Skin-derived fibroblasts for the treatment of refractory Achilles tendinosis: preliminary short-term results

Challenges and opportunities of medicines for treating tendon inflammation and fibrosis: A comprehensive and mechanistic review

BACKGROUND

Tendinopathy refers to conditions characterized by collagen degeneration within tendon tissue, accompanied by the proliferation of capillaries and arteries, resulting in reduced mechanical function, pain, and swelling. While inflammation in tendinopathy can play a role in preventing infection, uncontrolled inflammation can hinder tissue regeneration and lead to fibrosis and impaired movement.

OBJECTIVES

The inability to regulate inflammation poses a significant limitation in tendinopathy treatment. Therefore, an ideal treatment strategy should involve modulation of the inflammatory process while promoting tissue regeneration.

METHODS

The current review article was prepared by searching PubMed, Scopus, Web of Science, and Google Scholar databases. Several treatment approaches based on biomaterials have been developed.

RESULTS

This review examines various treatment methods utilizing small molecules, biological compounds, herbal medicine-inspired approaches, immunotherapy, gene therapy, cell-based therapy, tissue engineering, nanotechnology, and phototherapy.

CONCLUSION

These treatments work through mechanisms of action involving signaling pathways such as transforming growth factor-beta (TGF-β), mitogen-activated protein kinases (MAPKs), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), all of which contribute to the repair of injured tendons.

Advances toward transformative therapies for tendon diseases

Approved therapies for tendon diseases have not yet changed the clinical practice of symptomatic pain treatment and physiotherapy. This review article summarizes advances in the development of novel drugs, biologic products, and biomaterial therapies for tendon diseases with perspectives for translation of integrated therapies. Shifting from targeting symptom relief toward disease modification and prevention of disease progression may open new avenues for therapies. Deep evidence-based clinical, cellular, and molecular characterization of the underlying pathology of tendon diseases, as well as therapeutic delivery optimization and establishment of multidiscipline interorganizational collaboration platforms, may accelerate the discovery and translation of transformative therapies for tendon diseases.

An Assessment of Randomized Controlled Trial Quality in The Journal of Bone & Joint Surgery: Update from 2001 to 2013

BACKGROUND

The quality of reporting of randomized controlled trials (RCTs) published in The Journal of Bone & Joint Surgery (JBJS) from 1988 to 2000 was previously analyzed. The purpose of this current study was to analyze the quality of reporting of RCTs published in JBJS from 2001 to 2013 to identify trends over time and potential areas of improvement for future clinical trials.

METHODS

A manual search of the JBJS database identified RCTs published between January 2001 and December 2013. Quality assessments, using the Detsky quality-of-reporting index (Detsky score), a modified Cochrane risk-of-bias tool, and abstraction of relevant data identifying predictors of quality, were conducted.

RESULTS

A total of 5,780 publications were identified in JBJS from 2001 to 2013, with 285 RCTs (4.9%), representing an increase from the prior 13-year period. The overall mean transformed Detsky score (and standard error) increased significantly (p < 0.001) from 68.1% ± 1.67% to 76.24% ± 0.72%. The percentage of multicenter RCTs decreased from 67% to 31%. The percentage of positive trials also decreased from 80% to 50.5%, as did the mean sample size (212 to 166). Regression analysis indicated that trials with an epidemiologist as the first author and nonsurgical trials were significantly associated (p = 0.001) with a higher overall trial quality score. The categories of the lowest mean methodology scores were randomization and concealment, eligibility criteria, and reasons for patient exclusion, as identified with the Detsky score, and patient and assessor blinding, as identified with the risk-of-bias assessment.

CONCLUSIONS

The quantity and quality of published RCTs in JBJS have increased in the 2001 to 2013 time period compared with the previous time period. Although these improvements are encouraging, trends to smaller, single-center trials were also observed. To efficiently determine the efficacy of orthopaedic treatments and limit bias, high-quality randomized trials of appropriate sample size and rigorous design are needed.

