Joint

Background and Objectives: The medial collateral ligament (MCL) is one of the major supporting ligaments of the knee joint, and MCL injuries are common where excessive valgus loading is applied to the knee joint. Although most MCL injuries can be treated conservatively, healing of the MCL can take several weeks to months. Furthermore, once injured, the biomechanical properties of the healed MCL differ from those of the native MCL, resulting in an increased risk of re-injury and chronic remnant symptoms. Mesenchymal stem cells (MSCs), owing to their therapeutic potential, have been investigated in various musculoskeletal injuries, and some preclinical studies regarding MSC-based approaches in MCL injuries have shown promising results. Despite satisfactory results in preclinical studies, there is still a lack of clinical studies in the orthopedic literature. This article describes the basic knowledge of the MCL, standard treatments for MCL injuries, and recent studies regarding the application of MSCs for enhanced healing of the MCL. MSC-based approaches are expected to be a potential therapeutic option for enhanced healing of the MCL in the future.

Tendon and Ligament Healing and Current Approaches to Tendon and Ligament Regeneration

Ligament and tendon injuries are common problems in orthopedics. There is a need for treatments that can expedite nonoperative healing or improve the efficacy of surgical repair or reconstruction of ligaments and tendons. Successful biologically-based attempts at repair and reconstruction would require a thorough understanding of normal tendon and ligament healing. The inflammatory, proliferative, and remodeling phases, and the cells involved in tendon and ligament healing will be reviewed. Then, current research efforts focusing on biologically-based treatments of ligament and tendon injuries will be summarized, with a focus on stem cells endogenous to tendons and ligaments. Statement of clinical significance: This paper details mechanisms of ligament and tendon healing, as well as attempts to apply stem cells to ligament and tendon healing. Understanding of these topics could lead to more efficacious therapies to treat ligament and tendon injuries. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:7-12, 2020.

Evaluation of a magnesium ring device for mechanical augmentation of a ruptured ACL: Finite element analysis

BACKGROUND

Recently, a ring device was used for mechanical augmentation to aid the healing of ACL. In-vivo study using goat showed improved joint stability after ring repair in comparison to using biological augmentation alone. Objective of this study was to quantify the load and stress levels in the ACL and its femoral insertion site following ring repair.

METHODS

A three dimensional finite element model of a goat stifle joint was developed to find the load and stress level in the ACL and at its femoral insertion site following ring repair.

FINDINGS

Ring repair led to approximately a 50% reduction in anterior-posterior tibial translation over the model with a deficient ACL: 5.2 mm vs 10.6 mm, 4.4 mm vs 9.0 mm, and 2.9 mm vs 5.2 mm at joint flexion angles of 37°, 60° and 90° respectively. After ring repair, the in situ force in the ACL was restored to be nearly 60% of the intact ACL. The maximum Von Mises stress at the femoral insertion site was up to 71% of those for the intact ACL.

INTERPRETATION

This study offers new knowledge on the function of a ring device to mechanically augment ACL repair in order to improve its healing. Quantitative data on loading levels in the repaired ACL and its insertion site that led to its healing could be used as basis for developing novel devices to mechanically augment the healing of ACL in humans.

Cell Therapies in Tendon, Ligament, and Musculoskeletal System Repair

In the last few decades, several techniques have been used to optimize tendon, ligament, and musculoskeletal healing. The evidence in favor of these techniques is still not proven, and level I studies are lacking. We performed an analysis of the therapeutic strategies and tissue engineering projects recently published in this field. Here, we try to give an insight into the current status of cell therapies and the latest techniques of bioengineering applied to the field of orthopedic surgery. The future areas for research in the management of musculoskeletal injuries are outlined. There are emerging technologies developing into substantial clinical treatment options that need to be critically evaluated. Mechanical stimulation of the constructs reproduces a more propitious environment for effective healing.

The effect of a human acellular amniotic membrane loaded with mechanical stretch-stimulated bone marrow mesenchymal stem cells for the treatment of pelvic floor dysfunction

Pelvic floor dysfunction (PFD) has a severe impact on the quality of life of middle-aged and elderly women and is closely related to the damage of pelvic support tissues, especially ligaments.

