Osteogenic Differentiation of Human Bone Marrow Stromal Cells in Hydroxyapatite-Loaded Microsphere-Based Scaffolds

Abstract

Calcium-based minerals have consistently been shown to stimulate osteoblastic behavior in vitro and in vivo. Thus, use of such minerals in biomaterial applications has become an effective method to enhance bone tissue engineered constructs. In the present study, for the first time, human bone marrow stromal cells (hBMSC) were osteogenically differentiated on scaffolds consisting only of hydroxyapatite (HAp)-loaded poly(d,l-lactic acidco-glycolic acid) (PLGA) microspheres of high monodispersity. Scaffold formulations included 0, 5, 10, and 20 wt% Hap, and the hBMSC were cultured for 6 weeks. Results demonstrated suppression of some osteogenic genes during differentiation in the HAp group, but higher end-point glycosaminoglycan and collagen content in 10% and 20% HAp samples, as evidenced by biochemical tests, histology, and immunohistochemistry. After 6 weeks of culture, constructs with 0% and 5% HAp had average compressive moduli of 0.7 -0.2 and 1.5 -0.9 kPa, respectively, whereas constructs with 10% and 20% HAp had higher average moduli of 17.6 -4.6 and 18.9 -8.1 kPa, respectively. The results of this study indicate that HAp inclusion in microsphere-based scaffolds could be implemented as a physical gradient in combination with bioactive signal gradients seen in previous iterations of these microsphere-based scaffolds to enhance osteoconduction and mechanical integrity of a healing site.

Tailoring of processing parameters for sintering microsphere‐based scaffolds with dense‐phase carbon dioxide

“…The most crucial process that microsphere-based scaffolds have in common is the need to sinter the microspheres into a single, cohesive structure. Heat 7–11 or ethanol 5,12,13 (or 5% acetone in ethanol for some nanocomposites) 14,15 have traditionally been used to join microspheres together, and approaches to compare various solvents such as acetone and tetrahydrofuran (together with hexane as a non-solvent) have been investigated as well for sintering microspheres. 16 However, CO 2 may be an attractive alternative for sintering these scaffolds.…”

Microsphere-Based Gradient Implants for Osteochondral Regeneration: a Long-Term Study in Sheep

“…Hence, the current study investigated the potential of implanting gradient scaffolds engineered to recruit stem cells from the bone marrow into large defects for the purpose of regenerating bone and cartilage. We have previously investigated the potential of the microsphere-based scaffolds with gradients of growth factors, raw materials and combinations for both osteochondral tissue engineering in vitro and osteochondral regeneration in vivo in rabbits [10,20,[35][36]. This is our first report on the long-term outcome of the implant of these gradient scaffolds in critical size osteochondral defects (6 mm diameter × 6 mm depth) in a large animal model.…”

“…Instead, a 'raw materials' approach was taken whereby natural materials are leveraged both as building blocks to be incorporated into regenerating tissue and as signaling molecules to elicit desirable responses from infiltrating cells [40]. Our previous studies have demonstrated favorable cell responses to chondroitin sulfate [20,[41][42], and β-TCP is a well-known building block for bone regeneration, which is more easily integrated into regenerating bone than the hydroxyapatite we have used in our previous microsphere-based scaffold studies [10,35,43].…”

Microsphere-based scaffolds encapsulating tricalcium phosphate and hydroxyapatite for bone regeneration

“…The net ceramic content encapsulated in TCP/HAp 7:3 and TCP/HAp 1:1 groups was 30 wt%. Using the PLGA-protein and PLGA-TCP/HAp emulsions, microspheres with mean diameters ranging from 172–186 µm (Supplementary Figure 1), were fabricated via our previously reported technology [32, 21, 33, 22, 23, 27, 34, 24, 35, 28, 25, 26, 36–38]. Briefly, using acoustic excitation produced by an ultrasonic transducer (Branson Ultrasonics, Danbury, CT), regular jet instabilities were created in the polymer stream, thereby creating uniform polymer droplets.…”