Multifactorial bottom-up bioengineering approaches for the development of living tissue substitutes

Bottom-up bioengineering utilizes the inherent capacity of cells to build highly sophisticated structures with high levels of biomimicry. Despite the significant advancements in the field, monodomain approaches require prolonged culture time to develop an implantable device, usually associated with cell phenotypic drift in culture. Herein, we assessed the simultaneous effect of macromolecular crowding (MMC) and mechanical loading in enhancing extracellular matrix (ECM) deposition while maintaining tenocyte (TC) phenotype and differentiating bone marrow stem cells (BMSCs) or transdifferentiating neonatal and adult dermal fibroblasts toward tenogenic lineage. At d 7, all cell types presented cytoskeleton alignment perpendicular to the applied load independently of the use of MMC. MMC enhanced ECM deposition in all cell types. Gene expression analysis indicated that MMC and mechanical loading maintained TC phenotype, whereas tenogenic differentiation of BMSCs or transdifferentiation of dermal fibroblasts was not achieved. Our data suggest that multifactorial bottom-up bioengineering approaches significantly accelerate the development of biomimetic tissue equivalents.-Gaspar, D., Ryan, C. N. M., Zeugolis, D. I. Multifactorial bottom-up bioengineering approaches for the development of living tissue substitutes.

Lateral Elbow Tendinopathy: Development of a Pathophysiology-Based Treatment Algorithm

Lateral elbow tendinopathy, commonly known as tennis elbow, is a condition that can cause significant functional impairment in working-age patients. The term tendinopathy is used to describe chronic overuse tendon disorders encompassing a group of pathologies, a spectrum of disease. This review details the pathophysiology of tendinopathy and tendon healing as an introduction for a system grading the severity of tendinopathy, with each of the 4 grades displaying distinct histopathological features. Currently, there are a large number of nonoperative treatments available for lateral elbow tendinopathy, with little guidance as to when and how to use them. In fact, an appraisal of the clinical trials, systematic reviews, and meta-analyses studying these treatment modalities reveals that no single treatment reliably achieves outstanding results. This may be due in part to the majority of clinical studies to date including all patients with chronic tendinopathy rather than attempting to categorize patients according to the severity of disease. We relate the pathophysiology of the different grades of tendinopathy to the basic science principles that underpin the mechanisms of action of the nonoperative treatments available to propose a treatment algorithm guiding the management of lateral elbow tendinopathy depending on severity. We believe that this system will be useful both in clinical practice and for the future investigation of the efficacy of treatments.

American Medical Society for Sports Medicine (AMSSM) position statement: interventional musculoskeletal ultrasound in sports medicine

The use of diagnostic and interventional ultrasound has significantly increased over the past decade. A majority of the increased utilization is by nonradiologists. In sports medicine, ultrasound is often used to guide interventions such as aspirations, diagnostic or therapeutic injections, tenotomies, releases, and hydrodissections. This American Medical Society for Sports Medicine (AMSSM) position statement critically reviews the literature and evaluates the accuracy, efficacy, and cost-effectiveness of ultrasound-guided injections in major, intermediate, and small joints, and soft tissues, all of which are commonly performed in sports medicine. New ultrasound-guided procedures and future trends are also briefly discussed. Based upon the evidence, the official AMSSM position relevant to each subject is made.

Injection therapies for Achilles tendinopathy

BACKGROUND

Achilles tendinopathy is a common condition, often with significant functional consequences. As a wide range of injection treatments are available, a review of randomised trials evaluating injection therapies to help inform treatment decisions is warranted.

OBJECTIVES

To assess the effects (benefits and harms) of injection therapies for people with Achilles tendinopathy.

SEARCH METHODS

We searched the following databases up to 20 April 2015: the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, AMED, CINAHL and SPORTDiscus. We also searched trial registers (29 May 2014) and reference lists of articles to identify additional studies.