Platelet-rich plasma did not improve early healing of medial collateral ligament in rats

BACKGROUND

The medial collateral ligament (MCL) is the most frequently injured ligament of the knee. Platelet-rich plasma (PRP) is a relatively new treatment option developed to enhance the healing response after injury to different tissue types. This study aimed at investigating whether the addition of PRP to MCL tears in rats would alter healing both biomechanically and histologically.

METHODS

Bilateral full-thickness tears of the MCL were surgically induced in the knees of 32 rats. Right ligament was saturated with PRP (n = 32, study group), and the left ligament was saturated with saline (n = 32, control group). The animals were killed 3 weeks later and the surgical sites were evaluated by gross inspection, biomechanically and histologically.

RESULTS

There was no gross difference in the mass of granulation tissue, load to failure, stiffness and displacement between the study and control groups. Histological examination by means of maturity score revealed no significant differences between the study and control groups.

CONCLUSION

The addition of PRP to a healing MCL did not improve any of the outcome measures in this model.

Cross-Talk Between Human Tenocytes and Bone Marrow Stromal Cells Potentiates Extracellular Matrix Remodeling In Vitro

Tendon and ligament (T/L) pathologies account for a significant portion of musculoskeletal injuries and disorders. Tissue engineering has emerged as a promising solution in the regeneration of both tissues. Specifically, the use of multipotent human mesenchymal stromal cells (hMSC) has shown great promise to serve as both a suitable cell source for tenogenic regeneration and a source of trophic factors to induce tenogenesis. Using four donor sets, we investigated the bidirectional paracrine tenogenic response between human hamstring tenocytes (hHT) and bone marrow-derived hMSC. Cell metabolic assays showed that only one hHT donor experienced sustained notable increases in cell metabolic activity during co-culture. Histological staining confirmed that co-culture induced elevated collagen protein levels in both cell types at varying time-points in two of four donor sets assessed. Gene expression analysis using qPCR showed the varied up-regulation of anabolic and catabolic markers involved in extracellular matrix maintenance for hMSC and hHT. Furthermore, analysis of hMSC/hHT co-culture secretome using a reporter cell line for TGF-β, a potent inducer of tenogenesis, revealed a trend of higher TGF-β bioactivity in hMSC secretome compared to hHT. Finally, hHT cytoskeletal immunostaining confirmed that both cell types released soluble factors capable of inducing favorable tenogenic morphology, comparable to control levels of soluble TGF-β1. These results suggest a potential for TGF-β-mediated signaling mechanism that is involved during the paracrine interplay between the two cell types that is reminiscent of T/L matrix remodeling/turnover. These findings have significant implications in the clinical use of hMSC for common T/L pathologies.

Role of angiogenesis after muscle derived stem cell transplantation in injured medial collateral ligament

We performed this study to investigate the therapeutic role of vascular endothelial growth factor (VEGF) in medial collateral ligament (MCL) healing. Murine muscle derived stem cells (MDSCs) obtained via the preplate technique were retrovirally transduced to express: (1) VEGF and nLacZ (MDSC-VEGF), (2) soluble fms-like tyrosine kinase-1 (sFLT1, a VEGF-specific antagonist) and nLacZ (MDSC-sFLT1), and (3) nLacZ (MDSC-nLacZ). After transecting the MCL of immunodeficient rats, 5 × 10(5)  cells of each of the transduction groups list above were transplanted into the MCL injury site. A control group was injected with phosphate-buffered saline (PBS) only. Immunohistochemical staining demonstrated that there were more Isolectin B4 and β-galactosidase double positive cells in the rats transplanted with MDSC-VEGF transduced cells than the other groups at week 1. Capillary density was significantly higher in the MDSC-VEGF group than the other groups at week 2; however, there were no significant differences in the biomechanical assessment between the MDSC-VEGF and MDSC-nLacZ groups. On the other hand, the MDSC-sFLT1 group revealed a lower capillary density than the other two groups and the functional ligament healing of the MDSC-sFLT1 group was significantly decreased compared to the other groups when assessed biomechanically. The findings of the present study suggest that angiogenesis plays a critical role in the healing process of injured MCL.

