Bone marrow derived mesenchymal stem cell (BM MSC) application in articular cartilage repair 1

BONE MARROW DERIVED MESENCHYMAL STEM CELL BM MSC APPLICATION IN ARTICULAR CARTILAGE REPAIR HOSSEIN NEJADNIK M.D., Isfahan University of Medical Sciences, Isfahan, Iran A THESIS SUBMIT

BONE MARROW DERIVED MESENCHYMAL STEM

CELL (BM MSC) APPLICATION IN ARTICULAR

CARTILAGE REPAIR

HOSSEIN NEJADNIK

(M.D., Isfahan University of Medical Sciences, Isfahan, Iran)

A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF ORTHOPEDIC SURGERY YONG LOO LIN SCHOOL OF MEDICINE

NATIONAL UNIVERSITY OF SINGAPORE

2013

ACKNOWLEDGEMENTS

It is my pleasure to thank all the kind people who made this thesis possible with their great help and support I would like to thank my supervisor, Associate Professor James Hui, Department of Orthopedic Surgery, Yong Loo Lin School of Medicine, National University of Singapore (NUS), for his critical supervision and active support during my PhD study

I am also deeply indebted to my co-supervisor Professor Shih-Chang Wang, Head of Discipline of Medical Imaging at Sydney Medical School, University of Sydney, for his constant support and encouragement

My gratitude is also towards Professor Wong Hee Kit, the Head of Orthopedic Surgery Department, for giving me this chance to pursue my PhD degree and use the facilities in the department, and Professor Lee Eng Hin and Professor James Goh Cho Hong, Head of National University of Singapore Tissue Engineering Program (NUSTEP), for giving me the opportunity to use the NUSTEP facilities

I also would like to thank Professor Vincent Chong, Head of Radiology Department, and Associate Professor Sudhakar Venkatesh for their help and support

I am most grateful to Professor Roger Kamm, lead investigator of BioSystems and Micromechanics (BioSyM) at Singapore-MIT Alliance for Research & Technology (SMART) and Cecil and Ida Green Distinguished Professor of Biological and Mechanical Engineering at MIT University, for his mentorship and support and Dr Amirreza Aref, and Dr Choong Kim for their support in performing the bioengineering parts of my projects

I also would like to extend my sincere gratitude to Professor Kishore Bhakoo, Head of Translational Molecular Imaging Group at Singapore Bioimaging Consortium (SBIC), who provided me a great support in the MR imaging

I owe my deepest gratitude to my colleagues and students in the NUSTEP lab: Dr Kenon Chua, Dr Xiafei Ren, Dr Zheng Yang, Dr Sintje Böhrensen, Afizah Binte Mohd Hassan, and Dr Sari Panjang, who have taught me a lot They have been wonderful friends

I am thankful to all the colleagues, students and staff members of Department of Orthopedics Surgery, specially Ms Perumal Premalatha, and

Ms Sarojeni Shanmugam, Orthopaedic Surgery Department management assistant officers, Yong Loo Lin School of Medicine for their timely help

I would like to thank A*STAR and NUS for granting me graduate student scholarship This work was supported by grants from Singapore Bioimaging Consercium (to A/P James Hui)

I wish to thank my great friends who made my PhD life a great memory for me and I owe my loving thanks to my wife, Pooneh, and my parents and

I dedicate this thesis to them

TABLE OF CONTENTS

1.4.1 Palliative technique: Arthroscopic lavage and debridement 7 1.4.2 Intrinsic repair enhancement: Microfracture 8 1.4.3 Whole tissue transplantation: Osteochondral Autograft

1.4.5.1 Autologous chondrocyte implantation (ACI) 11

1.4.5.3 Stem Cells in Articular Cartilage repair 13

1.11.1 Cellular Imaging with Iron Oxide Particles 25

Chapter 3 In vivo monitoring of the intra articular injected

3.4.2 Prussian blue staining of SPIO-labeled MSCs 60

3.4.4 Iron content quantification in labeled-MSCs 61 3.4.5 Viability and proliferation of labeled MSCs 62

4.3.2 Computational modeling of concentration gradient 88

4.3.4 MSC characterization and culture in microfluidic devices 90

4.3.7 MSCs migration toward injured cartilage conditioned media 92

4.4.4 MSCs migration stimulated by conditioned media 103

4.4.6 Quantitative real-time reverse transcriptase-polymerase chain

5.4.1 ICRS package SF-36 components clinical outcomes 127

5.4.5 Second-look arthroscopy and histological outcomes 133

Summary

Articular cartilage repair is one the most challenging issues in orthopedic surgery due to the avascular and aneural nature of the cartilage, which affects its self-repair capability Cell therapy shows a great potential for cartilage defect repair Brittberg et al in 1994 used autologous chondrocytes as a cell source to repair the injured knee cartilage, which remains a promising method even to date However, this method has some limitations such as inadequate cell number, age dependent quality of the chondrocytes and donor site

