Perivascular Stem Cells: A Prospectively Purified Mesenchymal Stem Cell Population for Bone Tissue Engineering

Abstract

Adipose tissue is an ideal source of mesenchymal stem cells for bone tissue engineering: it is largely dispensable and readily accessible with minimal morbidity. However, the stromal vascular fraction (SVF) of adipose tissue is a heterogeneous cell population, which leads to unreliable bone formation. In the present study, we prospectively purified human perivascular stem cells (PSCs) from adipose tissue and compared their bone-forming capacity with that of traditionally derived SVF. PSCs are a population (sorted by fluorescence-activated cell sorting) of pericytes (CD146؉CD34−CD45−) and adventitial cells (CD146−CD34؉CD45−), each of which we have previously reported to have properties of mesenchymal stem cells. Here, we found that PSCs underwent osteogenic differentiation in vitro and formed bone after intramuscular implantation without the need for predifferentiation. We next sought to optimize PSCs for in vivo bone formation, adopting a demineralized bone matrix for osteoinduction and tricalcium phosphate particle formulation for protein release. Patient-matched, purified PSCs formed significantly more bone in comparison with traditionally derived SVF by all parameters. Recombinant bone morphogenetic protein 2 increased in vivo bone formation but with a massive adipogenic response. In contrast, recombinant Nel-like molecule 1 (NELL-1; a novel osteoinductive growth factor) selectively enhanced bone formation. These studies suggest that adipose-derived human PSCs are a new cell source for future efforts in skeletal regenerative medicine. Moreover, PSCs are a stem cell-based therapeutic that is readily approvable by the U.S. Food and Drug Administration, with potentially increased safety, purity, identity, potency, and efficacy. Finally, NELL-1 is a candidate growth factor able to induce human PSC osteogenesis. STEM CELLS TRANSLATIONAL MEDICINE 2012;1:510 -519

Pericytes, mesenchymal stem cells and their contributions to tissue repair

“…Cultured, osteogenically-stimulated hiPSC-pericytes have also demonstrated mineral deposition and the formation of bone-like structures when implanted in vivo (Dar et al, 2012). Perivascular cells isolated from the SVF have been shown to generate greater ectopic bone formation in a humanmouse xenograft using biological scaffolds as compared to unsorted SVF, suggesting that these are the crucial SVF cells involved in osteogenesis (James et al, 2012a;James et al, 2012c). This is in line with the literature claiming that the quintessential MSC derives from the perivascular niche (Crisan et al, 2008).…”

“…Pericytes can also be differentiated from human induced pluripotent stem cells (hiPSC) by the generation of embryoid bodies or, more reproducibly, by culturing in standardised mTesR1 medium, replacing with mesoderm induction medium, and differentiating magnetically-isolated CD31-cells in 10% FBS DMEM supplemented with TGF-β3 and PDGF-BB (Orlova et al, 2014b). Another perivascular population located in the tunica adventitia of larger vessels (and therefore commonly referred to as adventitial cells) are, unlike other MSC, CD34+, and have also been shown to participate in tissue regeneration; many studies combine pericytes and adventitial cells for tissue engineering strategies (Askarinam et al, 2013;James et al, 2012a;James et al, 2012b;James et al, 2012c). This section reviews the current therapeutic potential for these perivascular populations in the fairly novel field of cell-based tissue engineering.…”

“…These populations may be combined to increase cell yield, and have been shown to undergo osteogenesis both in vitro as assessed by positive alkaline phosphatase staining and formation of bone nodules, and in vivo, whereby intramuscular insertions of perivascular cells on collagen sponges induced spontaneous mineralisation (James et al, 2012a;James et al, 2012c). Cultured, osteogenically-stimulated hiPSC-pericytes have also demonstrated mineral deposition and the formation of bone-like structures when implanted in vivo (Dar et al, 2012).…”

Antioxidative fullerol promotes osteogenesis of human adipose-derived stem cells

“…[6][7][8][9][10][11] While combined delivery of ADSCs and growth factors has been reported to enhance osteogenesis in vivo, 9,10,12 contradictory reports have been published that raise a serious concern about the efficacy of this approach. For example, ADSCs do not respond to various bone morphogenetic proteins (BMPs) in vitro.…”

Human Perivascular Stem Cell-Based Bone Graft Substitute Induces Rat Spinal Fusion

“…The evidence supporting the use of human perivascular stem cells (hPSCs) for bone tissue engineering is based on our prior studies: firstly, human pericytes derived from pancreas (and other organs) exhibit robust in vitro osteogenic differentiation and intramuscular bone formation and angiogenesis [31]. Next, adipose-derived hPSCs form significantly increased intramuscular bone compared with patient-matched unpurified cells and demonstrate in vivo trophic and angiogenic effects [32,33]. Lastly adipose-derived hPSCs exhibited improved calvarial bone defect healing as compared with unsorted SVF [34].…”