Tissue engineering strategies in ligament regeneration

Ligaments are dense fibrous connective tissues that connect bones to other bones and their injuries are frequently encountered in the clinic. The current clinical approaches in ligament repair and regeneration are limited to autografts, as the gold standard, and allografts. Both of these techniques have their own drawbacks that limit the success in clinical setting; therefore, new strategies are being developed in order to be able to solve the current problems of ligament grafting. Tissue engineering is a novel promising technique that aims to solve these problems, by producing viable artificial ligament substitutes in the laboratory conditions with the potential of transplantation to the patients with a high success rate. Direct cell and/or growth factor injection to the defect site is another current approach aiming to enhance the repair process of the native tissue. This review summarizes the current approaches in ligament tissue engineering strategies including the use of scaffolds, their modification techniques, as well as the use of bioreactors to achieve enhanced regeneration rates, while also discussing the advances in growth factor and cell therapy applications towards obtaining enhanced ligament regeneration.

Tissue engineered strategies for skeletal muscle injury

Skeletal muscle injuries are common in athletes, occurring with direct and indirect mechanisms and marked residual effects, such as severe long-term pain and physical disability. Current therapy consists of conservative management including RICE protocol (rest, ice, compression and elevation), nonsteroidal anti-inflammatory drugs, and intramuscular corticosteroids. However, current management of muscle injuries often does not provide optimal restoration to preinjury status. New biological therapies, such as injection of platelet-rich plasma and stem-cell-based therapy, are appealing. Although some studies support PRP application in muscle-injury management, reasons for concern persist, and further research is required for a standardized and safe use of PRP in clinical practice. The role of stem cells needs to be confirmed, as studies are still limited and inconsistent. Further research is needed to identify mechanisms involved in muscle regeneration and in survival, proliferation, and differentiation of stem cells.

Autologous tenocyte therapy for experimental Achilles tendinopathy in a rabbit model

BACKGROUND

Tendinopathy of the Achilles tendon is a chronic degenerative condition that frequently does not respond to treatment. In the current study, we propose that autologous tenocytes therapy (ATT) is effective in treating tendon degeneration in a collagenase-induced rabbit Achilles tendinopathy model.

METHODS

Chronic tendinopathy was created in the left Achilles tendon of 44 rabbits by an intratendonous injection of type I collagenase. Forty-two rabbits were randomly allocated into three groups of 14 and received control treatment; autologous tenocytes digested from tendon tissue; and autologous tenocytes digested from epitendineum tissue. For cell tracking in vivo, the remaining two animals were injected with autologous tenocytes labeled with a nano-scale super-paramagnetic iron oxide (Feridex). Rabbits were sacrificed at 4 and 8 weeks after the therapeutic injection, and tendon tissue was analyzed by histology, immunostaining, and biomechanical testing to evaluate tissue repair.

RESULTS

Autologous tenocyte treatment improved tendon remodeling, histological outcomes, collagen content, and tensile strength of tendinopathic Achilles tendons. Injected tenocytes were integrated into tendon matrix and could be tracked up to 8 weeks in vivo. Immunohistochemistry showed that ATT improved type I collagen expression in repaired tendon but did not affect type III collagen and secreted protein, acidic and rich in cysteine expression.

CONCLUSION

ATT may be a useful treatment of chronic Achilles tendinopathy.

The influence of interleukin-4 on ligament healing

Despite a complex cascade of cellular events to reconstruct the damaged extracellular matrix, ligament healing results in a mechanically inferior scarred ligament. During normal healing, granulation tissue expands into any residual normal ligamentous tissue (creeping substitution), resulting in a larger region of healing, greater mechanical compromise and an inefficient repair process. To control creeping substitution and possibly enhance the repair process, the antiinflammatory cytokine, interleukin-4 (IL-4), was administered to rats before and after rupture of their medial collateral ligaments. In vitro experiments showed a time-dependent effect on fibroblast proliferation after IL-4 treatment. In vivo treatments with IL-4 (100 ng/mL IV) for 5 days resulted in decreased wound size and type III collagen and increased type I procollagen, indicating a more regenerative early healing in response to the IL-4 treatment. However, continued treatment of IL-4 to day 11 antagonized this early benefit and slowed healing. Together, these results suggest that IL-4 not only influences the macrophages and T lymphocytes but also stimulates fibroblasts associated with the proliferative phase of healing in a dose-, cell-, and time-dependent manner. Although treatment significantly influenced healing in the first week after injury, IL-4 alone was unable to maintain this early regenerative response.

