Optimal conditions of collagenase treatment for isolation of articular chondrocytes from aged human tissues

Arthroscopic Shaver-based Harvest of Minced Cartilage Results in Reduced Chondrocyte Viability and Reduced Quality of Cartilaginous Repair Tissue Compared With Open Harvest and Conventional Fragmentation

PURPOSE

To characterize and compare the quality of regenerative cartilage tissue (ReCT) after conventional minced cartilage (CMC) and arthroscopic minced cartilage (AMC), in terms of cell viability, gene expression, and matrix synthesis and to investigate the influence of different shaver types.

METHODS

Chondral tissue was harvested from the knees of 8 porcine donors. Porcine specimens were euthanized one day before harvest. AMC was created with 2 shaver blades in 2 operating modes (oscillating vs forward) and compared with a scalpel-fragmented CMC control. Before histologic analysis, 50% of the tissue was digested to prevent dedifferentiation of chondrocytes to fibroblasts. Cells were cultured and analyzed for cell viability, gene expression of cartilage-specific markers (aggrecan [ACAN], collagen type II, alpha1 [COL2A1], collagen type I, alpha1 [COL1A1], fibronectin-1 [FN1]), and matrix synthesis (Alcian-blue).

RESULTS

AMC tissue contained fewer viable chondrocytes (41%-54% vs 91%; P = .001-.048) compared with CMC. After culture, CMC showed greater expressions of ACAN (27 virtual copy numbers [VCN]/housekeeping gene) and COL2A1 (30 VCN) compared with AMC (ACAN 2-9 VCN, COL2A1 2-7 VCN, P = .001-.039). AMC presented greater expressions of COL1A1 (9-21 VCN) and FN1 (12-17 VCN) than CMC (1 and 6 VCN, P = .001-.050). The signal intensity of the cartilage matrix formed by CMC (86/mm2) was greater than by AMC (7-10 mm2, P = .001-.032).

CONCLUSIONS

CMC contained high numbers of viable chondrocytes, resulting in high-quality, hyaline-like ReCT. In contrast, AMC showed impaired chondrocyte quantity and viability, showing greater expressions of fibroblast markers and a decreased formation of mature cartilage matrix in porcine samples. The high chondrogenic potential of CMC to form hyaline-like ReCT was not confirmed for AMC.

CLINICAL RELEVANCE

On the basis of our findings, arthroscopic harvest of minced cartilage leads to reduced chondrocyte viability and ReCT quality. Accordingly, CMC and AMC cannot be regarded as synonymous techniques, as arthroscopic techniques seem to be less efficacious.

Insufficiency of collagenases in establishment of primary chondrocyte culture from cartilage of elderly patients receiving total joint replacement

Background Collagenases are frequently used in chondrocyte isolation from articular cartilage. However, the sufficiency of this enzyme in establishing primary human chondrocyte culture remains unknown. Methods Cartilage slices shaved from femoral head or tibial plateau of patients receiving total joint replacement surgery (16 hips, 8 knees) were subjected to 0.02% collagenase IA digestion for 16 h with (N = 19) or without (N = 5) the pre-treatment of 0.4% pronase E for 1.5 h. Chondrocyte yield and viability were compared between two groups. Chondrocyte phenotype was determined by the expression ratio of collagen type II to I. The morphology of cultured chondrocytes was monitored with a light microscope.Results Cartilage with pronase E pre-treatment yielded significantly higher chondrocytes than that without the pre-treatment (3,399 ± 1,637 cells/mg wet cartilage vs. 1,895 ± 688 cells/mg wet cartilage; P = 0.0067). Cell viability in the former group was also significantly higher than that in the latter (94% ± 2% vs. 86% ± 6%; P = 0.03). When cultured in monolayers, cells from cartilage with pronase E pre-treatment grew in a single plane showing rounded shape while cells from the other group grew in multi-planes and exhibited irregular shape. The mRNA expression ratio of collagen type II to I was 13.2 ± 7.5 in cells isolated from cartilage pre-treated with pronase E, indicating a typical chondrocyte phenotype. Conclusions Collagenase IA was not sufficient in establishing primary human chondrocyte culture. Cartilage must be treated with pronase E prior to collagenase IA application.

