Background: Stem cell therapy has attracted much interest in the 21st century, not only because of the controversy surrounding the ethics involving pluripotent stem cells, but their potential for clinical use. Objectives: The present review highlights the stem cells niche, types, identification, and characterization, mechanisms of regeneration by using stem cells, and applications in joint disease remedy. Stem cells could be well differentiated cells with the potential to display different cell types depending on the host niche. Niche is defined as the cellular microenvironment providing support and stimuli to control the properties of stem cells. It consists of signaling molecules, inter-cell contacts and interaction between stem cells and their extracellular matrix neighbors. Stem cells are classified according to their sources into two main types, the embryonic and non-embryonic. Embryonic stem cells are pluripotent and can differentiate into all germ layers. Non-embryonic stem cells can be sub-classified into fetal stem cells and adult stem cells. Cultured cells can be made to differentiate into exclusive lineages by providing selective media components that can be identified by histochemical staining and quantified by quantitative Real-time polymerase chain reaction. Mesenchymal stem cells (MSCs) can be identified based on the expression of specific proteins called surface antigen phenotype of mesenchymal stem cell markers. MSCs secrete a variety of interleukins, several neurotrophic factors, many cytokines, and growth factors. These secreted bioactive factors have both paracrine and autocrine effects, which are anti-fibrotic and anti-apoptotic, as well as enhance angiogenesis. Furthermore, they stimulate mitosis and differentiation of tissue-intrinsic reparative stem cells. Systemic MSC transplantation can engraft to an injured tissue and promote wound healing through differentiation, and proliferation in synergy with hematopoietic stem cells. MSCs have been shown to express a variety of chemokines and chemokine receptors and can home to sites of inflammation by migrating towards injury or inflammatory chemokines and cytokines. MSCs are proven to have immunomodulatory properties that are among the most intriguing aspects of their biology. The immunosuppressive properties of MSCs inhibit the immune response of naive and memory T cells in a mixed lymphocyte culture and induce mitogen. The systemic infusion of MSCs can be used in immunosuppressive therapy of various disorders. MSCs have become an alternative source of cells that can be drawn from several these cells have been used as treatment to repair cartilage defects at early stages sources. Using the MSCs and directing them into chondrogenic differentiation might lead to the formation of higher quality cartilage, which has a great composition of hyaline, adequate structural reorganization and therefore improved biomechanical properties. Conclusion: It can be concluded that stem cells are classified according to their sources into two main types, the embryonic and non-embryonic. Embryonic stem cells are pluripotent and can differentiate into all germ layers. Non-embryonic stem cells can be sub-classified into fetal stem cells and adult stem cells. MSCs secrete bioactive factors that are anti-fibrotic and anti-apoptotic, as well as enhance angiogenesis. The systemic infusion of MSCs can be used in immunosuppressive therapy of various disorders. These cells have been used as treatment to repair cartilage defects at early stages.

Coronaviruses are a diverse group of viruses infecting many different animals, and they can cause mild to severe respiratory infections in humans. In 2002 and 2012, respectively, two highly pathogenic coronaviruses with zoonotic origin, severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV), emerged in humans and caused fatal respiratory illness, making emerging coronaviruses a new public health concern in the twenty-first century1. In early December 2019, an outbreak of coronavirus disease 2019 (COVID-19), caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), occurred in Wuhan City, Hubei Province, China. On January 30, 2020 the World Health Organization declared the outbreak as a Public Health Emergency of International Concern. As of February 14, 2020, 49,053 laboratory-confirmed and 1,381 deaths have been reported globally.