SELECTION CRITERIA

We included randomised and quasi-randomised controlled trials evaluating injection therapies in adults with an investigator-reported diagnosis of Achilles tendinopathy. We accepted comparison arms of placebo (sham) or no injection control, or other active treatment (such as physiotherapy, pharmaceuticals or surgery). Our primary outcomes were function, using measures such as the VISA-A (Victorian Institute of Sport Assessment-Achilles questionnaire), and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data from the included studies. We assessed treatment effects using mean differences (MDs) and 95% confidence intervals (CIs) for continuous variables and risk ratios (RRs) and 95% CIs for dichotomous variables. For follow-up data, we defined short-term as up to six weeks, medium-term as up to three months and longer-term as data beyond three months. We performed meta-analysis where appropriate.

MAIN RESULTS

We included 18 studies (732 participants). Seven trials exclusively studied athletic populations. The mean ages of the participants in the individual trials ranged from 20 years to 50 years. Fifteen trials compared an injection therapy with a placebo injection or no injection control, four trials compared an injection therapy with active treatment, and one compared two different concentrations of the same injection. Thus no trials compared different injection therapies. Two studies had three trial arms and we included them twice in two different categories. Within these categories, we further subdivided injection therapies by mode of action (injury-causing versus direct repair agents).The risk of bias was unclear (due to poor reporting) or high in six trials published between 1987 and 1994. Improved methodology and reporting for the subsequent trials published between 2004 and 2013 meant that these were at less risk of bias.Given the very low quality evidence available from each of four small trials comparing different combinations of injection therapy versus active treatment and the single trial comparing two doses of one injection therapy, only the results of the first comparison (injection therapy versus control) are presented.There is low quality evidence of a lack of significant or clinically important differences in VISA-A scores (0 to 100: best function) between injection therapy and control groups at six weeks (MD 0.79, 95% CI -4.56 to 6.14; 200 participants, five trials), three months (MD -0.94, 95% CI -6.34 to 4.46; 189 participants, five trials) or between six and 12 months (MD 0.14, 95% CI -6.54 to 6.82; 132 participants, three trials). Very low quality evidence from 13 trials showed little difference between the two groups in adverse events (14/243 versus 12/206; RR 0.97, 95% CI 0.50 to 1.89), most of which were minor and short-lasting. The only major adverse event in the injection therapy group was an Achilles tendon rupture, which happened in a trial testing corticosteroid injections. There was very low quality evidence in favour of the injection therapy group in short-term (under three months) pain (219 participants, seven trials) and in the return to sports (335 participants, seven trials). There was very low quality evidence indicating little difference between groups in patient satisfaction with treatment (152 participants, four trials). There was insufficient evidence to conclude on subgroup differences based on mode of action given that only two trials tested injury-causing agents and the clear heterogeneity of the other 13 trials, which tested seven different therapies that act directly on the repair pathway.

AUTHORS' CONCLUSIONS

There is insufficient evidence from randomised controlled trials to draw conclusions on the use, or to support the routine use, of injection therapies for treating Achilles tendinopathy. This review has highlighted a need for definitive research in the area of injection therapies for Achilles tendinopathy, including in older non-athletic populations. This review has shown that there is a consensus in the literature that placebo-controlled trials are considered the most appropriate trial design.

Muscle and tendon injuries: the role of biological interventions to promote and assist healing and recovery

PURPOSE

To summarize clinical studies after platelet-rich plasma (PRP) therapy for tendinopathy, plantar fasciopathy, and muscle injuries; to review PRP formulations used across studies; and to identify knowledge deficits that require further investigation.

METHODS

After a systematic review in PubMed, we identified clinical studies assessing PRP efficacy in tendon and muscle during the past decade. We standardized data extraction by grouping studies based on anatomic location; summarized patient populations, PRP formulations, and clinical outcomes; and identified knowledge deficits that require further investigation.