Isolation of High-Quality Total RNA from Small Animal Articular Cartilage for Next-Generation Sequencing

Articular cartilage is characterized by a low density of chondrocytes surrounded by an abundant extracellular matrix (ECM) consisting of a dense mixture of collagens, proteoglycans, and glycosaminoglycans. Due to its low cellularity and high proteoglycan content, it is particularly challenging to extract high-quality total RNA suitable for sensitive high-throughput downstream applications such as RNA sequencing (RNA-Seq). Available protocols for high-quality RNA isolation from articular chondrocytes are inconsistent, resulting in suboptimal yield and compromised quality. This poses a significant difficulty in the application of RNA-Seq to study the cartilage transcriptome. Current protocols rely either on dissociation of cartilage ECM by collagenase digestion or pulverizing cartilage using various methods prior to RNA extraction. However, protocols for cartilage processing vary significantly depending on the species and source of cartilage within the body. Protocols for isolating RNA from human or large mammal (e.g., horse or cattle) cartilage samples are available, but this is not the case for chicken cartilage, despite the species being extensively used in cartilage research. Here, we present two improved RNA isolation protocols based on pulverization of fresh articular cartilage using a cryogenic mill or on enzymatic digestion using 1.2% (w/v) collagenase II. Our protocols optimize the collection and tissue processing steps to minimize RNA degradation and enhance RNA purity. Our results show that RNA purified from chicken articular cartilage using these methods has appropriate quality for RNA-Seq experiments. The procedure is applicable for RNA extraction from cartilage from other species such as dog, cat, sheep, and goat. The workflow for RNA-Seq analysis is also described here. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Extraction of total RNA from pulverized chicken articular cartilage Alternate Protocol: Extraction of total RNA from collagen-digested articular cartilage Support Protocol: Dissection of chicken articular cartilage from the knee joint Basic Protocol 2: RNA sequencing of total RNA from chicken articular cartilage.

Optimization of chondrocyte isolation from human articular cartilage to preserve the chondrocyte transcriptome

The isolation of chondrocytes from human articular cartilage for single-cell RNA sequencing requires extensive and prolonged tissue digestion at 37 C. Modulations of the transcriptional activity likely take place during this period such that the transcriptomes of isolated human chondrocytes no longer match their original status in vivo. Here, we optimized the human chondrocyte isolation procedure to maximally preserve the in vivo transcriptome. Cartilage tissues were transferred into a hypoxia chamber (4% O2) immediately after being removed from OA patients and minced finely. Collagenase II at concentrations of 0.02%, 0.1%, 0.25%, 0.5%, 1%, and 2% was applied for 0.5, 1, 2, 4, and 18 h to digest the minced tissue. Actinomycin D (ActD) was added to test its capacity in stabilizing the transcriptome. Cell yield, viability, cell size, and transcriptome were determined using counter chamber, flow cytometry, and RNA sequencing (RNA-seq). Collagenase II at 2% concentration released small chondrocytes from cartilage matrix during the first digestion hour and started to release large cells thereafter, reaching a complete release at 4 h. During 4-h digestions, collagenase II at 2% and 1% but not at lower concentrations yielded maximal release also of the large chondrocyte population. RNA-seq analysis revealed that a 4-h digestion period with 1% or 2% collagenase II plus Actinomycin D optimally preserved the transcriptome. Thus, this study provides an isolation protocol for single chondrocytes from human articular cartilage optimized for transcriptome preservation and RNA-seq analysis.

Evaluation of enzymatic proteoglycan loss and collagen degradation in human articular cartilage using ultrashort echo time-based biomarkers: A feasibility study