morbidity Recently bone marrow derived mesenchymal stem cells (MSCs) become an alternative cell source for cartilage repair Our group and others had demonstrated the tri-lineage differentiation ability of MSCs to

chondrocytes, osteocytes and adipocytes Wakitani et al and our group

demonstrated that MSCs could be used as a new source for cartilage repair However, in order to develop this into an effective cell therapy treatment we need to understand the behavior of cells, especially the proliferation,

differentiation, migration and engraftment of MSCs after implantation and in

vivo

The use of MSCs for cartilage repair relies on their homing and engraftment to the injured cartilage tissue Although there is some theory that injured tissue expresses ligands and chemotactic factors that encourage homing of MSCs,

these factors and their mechanism are not fully understood In vitro modeling

of the in vivo simulation can be challenging Microfluidic platforms allow the

study of cell migration in 3D environment, and at the same time, provide live

injection The technique is useful tool to monitor the migration and localization

by MRI, a non-invasive and repeatable imaging method for in vivo evaluation

In addition, we showed that labeled MSCs have tendency to move to the injured cartilage site, engraft and increase the quality of the repaired cartilage

by production of hyaline-like cartilage The MSCs also have tendency to home

in the other sources of the inflammation such as surgery site

To have a better understanding of the migration behavior of the MSCs toward injured cartilage, we developed a microfluidic device, and confirmed the

migration capacity of the MSCs in a three dimensional model system An increased migration of the MSCs was observed due to an increase in the chemo-attractant factors secreted by the injured tissue Cartilage injuries up-regulated the expression of the chemotactic factors such as collagen type I A1 (COL1A1), chemokine C-X-C motif 10 (CXCL10), transforming growth factor alpha (TGFA), insulin-like growth factor 2 (IGF2), chemokine C-X-C motif 12 (CXCL12), angiopoietin 1 (ANGPT1), fibroblast growth factor 2 (FGF2),

transforming growth factor beta-3 (TGFB3), bone morphogenetic protein 4 (BMP4), and vitronectin (VTN) ligands

Furthermore, to assess the cartilage repair outcome by using MSCs, we compared the clinical outcome of cartilage repair by using MSCs vs

chondrocytes, which is an FDA approved methods In this part of our study,

we demonstrated that MSCs were as effective as chondrocytes for articular

cartilage repair The use of MSCs offers advantages such as being less invasiveness (bone marrow biopsy comparing with knee arthroscopy), having little or no damage to normal articular cartilage, and requiring only regional anesthesia All of which leads to lower treatment costs for patient

In conclusion, we demonstrated that MSCs are a promising cell source for cartilage repair, and due to the migration capability of the cells and

chemotaxis factors secretion of the injured cartilage Their use as an

injectable cell therapy treatment will increase in the coming years

TABLE 1-2 DIFFERENT METHODS OF CARTILAGE REPAIR (12) 7

TABLE 1-3 SCAFFOLDS USED IN VIVO STUDIES (ADAPTED FROM (21))

