Use of Human Placenta-Derived Cells in a Preclinical Model of Tendon Injury

Viable tendon neotissue from adult adipose-derived multipotent stromal cells

Background: Tendon healing is frequently prolonged, unpredictable, and results in poor tissue quality. Neotissue formed by adult multipotent stromal cells has the potential to guide healthy tendon tissue formation. Objectives: The objective of this study was to characterize tendon neotissue generated by equine adult adipose-derived multipotent stromal cells (ASCs) on collagen type I (COLI) templates under 10% strain in a novel bioreactor. The tested hypothesis was that ASCs assume a tendon progenitor cell-like morphology, express tendon-related genes, and produce more organized extracellular matrix (ECM) in tenogenic versus stromal medium with perfusion and centrifugal fluid motion. Methods: Equine ASCs on COLI sponge cylinders were cultured in stromal or tenogenic medium within bioreactors during combined perfusion and centrifugal fluid motion for 7, 14, or 21 days under 10% strain. Viable cell distribution and number, tendon-related gene expression, and micro- and ultra-structure were evaluated with calcein-AM/EthD-1 staining, resazurin reduction, RT-PCR, and light, transmission, and scanning electron microscopy. Fibromodulin was localized with immunohistochemistry. Cell number and gene expression were compared between culture media and among culture periods (p < 0.05). Results: Viable cells were distributed throughout constructs for up to 21 days of culture, and cell numbers were higher in tenogenic medium. Individual cells had a round or rhomboid shape with scant ECM in stromal medium in contrast to clusters of parallel, elongated cells surrounded by highly organized ECM in tenogenic medium after 21 days of culture. Transcription factor, extracellular matrix, and mature tendon gene expression profiles confirmed ASC differentiation to a tendon progenitor-like cell in tenogenic medium. Construct micro- and ultra-structure were consistent with tendon neotissue and fibromodulin was present in the ECM after culture in tenogenic medium. Conclusion: Long-term culture in custom bioreactors with combined perfusion and centrifugal tenogenic medium circulation supports differentiation of equine adult ASCs into tendon progenitor-like cells capable of neotissue formation.

Preclinical assessment of IL-1β primed human umbilical cord mesenchymal stem cells for tendon functional repair through TGF-β/IL-10 signaling

Background

Inadequate repair capacity and disturbed immune compartments are the main pathological causes of tendinopathy. Transplantation of mesenchymal stem cells (MSCs) become an effective clinic option to alleviate tendinopathy. Interleukin-1β (IL-1β) could confer on MSCs enhanced immunoregulatory capability to remodel the repair microenvironment favoring tissue repair. Therefore, IL-1β activated UC-MSCs (1βUC-MSCs) may exert favorable efficacy in promoting tendon repair in a preclinical tendinopathy rat model.

Methods

Tendon-derived stem cells (TDSCs) were isolated and characterized. In vitro, the levels of immunoregulatory-related cytokines such as IL-1β, IL-6, IL-10, and TGF-β secreted by 1βUC-MSCs and unprimed UC-MSCs was measured. And tendon-specific markers expressed by TDSCs cultured with primed cultured medium (CM) or unprimed CM were detected. In vivo, Achilles tendinopathy was induced by 30 μL collagenase I injection in Sprague Dawley rats. One week later, the rats were randomly injected with UC-MSCs primed with IL-1β (106 cells per tendon), UC-MSCs, or PBS. After rats were sacrificed, histological evaluation, electron microscopy, biomechanical tests, gait performance were conducted to evaluate the structural and functional recovery of Achilles tendons. The inflammation and metabolic state of the extracellular matrix, and the potential mechanism were assessed by immunohistochemical staining and Western blot.

Results

UC-MSCs were activated by IL-1β to secrete higher levels of IL-10 and TGF-β while the secretion levels of IL-6 and IL-1β were not changed significantly, promoting a higher expression level of COL I and TNMD in TDSCs under proinflammatory environment. In vivo, the transplanted 1βUC-MSCs could survive up to 5 weeks after injection with tenogenic differentiation and improved tendon healing histologically semi-quantified by modified Bonar scores. This structural regeneration was further confirmed by observation of ultrastructural morphology, and led to good functional recovery including improved biomechanical properties and gait performance. During this process, the inflammatory response and metabolism of the extracellular matrix was improved through TGF-β/IL-10 pathway.

Conclusion

This study demonstrated that the transplantation of UC-MSCs activated by IL-1β exhibited satisfactory ability for promoting tendon functional repair in a tendinopathy rat model. During this process, the balance of inflammatory response and extracellular matrix metabolism was remodeled, and the TGF-β/Smad2/3 and IL-10 signaling pathways were activated simultaneously. We cautiously conclude that the IL-1β primed UC-MSCs could be a promising strategy for enhancing the ability of MSCs to treat tendinopathy.

