Stem and Progenitor Cells for Cartilage Repair: Source, Safety, Evidence, and Efficacy

Multiplex gene editing to promote cell survival using low-pH clustered regularly interspaced short palindromic repeats activation (CRISPRa) gene perturbation

BACKGROUND AIMS

Lower back pain is the leading cause of disability worldwide and is often linked to degenerative disc disease (DDD), the breakdown of intervertebral discs. The majority of treatment options for DDD are palliative, with clinicians prescribing medication or physical therapy to return the patient to work. Cell therapies are promising treatment options with the potential to restore functional physiological tissue and treat the underlying causes of DDD. DDD is characterized by biochemical changes in the microenvironment of the disc, including changes in nutrient levels, hypoxia, and changes in pH. Stem cell therapies are promising therapies to treat DDD, but the acidic environment in a degenerating disc significantly hinders the viability of stem cells, affecting their efficacy. Clustered regularly interspaced short palindromic repeats (CRISPR) systems allow us to engineer cell phenotypes in a well-regulated and controlled manner. Recently, CRISPR gene perturbation screens have assessed fitness, growth and provided a means for specific cell phenotype characterization.

METHODS

In this study, we use a CRISPR-activation (a) gene perturbation screen to identify gene upregulation targets that enhance adipose-derived stem cell survival in acidic culture conditions.

RESULTS

We identified 1213 prospective pro-survival genes and systematically narrowed these down to 20 genes for validation. We further narrowed down our selection to the top five prospective genes using Cell Counting Kit-8 cell viability assays in naïve adipose-derived stem cells and ACAN/Col2 CRISPRa upregulated stem cells. Finally, we examined the extracellular matrix-producing abilities of multiplex ACAN/Col2-pro-survival edited cells in pellet culture.

CONCLUSIONS

Using the results from the CRISPRa screen, we are able to engineer desirable cell phenotypes to improve cell viability for the potential treatment of DDD and other disease states that expose cell therapies to acidic environments, while also providing broader knowledge on genes regulating low-pH cell survival.

Positive early clinical outcomes of bone marrow aspirate concentrate for osteoarthritis using a novel fenestrated trocar

BACKGROUND

This study sought to assess early clinical outcomes for knee osteoarthritis (OA) patients undergoing bone marrow aspirate concentrate (BMAC) treatment using a novel closed-end, fenestrated trocar (FT) that does not require centrifugation.

METHODS

A prospective cohort of 17 knee OA patients undergoing BMAC treatment with the FT system from March 2018 to March 2019 was retrospectively evaluated. Approximately 10 mL of BMAC was harvested, no centrifugation was performed, and the BMAC was injected into the affected knee. Clinical outcomes were assessed at baseline, six weeks, and 12 weeks. This study has no affiliation with/vested-interest in the FT system.

RESULTS

There were significant improvements in nearly all outcomes from baseline to 12 weeks. Specific improvements included Knee Injury and OA Outcome Score (KOOS) activities-of-daily-living (61.1 ± 9.2 [mean ± 95% confidence interval] to 89.3 ± 6, p = 0.001), quality-of-life (32.7 ± 9.3 to 66.1 ± 17.9, p = 0.003), sports/recreation (36.9 ± 10.6 to 72.6 ± 26.3, p = 0.006), and pain (53.8 ± 9.3 to 83 ± 10.2, p = 0.001); Lysholm scores (55.5 ± 8.4 to 77.3 ± 10.5, p = 0.009); and visual analog pain scores (5.68 ± 1.14 to 2.07 ± 1.86, p = 0.003). Individually, at least 75% of patients exhibited improvement in all KOOS categories at six weeks and at least 85% at 12 weeks.

CONCLUSIONS

BMAC treatment with an FT system that does not require centrifugation resulted in significant improvements in early pain and function scores for knee OA. The symptomatic improvements in this study were similar to or greater than what has been reported using traditional needles. These data may provide clinicians with comfort in using an FT system and provide motivation for future randomized-controlled trials comparing aspiration techniques.

Assessment of cartilage regeneration on 3D collagen-polycaprolactone scaffolds: Evaluation of growth media in static and in perfusion bioreactor dynamic culture

Efforts on bioengineering are directed towards the construction of biocompatible scaffolds and the determination of the most favorable microenvironment, which will better support cell proliferation and differentiation. Perfusion bioreactors are attracting growing attention as an effective, modern tool in tissue engineering. A natural biomaterial extensively used in regenerative medicine with outstanding biocompatibility, biodegradability and non-toxic characteristics, is collagen, a structural protein with undisputed beneficial characteristics. This is a study designed according to the above considerations. 3D printed polycaprolactone (PCL) scaffolds with rectangular pores were coated with collagen either as a coating on the scaffold's trabeculae, or as a gel-cell solution penetrating scaffolds' pores. We employed histological, molecular and imaging techniques to analyze colonization, proliferation and chondrogenic differentiation of Adipose Derived Mesenchymal Stem Cells (ADMSCs). Two different differentiation culture media were employed to test chondrogenic differentiation on gelated and non gelated PCL scaffolds in static and in perfusion bioreactors dynamic culture conditions. In dynamic culture, non gelated scaffolds combined with our in house TGF-β₂ based medium, augmented chondrogenic differentiation performance, which overall was significantly less favorable compared to StemPro™ propriety medium. The beneficial mechanical stimulus of dynamic culture, appears to outgrow the disadvantage of the "weaker" TGF-β₂ medium used for chondrogenic differentiation. Even though cells in static culture grew well on the scaffold, there was limited penetration inside the construct, so the purpose of the 3D culture was not fully served. In contrast dynamic culture achieved better penetration and uniform distribution of the cells within the scaffold.

