Chondrogenic Differentiation Induction of Adipose-derived Stem Cells by Centrifugal Gravity

Summary

Mechanical stress can induce the chondrogenic differentiation of stem cells, providing a potential therapeutic approach for the repair of impaired cartilage. We present a protocol to induce the chondrogenic differentiation of adipose-derived stem cells (ASCs) using centrifugal gravity (CG). CG-induced upregulation of SOX9 results in the development of chondrogenic phenotypes.

Abstract

Impaired cartilage cannot heal naturally. Currently, the most advanced therapy for defects in cartilage is the transplantation of chondrocytes differentiated from stem cells using cytokines. Unfortunately, cytokine-induced chondrogenic differentiation is costly, time-consuming, and associated with a high risk of contamination during in vitro differentiation. However, biomechanical stimuli also serve as crucial regulatory factors for chondrogenesis. For example, mechanical stress can induce chondrogenic differentiation of stem cells, suggesting a potential therapeutic approach for the repair of impaired cartilage. In this study, we demonstrated that centrifugal gravity (CG, 2,400 × g), a mechanical stress easily applied by centrifugation, induced the upregulation of sex determining region Y (SRY)-box 9 (SOX9) in adipose-derived stem cells (ASCs), causing them to express chondrogenic phenotypes. The centrifuged ASCs expressed higher levels of chondrogenic differentiation markers, such as aggrecan (ACAN), collagen type 2 alpha 1 (COL2A1), and collagen type 1 (COL1), but lower levels of collagen type 10 (COL10), a marker of hypertrophic chondrocytes. In addition, chondrogenic aggregate formation, a prerequisite for chondrogenesis, was observed in centrifuged ASCs.

Introduction

Defects in articular cartilage do not heal naturally. Consequently, stem cell transplantation has been proposed as a promising approach for the repair of impaired cartilage. However, this method requires both the acquisition of a sufficient number of stem cells and the induction of these cells to undergo chondrogenic differentiation. Bone marrow (BM) has been widely used as a source of stem cells, but cell isolation from BM has two major disadvantages: invasiveness and insufficient yield. Because of its ease of acquisition, adipose tissue is a preferable source of stem cells. Previous studies demonstrated the feasibility of isolating stem cells from adipose tissue and....

Protocol

This study protocol was approved by the institutional review board of The Catholic University of Korea (KC16EAME0162) and performed according to NIH guidelines. All tissues were obtained with written informed consent.

1. Centrifugal Gravity Loading and Pellet Culture

1. Cell culture and harvest
   1. Culture ASCs (P2-P3; see List of Materials) in Dulbecco's Modified Eagle's Medium-low glucose (DMEM-LG) supplemented with 10% fetal bovine serum (FBS) and 1% penicillin/streptomycin (P/S) at 37 °C in a humidified incubator containing 5% CO₂.
   2. When the cells reach 80% confluence, discard the mediu....

Results

Centrifugal gravity induces the overexpression of chondrogenic differentiation markers in adipose-derived stem cells.

To determine the degree of centrifugal gravity force that is suitable to induce chondrogenic differentiation, ASCs were stimulated with different degrees of CG (0, 300, 600, 1,200, and 2,400 x g) for 15 min. After stimulation, the ASCs were re-seeded onto culture plates and cultured for 24 h. As shown in .......

Discussion

The stemness state of cells is very important for CG-induced overexpression of SOX9. In our study, SOX9 expression could be induced by CG in early-passage ASCs (2-3), but not in later-passage ASCs. It has been reported that, during cultivation, ASCs contain CD34+ cells until 3 passages¹⁶. ASCs tend to lose the expression of CD34 as the cells are passaged, resulting in a low response to CG.

With centrifugal gravity force, hydrostatic pressure can be loaded onto cells dur.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Plasticware
100 mm Dish	TPP	93100
60 mm Dish	TPP	93060
50 mL Cornical Tube	SPL	50050
15 mL Cornical Tube	SPL	50015
10 mL Disposable Pipette	Falcon	7551
5 mL Disposable Pipette	Falcon	7543
ASC Culture Media Materials
DPBS	Life Technologies	14190-144
DMEM Low glucose	Life Technologies	11885-084	growth base media
Penicilin Streptomycin	Sigma Aldrich	P4333	1%
Fetal Bovine Serum	Life Technologies	16000-044	10%
PBS/1 mM EDTA	Life Technologies	12604-039
Chondrogenic Differentiation Media Materials
DMEM High glucose	Life Technologies	11995	chondrogenic differentiation base media
MEM Non-Essential Amino Acids Solution (100x)	Life Technologies	11140-050
Dexamethasone	Sigma Aldrich	D2915	100 nM
Penicilin Streptomycin	Life Technologies	P4333	1%
Fetal Bovine Serum	Life Technologies	16000-044	1%
Ascorbate-2-phosphate	Sigma Aldrich	A8960	50 μg/mL
L-proline	Sigma Aldrich	P5607	50 μg/mL
ITS	BD	354352	1%
Human TGFβ1	Peprotech	100-21	10 ng/mL
Materials
18 mm Cover Glass	Superior	HSU-0111580
4% Paraformaldyhyde	Tech & Innovation	BPP-9004
Tween 20	BIOSESANG	T1027
Bovine Serum Albumin	Vector Lab	SP-5050
Anti-Collagen II antibody	abcam	ab34712	1:100
Goat anti-Rabbit IgG (H+L) Secondary Antibody, Alexa Fluor 594 conjugate	Molecular Probe	A-11037	1:200
DAPI	Molecular Probe	D1306
Prolong gold antifade reagent	Invitrogen	P36934
Slide Glass, Coated	Hyun Il Lab-Mate	HMA-S9914
Trizol	Invitrogen	15596-018
Chloroform	Sigma Aldrich	366919
Isoprypylalcohol	Millipore	109634
Ethanol	Duksan	64-17-5
RevertAid First Strand cDNA Synthesis kit	Thermo Scientfic	K1622
i-Taq DNA Polymerase	iNtRON BIOTECH	25021
UltraPure 10x TBE Buffer	Life Technologies	15581-044
loading star	Dyne Bio	A750
Agarose	Sigma-Aldrich	9012-36-6
1 kb (+) DNA ladder marker	Enzynomics	DM003
Human adipose-derived stem cells (ASCs)	Catholic MASTER Cells