Solmaz Zakhireh
1,2 
, Jaleh Barar
3,4* , Younes Beygi-Khosrowshahi
5, Abolfazl Barzegari
3, Yadollah Omidi
6, Khosro Adibkia
1,3,4* 1 Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
2 Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran
3 Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran
4 Department of Pharmaceutics, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran
5 Chemical Engineering Department, Faculty of Engineering, Azarbaijan Shahid Madani University, Tabriz, Iran
6 Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL 33328, USA
*Corresponding Author: Department of Pharmaceutics, Faculty of Pharmacy, Tabriz University of Medcal Sciences, Tabriz, Iran Email jbarar@tbzmed.ac.ir, adibkia@tbzmed.ac.ir
Abstract
Introduction: The current study, for the first time, suggests nature-made pollen grains (PGs) of Pistacia vera L. as a potential candidate for using as scaffolding building blocks with encapsulation capability of bioactive compounds, such as bone morphogenetic protein 4 (BMP4).
Methods: A modified method using KOH (5%, 25ºC) was developed to produce nonallergic hollow pollen grains (HPGs), confirmed by energy dispersive X-ray (EDX) analysis, field emission scanning electron microscopy (FESEM), and DNA and protein staining techniques. The in-vitro study was conducted on human adipose-derived mesenchymal stem cells (hAD-MSCs) to investigate the applicability of HPGs as bone scaffolding building blocks. Cytocompability was evaluated by FESEM, MTT assay, and gene expression analysis of apoptotic markers (BAX and BCL2). The osteoconductive potential of HPGs was assessed by alkaline phosphatase (ALP) activity measurement and gene expression analysis of osteogenic markers (RUNX2 and osteocalcin).
Results: Findings demonstrated that HPGs can be considered as biocompatible compounds increasing the metabolic activities of the cells. Further, the bioactive nature of HPGs resulted in suitable cellular adhesion properties, required for a potent scaffold. The investigation of apoptotic gene expression indicated a reduced BAX/BCL2 ratio reflecting the protective effect of HPGs on hAD-MSCs. The increased ALP activity and expression of osteogenic genes displayed the osteoconductive property of HPGs. Moreover, the incorporation of BMP4 in HPGs initiated a synergistic effect on osteoblast maturation.
Conclusion: Owing to the unique compositional and surface nanotopographical features of the Pistacia vera L. HPG, this microscale architecture provides a favorable microenvironment for the bottom-up remodeling of bone.