# PC12 and THP-1 Cell Lines as Neuronal and Microglia Model in Neurobiological Research
## 3 Results and Discussion  
### PC12 Cell Line as Neurobiological Model  
The undifferentiated pheochromocytoma PC12 cells, due to their neoplastic origin, can be used in cancer research or pharmacological testing of newly discovered anticancer treatment [16]. However, incubation with NGF induces differentiation of these cells to sympathetic-like neurons, making them a valuable neuronal model used to study neurotoxicity or neuroprotective effect of newly synthesized drugs or discovered natural substances [15; 17; 18]. Differentiated PC12 cells also allow the study of the impact of these compounds on neurite outgrowth and neurodevelopment [19; 20]. PC12 cells expressing neuron-like properties, cultured in properly adjusted conditions, constitute an easily accessible and reliable model for studying pathomechanisms of neurodegenerative diseases like AD or Parkinson's disease and developing potentially effective treatments (Table 2) [10; 21; 22; 23; 24]. \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{2}{c}{**Undifferentiated PC12 Cells**} & \multicolumn{2}{c}{**Differentiated PC12 Cells**} \\ \hline \(\bullet\) & Pheochromocytoma cells & \(\bullet\) & Morphologically similar to sympathetic neurons \\ \(\bullet\) & Synthesize and secrete catecholamines & \(\bullet\) & Synthesize and secrete dopamine \\ \(\bullet\) & Express NGF receptors & \(\bullet\) & Express various neuronal markers \\ \(\bullet\) & Regarded as a model for adrenal & \(\bullet\) & Form synapses with primary neurons \\  & chromaffin tumor & \(\bullet\) & Sensitive to neurotransmitters and electrically excitable \\  & & \(\bullet\) & Regarded as a model of neuronal cells \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Characteristic properties of undifferentiated and differentiated PC12 cells [19; 21; 22; 25]. Although the protocols for proper preparation of PC12 cell line to serve as a neuronal model have already been described, numerous studies on neurodegeneration do not include cell differentiation in their study design, therefore conducting their experiments on cells expressing properties of the adrenal pheochromocytoma cells. [PERSON] et al. proved that PC12 cells, after neuronal differentiation with NGF, develop resistance to some anticancer drugs [26]. Scientists quite often use undifferentiated PC12 cells to test neurotoxicity or antiinflammatory or neuroprotective properties of new pharmacotherapeutics, searching for effective treatment for neurodegenerative and neuroinflammatory diseases like AD. LPS and A\(\beta\) are often used to induce a state of inflammation and simulate conditions found in the AD-affected brain [27; 28; 29; 30; 31]. Unfortunately, as we prove in our study, undifferentiated PC12 cells show altered response to A\(\beta_{25\text{-}35}\) and LPS compared to NGF-treated cultures induced to differentiation. Therefore, results obtained with undifferentiated PC12 pheochromocytoma cells cannot be interpreted as representative of neuronal cells. Two main types of PC12 cell lines are available from the ATCC collection--cells growing in suspension or adherent. Previous work proved that only PC12 cells growing in suspension could be an appropriate research model in neurobiology experiments. To use the PC12 cells for these studies, it is necessary to prepare the culture plates' surface properly [15]. The PC12 cells growing in suspension form aggregates and are round and small (Figure 1A). In order to differentiate them into neuron-like cells, they must first adhere to the surface of the culture vessel. Meanwhile, these cells do not adhere to plastic surfaces, and a modification of the surface of wells is necessary, e.g., by coating with type I collagen. PC12 cells seeded on the modified surface become flattened due to the reorganization of the cytoplasm, and the shape of the cells becomes polygonal (Figure 1B).