TABLE 1-6 COMPARISON OF IMAGING MODALITIES SCALE 22

TABLE 1-7 CLASSIFICATION OF MRI CONTRAST AGENTS (ADAPTED FROM (101)) 23

TABLE 1-8 COMPARISON OF CELL TRANSPLANTATION AND HOMING FOR CARTILAGE REGENERATION (ADAPTED FROM(141)) 30

TABLE 3-1 HISTOLOGICAL GRADING SCALE FOR CARTILAGE REPAIR 56

TABLE 4-1 LIST OF CANDIDATE LIGANDS USED FOR RT-PCR

FIGURE 1-1 LAYERS IN THE ARTICULAR CARTILAGE (2, 3) 3

FIGURE 1-2 THE ICRS CARTILAGE INJURY CLASSIFICATION (8) 5

FIGURE 1-3 SCHEMATIC OF MICROFRACTURE TECHNIQUE OF

CARTILAGE REPAIR (18) 8

FIGURE 1-4 SCHEMATIC OF OSTEOCHONDRAL AUTOGRAFT TRANSPLANTATION (OAT) TECHNIQUE OF CARTILAGE REPAIR (18) 9

FIGURE 1-5 SCHEMATIC OF AUTOLOGOUS CHONDROCYTE IMPLANTATION (ACI) TECHNIQUE OF CARTILAGE REPAIR (62) 12 FIGURE 1-6 THE CARTILAGE REPAIR STRATEGY ALGORITHM BASED ON THE LESION LOCATION AND CHARACTERISTICS 13

FIGURE 1-7 STEM CELL CLASSIFICATION AND DIFFERENTIATION POTENTIAL (71) 14

FIGURE 1-8 MECHANISMS OF CELLULAR UPTAKE OF NANO SIZED PARTICLES 28

FIGURE 1-9 MECHANISMS OF PARTICLE UPTAKE BY ENDOCYTOSIS 29

FIGURE 1-10 CELL MIGRATION PROCESS 31

FIGURE 1-11 EXISTING MIGRATION ASSAY DEVICES 32

FIGURE 3-1 MINI-PIGS AS AN ANIMAL MODEL 52

FIGURE 3-2 MR IMAGING OF THE MINI-PIGS' KNEE JOINT 54

FIGURE 3-3 FLOW CYTOMETRY ANALYSIS OF THE STEM CELLS SURFACE MARKERS 59

FIGURE 3-4 PRUSSIAN BLUE STAINING OF THE UNLABELED AND LABELED MSCS 60

FIGURE 3-5 TRANSMISSION ELECTRON MICROSCOPY OF THE LABELED MSCS 61

FIGURE 3-6 IRON CONTENT QUANTIFICATION 62

FIGURE 3-7 TRYPAN BLUE VIABILITY TEST 63

FIGURE 3-8 MTS ASSAY 64

FIGURE 3-9 OIL RED O STAINING 65

FIGURE 3-10 ALIZARIN RED STAINING 65

FIGURE 3-11 CHONDROGENIC DIFFERENTIATION POTENTIAL EVALUATION OF THE MSCS 67

FIGURE 3-12 MR IMAGING OF THE PIG'S KNEE EXPLANT 69

FIGURE 3-13 MR SEQUENCE OPTIMIZATION 70

FIGURE 3-14 POST INJECTION MR IMAGES 71

FIGURE 3-15 MR IMAGING OF THE MINI-PIG'S FEMORAL CONDYLE 72FIGURE 3-16 MRI OF THE DISTRIBUTION OF THE LABELED MSCS IN THE MINI-PIG KNEE JOINT 73