This work was for "Impression during Coronavirus Pandemic (CVP) on Behaviour of Infectious-microbial-disease (IMD) and Home-physical-tools (HPTs) in Saudi-public (SP)". The aim was for a clarify impression during CVP on changing behaviour of IMD and HPTs in SP. That was by making a questionnaire to obtain information from people in SP. It found participating 28.5% for < 20 yr and was 71.5% for > 20 yr, 31.5% were men and 68.5% were women. While 92.5% lived in families, were HPTs differed in 83.5%, 75.5% agreed presence source Coronavirus infection (CVI) in the HPTs. As well as 11.5% individuals had CVI, where 84.5% refused to use HPTs if were suspected of carrying the CVI patient. Once 94.5% was not dealing with individuals infected with CV. Anywhere, 69.5% agreed for good treatment with the CVI patient after recovery and so 73.5% acquired skills to change the behaviour of HPTs. From the whole caution handle was 29.5%, hand washing considered 20%, permanent sterilization was 18.5%. The use of gloves and facemasks was 16.5%, not use other peoples tools, it took 15.5%. That concluded from this paper the approved changes behaviour of IMD and HPTs in SP, that which had important for the decrease of CVP presence in SP and worldwide. That recommended the CVP is very risk in SP and worldwide and must take care of every behaviour in house to decrease CVI. We intend to do future research in changes behaviour in house to protect family members from CVI and save SP.

This research was for "Influence of Applying Preventive Health Conditions Strategy (PHCS) during Coronavirus Pandemic (CVP) in Kingdom of Saudi Arabia (KSA)". The target was through questionnaire to individuals in KSA. That application of PHCS and persons contribution accountable establishments, to cover Coronavirus infection (CVI), caused CVP and control to redact it, numbers to maintain Saudi health (SH). Using "Cross-sectional Study Method", were on Network for survey study in Saudi community (SC), collected data and had analyzed. Remained 99% participants to questionnaire about everyone, remained 89% dedicated to smearing PHCS closely a total. It was 100% reinforced PHCS, that 98% had approving support non-compliance PHCS. As stayed 83% stationary numerous parties from their doings, and was 100% all individuals, braked family visits in anticipation of any CVI. That stared 85% immobile market exit except for about individuals since it was a need to achieve family responsibilities, and others dedicated at home to decrease CVI. Experiential 74% produced the PHCS to have injury in three quarters because of discontinuing the numerous doings. Here 26% originated that a quarter of persons had cases of CVI, where 55% the relations applied the PHCS about partial because of the attendance of people with the similar family. That concluded the results showed the existence of the PHCS importance in the existence and importance of the CVP. The extent to KSA individuals helped to reduce CVI and protect SH. That recommended PHCS position to SH reserve, deliver a fit culture, and reinforce persons for their help.

This paper was for "Individuals Expectations Once Coronavirus Vaccine (CVV) Successful and Available in Saudi Society (SS)". The aim was for review community members opinion importance during the Coronavirus pandemic (CVP), obtaining Coronavirus infection (CVI) protection, thereby reducing CVI, protection, and maintaining the public health (PH) in SS, that used as survey by questionnaire in SS. The results showed all participating < 20*yr were 40% and > 20yr were 60%, the women were 50% equal to men 50% participating. The participants 85.5% stated about the difficulty of the CVP period. It was 83.5% of the participants agreed prefer a CVV if it is available. That cleared 38.5% agreed on the presence of the CVV for protection a period of six months only. That was 72.5% they want and prefer for the protection of the CVV be for a period of one year. So appeared 52.5% agreed to buy the vaccine from his own money. It was 85.5% of the participants confirmed to protect family members by using the CVV if it is available; also 85.5% strongly affirm that individual members of SS must take the CVV, if it is available. That presented 47.5% of the participants confirmed the use of the CVV if it is available and even if it had side effects. That concluded CVV presence important for individuals to CVI protect and affect life in SS. Recommended the CVV important to protect against CVI and must be dealt with when its quality and use in SS and worldwide.

Viruses mutate all the time, and the coronavirus that causes COVID-19 is no exception. As new variants of the COVID-19 emerge, a slew of new studies suggest that some may be able to evade immune responses triggered by a previous infection or by a vaccine. The novel variants of SARS-CoV-2 including those seen in the UK (2OI/5O1Y.V1/B.1.1.7), South Africa (2OH/5O1Y.V2/B.1.351), Brazil (P.1/2OJ/5O1Y.V3/B.1.1.248) have emerged with the concern of increased infectivity and virulence. Scientists are working to learn more about the characteristics of these strains whether they could cause more severe illness, and whether currently authorized vaccines will protect people against them. All viruses naturally mutate and evolve over time. For example, flu virus change often, which is why doctors recommend that you get a flu shot every year. Various mRNA vaccine platforms have been developed in recent years and validated in studies of immunogenicity and efficacy.