You are presented with a paragraph from a COVID-19 literature. Classify the topics of this piece of text by choosing from the following categories:

- Epidemic Forecasting: The content relates to predictions about the spread of COVID-19.
- Treatment: The paragraph discusses therapeutic methods or medication for COVID-19.
- Prevention: The content covers measures to prevent the spread of COVID-19.
- Mechanism: The paragraph explains the biological mechanisms of the virus.
- Case Report: The content is a report of a COVID-19 case.
- Transmission: The paragraph discusses how COVID-19 is transmitted.
- Diagnosis: The content is about diagnosing COVID-19 in individuals.

Your classification should be provided as an element within a JSON array. The array should be formatted with topics enclosed in double quotes and separated by commas, following the JSON format, for example: ["Topic1", "Topic2", ...]. Include all applicable topics within the array. Your output should be a valid JSON array, and no additional text should be included in your response.

Article:

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is causing an ongoing pandemic of coronavirus disease 2019 (Covid-19). Effective therapies are required for the treatment of patients with severe stages of the disease. Mesenchymal stem cells (MSCs) have been evaluated in numerous clinical trials, but present challenges, such as carcinogenic risk and special storage conditions, coupled with insufficient data about their mechanism of action. The majority of unique properties of MSCs are related to their paracrine activity and especially to their exosomes. The impact of MSCs-derived exosomes (MSC-Es) on complications of Covid-19 has been investigated in several studies. MSC-Es may improve some complications of Covid-19 such as cytokine storm, acute respiratory distress syndrome (ARDS) and acute lung injury (ALI). Additionally, these exosomes can be evaluated as an applicable nano-size carrier for antiviral therapeutic agents. Herein, we consider several potential applications of MSCs and their derived exosomes in the treatment of Covid-19.
["Treatment"]