What we should know before using tissue engineering techniques to repair injured tendons: a developmental biology perspective

Tendons connect muscles to bones, and serve as the transmitters of force that allow all the movements of the body. Tenocytes are the basic cellular units of tendons, and produce the collagens that form the hierarchical fiber system of the tendon. Tendon injuries are common, and difficult to repair, particularly in the case of the insertion of tendon into bone. Successful attempts at cell-based repair therapies will require an understanding of the normal development of tendon tissues, including their differentiated regions such as the fibrous mid-section and fibrocartilaginous insertion site. Many genes are known to be involved in the formation of tendon. However, their functional roles in tendon development have not been fully characterized. Tissue engineers have attempted to generate functional tendon tissue in vitro. However, a lack of knowledge of normal tendon development has hampered these efforts. Here we review studies focusing on the developmental mechanisms of tendon development, and discuss the potential applications of a molecular understanding of tendon development to the treatment of tendon injuries.

Functional tissue engineering of ligament healing

Ligaments and tendons are dense connective tissues that are important in transmitting forces and facilitate joint articulation in the musculoskeletal system. Their injury frequency is high especially for those that are functional important, like the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) of the knee as well as the glenohumeral ligaments and the rotator cuff tendons of the shoulder. Because the healing responses are different in these ligaments and tendons after injury, the consequences and treatments are tissue- and site-specific. In this review, we will elaborate on the injuries of the knee ligaments as well as using functional tissue engineering (FTE) approaches to improve their healing. Specifically, the ACL of knee has limited capability to heal, and results of non-surgical management of its midsubstance rupture have been poor. Consequently, surgical reconstruction of the ACL is regularly performed to gain knee stability. However, the long-term results are not satisfactory besides the numerous complications accompanied with the surgeries. With the rapid development of FTE, there is a renewed interest in revisiting ACL healing. Approaches such as using growth factors, stem cells and scaffolds have been widely investigated. In this article, the biology of normal and healing ligaments is first reviewed, followed by a discussion on the issues related to the treatment of ACL injuries. Afterwards, current promising FTE methods are presented for the treatment of ligament injuries, including the use of growth factors, gene delivery, and cell therapy with a particular emphasis on the use of ECM bioscaffolds. The challenging areas are listed in the future direction that suggests where collection of energy could be placed in order to restore the injured ligaments and tendons structurally and functionally.

Effect of human bone marrow stromal cell allograft on proliferation and collagen synthesis of diabetic fibroblasts in vitro

In previous pilot studies, the authors reported that bone marrow stromal cells (BSCs) have a superior effect on healing of acute wounds compared with fibroblasts in vitro and in vivo. The present study was designed to compare the effect of allograft of normal BSCs with that of normal fibroblasts on the activity of diabetic fibroblasts in vitro. Diabetic fibroblasts were cultured in 24-well culture plates. Three groups were evaluated: group I, diabetic fibroblasts only; group II, diabetic fibroblasts co-cultured with normal fibroblasts; group III, diabetic fibroblasts co-cultured with normal BSCs. After 3-day incubation, cell proliferation and collagen synthesis, which are the major contributing factors in wound healing, were measured. Group III showed the highest level in both cell proliferation and collagen synthesis, followed by group II and group I (p<0.05). These results demonstrate that BSCs are superior to fibroblasts in stimulating the activity of diabetic fibroblasts.

The therapeutic applications of multipotential mesenchymal/stromal stem cells in skeletal tissue repair

Four decades after the first isolation and characterization of clonogenic bone marrow stromal cells or mesenchymal stem cells (MSC) in the laboratory of Dr. Alexander Friedenstien, the therapeutic application of their progeny following ex vivo expansion are only now starting to be realized in the clinic. The multipotency, paracrine effects, and immune-modulatory properties of MSC present them as an ideal stem cell candidate for tissue engineering and regenerative medicine. In recent years it has come to light that MSC encompass plasticity that extends beyond the conventional bone, adipose, cartilage, and other skeletal structures, and has expanded to the differentiation of liver, kidney, muscle, skin, neural, and cardiac cell lineages. This review will specifically focus on the skeletal regenerative capacity of bone marrow derived MSC alone or in combination with growth factors, biocompatible scaffolds, and following genetic modification.

