Mesenchymal Stem Cell Differentiation in an Experimental Cartilage Defect: Restriction of Hypertrophy to Bone-Close Neocartilage

Abstract

Mesenchymal stem cells (MSCs) are promising for the treatment of articular cartilage defects; however, common protocols for in vitro chondrogenesis induce typical features of hypertrophic chondrocytes reminiscent of endochondral bone formation. Aim of the study was to compare chondrogenic differentiation of MSCs in vitro and in vivo in experimental full-thickness cartilage defects, asking whether MSCs can differentiate into collagen type X-negative chondrocytes in an orthotopic environment. Cartilage defects in knees of minipigs were covered with a collagen type I/III membrane, and half of them received transplantation of expanded autologous MSCs. At 1, 3, and 8 weeks, morphological and molecular aspects of repair were assessed. The orthotopic environment triggered a spatially organized repair tissue with upper fibrous, intermediate chondrogenic, and low layer hypertrophic differentiation of cells and a trend to more safranin-O and collagen type II-positive samples after MSC transplantation at 8 weeks. Compared to in vitro chondrogenesis, significant lower COL10A1/COL2A1 and MMP13/COL2A1 ratios were obtained for in vivo differentiation. This indicates that, as opposed to in vitro chondrogenic induction of MSCs, the in vivo signaling molecules and biomechanical stimuli provide an appropriate environment for progenitor cells to differentiate into collagen type X-negative chondrocytes. Thus, until better in vitro induction protocols become available for chondrogenesis of MSCs, their predifferentiation before transplantation may be unfavorable.

The chondrogenic differentiation of mesenchymal stem cells on an extracellular matrix scaffold derived from porcine chondrocytes

“…The adverse events of matrix calcification and hypertrophic changes were also much delayed and less significant in the ECM group. The defect area of the cartilage might not be the same as subcutaneous environment but is still under harsh conditions that are not favorable for chondrogenic differentiation and cartilage tissue formation of stem cells [36,37]. Therefore, we speculate that our ECM scaffold could also be a promising scaffold that can both support well chondrogenic differentiation of MSCs and reduce degenerative changes of engineered tissue in cartilage defect.…”

Cyclic hydrostatic pressure promotes a stable cartilage phenotype and enhances the functional development of cartilaginous grafts engineered using multipotent stromal cells isolated from bone marrow and infrapatellar fat pad

“…modulus of engineered cartilage is known to be strongly correlated to the sGAG content (Kelly et al, 2007;Vinardell et al, 2011), the dynamic modulus also strongly depends on the functionality of the collagen network, as it plays a key role in enabling the tissue to generate fluid load support (Ateshian, 2009). Within full thickness cartilage defects, it has been demonstrated that hypertrophy of implanted MSCs is restricted to a region of the regenerating tissue close to the bone, suggesting that biomechanical stimuli play a key role in determining the stability of the chondrogenic phenotype (Steck et al, 2009). The results of this study support this hypothesis, with the application of HP found to dramatically reduce the mineralisation of BMSC constructs cultured in a chondro-inductive medium.…”

“…Within the orthotopic environment of a full thickness cartilage defect, it has been demonstrated that hypertrophy of implanted multipotent stromal cells (MSCs) is restricted to a region of the regenerating tissue close to the bone, demonstrating that in vivo signalling molecules and biomechanical stimuli play a key role in regulating the chondrogenic phenotypic (Steck et al, 2009). Identifying how such in vivo specific environmental cues regulate the terminal phenotype of MSCs may play a key role in realising their full therapeutic potential.…”

Metabolic programming of mesenchymal stromal cells by oxygen tension directs chondrogenic cell fate

“…Unfortunately, it is not yet possible to steer the differentiation of MSCs into the formation of permanent hyaline cartilage. Instead, the present protocols for chondrogenically differentiating MSCs result in the production of neocartilage that is characterized by hypertrophic differentiation (6)(7)(8)(9). Consequently, the newly formed cartilage undergoes endochondral ossification upon implantation (8,(10)(11)(12).…”

“…Instead, the present protocols for chondrogenically differentiating MSCs result in the production of neocartilage that is characterized by hypertrophic differentiation (6)(7)(8)(9). Consequently, the newly formed cartilage undergoes endochondral ossification upon implantation (8,(10)(11)(12). In fact, it has been reported that, currently, the most efficient way to engineer new bone from multipotent progenitor cells is via implantation of in vitro-generated neocartilage (6).…”