FIGURE 3-17 POSTMORTEM HISTOLOGICAL EVALUATION OF THE REPAIRED CHONDRAL DEFECTS 6 WEEKS AFTER STEM CELL INJECTION 74

FIGURE 3-18 PRUSSIAN BLUE STAINING OF THE REPAIRED

CARTILAGE DEFECT 74

FIGURE 3-19 PRUSSIAN BLUE STAINING OF THE IRON LABELED MSCS

IN THE SURGICAL SCAR SITE 75

FIGURE 3-20 PRUSSIAN BLUE STAINING OF IRON LABELED MSCS IN THE PARA-PATELLAR FAT 75

FIGURE 4-1 HISTORY OF MICROFLUIDIC DEVICE DESIGN 86

FIGURE 4-2 SCHEMATIC DESIGN AND DIMENSION OF MICROFLUIDIC DEVICE 88

FIGURE 4-3 CARTILAGE TISSUE CONDITIONED MEDIA PREPARATION 93

FIGURE 4-4 THE GROWTH FACTORS DIFFUSION SIMULATION IN 3D SCAFFOLD 99

FIGURE 4-5 FLOW CYTOMETRY ANALYSIS OF THE STEM CELLS

SURFACE MARKERS 100

FIGURE 4-6 MICROFLUIDIC DEVICE MIGRATION VALIDATION 102

FIGURE 4-7 MIGRATION EVALUATION OF THE MSCS TOWARD

UNINJURED AND INJURED CONDITIONED MEDIA 104

FIGURE 4-8 MIGRATION QUALIFICATION OF THE MSCS TOWARD

UNINJURED AND INJURED CONDITIONED MEDIA 105

FIGURE 4-9 MIGRATION EVALUATION OF THE MSCS TOWARD

UNINJURED AND INJURED CARTILAGE TISSUE 106

FIGURE 4-10 MIGRATION QUANTIFICATION OF THE MSCS TOWARD UNINJURED AND INJURED CARTILAGE TISSUE 107

FIGURE 4-11 GENE EXPRESSION CHANGE OF CANDIDATE LIGANDS IN INJURED CARTILAGE 109

FIGURE 5-1 IKDC, TEGNER, AND LYSHOLM ACTIVITY LEVEL

OUTCOME 131FIGURE 5-2 FEMORAL CONDYLE CARTILAGE DEFECT 133FIGURE 5-3 HISTOLOGIC EVALUATION OF BIOPSY SPECIMENS.134

LIST OF ABBREVIATIONS

3D-GRE 3D Gradient Echo

AAS Atomic Absorption Spectroscopy

ACI Autologous chondrocyte implantation

ADSC Adipose derived stem cells

AMNP Anionic magnetic nanoparticle

BM MSC Bone marrow derived stem cells

CD Cluster of differentiation

CEST Chemical exchange saturation transfer

CPM Continuous passive motion

ECM Extracellular matrix

ESC Embryonic stem cells

ETL Echo train length

FDA Food and drug administration

FIESTA Fast imaging employing steady state acquisition

FISH Fluorescent in situ hybridization

FSE PD FS Proton density fast spin echo with fat saturation

G-CSF Granulocyte colony stimulating factor

Gd-DTPA Gadolinium-diethylenetriamine pentaacetic acid

GFP Green fluorescence protein

H&E Haematoxylin and eosin

HLA Human leukocyte antigen

ICRS International Cartilage Repair Society

IGF-1 Insulin-like growth factor-1

IKDC International Knee Documentation Committee

iPS cell Induced pluripotent stem cell

IVM Intra-vital microscopy

MACI Matrix-associated autologous chondrocyte implantation

MACT Matrix-associated autologous chondrocyte transplantation MERGE Multiple Echo Recombined Gradient Echo

MION Monocrystalline iron oxide nanocompound

MPIO Micron-size iron oxide particles

MRI Magnetic Resonance Imaging

MTS 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium)

OAT Osteochondral Autograft Transplantation

OCD Osteochondritis dissecans

PBS Phosphate buffered saline

PET Positron emission tomography

SCF Stem cell factor

SDF-1 Stromal derived factor-1

SE MT Spin echo with magnetization transfer

SMSC Synovium derived mesenchymal stem cells

SNR Signal to noise ratio

SPECT Single photon emission computed tomography

SPGR Spoiled gradient recalled

SPIO Superparamagnetic iron oxide nanoparticles

TEM Transmission Electron Microscopy

USPIO Ultra small superparamagnetic iron oxide

VSOP Very small superparamagnetic iron oxide particles

- Nejadnik H, Aref AR, Kim C, Ren X, Yang Z, Kamm RD, Hui J

Simulating Injured Articular Cartilage Environment for

Mesenchymal Stem Cell Migration Evaluation in A Three

Poster

- Nejadnik H, Hui J Iron oxide labeling does not affect the

chondrogenic differentiation capacity of mesenchymal stem cells ICRS 2010 - 9th World Congress of the International Cartilage

Repair Society, Barcelona, Spain September 2010

- Nejadnik H, Aref A, Hui J, Kamm R Simulating Injured Cartilage Environment by Microfluidic Platform for Mesenchymal Stem Cell Homing Evaluation 6th World Congress on Biomechanics,

Singapore, August 2010

Honors and Awards

- International Cartilage Repair Society Conference travel award (2010)

- National University of Singapore School of Medicine (SoM)

Scholarship award (2009 and 2010)

- International Cartilage Repair Society Conference travel award (2009)

- A* STAR International Graduate Scholarship award (IGS)(2007 and 2008)