Effect of human bone marrow stromal cells and dermal fibroblasts on collagen synthesis and epithelization

In a previous in vitro study, the authors reported that bone marrow stromal cells (BSCs) have better wound-healing activities than fibroblasts. The purpose of this study was to evaluate the effect of BSCs and fibroblasts on wound-healing activity in vivo. Cultured human BSCs and dermal fibroblasts taken from the same patients were tested to compare collagen synthesis and epithelization in a rat wound model. No-cell-treated animals were used as controls. The BSC group showed the highest collagen level, followed by the fibroblast group, and then the no-cell group (P < 0.05). In addition, the best epithelization was observed in the BSC group. These results demonstrate that BSCs better stimulate wound healing than fibroblasts in vivo and in vitro.

Systemic vanadate ingestion improves early medial collateral ligament repair

The medial collateral ligament (MCL) of the knee is frequently injured in sport. Repair is slow and often complicated by scar formation which may result in impairment of function. Vanadate is a promising efficacious treatment for tissue injuries and this study aimed to examine its effect in rats on the histological and biomechanical features of MCL healing. Rats received either 0.025 g/kg per day vanadate or equivalent amounts of drinking water (control) by intragastric gavage for 1 week before and 2 weeks after wounding. Repaired sites were dissected out for histological and biomechanical tests 28 days after wounding. Fibre bundles in the vanadate-treated group were uniform and evenly spaced. Furthermore, vanadate significantly increased the diameter of collagen fibrils in the healing tissue. Stiffness and ultimate force of the femur-medial collateral ligament-tibia complex for the vanadate-treated group were significantly higher than for the controls. The results suggest that vanadate significantly improves the histological and biomechanical properties of healing MCL.

Administrations of peripheral blood CD34-positive cells contribute to medial collateral ligament healing via vasculogenesis

Neoangiogenesis is a key process in the initial phase of ligament healing. Adult human circulating CD34+ cells, an endothelial/hematopoietic progenitor-enriched cell population, have been reported to contribute to neoangiogenesis; however, the therapeutic potential of CD34+ cells for ligament healing is still unclear. Therefore, we performed a series of experiments to test our hypothesis that ligament healing is supported by CD34+ cells via vasculogenesis. Granulocyte colony-stimulating factor-mobilized peripheral blood (GM-PB) CD34+ cells with atelocollagen (CD34+ group), GM-PB mononuclear cells (MNCs) with atelocollagen (MNC group), or atelocollagen alone (control group) was locally transplanted after the creation of medial collateral ligament injury in immunodeficient rats. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemical staining at the injury site demonstrated that molecular and histological expression of human-specific markers for endothelial cells was higher in the CD34+ group compared with the other groups at week 1. Endogenous effect, assessed by capillary density and mRNA expression of vascular endothelial growth factor, was significantly higher in CD34+ cell group than the other groups. In addition to the observation that, as assessed by real-time RT-PCR, gene expression of ligament-specific marker was significantly higher in the CD34+ group than in the other groups, ligament healing assessed by macroscopic, histological, and biomechanical examination was significantly enhanced by CD34+ cell transplantation compared with the other groups. Our data strongly suggest that local transplantation of circulating human CD34+ cells may augment the ligament healing process by promoting a favorable environment through neovascularization.

ACL reconstruction in a rabbit model using irradiated Achilles allograft seeded with mesenchymal stem cells or PDGF-B gene-transfected mesenchymal stem cells

The present study was conducted to develop a new strategy to accelerate reconstruction of the anterior cruciate ligament (ACL) by modifying the Achilles allograft with autogenous mesenchymal stem cells (MSCs) or PDGF-B transfected MSCs in a rabbit model. The allografts were first irradiated with Co60, stored at -80 degrees C, and then seeded with cells for implantation. Bilateral ACL reconstructions were performed. On the left, the allograft was either seeded with MSCs or PDGF-B transfected MSCs and acted as the experimental group. On the right, the graft without any cells seeded acted as control. At 3, 6 and 12 weeks after surgery, histological observation found that implantation of MSCs or PDGF-B transfected MSCs accelerated cellular infiltration into the ACL and enhanced collagen deposition in the wound. PDGF-B transfected MSCs could also lead to an initial promotion of angiogenesis. This gene transfer technique or cell implantation may be a potentially useful tool for improving ligament remodeling.