RESULTS

Overall, 1,541 patients had been treated with PRP in 58 clinical studies; of these, 26 addressed upper limb tendinopathies and 32 addressed the lower limb (810 patients and 731 patients treated with PRP, respectively). The quality of research is higher for the upper limb than for the lower limb (23 controlled studies, of which 17 are Level I, v 19 controlled studies, of which 6 are Level I, respectively). Patients have been treated mostly with leukocyte-platelet-rich plasma, except in the arthroscopic management of the rotator cuff. The safety and efficacy of PRP for muscle injuries has been addressed in 7 studies including 182 patients. Differences across results are mainly attributed to dissimilarities between tissues and different stages of degeneration, numbers of PRP applications, and protocols.

CONCLUSIONS

Given the heterogeneity in tendons and tendinopathies, currently, we are not able to decide whether PRP therapies are useful. Despite advances in PRP science, data are insufficient and there is a clear need to optimize protocols and obtain more high-quality clinical data in both tendinopathies and muscle injuries before making treatment recommendations.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I through IV studies.

Progress in cell-based therapies for tendon repair

The last decade has seen significant developments in cell therapies, based on permanently differentiated, reprogrammed or engineered stem cells, for tendon injuries and degenerative conditions. In vitro studies assess the influence of biophysical, biochemical and biological signals on tenogenic phenotype maintenance and/or differentiation towards tenogenic lineage. However, the ideal culture environment has yet to be identified due to the lack of standardised experimental setup and readout system. Bone marrow mesenchymal stem cells and tenocytes/dermal fibroblasts appear to be the cell populations of choice for clinical translation in equine and human patients respectively based on circumstantial, rather than on hard evidence. Collaborative, inter- and multi-disciplinary efforts are expected to provide clinically relevant and commercially viable cell-based therapies for tendon repair and regeneration in the years to come.

Pharmacological interventions for the treatment of Achilles tendinopathy: a systematic review of randomized controlled trials

INTRODUCTION

Several pharmacological interventions have been proposed for the management of Achilles tendinopathy, with no agreement on which is the overall best option available. This systematic review investigates the efficacy and safety of different local pharmacological treatments for Achilles tendinopathy.

SOURCES OF DATA

We included only randomized controlled studies (RCTs) focusing on clinical and functional outcomes of therapies consisting in injection of a substance or local application. Assessment of the methodological quality was performed using a modified version of the Coleman methodology score (CMS) to determine possible risks of bias.

AREAS OF AGREEMENT

Thirteen RCTs were included with a total of 528 studied patients. Eleven studies reported the outcomes of injection therapies. Two studies examined the outcomes of patients who applied glyceryl trinitrate patch. The mean modified CMS was 70.6 out of 90.

AREAS OF CONTROVERSY

There was no significant evidence of remarkable benefits provided by any of the therapies studied.

GROWING POINTS

There is not univocal evidence to advise any particular pharmacological treatment as the best advisable non-operative option for Achilles tendinopathy as equivalent alternative to the most commonly used eccentric loading rehabilitation program. However, potential was shown by the combination of different substances administered with physical therapy.

RESEARCH

There is a need for more long-term investigations, studying large enough cohort with standardized scores and evaluations shared by all the investigations to confirm the healing potential, and provide a stronger statistical comparison of the available treatments.

Mesenchymal stem cells modulate release of matrix proteins from tendon surfaces in vitro: a potential beneficial therapeutic effect

AIM

Injury of tendons contained within a synovial environment, such as joint, bursa or tendon sheath, frequently fails to heal and releases matrix proteins into the synovial fluid, driving inflammation. This study investigated the effectiveness of cells to seal tendon surfaces and provoke matrix synthesis as a possible effective injectable therapy.

MATERIALS & METHODS

Equine flexor tendon explants were cultured overnight in suspensions of bone marrow and synovium-derived mesenchymal stems cells and, as controls, two sources of fibroblasts, derived from tendon and skin, which adhered to the explants. Release of the most abundant tendon extracellular matrix proteins into the media was assayed, along with specific matrix proteins synthesis by real-time PCR.

