Comparative evaluation of MSCs from bone marrow and adipose tissue seeded in PRP-derived scaffold for cartilage regeneration

Abstract

The aims of this study were to (1) determine whether platelet-rich plasma (PRP) could be prepared as a bioactive scaffold capable of endogenous growth factor release for cartilage repair; (2) compare the chondrogenic differentiation ability of mesenchymal stem cells (MSCs) from bone marrow (BMSC) and from adipose (ADSC) seeded within the PRP scaffold; and (3) test the efficacy of ADSC-PRP construct in cartilage regeneration in vivo. In vitro evaluation showed that a 3-dimensional scaffold with a mesh-like microstructure was formed from PRP, with the capability of endogenous growth factor release and ready cell incorporation. Upon seeding in the PRP scaffold, BMSC showed higher proliferation rate, and higher expression of cartilage-specific genes and proteins than ADSC. In an osteochondral defect model in rabbits, implanted BMSC seeded within PRP scaffold also exhibited better gross appearance and histological and immunohistochemical characteristics, higher cartilage-specific gene and protein expression as well as subchondral bone regeneration. ADSC seeded constructs developed into functional chondrocytes secreting cartilaginous matrix in rabbits at 9 weeks post-implantation. Our findings suggest that PRP is a candidate bioactive scaffold capable of releasing endogenous growth factors and that BMSC and ADSC seeded within the PRP scaffold differentiate into chondrocytes and may be suitable for cell-based cartilage repair.

Introduction

Due to the poor regenerative capability of articular cartilage and currently limited clinical treatments, cartilage repair through tissue engineering has become a promising alternative in recent years. The engineered cartilage constructs classically require a combination of 3-dimensional scaffolds, chondrogenic cells and chondroinductive biofactors [1]. A number of natural and synthetic biomaterials have been developed as scaffolds for cartilage regeneration, but their biological efficiency as well as safety remains unsettled. Therefore, scaffold biomaterials harvested from the patients' own body have long been an appealing option. Among them, fibrin glue or fibrin gel has been widely employed as a cell carrier due to its excellent biodegradability, biocompatibility and cost-effectiveness [2], [3], [4]. Furthermore, cartilage regeneration can be enhanced if proper biofactors are added into fibrin-based scaffolds [5], [6].

Platelet-rich plasma (PRP), which can be easily isolated from autologous blood, has been used in clinical practice for decades. PRP is rich in growth factors, including those that promote proliferation of chondrogenic cells and secretion of cartilaginous matrix, such as transforming growth factor (TGF-β), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) [7], [8], [9]. PRP is most often considered as a bioaggregate of growth factors and used to supplement biomaterials. PRP can also be prepared with fibrinogen, which can be easily activated to form fibrin gel with thrombin or calcium. In this study, we hypothesized that autologous PRP could be employed alone as a 3-D scaffold capable of releasing endogenous growth factors for cartilage tissue engineering.

As chondrogenic cells, mesenchymal stem cells (MSCs) have advantages over chondrocytes, since they can be obtained autologously in a less invasive procedure and can be utilized to fabricate complex constructs to repair osteochondral defects. Bone marrow-derived MSCs (BMSC) was the original MSCs source and has been studied extensively in cartilage engineering and regeneration. However, there remain concerns over donor site morbidity and cell number decreasing with age. In recent years, MSCs derived from adipose tissue (ADSC) have been considered a potential alternative due to minimal donor site morbidity and more abundant availability. ADSC have been increasingly employed to repair cartilage defects with satisfactory results [10], [11], and the comparison between ADSC and BMSC in chondrogenic potential was also investigated [12], [13], [14]. However, these comparisons were overwhelmingly performed in vitro, and in vivo evaluations were seldom reported [15]. Accordingly, our second hypothesis was that, with the presence of PRP, ADSC are comparable to BMSC in terms of chondrogenesis in vitro and in vivo. In our study, ADSC were implanted and traced in rabbits to yield information on how ADSC contribute to cartilage regeneration.