Adjuvant neuropeptides can improve neuropathic ligament healing in a rat model

Diminished healing in neuropathic tissues suggests an important regulatory role for peripheral neurogenic factors in connective tissue healing. Although neurogenic factors, including neuropeptides, can induce cell proliferation and influence inflammatory cell chemotaxis in vitro, there is little appreciation of the potential of neuropeptides to affect connective tissue healing in vivo. We created both efferent and afferent peripheral neuropathies in 55 female Wistar rats. First, we showed that neuropathy led to impaired healing of ruptured ligaments. We then showed that local delivery of specific neuropeptides could reverse the functional deficits of these neuropathic ligaments in only 2 weeks. In substance P and vasoactive intestinal peptide-treated medial collateral ligaments (MCLs), the mechanical properties of these healing neuropathic tissues returned to values at or above normally innervated, intact ligaments. In addition, neuropeptide Y stimulated MCL healing in this model. These findings suggest a new paradigm to improve neuropathic soft connective tissue healing.

Bone Marrow Stromal Cells Act as Feeder Cells for Tendon Fibroblasts through Soluble Factors

Feeder effects of bone marrow stromal cells (BMSCs) on tendon fibroblasts were investigated using a co-culture method for the application of ligament or tendon tissue engineering and cell therapy. BMSCs had significant effects on enhancing cell proliferation, the ability of cells to migrate, and cell adhesivity but little effect on the extracellular matrix (ECM) synthesis of tendon fibroblasts without cell-cell contact. Furthermore, the conditioned medium from BMSCs, despite the existence of fibroblasts, significantly increased the number of fibroblasts. Based on these results, the mechanism of the feeder effects is considered to be a certain signal of soluble factors from BMSCs to the fibroblasts. Comparative proteome analysis of the conditioned medium from co-culture of fibroblasts and BMSCs revealed less expression of plasminogen, which showed inhibitory effects on fibroblast proliferation. With regard to the relationships between plasminogen and BMSCs in the co-culture system, we speculate that BMSCs allow resolution of plasminogen or its cleavage activity in the medium via some mechanism.

Translation from Research to Applications

The article summarizes the collective views expressed at the fourth session of the workshop Tissue Engineering--the Next Generation, which was devoted to the translation of results of tissue engineering research into applications. Ernst Hunziker described the paradigm of a dual translational approach, and argued that tissue engineering should be guided by the dimensions and physiological setting of the bodily compartment to be repaired. Myron Spector discussed collagen-glycosaminoglycan (GAG) scaffolds for musculoskeletal tissue engineering. Jeanette Libera focused on the biological and clinical aspects of cartilage tissue engineering, and described a completely autologous procedure for engineering cartilage using the patient's own chondrocytes and blood serum. Arthur Gertzman reviewed the applications of allograft tissues in orthopedic surgery, and outlined the potential of allograft tissues as models for biological and medical studies. Savio Woo discussed a list of functional tissue engineering approaches designed to restore the biochemical and biomechanical properties of injured ligaments and tendons to be closer to that of the normal tissues. Specific examples of using biological scaffolds that have chemoattractants as well as growth factors with unique contact guidance properties to improve their healing process were shown. Anthony Ratcliffe discussed the translation of the results of research into products that are profitable and meet regulatory requirements. Michael Lysaght challenged the proposition that commercial and clinical failures of early tissue engineering products demonstrate a need for more focus on basic research. Arthur Coury described the evolution of tissue engineering products based on the example of Genzyme, and how various definitions of success and failure can affect perceptions and policies relative to the status and advancement of the field of tissue engineering.

Vanadate ingestion enhances the organization and collagen fibril diameters of rat healing medical collateral ligaments

Although an injured medial collateral ligament (MCL) will naturally heal, the quality of healing tissue is inferior to the uninjured MCL tissue. Previous studies have shown promising results of sodium orthovanadate (vanadate) in enhancing the quality of rat skin wounds. This study therefore investigated whether vanadate enhances the quality of the rat healing MCL in terms of the collagen fibril organization and diameter. Six mature male Sprague-Dawley rats, with weight ranges of 475-505 g and ages of 25 weeks, were used in this study. Three rats in the experimental group received vanadate (0.2 mg/ml) in their saline drinking water (150 mM NaCl), whereas three rats in the control group were only given saline water. Three weeks after transection, the rat MCLs were harvested for hematoxylin and eosin (H&E) staining and transmission electron microscopy. It was found that vanadate promoted organization of collagen fibrils and significantly increased the diameters of collagen fibrils by 14% in healing MCL (P<0.001). These results indicate that application of vanadate may be a promising tissue engineering approach to enhance the quality of healing tissues such as injured MCLs.