RESULTS

Release of extracellular matrix proteins was influenced by the coating cell type. Fibroblasts from skin and tendon appeared less capable of preventing the release of matrix proteins than mesenchymal stems cells.

CONCLUSION

The source of cell is an important consideration for cell therapy.

American Medical Society for Sports Medicine position statement: interventional musculoskeletal ultrasound in sports medicine

The use of diagnostic and interventional ultrasound has significantly increased over the past decade. A majority of the increased utilization is by nonradiologists. In sports medicine, ultrasound is often used to guide interventions such as aspirations, diagnostic or therapeutic injections, tenotomies, releases, and hydrodissections. This American Medical Society for Sports Medicine (AMSSM) position statement critically reviews the literature and evaluates the accuracy, efficacy, and cost-effectiveness of ultrasound-guided injections in major, intermediate, and small joints, and soft tissues, all of which are commonly performed in sports medicine. New ultrasound-guided procedures and future trends are also briefly discussed. Based on the evidence, the official AMSSM position relevant to each subject is made.

American Medical Society for Sports Medicine (AMSSM) position statement: interventional musculoskeletal ultrasound in sports medicine

BACKGROUND

The use of diagnostic and interventional ultrasound has significantly increased over the past decade. A majority of the increased utilisation is by non-radiologists. In sports medicine, ultrasound is often used to guide interventions such as aspirations, diagnostic or therapeutic injections, tenotomies, releases and hydrodissections.

OBJECTIVE

Critically review the literature related to the accuracy, efficacy and cost-effectiveness of ultrasound-guided injections (USGIs) in major, intermediate and small joints; and soft tissues.

DESIGN

Systematic review of the literature.

RESULTS

USGIs are more accurate than landmark-guided injections (LMGIs; strength of recommendation taxonomy (SORT) Evidence Rating=A). USGIs are more efficacious than LMGIs (SORT Evidence Rating=B). USGIs are more cost-effective than LMGIs (SORT Evidence Rating=B). Ultrasound guidance is required to perform many new procedures (SORT Evidence Rating=C).

CONCLUSIONS

The findings of this position statement indicate there is strong evidence that USGIs are more accurate than LMGI, moderate evidence that they are more efficacious and preliminary evidence that they are more cost-effective. Furthermore, ultrasound-guided (USG) is required to perform many new, advanced procedures and will likely enable the development of innovative USG surgical techniques in the future.

A review on the use of cell therapy in the treatment of tendon disease and injuries

Tendon disease and injuries carry significant morbidity worldwide in both athletic and non-athletic populations. It is estimated that tendon injuries account for 30%−50% of all musculoskeletal injuries globally. Current treatments have been inadequate in providing an accelerated process of repair resulting in high relapse rates. Modern concepts in tissue engineering and regenerative medicine have led to increasing interest in the application of cell therapy for the treatment of tendon disease. This review will explore the use of cell therapy, by bringing together up-to-date evidence from in vivo human and animal studies, and discuss the issues surrounding the safety and efficacy of its use in the treatment of tendon disease.

Repairing damaged tendon and muscle: are mesenchymal stem cells and scaffolds the answer?

Mesenchymal stem cells (MSCs) have become an area of intense interest in the treatment of musculoskeletal conditions, such as muscle and tendon injury, as various animal and human trials have demonstrated that implantation with MSCs leads to improved healing and function. However, these trials have usually been relatively small scale and lacking in adequate controls. Additionally, the optimum source of these cells has yet to be determined, partly due to a lack of understanding as to how MSCs produce their beneficial effects when implanted. Scaffolds have been shown to improve tissue-engineering repairs but require further work to optimize their interactions with both native tissue and implanted MSCs. Robust, well-controlled trials are therefore required to determine the usefulness of MSCs in musculoskeletal tissue repair.