The objective of the current study was to investigate the feasibility of quantitative 3D ultrashort echo time (UTE)-based biomarkers in detecting proteoglycan (PG) loss and collagen degradation in human cartilage. A total of 104 cartilage samples were harvested for a trypsin digestion study (n = 44), and a sequential trypsin and collagenase digestion study (n = 60), respectively. Forty-four cartilage samples were randomly divided into a trypsin digestion group (tryp group) and a control group (phosphate-buffered saline [PBS] group) (n = 22 for each group) for the trypsin digestion experiment. The remaining 60 cartilage samples were divided equally into four groups (n = 15 for each group) for sequential trypsin and collagenase digestion, including PBS + Tris (incubated in PBS, then Tris buffer solution), PBS + 30 U col (incubated in PBS, then 30 U/ml collagenase [30 U col] with Tris buffer solution), tryp + 30 U col (incubated in trypsin solution, then 30 U/ml collagenase with Tris buffer solution), and tryp + Tris (incubated in trypsin solution, then Tris buffer solution). The 3D UTE-based MRI biomarkers included T₁ , multiecho T₂ *, adiabatic T_1ρ (AdiabT_1ρ ), magnetization transfer ratio (MTR), and modeling of macromolecular proton fraction (MMF). For each cartilage sample, UTE-based biomarkers (T₁ , T₂ *, AdiabT_1ρ , MTR, and MMF) and sample weight were evaluated before and after treatment. PG and hydroxyproline assays were performed. Differences between groups and correlations were assessed. All the evaluated biomarkers were able to differentiate between healthy and degenerated cartilage in the trypsin digestion experiment, but only T₁ and AdiabT_1ρ were significantly correlated with the PG concentration in the digestion solution (p = 0.004 and p = 0.0001, respectively). In the sequential digestion experiment, no significant differences were found for T₁ and AdiabT_1ρ values between the PBS + Tris and PBS + 30 U col groups (p = 0.627 and p = 0.877, respectively), but T₁ and AdiabT_1ρ values increased significantly in the tryp + Tris (p = 0.031 and p = 0.024, respectively) and tryp + 30 U col groups (both p < 0.0001). Significant decreases in MMF and MTR were found in the tryp + 30 U col group compared with the PBS + Tris group (p = 0.002 and p = 0.001, respectively). It was concluded that AdiabT_1ρ and T₁ have the potential for detecting PG loss, while MMF and MTR are promising for the detection of collagen degradation in articular cartilage, which could facilitate earlier, noninvasive diagnosis of osteoarthritis.

Sequential Enzymatic Digestion of Different Cartilage Tissues: A Rapid and High-Efficiency Protocol for Chondrocyte Isolation, and Its Application in Cartilage Tissue Engineering

OBJECTIVE

The classic chondrocyte isolation protocol is a 1-step enzymatic digestion protocol in which cartilage samples are digested in collagenase solution for a single, long period. However, this method usually results in incomplete cartilage dissociation and low chondrocyte quality. In this study, we aimed to develop a rapid, high-efficiency, and flexible chondrocyte isolation protocol for cartilage tissue engineering.

DESIGN

Cartilage tissues harvested from rabbit ear, rib, septum, and articulation were minced and subjected to enzymatic digestion using the classic protocol or the newly developed sequential protocol. In the classic protocol, cartilage fragments were subjected to one 12-hour digestion. In the sequential protocol, cartilage fragments were sequentially subjected to 2-hour first digestion, followed by two 3-hour digestions. The collected cells were then subjected to analyses of cell-yield efficiency, viability, proliferation, phenotype, and cartilage matrix synthesis capacity.

RESULTS

Overall, the sequential protocol exhibited higher cell-yield efficiency than the classic protocol for the 4 cartilage types. The cells harvested from the second and third digestions demonstrated higher cell viability, more proliferative activity, a better chondrocyte phenotype, and a higher cartilage-specific matrix synthesis ability than those harvested from the first digestion and after the classic 1-step protocol.

CONCLUSIONS

The sequential protocol is a rapid, flexible, high-efficiency chondrocyte isolation protocol for different cartilage tissues. We recommend using this protocol for chondrocyte isolation, and in particular, the cells obtained after the subsequent 3-hour sequential digestions should be used for chondrocyte-based therapy.