Comparison of Regenerative Injection Therapy and Conventional Therapy for Proximal Plantar Fasciitis

Treatment of subacute and chronic heel pain often presents a unique challenge to the physician. Regenerative therapies, such as injectable amnion and connective tissue matrix, may represent a promising new approach in these patients, and have become increasingly popular in the United States. However, little literature exists evaluating these injections compared to conventional nonoperative means. As such, we designed a retrospective comparative study evaluating patients in our practice who received a standardized plantar fascial treatment protocol only (standard therapy), and those who received regenerative plantar fascial injections in addition to standard therapy. A total of 54 patients were followed over a 3-month observation period (91.7 ± 73.9 days), with numeric pain rating (NPR) serving as the primary outcome. Both groups saw an improvement in NPR at the end of the observation period, but patients in the regenerative therapy group demonstrated lower pain scores than those receiving standard therapy alone (mean NPR 2.1 ± 2.3 vs 4.4 ± 2.8, p = .004). Additionally, those in the standard therapy group were significantly more likely to proceed onto surgical intervention compared to the regenerative therapy group (unadjusted odds ratio 15.6, 95% CI 3.0-27.9). The use of regenerative injections for subacute and chronic plantar fasciitis showed promise in our study, and may help mitigate against the need for invasive surgical intervention.

Intermittent parathyroid hormone increases stability and improves osseointegration of initially unstable implants

Aims

To develop an early implant instability murine model and explore the use of intermittent parathyroid hormone (iPTH) treatment for initially unstable implants.

Methods

3D-printed titanium implants were inserted into an oversized drill-hole in the tibiae of C57Bl/6 mice (n = 54). After implantation, the mice were randomly divided into three treatment groups (phosphate buffered saline (PBS)-control, iPTH, and delayed iPTH). Radiological analysis, micro-CT (µCT), and biomechanical pull-out testing were performed to assess implant loosening, bone formation, and osseointegration. Peri-implant tissue formation and cellular composition were evaluated by histology.

Results

iPTH reduced radiological signs of loosening and led to an increase in peri-implant bone formation over the course of four weeks (timepoints: one week, two weeks, and four weeks). Observational histological analysis shows that iPTH prohibits the progression of fibrosis. Delaying iPTH treatment until after onset of peri-implant fibrosis still resulted in enhanced osseointegration and implant stability. Despite initial instability, iPTH increased the mean pull-out strength of the implant from 8.41 N (SD 8.15) in the PBS-control group to 21.49 N (SD 10.45) and 23.68 N (SD 8.99) in the immediate and delayed iPTH groups, respectively. Immediate and delayed iPTH increased mean peri-implant bone volume fraction (BV/TV) to 0.46 (SD 0.07) and 0.34 (SD 0.10), respectively, compared to PBS-control mean BV/TV of 0.23 (SD 0.03) (PBS-control vs immediate iPTH, p < 0.001; PBS-control vs delayed iPTH, p = 0.048; immediate iPTH vs delayed iPTH, p = 0.111).

Conclusion

iPTH treatment mediated successful osseointegration and increased bone mechanical strength, despite initial implant instability. Clinically, this suggests that initially unstable implants may be osseointegrated with iPTH treatment.

Cite this article: Bone Joint Res 2022;11(5):260–269.

Intramuscular and intratendinous placenta-derived mesenchymal stromal-like cell treatment of a chronic quadriceps tendon rupture

BACKGROUND

Quadriceps tendon ruptures (QTRs) are rare but debilitating injuries, often associated with chronic metabolic conditions or long-term steroid treatment. While the surgical treatment for acute QTRs is described thoroughly, no common strategy exists for the often frustrating treatment of chronic, reoccurring QTRs. The pro-angiogenic and immunomodulatory properties of placenta-derived adherent mesenchymal stromal-like (PLX-PAD) cells have been described to protect musculoskeletal tissues from inflammation and catabolic cytokine migration, yet little is known about the regenerative potential of PLX-PAD cells in repetitively damaged tendon tissue.