The gap between the physiological and therapeutic roles of mesenchymal stem cells

Several investigators have cultivated marrow stromal cells and have identified a population of mesenchymal stem cells (MSCs). These cells expand extensively in vitro and exhibit multilineage differentiation potential. The lack of MSC-specific markers impedes identification of MSC functions. Further in vivo studies of these cells may elucidate the nature of MSCs. Although the nature of MSCs remains unclear, nonclonal stromal cultures are used as a source of putative MSCs for therapeutic purposes. Preclinical studies and clinical trials assumed that transplanted MSCs exert their effects through their differentiation properties or through the release of molecules that restore tissue functions and modulate immune cells. These studies reported contradictory results and failed to meet expectations. Thus, it is important to note that current protocols for MSC therapy are primarily based on the use of in vitro expanded nonclonal MSCs. Clearly defining the physiological features of in situ MSCs and the in vitro and in vivo properties of nonclonal cultures of stromal cells, which are often misidentified as pure stem cell cultures, may explain the reported failures of MSC therapy. This review will address these issues.

Alteration of skin properties with autologous dermal fibroblasts

Dermal fibroblasts are mesenchymal cells found between the skin epidermis and subcutaneous tissue. They are primarily responsible for synthesizing collagen and glycosaminoglycans; components of extracellular matrix supporting the structural integrity of the skin. Dermal fibroblasts play a pivotal role in cutaneous wound healing and skin repair. Preclinical studies suggest wider applications of dermal fibroblasts ranging from skin based indications to non-skin tissue regeneration in tendon repair. One clinical application for autologous dermal fibroblasts has been approved by the Food and Drug Administration (FDA) while others are in preclinical development or various stages of regulatory approval. In this context, we outline the role of fibroblasts in wound healing and discuss recent advances and the current development pipeline for cellular therapies using autologous dermal fibroblasts. The microanatomic and phenotypic differences of fibroblasts occupying particular locations within the skin are reviewed, emphasizing the therapeutic relevance of attributes exhibited by subpopulations of fibroblasts. Special focus is provided to fibroblast characteristics that define regional differences in skin, including the thick and hairless skin of the palms and soles as compared to hair-bearing skin. This regional specificity and functional identity of fibroblasts provides another platform for developing regional skin applications such as the induction of hair follicles in bald scalp or alteration of the phenotype of stump skin in amputees to better support their prosthetic devices.

Efficacy of tendon stem cells in fibroblast-derived matrix for tendon tissue engineering

BACKGROUND AIMS

After injury, tendons often heal with poor tissue quality and inferior mechanical properties. Tissue engineering using tendon stem cells (TSCs) is a promising approach in the repair of injured tendon. Tenogenic differentiation of TSCs needs an appropriate environment. More recently, the acellular extracellular matrix (ECM) generated from fibroblasts has been used to construct various engineering tissues. In this study, we successfully developed an engineered tendon tissue formed by seeding TSCs in de-cellularized fibroblast-derived matrix (dFM).

METHODS

Patellar TSCs and dermal fibroblast were isolated and cultured. Using the method of osmotic shock, dFM was obtained from dermal fibroblast. ECM proteins in dFM were examined. TSCs at passage 3 were seeded in dFM for 1 week. Proliferative capacity and characterization of TSCs cultured in dFM were determined by population doubling time, immunofluorescence staining and quantitative reverse transcriptase polymerase chain reaction. Engineered tendon tissue was prepared with dFM and TSCs. Its potentials for neo-tendon formation and promoting tendon healing were investigated.

RESULTS

dFM is suitable for growth and tenogenic differentiation of TSCs in vitro. Neo-tendon tissue was formed with tendon-specific protein expression when TSCs were implanted together with dFM. In a patellar tendon injury model, implantation of engineered tendon tissue significantly improved the histologic and mechanical properties of injured tendon.

CONCLUSIONS

The findings obtained from our study provide a basis for potential use of engineered tendon tissue containing dFM and TSCs in tendon repair and regeneration.