The effect of human bone marrow stromal cells and dermal fibroblasts on angiogenesis

BACKGROUND

A cell therapy methodology for angiogenesis using fibroblasts has already been developed. Bone marrow stromal cells, which contain mesenchymal stem cells, have a low rate of immunity-assisted rejection and are capable of expanding profoundly in culture. Therefore, these cells offer several advantages for transplantation over mature cells. The aim of this study was to compare the angiogenic activity of bone marrow stromal cells with that of fibroblasts.

METHODS

For in vitro study, cultured human bone marrow stromal cells and dermal fibroblasts were seeded onto 96-well culture plates. After 1, 3, and 5 days, the levels of the basic fibroblast growth factor and vascular endothelial growth factor were compared. For in vivo study, porous polyethylene disks were loaded with bone marrow stromal cells, fibroblasts, or no cells and then implanted in the backs of rats. At three time intervals ranging from 1 to 3 weeks, the microvascular density was measured.

RESULTS

In the in vitro study, the basic fibroblast growth factor levels in the bone marrow stromal cell group were 47, 89, and 68 percent higher than in the fibroblast group at each time interval (p < 0.05). The vascular endothelial growth factor levels of the bone marrow stromal cell group were seven, 12, and 12 times higher than those of the fibroblast group (p < 0.05). In the in vivo study, there was little difference in the microvascular density among the three groups by the second week. However, the 3-week specimens showed a significantly greater difference. The microvascular density averaged 52.88, 26.12, and 17.50 for the bone marrow stromal cell, fibroblast, and no-cell groups, respectively.

CONCLUSION

These results suggest that bone marrow stromal cells may possibly be used as a replacement for fibroblasts for angiogenesis.

Long-term effects of porcine small intestine submucosa on the healing of medial collateral ligament: a functional tissue engineering study

Porcine small intestinal submucosa (SIS) was previously shown to enhance the mechanical properties of healing medial collateral ligaments (MCL), and the histomorphological appearance and collagen type V/I ratio were found to be close to those of normal MCL. We hypothesized that at a longer term, 26 weeks, SIS could guide a better organized neo-ligament formation, increasing mechanical properties and increasing collagen fibril diameters mediated by a reduction in collagen type V. A 6 mm gap injury in the right MCL was surgically created in 38 rabbits, while the contralateral intact MCL served as a sham-operated control. In half the animals, a strip of SIS was sutured onto the severed ends. In the other half, no SIS was applied. The cross-sectional area (CSA) was determined with a laser micrometer system. The femur-MCL-tibia complex was mechanically tested in uniaxial tension. Histomorphology was determined through H&E and immunofluorescent staining and transmission electron microscopy (TEM). Sodium-dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was used to determine collagen type V/I ratio. SIS-treated MCLs displayed a 28% reduction in CSA, a 33% increase in tangent modulus, and a 50% increase in tensile strength compared with the nontreated group (p < 0.05). TEM showed groups of collagen fibrils with larger diameters in the SIS-treated ligaments in comparison with uniformly small fibrils for the nontreated group. H&E staining showed more densely stained collagen fibers in the SIS-treated group aligned along the longitudinal axis with more interspersed spindle-shaped cells. Immunofluorescent staining showed less collagen type V signals, confirmed by a 5% lower ratio of collagen type V/I compared with the nontreated controls (p < 0.05). The findings extend the shorter term 12-week results, and support the potential of porcine SIS as a bioscaffold to enhance ligament healing.