1

1.1 Basic Science of Articular Cartilage

Articular cartilage is the hyaline cartilage, which covers the articular surfaces

of bones The hyaline cartilage of the articular surface is an aneural,

avascular tissue with a relatively simple structure 65-80% of the wet weight of articular cartilage is made of water, 10-20% is collagen, while predominantly type II Collagen and proteoglycans (PG) make up for another 10-20% These molecules are secreted by chondrocytes which themselves make up for 1-5%

of the volume of articular The ultra structure of articular cartilage varies

depending on the depth from the surface, which is shown in figure 1.1

The superficial (tangential) zone is composed of flattened cells, a high

collagen content, which is packed tightly parallel to the surface and the lowest concentration of proteoglycans This zone provides tensile and shear

strength to the tissue The transitional zone has a lower density of cells, which are spheroid in shape, an abundant extracellular matrix (ECM), and collagen fibers placed in a random pattern The deep (radial) zone has the lowest cell density and the highest proteoglycan content In this zone collagen fibers are oriented perpendicular to the articular surface to resist compressive loads Finally, the calcified zone is separated from the deep zone by the tidemark, has few cells and the extracellular matrix is calcified (Table 1.1) In this zone, production of type X collagen provides adhesive properties for tissue to

adhere to the underlying subchondral bone (1)

Figure 1-1 Layers in the articular cartilage (2, 3)

H&E staining of the articular cartilage (A), schematic of hyaline cartilage collagen fiber arrangements (B)

Table 1-1 Composition of the different layers of articular cartilage (4)

1.2 Cartilage injuries

1.2.1 Focal cartilage defects

Focal cartilage lesions involve only the articular cartilage and preserve the integrity of the subchondral bone These lesions can be partial or full

thickness

Outerbridge developed the very first cartilage injury classification system (5)

In this system lesions are divided to four grades (I-IV) but there was no

description on depth of the lesions in grades II and III Other classification systems using factors such as surface appearance, location of lesion and its diameter were not suitable for focal lesions and were not used frequently (6-8) Currently, most researchers use the International Cartilage Repair Society (ICRS) classification system which focuses on the lesion depth and area of damage (Figure 1.2) (8)

Figure 1-2 The ICRS cartilage injury classification (8)

According to ICRS classification system (figure 1.2), normal cartilage is grade

0 When there is softening and swelling of the cartilage it is classified as grade 1a and when there are additional fissures and cracks on the surface it is classified as grade 1b Grade 2 is when the fissuring extends down to less than 50% of cartilage depth Grade 3a is when the lesions extend down to more than 50% of cartilage thickness When lesions extending down to

calcified layer and to subcortical bone (but not through it), they are classified

as grade 3b and 3c, respectively Blisters are classified as grade 3d and finally grade 4 is when the erosion of cartilage extends into the bone (8)

1.2.2 Osteochondritis dissecans (OCD)

OCD is an osteochondral disease that affects the subchondral bone and then the articular cartilage If the lesion does not heal, the bony part will detach from the bone and the overlying cartilage will detach from the rest causing the complete separation of the fragment Most of the time no clear etiology can be defined for OCD suggesting multifactorial causes such as trauma, repetitive micro-trauma and loss of subchondral vascularity (9)

1.3 Importance of cartilage repair

Since articular cartilage is relatively avascular, its ability in self-regeneration and self-repair is limited Moreover there are only a few cells with low mitotic activity and little or no migration ability due to tight ECM which all contribute to the problem of repair and regeneration (10, 11) Besides, articular cartilage is under constant load, which makes the healing process more challenging Articular cartilage lesions are associated with pain, effusion, locking

phenomena, and disturbed function Generally, even small cartilage defects can progress to osteoarthritis (OA) over time and all of these, highlight the importance of cartilage defect repair (9, 12)

1.4 Different methods of cartilage repair

Because of the avascular nature of the cartilage and other reasons discussed above, intrinsic capacity of cartilage repair is limited and even small damages

Table 1-2 Different methods of cartilage repair (12)

1.4.1 Palliative technique: Arthroscopic lavage and debridement

Debridement and lavage is typically beneficial for older patients with small lesions who present with acute pain and localized mechanical symptoms (catching or locking) Using video-fiber-optics through 2-3 small incisions above the knee, arthroscopy evaluates and treats the repair visually and surgery can be accomplished with the same equipment Debridement

includes the smoothing of fibrillated surfaces and the removal of inflamed synovium, loose flaps and osteophytes (9-12) The recovery is short but