Identification of endogenous migratory MSC-like cells and their interaction with the implant materials guiding osteochondral defect repair

Abundant BMSCs and MSC-like cells move up to the defect area and interact with the implant materials, guiding the osteochondral defect repair.

Osteoarthritis and stem cell therapy in humans: a systematic review

OBJECTIVE

Osteoarthritis (OA) is a leading cause of disability in the world. Mesenchymal stem cells (MSCs) have been studied to treat OA. This review was performed to systematically assess the quality of literature and compare the procedural specifics surrounding MSC therapy for osteoarthritis.

DESIGN

PubMed, CINAHL, EMBASE and Cochrane Central Register of Controlled Trials were searched for studies using MSCs for OA treatment (final search December 2017). Outcomes of interest included study evidence level, patient demographics, MSC protocol, treatment results and adverse events. Level I and II evidence articles were further analyzed.

RESULTS

Sixty-one of 3,172 articles were identified. These studies treated 2,390 patients with osteoarthritis. Most used adipose-derived stem cells (ADSCs) (n = 29) or bone marrow-derived stem cells (BMSCs) (n = 30) though the preparation varied within group. 57% of the sixty-one studies were level IV evidence, leaving five level I and nine level II studies containing 288 patients to be further analyzed. Eight studies used BMSCs, five ADSCs and one peripheral blood stem cells (PBSCs). The risk of bias in these studies showed five level I studies at low risk with seven level II at moderate and two at high risk.

CONCLUSION

While studies support the notion that MSC therapy has a positive effect on OA patients, there is limited high quality evidence and long-term follow-up. The present study summarizes the specifics of high level evidence studies and identifies a lack of consistency, including a diversity of MSC preparations, and thus a lack of reproducibility amongst these articles' methods.

Early Clinical Outcomes of Intra-Articular Injections of Bone Marrow Aspirate Concentrate for the Treatment of Early Osteoarthritis of the Hip and Knee: A Cohort Study

BACKGROUND

Bone marrow aspirate concentrate (BMC) is one of the few cell-based therapies available as a possible biological treatment for early osteoarthritis (OA). Its efficacy, safety, and benefit compared with other treatments are still to be determined.

OBJECTIVE

To assess the clinical outcomes of patients undergoing intra-articular injection of BMC for the treatment of early knee and hip OA.

DESIGN

Prospective, cohort study.

SETTING

Single institution, quaternary level of care.

PATIENTS

Nineteen patients (16 female and 3 male), totaling 25 joints (10 knees, 15 hips), treated with intra-articular BMC for early OA between 2014 and 2016. The mean age at time of the procedure was 58 ± 12.7 years (range, 30-80 years). The mean follow-up was 13.2 ± 6.3 months (range, 6-24 months). Inclusion criteria included ≥18 years; knee OA, Kellgren-Lawrence grade I-II; hip OA, Tönnis grade I-II; first-time intra-articular BMC therapy, after unsuccessful symptomatic and conservative treatments (ie, physical therapy, analgesics and anti-inflammatory drugs) for 6 months. Exclusion criteria included pregnancy; malignancy; rheumatologic diseases; infection; Kellgren-Lawrence grade III-IV; Tönnis grade III; and previous intra-articular injections or surgery.

INTERVENTIONS

All patients had autologous bone marrow aspirate harvested from the iliac crest and centrifuged to achieve BMC, for intra-articular injection.

MAIN OUTCOME MEASUREMENTS

The hypothesis was formulated before the study. Patient-reported outcomes measures were assessed preoperatively and at last follow-up using the Western Ontario and McMaster Universities Arthritis Index.

RESULTS

Western Ontario and McMaster Universities Arthritis Index improved from a baseline of 40.8 ± 18.3% to 20.6 ± 17% (P < .001) at final follow-up. The satisfaction rate was 63.2%. The minimal clinically important difference threshold of 9.15 points was reached by 64% of the patients. Two patients were converted to total hip arthroplasty at 8 months after BMC injection.

CONCLUSIONS

Intra-articular injections of BMC for the treatment of early knee or hip OA were safe and demonstrated satisfactory results in 63.2% of patients. Future studies are necessary to determine the efficacy of this technique and its safety profile.

LEVEL OF EVIDENCE

II.

Mimetic Hierarchical Approaches for Osteochondral Tissue Engineering

In order to engineer biomimetic osteochondral (OC) construct, it is necessary to address both the cartilage and bone phase of the construct, as well as the interface between them, in effect mimicking the developmental processes when generating hierarchical scaffolds that show gradual changes of physical and mechanical properties, ideally complemented with the biochemical gradients. There are several components whose characteristics need to be taken into account in such biomimetic approach, including cells, scaffolds, bioreactors as well as various developmental processes such as mesenchymal condensation and vascularization, that need to be stimulated through the use of growth factors, mechanical stimulation, purinergic signaling, low oxygen conditioning, and immunomodulation. This chapter gives overview of these biomimetic OC system components, including the OC interface, as well as various methods of fabrication utilized in OC biomimetic tissue engineering (TE) of gradient scaffolds. Special attention is given to addressing the issue of achieving clinical size, anatomically shaped constructs. Besides such neotissue engineering for potential clinical use, other applications of biomimetic OC TE including formation of the OC tissues to be used as high-fidelity disease/healing models and as in vitro models for drug toxicity/efficacy evaluation are covered.

HIGHLIGHTS

Biomimetic OC TE uses "smart" scaffolds able to locally regulate cell phenotypes and dual-flow bioreactors for two sets of conditions for cartilage/bone Protocols for hierarchical OC grafts engineering should entail mesenchymal condensation for cartilage and vascular component for bone Immunomodulation, low oxygen tension, purinergic signaling, time dependence of stimuli application are important aspects to consider in biomimetic OC TE.