The role of stem cells and tissue engineering in orthopaedic sports medicine: current evidence and future directions

Enhancing regenerative potential: A comprehensive review of stem cell transplantation for sports-related neuronal injuries, with a focus on spinal cord injuries and peripheral nervous system damage

Neuronal injuries, as one of the consequences of sports-related incidents, exert a profound influence on the athletes' future, potentially leading to complete immobility and impeding their athletic pursuits. In cases of severe damage inflicted upon the spinal cord (SC) and peripheral nervous systems (PNS), the regenerative process is notably compromised, rendering it essentially inefficient. Among the pivotal therapeutic approaches for the enhancement and prevention of secondary SC injuries (SCI), stem cell transplantation (SCT) stands out prominently. Stem cells, whether directly involved in replacement and reconstruction or indirectly through modification and secretion of crucial bioenvironmental factors, engage in the intricate process of tissue regeneration. Stem cells, through the secretion of neurotrophic factors (NTFs) (aiming to modulate the immune system), reduction of inflammation, axonal growth stimulation, and myelin formation, endeavor to facilitate the regeneration of damaged SC tissue. The fundamental challenges of this approach encompass the proper selection of suitable stem cell candidates for transplantation and the establishment of an appropriate microenvironment conducive to SC repair. In this article, an attempt has been made to explore sports-related injuries, particularly SCI, to comprehensively review innovative methods for treating SCI, and to address the existing challenges. Additionally, some of the stem cells used in neural injuries and the process of their utilization have been discussed.

Editorial Commentary: Tissue Engineering of the Meniscus: Are We at the Point That if Something Looks Like a Meniscus, We Can Call It a Meniscus?

It was thought that the meniscus together with articular cartilage would be among the first tissues to successfully engineer. However, despite extensive research in the field, this path was proven not to be easy. Tissue engineering of musculoskeletal tissues remains promising, and several advancements have further identified the role of biological treatments in meniscus repair and regeneration. To move forward, and advance from being promising to being forthcoming, an important step would be to improve the quality of presented studies. This editorial commentary proposes a checklist of necessary reported data for tissue engineering studies: macroscopic and histologic appearance, tissue composition, mechanical properties, and translational data.

Effect of Intraoperative Platelet-Rich Plasma Treatment on Postoperative Donor Site Knee Pain in Patellar Tendon Autograft Anterior Cruciate Ligament Reconstruction: A Double-Blind Randomized Controlled Trial

BACKGROUND

Donor site morbidity in the form of anterior knee pain is a frequent complication after bone-patellar tendon-bone (BPTB) autograft anterior cruciate ligament (ACL) reconstruction. Hypothesis/Purpose: The purpose was to examine the effect of the intraoperative administration of platelet-rich plasma (PRP) on postoperative kneeling pain. It was hypothesized that PRP treatment would reduce knee pain.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

Fifty patients (mean ± SD age, 30 ± 12 years) undergoing BPTB ACL autograft reconstruction were randomized to the PRP (n = 27) or sham (n = 23) treatment. In either case, 10 mL of venous blood was drawn before the induction of anesthesia and either discarded (sham) or processed (PRP) for preparation of a PRP gel to be later mixed with donor site bone chips and inserted into the patellar defect. At 12 weeks, 6 months, 1 year, and 2 years after surgery, patients completed International Knee Documentation Committee (IKDC) forms and visual analog scale pain scores for activities of daily living and kneeling. Healing indices at the donor site were assessed by routine noncontrast magnetic resonance imaging (MRI) at 6 months. Mixed-model analysis of variance was used to assess the effect of PRP on patient symptoms and MRI indices of donor site healing, as measured by the width of the donor site defect.

RESULTS

Kneeling pain, pain with activities of daily living, and IKDC scores were not different between treatment groups at any of the time intervals ( P = .08-.83). Kneeling pain improved from 12 weeks to 6 months and from 1 to 2 years ( P < .05). IKDC scores improved substantially from 12 weeks to 6 months ( P < .001) and continued to improve to 2 years (PRP, 86 ± 19; sham, 89 ± 10). MRI indices of donor site healing were not different between treatment groups ( P = .53-.90).

CONCLUSION

Whether randomized to receive PRP in their patellar defect or not, patients continued to have similar levels of kneeling pain and patellar defect sizes after autograft BPTB ACL reconstruction. Registration: NCT01765712 ( ClinicalTrials.gov identifier).

