2.Bone physiology and mineralization
Bone is a highly specialized connective tissue which has important physiological and mechanical functions 10. In addition to its role in providing rigidity to the skeleton for locomotion and protection of visceral organs; it plays other crucial vital functions 11. Bone formation occurs by either process: endochondral ossification or intramembraneous ossification 12.
Bone as a structure consists of matrix, minerals and osteogenic cells. The matrix is composed mainly of type I collagen, proteoglycans, and non-collagenous proteins including osteopontin (OPN), osteocalcin (OCN) and osteonectin secreted by osteoblasts. Two thirds of total bone matrix is made up of HA crystals or calcium phosphate ions. Other minerals include magnesium, potassium, and sodium 10.
Cells within the bone include osteoblast, osteoclast, and osteocytes. Osteoblasts major function is the synthesis of collagen and organic matrix. Osteoclasts functions in bone remodeling i.e. degradation of the bone matrix by the release of acid and lytic enzymes 13. Osteocytes act as mechanosensors converting the mechanical force stimulus into biochemical signals and actively involved in bone turnover 14.
2.1Biomineralization Process
Biomineralization is the process of mineral deposition in particular tissues leading to hardening and stiffening of the mineralized tissue. It occurs in various living organisms, of which are the vertebrates where the deposited mineral is HA. It is a well-orchestrated process of crystal formation within matrix vesicles (MVs) budding from the surface of hypertrophic chondrocytes, osteoblasts and odontoblast and their deposition in between collagen fibrils lying in the extracellular matrix.15 Recent in vitro studies have shown that MVs are not the exclusive vesicles which function in HA nucleation. Rather, in various osteoblastic cultures, nucleation occurs within various cell derived structures including in addition to MVs, calcospherulites and biomineralization foci.16 In this manuscript focus will be on MVs because these are the most studied and well defined. MVs are membrane invested vesicles that contain all necessary biochemical machinery required for availability of raw mineralization materials and balancing the inorganic pyrophposphate/ inorganic phosphate (PPi/Pi) ratio. A recent proposed mechanism for mineralization steps include: 1) HA crystals nucleation within MVs, 2) MVs bud from bone (cartilage or dentin) forming cells and interact with collagen fibrils through specific proteins and lipids, 3) MVs rupture and release HA into extracellular matrix (ECM).17 Tissue nonspecific alkaline phosphatase (TNAP) is an ectoenzyme linked to MVs membrane by glycosylphosphatidylinositol and function in hydrolysis of PPi providing Pi. 18PPi inhibit hydroxyapatite formation by binding to these crystals and preventing further growth. PPi is provided by ectonucleotidepyrophoshatase (NPP1) by the hydrolysis of adenosine triphosphate (ATP) preferentially and other nucleoside triphosphates such as guanosine triphosphates (GTP). PPi can also be provided from the membrane transporter: progressive Ankylosis protein homolog (ANKH). Within MVs Pi are provided by type III sodium/inorganic phosphate (Na/Pi) cotransporter and PHOSPHO1. PHOSPHO1 is a cytosolic phosphatase which cleaves Phosphatidylethanolamine (PE) and Phosphatidylcholine (PC) releasing Pi.19 The internal layer of MVs is rich in phosphatidylserine, a lipid with high affinity for both calcium and phosphate. MVs have the ability of interaction with collagen type II and X mediated by membrane bound annexin A5 (AnxA5) which are Ca2+ and phospholipid binding proteins stimulating Ca2+ influx into the vesicles.20 The process is mediated by the action of several molecules and steps making it highly regulated and complex(Figure 1).
Ectopic expression of TNAP is a very imortant factor behind pathological calciification knowing that TNAP and collagen type I proteins are sufficient for triggering extracellular matrix mineralization.20