Tendinopathy: a review of the pathophysiology and evidence for treatment

The understanding of tendinopathy has evolved over the past several decades. Initially thought to be a primarily inflammatory process, histologic evaluation has revealed that there is an absence of inflammatory cells, and rather, tendinopathy is more of a degenerative process. Various types of medications, rehabilitation, modalities, injections, and minimally invasive procedures have been described as treatment for this condition. The purpose of our article is to describe the pathophysiology of tendinopathy as currently understood and the evidence for the various available treatments. We performed a literature search to determine the types of reviews that have been performed previously regarding treatment for tendinopathy, and summarized these reviews. We then performed a systematic review of randomized controlled trials for treating patients with tendinopathy. It is our hope that our review of trial data will help providers to determine optimal management for their patients with tendinopathy.

Biologics in the management of rotator cuff surgery

The rotator cuff enthesis is not reestablished after a rotator cuff repair. Instead, a scar-mediated healing response occurs at the tendon-bone interface, which is notably weaker than the native enthesis and thus more prone to failure. Biological augmentation through growth factors, AASs, biomimetic scaffolds, or siRNA therapy has the potential to enhance the healing response. The ultimate key, however, is in determining which of these enables a more regenerative healing response of the native tissue rather than enhanced production of scar tissue. In addition, the optimal combination of factors, dosing, and delivery methods remains to be clearly elucidated. Biological augmentation and tissue engineering for tendon healing remains promising, but much work still needs to be done.

Autologous fibroblast transplantation at the vesico-ureteral junction as potential reconstructive cell replacement in an animal model

PURPOSE

To evaluate the cellular survival of donor fibroblasts after transplantation at the vesico-ureteral junction (VUJ) and to analyse their potential for reconstructive cell replacement in an animal model as autologous fibroblasts have been used as soft tissue augmentation material for scared and damaged tissue.

METHODS

Muscles biopsies were procured from the lower limb muscles of 4 pigs; cytoplasm of fibroblasts was labelled with nano-sized iron oxide particles. Six weeks after taking of the muscle biopsies, fibroblast transplantation was performed, 3 × 10(6) cells suspended in transplantation medium (in 1-ml syringes) were injected at the VUJ using the modified STING technique. Animals were killed 8 weeks later; seeded fibroblasts were identified using prussian blue staining protocol; histological evaluation and morphological analysis were performed by light microscopy (Mayer's haematoxylin-eosin staining); and bladders were scanned by MRI for visualization and localization of the iron-labelled donor cells.

RESULTS

Donor fibroblast cell colonization and cellular viability at the VUJ was demonstrated by MRI and histochemically indicating cellular uptake of iron particles at the VUJ. It was also evident that transplanted fibroblasts integrate into the extracellular matrix of the distal ureter augmenting ureteral host tissue.

CONCLUSIONS

Labelled implanted autologous fibroblasts were visualized by staining procedure as well as MRI scan demonstrating persistence at the VUJ, suggesting that in vitro expanded fibroblasts survived in vivo after transplantation.

Mesenchymal stromal cells and fibroblasts: a case of mistaken identity?

The plastic-adherent fibroblast-looking cells that can be isolated and culture-expanded from bone marrow and many other tissues are widely known as mesenchymal stromal cells (MSC). In addition to their fibroblast-like morphology, they are characterized by a panel of cell-surface markers and their potential to differentiate into bone, fat and cartilage. Based on their intriguing immunomodulatory and regenerative properties, MSC are being investigated as cellular therapeutics for a variety of clinical indications. However, many questions regarding the true identity and functionality of these cells in vivo remain unanswered. Fibroblasts, known for a much longer time but still poorly characterized, are also considered to be a ubiquitous stromal element of almost all tissues and are believed to play a role in tissue homeostasis. Despite the presence of MSC and fibroblasts in almost all tissues, similar morphology and other shared characteristics, the exact relationship between MSC and fibroblasts has remained undetermined. In this review, based on recent and old, but often neglected, literature it is suggested that ex vivo culture-expanded MSC and fibroblasts are indistinguishable by morphology, cell-surface markers, differentiation potential and immunologic properties.