CASE

We report the case of an 80-year-old male patient with a chronic three-time QTR of his right knee. The quadriceps tendon was reconstructed applying a conventional suture anchor repair procedure combined with a synthetic mesh augmentation and additional intramuscular and intratendineous PLX-PAD cell injections as an individualized treatment approach. No adverse events were reported, and excellent radiological and functional outcomes with a passive range of motion of 0/0/120° knee extension-flexion were observed at the 12 month follow-up. Gait analysis confirmed restoration of joint motion, including gait speed, deficit in step length, and knee extensor muscle strength (pre-surgery: 0.98 m/s, 40 cm, 42.4 ± 12.4 N; 9 months post-surgery: 1.07 m/s, 0 cm, 10.4 ± 18.9 N) as well as hyperextension throughout stance and late swing phases (pre-surgery: -11.2 ± 0.9°; 9 months post-surgery: -2.7 ± 1.6°). Postoperative lymphocyte and cytokine analyses from the patient's peripheral blood serum suggested a systemic short-term immunoregulatory reaction with postoperatively increased interleukin (IL)-6 (pre-surgery: 0.79 pg/mL; day 1: 139.97 pg/mL; day 5: 5.58 pg/mL; 9 months: 1.76 pg/mL) and IL-10 (pre-surgery: 0.9 pg/mL; day 1: 1.21 pg/ mL; day 5: 0.3 pg/mL; 9 months: 0.34 pg/mL) levels that decreased again over time.

CONCLUSIONS

Herein, we demonstrate a successfully treated chronic QTR with a synergistic surgical and biological reconstructive treatment approach. This local add-on treatment with PLX-PAD cells may be considered in specific cases of chronic QTRs, not susceptible to traditional suture anchor procedures and which exhibit a high risk of treatment failure. Further scientific engagement is warranted to explore underlying immunomodulatory mechanisms of action behind PLX-PAD cell treatment for tendon injuries.

Placenta-Expanded Stromal Cell Therapy in a Rodent Model of Simulated Weightlessness

Long duration spaceflight poses potential health risks to astronauts during flight and re-adaptation after return to Earth. There is an emerging need for NASA to provide successful and reliable therapeutics for long duration missions when capability for medical intervention will be limited. Clinically relevant, human placenta-derived therapeutic stromal cells (PLX-PAD) are a promising therapeutic alternative. We found that treatment of adult female mice with PLX-PAD near the onset of simulated weightlessness by hindlimb unloading (HU, 30 d) was well-tolerated and partially mitigated decrements caused by HU. Specifically, PLX-PAD treatment rescued HU-induced thymic atrophy, and mitigated HU-induced changes in percentages of circulating neutrophils, but did not rescue changes in the percentages of lymphocytes, monocytes, natural killer (NK) cells, T-cells and splenic atrophy. Further, PLX-PAD partially mitigated HU effects on the expression of select cytokines in the hippocampus. In contrast, PLX-PAD failed to protect bone and muscle from HU-induced effects, suggesting that the mechanisms which regulate the structure of these mechanosensitive tissues in response to disuse are discrete from those that regulate the immune- and central nervous system (CNS). These findings support the therapeutic potential of placenta-derived stromal cells for select physiological deficits during simulated spaceflight. Multiple countermeasures are likely needed for comprehensive protection from the deleterious effects of prolonged spaceflight.

Growth and Stem Cell Characteristics of Tendon-Derived Cells with Different Initial Seeding Densities: An In Vitro Study in Mouse Flexor Tendon Cells

Tendon stem/progenitor cells (TSPCs) are considered promising seed cells for tendon regeneration. Previous studies reported that a low seeding density favors TSPC growth, whereas a high seeding density favors tenocyte growth. We aimed to distinguish TSPCs from tenocytes by seeding tendon-derived cells at a density gradient. In this study, tendon-derived cells were isolated from flexor digitorum profundus tendons of mice and seeded at the initial densities of 50, 500, 5,000, and 50,000/cm². We found that distinct cell colonies were formed from cells with initial seeding densities of 50 and 500/cm², but colonies were not discernible for cells seeded at 5,000 and 50,000/cm². There was a positive correlation between cell proliferation rate and seeding density, but a negative correlation between cell senescence and seeding density. The cell proliferation rate decreased gradually during serial passages. All cells exhibited restricted differentiation potentials, and expressed stem cell markers and relatively high levels of tenogenic markers without notable differences among cells seeded at different densities. We concluded that a pure population of TSPCs could not be isolated from mouse digital flexor tendons through culturing cells at a density gradient. Cells seeded at low densities had very limited proliferative ability and did not show more prominent stem cell characteristics when compared with cells seeded at high densities.

Spectrum of Tendon Pathologies: Triggers, Trails and End-State

The biggest compartment of the musculoskeletal system is the tendons and ligaments. In particular, tendons are dense tissues connecting muscle to bone that are critical for the integrity, function and locomotion of this system. Due to the increasing age of our society and the overall rise in engagement in extreme and overuse sports, there is a growing prevalence of tendinopathies. Despite the recent advances in tendon research and due to difficult early diagnosis, a multitude of risk factors and vague understanding of the underlying biological mechanisms involved in the progression of tendon injuries, the toolbox of treatment strategies remains limited and non-satisfactory. This review is designed to summarize the current knowledge of triggers, trails and end state of tendinopathies.