2.Bone physiology and mineralization
Bone is a highly specialized connective tissue which has important physiological and mechanical functions 10. In addition to its role in providing rigidity to the skeleton for locomotion and protection of visceral organs; it plays other crucial vital functions 11. Bone formation occurs by either process: endochondral ossification or intramembraneous ossification 12.
Bone as a structure consists of matrix, minerals and osteogenic cells. The matrix is composed mainly of type I collagen, proteoglycans, and non-collagenous proteins including osteopontin (OPN), osteocalcin (OCN) and osteonectin secreted by osteoblasts. Two thirds of total bone matrix is made up of HA crystals or calcium phosphate ions. Other minerals include magnesium, potassium, and sodium 10.
Cells within the bone include osteoblast, osteoclast, and osteocytes. Osteoblasts major function is the synthesis of collagen and organic matrix. Osteoclasts functions in bone remodeling i.e. degradation of the bone matrix by the release of acid and lytic enzymes 13. Osteocytes act as mechanosensors converting the mechanical force stimulus into biochemical signals and actively involved in bone turnover 14.
2.1Biomineralization Process
Biomineralization is the process of mineral deposition in particular tissues leading to hardening and stiffening of the mineralized tissue. It occurs in various living organisms, of which are the vertebrates where the deposited mineral is HA. It is a well-orchestrated process of crystal formation within matrix vesicles (MVs) budding from the surface of hypertrophic chondrocytes, osteoblasts and odontoblast and their deposition in between collagen fibrils lying in the extracellular matrix.15 Recent in vitro studies have shown that MVs are not the exclusive vesicles which function in HA nucleation. Rather, in various osteoblastic cultures, nucleation occurs within various cell derived structures including in addition to MVs, calcospherulites and biomineralization foci.16 In this manuscript focus will be on MVs because these are the most studied and well defined. MVs are membrane invested vesicles that contain all necessary biochemical machinery required for availability of raw mineralization materials and balancing the inorganic pyrophposphate/ inorganic phosphate (PPi/Pi) ratio. A recent proposed mechanism for mineralization steps include: 1) HA crystals nucleation within MVs, 2) MVs bud from bone (cartilage or dentin) forming cells and interact with collagen fibrils through specific proteins and lipids, 3) MVs rupture and release HA into extracellular matrix (ECM).17 Tissue nonspecific alkaline phosphatase (TNAP) is an ectoenzyme linked to MVs membrane by glycosylphosphatidylinositol and function in hydrolysis of PPi providing Pi. 18PPi inhibit hydroxyapatite formation by binding to these crystals and preventing further growth. PPi is provided by ectonucleotidepyrophoshatase (NPP1) by the hydrolysis of adenosine triphosphate (ATP) preferentially and other nucleoside triphosphates such as guanosine triphosphates (GTP). PPi can also be provided from the membrane transporter: progressive Ankylosis protein homolog (ANKH). Within MVs Pi are provided by type III sodium/inorganic phosphate (Na/Pi) cotransporter and PHOSPHO1. PHOSPHO1 is a cytosolic phosphatase which cleaves Phosphatidylethanolamine (PE) and Phosphatidylcholine (PC) releasing Pi.19 The internal layer of MVs is rich in phosphatidylserine, a lipid with high affinity for both calcium and phosphate. MVs have the ability of interaction with collagen type II and X mediated by membrane bound annexin A5 (AnxA5) which are Ca2+ and phospholipid binding proteins stimulating Ca2+ influx into the vesicles.20 The process is mediated by the action of several molecules and steps making it highly regulated and complex(Figure 1).
Ectopic expression of TNAP is a very imortant factor behind pathological calciification knowing that TNAP and collagen type I proteins are sufficient for triggering extracellular matrix mineralization.20

2.5 Type of car seat material
To fabricate a ventilated car seat Nylon Fabric, Faux Vinyl, PCV, Vinyl, Faux Leather, Suede and Brushed Nylon is the common material used. Each material is described briefly in section 2.5.1 to 2.5.7.
2.5.1 Nylon Fabric
Nylon is a durable, hard-wearing upholstery fabric which comes in many colours. There are plain and patterned designs and you can choose a type which best suits the interior of your vehicle. Because nylon is weaved, it is harder to tear than some fabrics. It is also very stain resistant, providing you can wash out any spills before the dry. It is also the most popular form of fabric found in most automobiles. It is available in many colours and is the least expensive form of trim for your vehicle (Willis, 2014).
2.5.2 Faux Vinyl
This is actually a vinyl which takes on the characteristics of leather or suede or other types of material. It is hard-wearing and can have the appearance and shine of soft leather or the dullness of fabric trim. Faux vinyl is a mock vinyl which emulates the real article at a fraction of the cost (Willis, 2014).
2.5.3 PCV Leather
Commonly known as soft plastic, this is a vinyl style-material that is pliable and easy to form. It stretches well and is used in lower-end models of cars and vans. It can be coloured or made in black and white, but it is notorious for being sticky to sit on during the summer. Heat has a tendency to make the upholstery sweat and the driver of the vehicle is best advised not to wear shorts in the summer if their vehicle is lined with PVC (Willis, 2014).
2.5.4 Vinyl
Easy to wipe clean, durable and hard wearing, vinyl is another coonly used material in the making of automobile upholstery. It has similar properties to PVC but vinyl can soft, hard, pliable or firm. You might be aware that old LP records were made from vinyl but, because it is used in a different capacity for upholstery, it can be as soft as velvet although it will still make the skin sweat during hot periods of weather (Willis, 2014).
2.5.5 Faux Leather
Faux leather is a very versatile material that can be made to appear like almost anything. People have covered their car seats in fake crocodile skin, fake snake’s skin and even dinosaur prints. It behaves like leather and is easy to wipe clean. Spillages can be quickly dealt with so faux leather doesn’t stain easily and is very durable (Willis, 2014).
2.5.6 Suede
Cloth-based suede fabrics are a nice choice for an automobile interior. Suede is soft to the touch and feels like brushed cotton. This automobile fabric is not used as often because it stains easily and it not as durable for many types of automobile use (Willis, 2014).
2.5.7 Brushed Nylon
Brushed nylon is soft and warm and ideal for an interior seat cover or door trim. It is a thick fabric that is usually just under a ¼ thick when used in vehicles. It seems well and is a firm, durable material which is quite hard to tear (Willis, 2014).

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