Stem Cell Research & Therapy | Abstract | Adipose stem cells can secrete angiogenic factors that inhibit hyaline cartilage regeneration

Stem Cell Research & Therapy | Abstract | Adipose stem cells can secrete angiogenic factors that inhibit hyaline cartilage regeneration

Adipose stem cells can secrete angiogenic factors that inhibit hyaline cartilage regeneration

Christopher SD Lee, Olivia A Burnsed, Vineeth Raghuram, Jonathan Kalisvaart, Barbara D Boyan and Zvi Schwartz

Stem Cell Research & Therapy 2012, 3:35 doi:10.1186/scrt126
Published: 24 August 2012

Abstract (provisional)

Introduction

Adipose stem cells (ASCs) secrete many trophic factors that can stimulate tissue repair, including angiogenic factors, but little is known about how ASCs and their secreted factors influence cartilage regeneration. Therefore, the aim of this study was to determine the effects ASC-secreted factors have in repairing chondral defects.

Methods

ASCs isolated from male Sprague Dawley rats were cultured in monolayer or alginate microbeads supplemented with growth (GM) or chondrogenic medium (CM). Subsequent co-culture, conditioned media, and in vivo cartilage defect studies were performed.

Results

ASC monolayers and microbeads cultured in CM had decreased FGF-2 gene expression and VEGF-A secretion compared to ASCs cultured in GM. Chondrocytes co-cultured with GM-cultured ASCs for 7 days had decreased mRNAs for col2, comp, and runx2. Chondrocytes treated for 12 or 24 hours with conditioned medium from GM-cultured ASCs had reduced sox9, acan, and col2 mRNAs; reduced proliferation and proteoglycan synthesis; and increased apoptosis. ASC-conditioned medium also increased endothelial cell tube lengthening whereas conditioned medium from CM-cultured ASCs had no effect. Treating ASCs with CM reduced or abolished these deleterious effects while adding a neutralizing antibody for VEGF-A eliminated ASC-conditioned medium induced chondrocyte apoptosis and restored proteoglycan synthesis. FGF-2 also mitigated the deleterious effects VEGF-A had on chondrocyte apoptosis and phenotype. When GM-grown ASC pellets were implanted in 1 mm non-critical hyaline cartilage defects in vivo, cartilage regeneration was inhibited as evaluated by radiographic and equilibrium partitioning of an ionic contrast agent via microCT imaging. Histology revealed that defects with GM-cultured ASCs had no tissue ingrowth from the edges of the defect whereas empty defects and defects with CM-grown ASCs had similar amounts of neocartilage formation.

Conclusions

ASCs must be treated to reduce the secretion of VEGF-A and other factors that inhibit cartilage regeneration, which can significantly influence how ASCs are used for repairing hyaline cartilage.

Stem cells may prevent post-injury arthritis

Contact: Mary Jane Gore
mary.gore@duke.edu
919-660-1309
Duke University Medical Center

Stem cells may prevent post-injury arthritis

DURHAM, N.C.-- Duke researchers may have found a promising stem cell therapy for preventing osteoarthritis after a joint injury.
Injuring a joint greatly raises the odds of getting a form of osteoarthritis called post-traumatic arthritis, or PTA. There are no therapies yet that modify or slow the progression of arthritis after injury.
Researchers at Duke University Health System have found a very promising therapeutic approach to PTA using a type of stem cell, called mesenchymal stem cells (MSCs), in mice with fractures that typically would lead to them developing arthritis. Their findings could lead to a therapy that would be used after joint injury and before signs of significant osteoarthritis.
The scientists thought the stem cells would work to prevent PTA by altering the balance of inflammation and regeneration in knee joints, because these stem cells have beneficial properties in other regions of the body.
"The stem cells were able to prevent post-traumatic arthritis," said Farshid Guilak, Ph.D., director of orthopaedic research at Duke and senior author of the study.
The study was published on August 10 in Cell Transplantation.
The researchers also thought that a type of mice bred for their super-healing properties would probably fare better than typical mice, but they were wrong.
"We decided to investigate two therapies for the study, said lead author Brian Diekman, Ph.D., a postdoctoral researcher in the Guilak lab. "We thought that stem cells from so-called superhealer mice would be superior at providing protection, and instead, we found that they were no better than stem cells from typical mice. We thought that maybe it would take stem cells from superhealers to gain an effect as strong as preventing arthritis after a fracture, but we were surprised – and excited – to learn that regular stem cells work just as well."
Certain people appear to fall into the superhealer category, too. They bounce back quickly and heal well naturally after a fracture, while other people eventually form cases of arthritis at the fractured joint, said Guilak, who is a professor of orthopaedic surgery and biomedical engineering.
"The ability of the superhealer mice to have superior healing after a fracture may go beyond the properties of their stem cells and be some beneficial factor, like a growth factor, that we don't know about yet," Guilak said.
The delivery of 10,000 typical or superhealer stem cells to the joint prevented the mice from developing PTA, unlike a control group that received only saline.
Diekman said the team looked at markers of inflammation and saw that the stem cells affected the inflammatory environment of the joint after fracture.
"The stem cells changed the levels of certain immune factors, called cytokines, and altered the bone healing response," said Diekman, who is also with the Duke Department of Biomedical Engineering.
Guilak said that very few studies have purified stem cells to the degree they were purified for this study. They used mesenchymal stem cells, which are bone marrow cells not destined to become part of blood.
Diekman said that one of the challenges in the field is isolating and developing a system for sorting the specific cells they wanted, the mesenchymal stem cells, which form a very rare cell type in the bone marrow.
"We found that by placing the stem cells into low-oxygen conditions, they would grow more rapidly in culture so that we could deliver enough of them to make a difference therapeutically," Diekman said.

###

Funding came from the Arthritis Foundation and NIH grant AR50245.
Other authors include Craig R. Louer, Bridgette D. Furman and Steven A. Olson of the Duke Department of Orthopedic Surgery; Chia-Lung Wu of Orthopedic Surgery and the Department of Biomedical Engineering; and Janet L. Huebner and Virginia B. Kraus of the Duke Department of Medicine.