Factors affecting articular cartilage repair after open-wedge high tibial osteotomy

BACKGROUND

To evaluate the factors that affect articular cartilage repair after open-wedge high tibial osteotomy (OWHTO) and the relationship between regeneration of articular cartilage repair and clinical outcomes.

METHODS

Among the cases of OWHTO that were performed from March 2005 to February 2012, the patients who followed up for >2years and received a second-look arthroscopy were retrospectively reviewed. For clinical evaluation, the Knee Society scores and Western Ontario and McMaster Universities Osteoarthritis Index score were measured. For radiologic evaluation, the Kellgren-Lawrence scale, mechanical femorotibial angle, and joint line obliquity were used. In the initial and second-look arthroscopy, the status of the articular cartilage of the medial compartment was evaluated.

RESULTS

A total of 62 knees (61 patients) were included in this study. Articular cartilage repair was observed in 18 knees (29.0%). In multiple logistic regression analysis, patients with Kellgren-Lawrence Grade 4 (OR 0.076; 95% CI 0.007-0.822; P=0.034), the existence of a bipolar lesion (OR 0.108; 95% CI 0.016-0.724; P=0.022), or joint line obliquity >5° (OR 0.109; 95% CI 0.013-0.936; P=0.043) had significantly lower odds of articular cartilage repair compared to the corresponding counter group. In a comparison of clinical outcomes between a group that had articular cartilage repair and a group without repair, no significant difference was observed (P>0.05).

CONCLUSIONS

Severe arthrosis, existence of a bipolar lesion, and marked postoperative joint line obliquity had a negative impact on articular cartilage repair after OWHTO. However, articular cartilage repair showed unknown clinical significance.

Single- Versus Multiple-Site Harvesting Techniques for Bone Marrow Concentrate: Evaluation of Aspirate Quality and Pain

BACKGROUND

Bone marrow concentrate (BMC) is growing in popularity as an alternative treatment option in orthopaedics. The regenerative capacity of BMC has been linked to the number of mesenchymal stem cells (MSCs) present in the graft at the time of its clinical application. MSC counts in bone marrow aspirate (BMA) are affected by harvest technique, but controversy exists over which aspiration method optimizes cellular yield while taking patient comfort and risk into consideration.

PURPOSE

To compare a single- versus multiple-site bone marrow aspiration technique to determine which would generate a sufficient volume of high-quality BMA for concentration into a BMC graft. The level of pain experienced by the patient was monitored, since patient comfort should be included in the determination of a safe and effective aspiration technique.

STUDY DESIGN

Controlled laboratory study and cohort study; Level of evidence, 2.

METHODS

BMC samples from 6 patients were sent to an outside source for laboratory analysis. All 6 participants underwent bilateral bone marrow aspiration. Each patient received both techniques at the posterior iliac crest: one side underwent a multiple-site aspiration technique, and the contralateral side underwent a single-site technique with needle redirection. BMA and BMC samples were analyzed for concentrations white blood cells, total nucleated cells, red blood cells, neutrophils, and hematopoietic stem cells. One BMC sample was cultured, and MSC analysis was performed via flow cytometry. All patients underwent monitoring of pain scores during and after the procedure through a visual analog pain scale at 24 hours, 72 hours, and 7 days after BMA.

RESULTS

No significant difference was found between the cell ratios of the single- and multiple-site groups. Both aspiration techniques were found to provide ample colony-forming units without a marked difference in appearance. Additionally, no significant difference was found between groups with regard to MSC numbers. Pain during and 24 hours after the procedure was significantly greater with the multiple-site method than the single-insertion method.

CONCLUSION

The single-insertion method produced final cellular concentrations and culture results that were not significantly different from those of a multiple-insertion method. Additionally, the single-insertion site technique was significantly less painful to the patient at the time of the procedure as well as 24 hours after aspiration.

CLINICAL RELEVANCE

The results of this study indicated that a high-quality bone marrow aspirate is possible with a single-stick aspiration method.

Clinical efficacy and safety of mesenchymal stem cell transplantation for osteoarthritis treatment: A meta-analysis

Purpose

The aim of this study was to evaluate the therapeutic efficacy and safety of mesenchymal stem cells (MSCs) for the treatment of patients with knee osteoarthritis (OA).

Materials

We performed a meta-analysis of relevant published clinical studies. An electronic search was conducted for randomized controlled trials (RCTs) of MSC-based therapy in knee OA. The visual analogue scale (VAS), International Knee Documentation Committee (IKDC) form, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Lequesne algofunctional indices (Lequesne), Lysholm knee scale (Lysholm), Tegner activity scale (Tegner) and adverse events (AEs) were evaluated.