Approach Treatment Repair tissue Fill

Palliative 1.Arthroscopic debridement None None

Intrinsic repair

enhancement

1 Microfracture Fibrocartilage Partial

2 Drilling Fibrocartilage Partial

3 Abrasion arthroplasty Fibrocartilage Partial

Whole tissue

transplantation

1 Mosaicplasty Hyaline Cartilage Near total

2 Osteochondral autograft Hyaline Cartilage Near total

Cell-based

1 ACI Hyaline-like Near total

2 MACI Hyaline-like Near total

usually relief is temporary and incomplete, as the procedure does not include any repair of the lesion

1.4.2 Intrinsic repair enhancement: Microfracture

Patients with small to moderate-sized lesions are suitable candidates for

marrow- stimulating techniques, such as microfracture, which is the most

studied reparative technique This procedure is performed arthroscopically

and involves creating tiny fractures in the underlying bone to permit the efflux

of progenitor cells and growth factors into the lesion (figure 1.3), which leads

to generating fibrocartilage (13-17) The postoperative protocol involves a period of (~6 weeks) touchdown weight bearing and use of a continuous passive motion (CPM) machine (3)

Figure 1-3 Schematic of microfracture technique of cartilage repair (18) 1.4.3 Whole tissue transplantation: Osteochondral Autograft

Transplantation (OAT)

This technique is suitable for young patients with a medium-sized lesion The autografts are round cylinders of cartilage and its underlying bone, which are taken from non-weight-bearing parts and then grafted into the defect leading

to the transplantation of live hyaline cartilage in a single surgery (figure 1.4)

scaffold must have the properties to tolerate in vivo forces (20) The summary

of potential biomaterials, which are used currently, is listed in Table 1.3

Table 1-3 Scaffolds used in vivo studies (adapted from (21))

Scaffold Positive findings Negative findings References

I Autologous scaffolds

Perichondrium,

periosteum

- Contain progenitor cells

- Best results in young patients

- Uncomplicated surgical handling

- Incomplete filling of defects

- Unsatisfactory results, age >40 years

- Creates defects in weight-bearing areas

non Requires two surgical procedures (harvest, implantation)

- Autologous cells must be

expanded in vitro

- Technically difficult surgical technique

- Creates defects in non-weight-bearing areas

(33-35)

II Natural scaffolds, carrying cells, and/or growth factors

Fibrin

- Improved histological appearance, but not to normal levels

- As carrier of growth factor cDNAs, produced good result in rat model

- Poor mechanical properties

- May evoke immune response

- Does not permit host cell in-growth

(39-43)

Collagen

- Native to joints

- Excellent histological result when carrying cells

or BMP-2

- Good early repair may thin over time

- Incomplete integration with host tissues

- Possible transmission of prion-induced disease (?)

- Repair cartilage is thinner than native tissue

(52-54)

- With BMP-2, good integration with host tissues

- Biochemical properties inferior to native tissue

- Inconsistent bone regeneration

- Good early histological result in rabbit and goat

(59, 60)

1.4.5 Cell based cartilage repair

Cell-based therapies have generated promises in cartilage repair strategies Different cell sources have been tested: Brittberg et al started using the cells

in cartilage repair in 1994 by using the autologous chondrocytes (29) (figure 1.5); and other teams such as Wakitani et al continued by using MSCs (61)

To date an optimized method, which can repair all different size and grade of the cartilage defects, has not been developed (figure 1.6)

1.4.5.1 Autologous chondrocyte implantation (ACI)

ACI requires two surgeries In the first step, a biopsy of normal articular

cartilage using an arthroscopic procedure is prepared from a minor bearing area Then, the chondrocytes are cultured and injected into the defect through arthrotomy and covered with a periosteal flap (figure 1.5) The

load-outcome of this technique would be a hyaline-like cartilage (8, 29)

long-cartilage (27)

1.4.5.2 Other Cell-based therapy methods

There are some other cell sources used for cartilage repair such as bone marrow derived stem cells (BM MSCs), adipose derived stem cells (ADSCs), periostal cells, skeletal muscle and synovial fibroblasts derived cells (63-68),

which we will not discuss about them in this chapter

1.4.5.3 Stem Cells in Articular Cartilage repair

Few groups are working on the use of progenitor cells in articular cartilage repair The cells demonstrate the stem-cell characteristics like colony

formation, migration and homing capability and differentiation potential They also exhibit the potential of residing in the different layers of the cartilage, which could help the healing process even in the late stages of OA Although use of stem cells is still controversial, optimized application may be a

promising strategy for cartilage repair

Figure 1-6 The cartilage repair strategy algorithm based on the lesion location and characteristics

(Adapted from (3))