De novo neo-hyaline-cartilage from bovine organoids in viscoelastic hydrogels

Regenerative therapies for articular cartilage are currently clinically available. However, they are associated with several drawbacks that require resolution. Optimizing chondrocyte expansion and their assembly, can reduce the time and costs of these therapies and more importantly increase their clinical success. In this study, cartilage organoids were quickly mass produced from bovine chondrocytes with a new suspension expansion protocol. This new approach led to massive cell proliferation, high viability and the self-assembly of organoids. These organoids were composed of collagen type II, type VI, glycosaminoglycans, with Sox9 positive cells, embedded in a pericellular and interterritorial matrix similarly to hyaline cartilage. With the goal of producing large scale tissues, we then encapsulated these organoids into alginate hydrogels with different viscoelastic properties. Elastic hydrogels constrained the growth and fusion of the organoids inhibiting the formation of a tissue. In contrast, viscoelastic hydrogels allowed the growth and fusion of the organoids into a homogenous tissue that was rich in collagen type II and glycosaminoglycans. The encapsulation of organoids to produce in vitro neocartilage also proved to be superior to the conventional method of encapsulating 2D expanded chondrocytes. This study describes a multimodal approach that involves chondrocyte expansion, organoid formation and their assembly into neohyaline-cartilage which proved to be superior to the current standard approaches used in cartilage tissue engineering. STATEMENT OF SIGNIFICANCE: In this manuscript, we describe a new and simple methodology to quickly mass produce self-assembling cartilage organoids. Due to their matrix content and structure similarities with native cartilage, these organoids on their own have the potential to revolutionize cartilage research and the manner in which we study signaling pathways, disease progression, tissue engineering, drug development, etc. Furthermore, these organoids and their fast mass production were combined with a key relatively ignored hydrogel characteristic, viscoelasticity, to demonstrate their fusion into a neo-tissue. This has the potential to open the door for large scale cartilage regeneration such as for entire joint surfaces.

Primary culture of chondrocytes after collagenase IA or II treatment of articular cartilage from elderly patients undergoing arthroplasty

Background

Joint replacement surgery provides articular cartilage samples for chondrocyte isolation. To our knowledge, the effect of the collagenase type on releasing of chondrocytes from the extracellular matrix of cartilage is not reported.

Objectives

To determine whether cartilage digested with collagenase IA yielded more chondrocytes than that digested with collagenase II and determine whether chondrocytes isolated with collagenase IA could be cultured in vitro.

Methods

Cartilage slices collected from 18 elderly patients who received joint replacement surgery (16 hips, 2 knees) were digested sequentially with 0.4% pronase E and 0.02% collagenase IA, or with 0.15% collagenase II alone, or sequentially with 0.4% pronase E and 0.02% collagenase II. We compared cell yield from each method. Cell viability by the most effective method was calculated and plotted. The morphology of cultured monolayer chondrocytes was recorded with a light microscope.

Results

Sequential digestion with pronase E and collagenase IA yielded 2566 ± 873 chondrocytes per mg wet cartilage, which was more effective than the other isolation methods (P = 0.018). The average chondrocyte viability could reach 84% ± 8% (n = 11). Light microscopic images showed typical chondrocyte morphology in monolayer cultures.

Conclusion

Sequential digestion of human articular cartilage with pronase E and collagenase IA was more effective than collagenase II alone or collagenase II combined with pronase E for releasing chondrocytes from extracellular matrix of cartilage. Chondrocytes isolated with this method could be maintained in monolayer cultures for at least 2 passages with unaltered morphology.

Understanding factors affecting human chondrocyte culturing: an experimental study

Over the years, surgical strategies have been developed in hope of full regeneration of the injured cartilage. In our study, we aimed to develop an optimized chondrocyte culture isolation technique as an active ingredient of a standardized autologous chondrocte implantation product, which is able to maintain the phenotype along with the molecular features of the cartilage. We compared different enzymes, which suggested optimal performance with collagenase type II at 5 mg/ml concentration. Thereafter, we observed that COL2 and GAG expression is substantially reduced with passaging. There was a need to omit passaging to reach the optimal isolation method. We then tested various growth factors and media in order to maintain the natural character of chondrocytes. Our study also suggested the highest COL2 and GAG expressions with the highest recovery in the presence of Advanced DMEM. Autologous chondrocyte implantation manufacturing approval was recently received from the national competent authority, making it possible to utilize the process engineering protocol developed with this study at our Tissue and Cell Manufacturing Center as a part of the autologous chondrocyte implantation manufacturing standard operation procedure (SOP).