Results

Eleven eligible trials with 582 knee OA patients were included in the present meta-analysis. We demonstrated that MSC treatment could significantly decrease VAS and increase IKDC scoresafter a 24-month follow-up compared with controls (P<0.05). MSC therapy also showed significant decreases in WOMAC and Lequesne scores after the 12-month follow-up (P<0.01). Analysis of Lysholm (24-month) and Tegner (12- and 24-month) scores also demonstrated favorable results for MSC treatment (P<0.05).

Conclusion

Overall, MSC transplantation treatment was shown to be safe and has great potential as an efficacious clinical therapy for patients with knee OA.

Editorial Commentary: Thinking "Inside the Box" Yields the Possibility of Harvesting Stem Cells From "Inside the Injured Knee"

Looking to the injured knee for potential stem cell harvesting has attractive benefits. Stem cells can be successfully harvested but the concentrations with the current technology are lower than bone marrow or lipoaspirate sites. The technique of utilizing the knee effusion and tissue by-products after cruciate ligament injury shows future promise.

Cogels of Hyaluronic Acid and Acellular Matrix for Cultivation of Adipose-Derived Stem Cells: Potential Application for Vocal Fold Tissue Engineering

Stem cells based tissue engineering has been one of the potential promising therapies in the research on the repair of tissue diseases including the vocal fold. Decellularized extracellular matrix (DCM) as a promising scaffold has be used widely in tissue engineering; however, it remained to be an important issue in vocal fold regeneration. Here, we applied the hydrogels (hyaluronic acid [HA], HA-collagen [HA-Col], and HA-DCM) to determine the effects of hydrogel on the growth and differentiation of human adipose-derived stem cells (hADSCs) into superficial lamina propria fibroblasts. hADSCs were isolated and characterized by fluorescence-activated cell sorting. The results indicated that HA-DCM hydrogel enhanced cell proliferation and prolonged cell morphology significantly compared to HA and HA-Col hydrogel. Importantly, the differentiation of hADSCs into fibroblasts was also promoted by cogels of HA-Col and HA-DCM significantly. The differentiation of hADSCs towards superficial lamina propria fibroblasts was accelerated by the secretion of HGF, IL-8, and VEGF, the decorin and elastin expression, and the synthesis of chondroitin sulfate significantly. Therefore, the cogel of HA-DCM hydrogel was shown to be outstanding in apparent stimulation of hADSCs proliferation and differentiation to vocal fold fibroblasts through secretion of important growth factors and synthesis of extracellular matrix.

First, Do No Harm: Protect the Articular Cartilage When Performing Arthroscopic Knee Surgery!

It is not uncommon to damage the articular surface when performing routine arthroscopic surgical procedures of the knee. The article reviews the background, literature, and technique of performing a partial medial collateral ligament release in a tight knee when attempting to access the posterior medial compartment.

Secreted trophic factors of mesenchymal stem cells support neurovascular and musculoskeletal therapies

Adult mesenchymal stem cells (MSCs) represent a subject of intense experimental and biomedical interest. Recently, trophic activities of MSCs have become the topic of a number of revealing studies that span both basic and clinical fields. In this review, we focus on recent investigations that have elucidated trophic mechanisms and shed light on MSC clinical efficacy relevant to musculoskeletal applications. Innate differences due to MSC sourcing may play a role in the clinical utility of isolated MSCs. Pain management, osteochondral, nerve, or blood vessel support by MSCs derived from both autologous and allogeneic sources have been examined. Recent mechanistic insights into the trophic activities of these cells point to ultimate regulation by nitric oxide, nuclear factor-kB, and indoleamine, among other signaling pathways. Classic growth factors and cytokines-such as VEGF, CNTF, GDNF, TGF-β, interleukins (IL-1β, IL-6, and IL-8), and C-C ligands (CCL-2, CCL-5, and CCL-23)-serve as paracrine control molecules secreted or packaged into extracellular vesicles, or exosomes, by MSCs. Recent studies have also implicated signaling by microRNAs contained in MSC-derived exosomes. The response of target cells is further regulated by their microenvironment, involving the extracellular matrix, which may be modified by MSC-produced matrix metalloproteinases (MMPs) and tissue inhibitor of MMPs. Trophic activities of MSCs, either resident or introduced exogenously, are thus intricately controlled, and may be further fine-tuned via implant material modifications. MSCs are actively being investigated for the repair and regeneration of both osteochondral and other musculoskeletal tissues, such as tendon/ligament and meniscus. Future rational and effective MSC-based musculoskeletal therapies will benefit from better mechanistic understanding of MSC trophic activities, for example using analytical "-omics" profiling approaches.

