Megakaryocytes Enhance Mesenchymal Stromal Cells Proliferation and Inhibit Differentiation

Abstract

Megakaryocytes (MKs) can induce proliferation of calvarial osteoblasts [Ciovacco et al., 2009], but this same phenomenon has not been reported for bone marrow stromal populations from long bones. Bone marrow contains several types of progenitor cells which can be induced to differentiate into multiple cell types. Herein, we examined mesenchymal stromal cell proliferation and osteoblastic differentiation when rabbit or mouse MK were cultured with i) rabbit bone marrow stromal cells, ii) rabbit dental pulp stromal cells, or iii) mouse bone marrow stromal cells. Our results demonstrated that rabbit and mouse stromal cells co-cultured with rabbit MK or mouse MK, have significant increases in proliferation on day 7 by 52%, 46%, and 24%, respectively, compared to cultures without MK. Conversely, alkaline phosphatase (ALP) activity was lower at various time points in these cells when cultures contain MK. Similarly, calcium deposition observed at day 14 rabbit bone marrow and dental pulp stromal cells and day 21 mouse bone marrow stromal cells was 63%, 69%, and 30% lower respectively, when co-cultured with MK. Gene expression studies reveal transcriptional changes broadly consistent with increased proliferation and decreased differentiation. Transcript levels of c-fos (associated with cell proliferation) trended higher after 3, 7, and 14 days in culture. Also, expression of alkaline phosphatase, osteonectin, osterix, and osteopontin, which are markers for osteoblast differentiation, showed MK-induced decreases in a cell type and time dependent manner. Taken together, these data suggest that MK play a role in stromal cell proliferation and differentiation, from multiple sites/locations in multiple species. This article is protected by copyright. All rights reserved.

Effects of mechanobiological signaling in bone marrow on skeletal health

“…RT‐qPCR found that c‐Fos expression increased threefold in the loaded limb compared with the contralateral unloaded control limb, which is similar to the response of osteocytes . Multiple in vitro studies have shown that megakaryocytes affect osteoblast and osteoclast differentiation and activity . Interestingly, when megakaryocytes were exposed to fluid shear, the conditioned media inhibited osteogenesis in the MC3T3 osteoblast cell line .…”

“…Individual bone marrow–resident cells have been studied in in vitro culture and subjected to mechanical loads, demonstrating that the relevant cells are mechanosensitive. Coculture has further demonstrated that both mesenchymal and hematopoietic lineage cells in the marrow interact with osteocytes and osteoblast precursors through various signaling pathways . While understanding bone marrow response as a tissue has proven challenging, a seminal in vitro study of bone marrow aliquots subjected to compressive load and another novel in vivo study based on bone marrow transplantation have allowed us to separate mechanobiological signaling from osteocytes from that of marrow to identify potential biological pathways and cellular structures that affect bone adaptation through mechanical stimuli acting in the marrow cavity …”

Craniofacial Bone Tissue Engineering: Current Approaches and Potential Therapy

“…BMSCs are adult multipotent stem cells derived from bone marrow tissue [ 47 ]. BMSCs are a promising cell source due to their self-renewal and multipotency by differentiating into different cell types, such as osteoblasts, chondrocytes, and adipocytes [ 125 , 206 , 209 , 223 , 224 , 225 , 226 , 227 , 228 , 229 ]. BMSCs are attractive MSCs that have high therapeutic potential.…”

“…However, whether or not MKs can facilitate MSCs proliferation and differentiation to regenerate cranial bone defects is a question yet to be addressed. Particularly, the effects of increasing MK count to enhance viability and differentiation of BMSCs or DPSCs in vivo for cranial bone tissue engineering purposes has not been determined [ 125 ].…”

“…Studies have shown that increasing MKs, and ultimately platelets can be a potential risk causing bone marrow fibrosis [ 122 , 126 ]. Furthermore, a co-culture study of MKs with MSCs has reported that MKs inhibit MSC differentiation into osteoblast lineage cells by suppressing expression of ALP activity and calcium deposition [ 125 ].…”