Treatment with Bioscaffold Enhances the the Fibril Morphology and the Collagen Composition of Healing Medial Collateral Ligament in Rabbits

Porcine small intestinal submucosa (SIS) was shown to be an effective bioscaffold in enhancing the mechanical properties of healing medial collateral ligaments (MCL). The purpose of this study was to investigate whether there are corresponding improvements in morphology and tissue compositions. Fourteen rabbits were equally divided into two groups. In the SIS-treated group, a 6 mm gap was surgically created in the right MCL and a layer of SIS was sutured covering the gap. For the nontreated group, the gap-injured MCLs remained untreated. All the left MCLs were sham operated and used as controls. At 12 weeks, the status of collagen types I and V was evaluated with immunofluorescent staining. The collagen type V/I ratios were obtained using SDS-PAGE. Collagen fibril diameters were calculated from the transmission electron micrographs. The results revealed that in the SIS-treated group, the collagen fibers were more regularly aligned as were the cell nuclei. The collagen fibril diameters were 22.2% larger and the ratio of collagen type V/I was 28.4% lower than those for the nontreated group (p < 0.05). These improvements in the morphological characteristics and biochemical constituents of healing MCLs following SIS treatment are the likely reasons for improved mechanical properties.

Potential of Human Bone Marrow Stromal Cells to Accelerate Wound Healing in Vitro

The purpose of this pilot study was to compare proliferation, collagen synthesis, and growth factor production, which are important contributing factors for wound healing, of the bone marrow stromal cells (BSCs) with those of dermal fibroblasts in vitro. Cultured human BSCs and dermal fibroblasts from the same patients were seeded in 96-well culture plates. At 1, 3, and 5 days postincubating, cell proliferation, collagen synthesis, and secretion of basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and transforming growth factor beta (TFG-beta) were compared. We did not observe great differences in cell proliferation and TFG-beta secretion. In contrast, the amount of collagen synthesis and the levels of the bFGF and the VEGF were much higher in the BSC group than the fibroblast group at each time interval (P < 0.05). Our results suggest that the BSCs may have superior potential to accelerate wound healing than the fibroblasts.

Contribution of biomechanics, orthopaedics and rehabilitation: the past present and future

Biomechanics is a field that has a very long history. From its beginnings in ancient Chinese and Greek literature, the field of orthopaedic biomechanics has grown in the areas of biomechanics of bone, articular cartilage, soft tissues, upper extremities, spine and so on. Bioengineers in collaboration with orthopaedic surgeons have applied biomechanical principles to study clinically relevant problems, improving patient treatment and outcome. In the past 30 years, my colleagues and I have focused our research on the biomechanics of musculoskeletal soft tissues, ligaments and tendons in particular. Therefore, in this review article, the function of the knee ligaments and the associated homeostatic responses secondary to immobilisation and exercise will be described. Research on healing of the medial collateral ligament (MCL) of the knee and possible future approaches in improving the healing of the knee ligaments will be presented. Finally, improvement of the understanding of ligament reconstruction, specifically of the anterior cruciate ligament (ACL), through the use of robotics technology will be included. Throughout the manuscript, specific scientific findings that have guided or changed the clinical management of injury to these soft tissues will be emphasised.

Biomechanics of knee ligaments: injury, healing, and repair

Knee ligament injuries are common, particularly in sports and sports related activities. Rupture of these ligaments upsets the balance between knee mobility and stability, resulting in abnormal knee kinematics and damage to other tissues in and around the joint that lead to morbidity and pain. During the past three decades, significant advances have been made in characterizing the biomechanical and biochemical properties of knee ligaments as an individual component as well as their contribution to joint function. Further, significant knowledge on the healing process and replacement of ligaments after rupture have helped to evaluate the effectiveness of various treatment procedures. This review paper provides an overview of the current biological and biomechanical knowledge on normal knee ligaments, as well as ligament healing and reconstruction following injury. Further, it deals with new and exciting functional tissue engineering approaches (ex. growth factors, gene transfer and gene therapy, cell therapy, mechanical factors, and the use of scaffolding materials) aimed at improving the healing of ligaments as well as the interface between a replacement graft and bone. In addition, it explores the anatomical, biological and functional perspectives of current reconstruction procedures. Through the utilization of robotics technology and computational modeling, there is a better understanding of the kinematics of the knee and the in situ forces in knee ligaments and replacement grafts. The research summarized here is multidisciplinary and cutting edge that will ultimately help improve the treatment of ligament injuries. The material presented should serve as an inspiration to future investigators.