Tissue Engineering in Orthopaedics

➤It is important to carefully select the most appropriate combination of scaffold, signals, and cell types when designing tissue engineering approaches for an orthopaedic pathology.➤Although clinical studies in which the tissue engineering paradigm has been applied in the treatment of orthopaedic diseases are limited in number, examining them can yield important lessons.➤While there is a rapid rate of new discoveries in the basic sciences, substantial regulatory, economic, and clinical issues must be overcome with more consistency to translate a greater number of technologies from the laboratory to the operating room.

Combined effects of engineered tendon matrix and GDF-6 on bone marrow mesenchymal stem cell-based tendon regeneration

OBJECTIVES

To examine whether an engineered tendon matrix (ETM) environment and growth and differentiation factor-6 (GDF-6) have synergistic effects on the tenogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and the quality of tendon repair.

RESULTS

ETM and GDF-6 promote tenogenic differentiation of BMSCs in vitro. Implantation of GDF-6-incorporated ETM containing BMSCs into a tendon injury model significantly improved the histological and mechanical properties of the repaired tendon.

CONCLUSIONS

GDF-6-incorporated ETM containing BMSCs represents a promising strategy for tendon injury repair.

Editorial Commentary: "All That Glitters Is Not Gold"

For the treatment of osteochondral lesions of the talus, the addition of concentrated bone marrow aspirate to marrow stimulation procedures results in repair tissue that, by magnetic resonance imaging, appears to be similar to native articular cartilage. But, functional outcomes are no different when compared with marrow stimulation alone. Moreover, the true "gold" is that the repair tissue not only has the magnetic resonance imaging appearance of native articular cartilage but also should have the same organizational structure and composition so that it may function like native articular cartilage.

Editorial Commentary: Microfracture for Focal Cartilage Defects: Is the Hip Like the Knee?

Reading about microfracture for focal cartilage defects of the hip, we ponder whether the hip resembles the knee with regard to focal cartilage defects. Minimally invasive microfracture has been a first-line therapy for focal cartilage defects. Microfracture results in fibrous cartilage and unpredictable repair volume, which could be better than absent cartilage, particularly if knee symptoms abate. However, of late, microfracture is not recommended because destruction of subchondral anatomy may result in subchondral cyst formation.

Editorial Commentary: Effects of PRP on Cartilage Repair Using Scaffolds Are Inconclusive

Effects of PRP on cartilage repair using scaffolds are, in the clinical setting, inconclusive. Biologics research is confounded by the variety and heterogeneity of stem cells, scaffolds, PRP preparations, other growth factors, and other biological stimulants.

Editorial commentary: tissue engineering in knee arthroscopic and related surgery

Stem cells are guided by scaffolds, induced by growth factors, and stimulated by biomechanical forces, with a goal of engineering clinically competent cartilage, meniscus, tendon, or ligament tissue. Translational research, to move us from the preclinical to the clinical phase, is today necessary.

Editorial commentary: meniscal allograft yields acceptable outcomes (for a salvage procedure)

Meniscal allograft, for proper indications, shows adequate outcomes (for a salvage procedure). Addition of biologics (growth factors and cells) may improve future outcomes, and ultimately a tissue-engineered solution is anticipated, but in the end, host articular cartilage pathology may be a significant confounder of outcome.

Editorial commentary: collagen meniscal scaffolds

Small collagen meniscal scaffolds are a treatment for partial meniscectomy, which is clinically much more common than subtotal or total meniscectomy. The scaffold alone shows promising results, but readers must be mindful of risk of bias in the literature. Addition of stem cells and growth factors is the next step in meniscal tissue engineering.

Editorial commentary: synthetic ACL grafts are more important than clinical nonbelievers may realize

Artificial ACL grafts are structural ties, designed to resist tension, but not designed to undergo biologic ligamentization by the host. Strategically, an artificial ACL graft may be used as reinforcement to augment ACL repair, ACL autograft, ACL allograft, or tissue-engineered ACL. Most artificial ACL grafts have had poor reported outcomes. However, the Ligament Augmentation and Reconstruction System (LARS) artificial ACL graft shows positive clinical outcomes.