Repair of an Osteochondral Defect With Minced Cartilage Embedded in Atelocollagen Gel: A Rabbit Model

BACKGROUND

Autologous chondrocyte implantation (ACI) is often performed for large cartilage defects. Because this technique has several disadvantages, including the need for second-stage surgery, cartilage repair using minced cartilage has been suggested. However, this technique could be improved using 3-dimensional scaffolds.

PURPOSE

To examine the ability of chondrocyte migration and proliferation from minced cartilage in atelocollagen gel in vitro and evaluate the repairable potential of minced cartilage embedded in atelocollagen gel covered with a periosteal flap in a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Minced cartilage or isolated chondrocytes from rabbits were embedded in atelocollagen gel and cultured for 3 weeks. Chondrocyte proliferation and matrix production were evaluated in vitro. An osteochondral defect at the trochlear groove was created in 56 rabbits, which were divided into 4 groups. The defect was left empty (defect group), filled with allogenic minced cartilage (minced cartilage group), filled with isolated allogenic chondrocytes embedded in atelocollagen gel (ACI group), or filled with atelocollagen gel (atelocollagen with periosteal flap group). At 4, 12, and 24 weeks after surgery, repair of the defect was evaluated in these 4 groups.

RESULTS

In vitro, the number of chondrocytes and abundant matrix on the surface of the gel significantly increased in the minced cartilage group compared with the ACI group (P < .05). In vivo, the minced cartilage and ACI groups showed good cartilage repair compared with the empty defect and atelocollagen/periosteal flap groups (P < .05); there was no significant difference in the Pineda score between the minced cartilage and ACI groups.

CONCLUSION

Minced cartilage in atelocollagen gel had good chondrocyte migration and proliferation abilities in vitro, and osteochondral defects were well repaired by implanting minced cartilage embedded in the atelocollagen gel in vivo. Implantation of minced cartilage embedded in atelocollagen gel showed good cartilage repair equivalent to ACI.

CLINICAL RELEVANCE

Implantation of minced cartilage embedded in atelocollagen gel as a 1-step procedure has outcomes similar to those of ACI but is cheaper and more convenient than ACI.

Progenitor cells from different zones of human cartilage and their correlation with histopathological osteoarthritis progression

Cell-based therapies development for the treatment of osteoarthritis (OA) requires an understanding of the disease progression and attributes of the cells resident in cartilage. This study focused on quantitative assessment of the concentration and biological potential of stem and progenitor cells resident in different zones of cartilage displaying macroscopic Outerbridge grade 1-2 OA, and their correlation with OA progression based on established histologic scoring system. Lateral femoral condyles were collected from 15 patients with idiopathic OA and varus knees undergoing total knee arthroplasty. Superficial(C_sp , top ∼ 500 µm) and deep cartilage(C_dp ) was separated. Chondrogenic Connective Tissue Progenitors (CTP-C) were assayed by standardized Colony-Forming-Unit assay using automated image analysis (Colonyze^TM ) based on ASTM standard F-2944-12. Cell concentration (cells/mg) was significantly greater in C_sp (median: 7,000; range: 3,440-17,600) than C_dp (median: 5,340; range: 3,393-9,660), p = 0.039. Prevalence (CTPs/million cells) was not different between C_sp (median: 1,274; range: 0-3,898) and C_dp (median:1,365; range:0-6,330), p = 0.42. In vitro performance of CTP-C progeny varied widely within and between patients, manifest by variation in colony size and morphology. Mean histopathological Mankin score was 4.7 (SD = 1.2), representing mild to moderate OA. Tidemark breach by blood vessels was associated with lower C_sp cell concentration (p = 0.02). Matrix degradation was associated with lower C_dp cell and CTP-C concentration (p = 0.015 and p = 0.095, respectively), independent of articular surface changes. These findings suggest that the initiation of OA may occur in either superficial or deep zones. The pathological changes affect CTP-Cs in C_sp and C_dp cartilage zones differently. The heterogeneity among the available CTP-Cs in C_sp and C_dp suggests performance-based selection to optimize cell-sourcing strategies for therapy. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1728-1738, 2018.